RC. 8901

U.S. GEOLOGICAL SURVEY CIRCULAR 890

Borehole Gravimetry Reviews
Borehole Gravimetry Reviews

By STEPHEN L. ROBBINS

A. What is Borehole Gravimetry? A Summary

B. Borehole Gravity Measurements, Data 

Reduction, and Precision A Review and 

Update of U.S. Geological Survey Methods

C. Bibliography with Abridged Abstracts of 

Borehole (Subsurface) Gravimetry and 

Corresponding In-place Rock Density 

Determinations

U.S. GEOLOGICAL SURVEY CIRCULAR 890
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1989

Free on application to the Branch of Distribution, Books and Open-File 

Reports Section, U.S. Geological Survey, Federal Center, Box 25425, 

Denver, CO 80225

Library of Congress Cataloging-in-Publication Data

Robbins, Stephen L. (Stephen Leroy), 1936- 

Borehole gravimetry reviews.

(U.S. Geological Survey Circular; 890)

Bibliography: p.

1. Borehole gravimetry. 2. Borehole gravity meters. 

I. Title. II. Series. 

QB334.R63 1989 526'.7 88-21513

Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. 

Geological Survey.

The considerable citations from publications of the Society of Exploration Geophysicists in chapter C 

are with acquiescence of the Society, Tulsa, OK.

Entries 78 and 95 in chapter C are reproduced with the permission of the Institute for the Study of Earth 

and Man at Southern Methodist University, Dallas, Texas 75275.
BOREHOLE GRAVIMETRY REVIEWS 

By Stephen L. Robbins

Chapter A. What is Borehole Gravimetry? A Summary

CONTENTS

Page

Introduction ........................................................ 2

Advantages of borehole gravimetry .................................... 2

Applications for borehole gravimetry .................................. 4

Future study possibilities ............................................. 4

References .......................................................... 6

FIGURE

1. Graph of gravimetric effects at the axis of cylindrical plates .......... 3
INTRODUCTION

Borehole gravimetry is the measurement, in a 

borehole, and the interpretation of gravity or gravitational acceleration. To accomplish this measurement, 

a gravity meter adapted to the borehole environment 

is required (a borehole gravity meter, BHGM, described in chapter B) with an operating and recording 

system for leveling and nulling the meter's sensing element while it is hanging stationary at selected depths 

within the borehole. After the measurement readings 

have been reduced (meter values converted to milligals), and various corrections (tide, meter drift, terrane 

effects, for example) have been added (described in 

chapter B), gravity value differences between stations 

in the borehole (AG) are divided by the vertical separations between these stations (AZ). The resultant values 

are the vertical gravity gradients for the measured interval within the well.

These gradients are directly affected by all horizontal differences in in situ (in place) bulk-rock density. If a borehole is located in an area where there 

is no complicating subsurface structure (simple area) 

and all density variations are in the vertical sense (all 

beds are nearly horizontal), then the calculated in situ 

bulk densities are assumed to be real. However, in a 

structurally or stratigraphically complex area (for example, faults, dipping beds, facies changes and 

caverns), then an "apparent" bulk density is determined (LaFehr, 1983). These apparent values, when 

plotted against density values from conventional logs 

and (or) cores (assumed real values), yield curves that 

can elucidate the subsurface structure.

A very large horizontal radius of investigation 

and direct dependence of measurements on bulk-rock 

density are the two unique characteristics of BHGM 

surveys. Responses of conventional logging tools (such 

as a gamma-gamma density tool) is from rock from 

only the first few inches out from the borehole wall 

(Sherman and Locke, 1975). Therefore, if a well is 

cased, most measurements from conventional logs are 

not very meaningful. BHGM measurements are not 

significantly influenced by casing, borehole rugosity, 

or formation damage caused by drilling, and although 

expensive, can be very useful.

The BHGM has been in use for over 20 years. 

Its potential for some purposes was recognized more 

than 35 years ago (Smith, 1950). In 1966, as the first 

BHGM was being made for the USGS, McCulloh 

(1966) reviewed the principles of borehole gravimetry 

and provided us an insight as to what a BHGM is and 

how this new logging tool would be of use to us.

This report is a brief introduction to the principles of borehole gravimetry and a synopsis of the uses 

the BHGM has been put to in the 20+ years of its existence; it is written primarily for the earth scientist, 

engineer, or student who has little or no knowledge 

of gravimetry. The capabilities of the BHGM are 

examined, successful and unsuccessful uses are enumerated, and other areas of possible use are suggested.

Discussions of the equipment used in conducting 

a BHGM survey, reduction of field data, and the precision that can be expected are contained in chapter B. 

A complete listing (with abstracts) of references on 

borehole gravimetry occupies chapter C. A good detailed introduction to the fundamentals of conducting 

a borehole gravity survey is in Beyer (1983).

ADVANTAGES OF BOREHOLE GRAVIMETRY

The BHGM permits direct measurement of the 

average gravity gradient AG/AZ between two vertically 

separated points in a borehole. From this gradient, a 

density value can be determined (formula 1, chapter 

B, p. 15). In a structurally simple area, the density contrasts so derived between beds will be true, and the absolute in situ bulk-density values should be nearly 

accurate depending on the error in the free-air gravity 

gradient (F). (See Robbins, 1981.) At many borehole 

sites where F is not known, the BHGM logs can be 

normalized (adjusted) against core-sample density 

determinations and (or) conventional logs. The apparent bulk-density values (Beyer, 1983; LaFehr, 1983) 

that are determined in structurally complex areas must 

be compared with density values determined by other 

means in order to obtain useful information. Uses 

for the BHGM in these types of areas will be discussed in the section, "Applications for Borehole 

Gravimetry."

The in situ bulk-density value determined from 

BHGM data is an average value representative of a 

relatively large volume because of the BHGM's large 

horizontal radius of investigation. One common question is, "What is this large radius?" A value that is 

about five times the vertical spacing between the gravity stations (AZ) is cited as an approximate radius of 

investigation by several authors (McCulloh and others, 

1968; Parley, 1971; and Bradley, 1976). This value is 

simply the radial distance that produces 90 percent of 

the total gravimetric effect for that interval (AZ) 

(fig. 1). The actual radius of investigation is variable 

and is dependent on the density contrasts encountered 

horizontally from the borehole and on the precision
°o 4

10

a £ 12 ^°- <x

9* 14

16

50 60 70 80 90 100

PERCENTAGE OF THE TOTAL GRAVIMETRIC

EFFECT OF AN INFINITELY EXTENDED

PLATE OF THICKNESS A Z

Figure 1 . Graph of gravimetric effects at the axis of cylindrical plates (from McCulloh, 1966, p. 4).

of the gravity data (chapter B; Beyer, 1983; LaFehr, 

1983). Since the gravitational attraction (/) between 

two masses (ml and w2) is directly proportional to the 

product of the masses and inversely proportional to 

the square of the distance (r) between them as shown 

in the relationship

f=k (1)

(where k is the Newtonian gravitational constant 

(Robbins, 1981)), the greater the horizontal distance 

a contrasting mass is from a borehole, the larger the 

density contrast must be in order to be detectable. 

Thus, a large high-density-contrast body at a large 

distance from a borehole will be detectable, but the 

same sized body with a small-density-contrast at a 

smaller distance from the borehole may not be 

detectable.

One method used to determine the porosity (</>) 

of a unit is from the relationship:

(2)

(Sf pf-pg)

(where pb is the bulk-density, pg is the grain density, 

pf the fluid density, and Sf is the fluid saturation). 

Since the bulk-density values determined from BHGM 

data represent a very large volume of rock when compared to the very small-volumed values on conventional logs, the porosity values calculated from fully

corrected BHGM data using formula 2 more closely 

represent the true porosity values for a formation.

McCulloh (1967) presented a comprehensive 

discussion of density and porosity relationships in 

terms of hydrocarbon reservoirs and their recognition. 

For example, beds containing gas or gas-saturated oil 

in their pores are lower in density than when the same 

beds are water saturated or infiltrated, which occurs 

when the beds are adjacent to a borehole, due to the 

drilling process. Gamma-gamma (or most other conventional) logging tools "see" only this altered portion of the beds, therefore, anomalous porosity values 

will be calculated if the wrong pf is used.

The BHGM has several other advantages over 

conventional logs in addition to its large radius of 

investigation. Following is a summary list of BHGM 

advantages:

1. Large radius of investigation makes the density 

values more representative of the measured 

formation.

2. In cased holes, casing does not significantly influence BHGM measurements, but most conventional logging tools are either useless or 

marginally useful.

3. In boreholes where the sidewall has been altered 

during drilling (including caving (rugosity) and 

mud filtrate invasion), again BHGM readings 

are not significantly influenced.

4. Allows studying off-hole structures (such as 

remote sensing of faults, salt diapir overhangs, 

and edges of thrust sheets) which no other density logging tool is capable of.

5. The BHGM enables the determination of in situ 

bulk-density directly (for areas of horizontal 

structure) instead of indirectly as an effect of 

some other property, such as electron density 

in gamma-gamma logs where a (Z//4) ratio is 

assumed (Z is the number of electrons per atom 

and A is the atomic weight); see Robbins (1979) 

for an example in which the wrong assumed 

Z/A caused a 0.1 g/cm3 error in the gammagamma density log for lignite.

Disadvantages of the BHGM include the following:

1. It is a costly tool in terms of initial investment 

($300,000-$500,000), delivery delay (2 to 3 

years), and maintenance.

2. Logging time is longer (usually about 5 minutes 

per station reading) compared to most other 

tools, which record continuously at relatively 

high logging speeds.

3. Instrument limitations include that the ' 'slimhole'' 

BHGM is 41 inches in diameter, thus usually
requiring a minimum 5-inch-diameter borehole; 

maximum temperature that can be logged is 

about 120 °C (250 °F); and maximum tolerable 

borehole deviation is about 12°-14°. 

4. Thin beds are difficult and more costly to measure 

because the field data have to be of the highest 

precision possible, which requires several repeated occupations of each station and takes 

extra time (chapter B, fig. 6).

APPLICATIONS FOR BOREHOLE GRAVIMETRY

The first consideration as to whether a BHGM 

survey is useful is the characteristics of the borehole 

itself. If the hole is uncased and to gauge and the formation is undamaged or unaltered from drilling, then 

a gamma-gamma log may provide adequate density 

values. However, if the hole has been washed out, 

damaged, or otherwise altered, then a BHGM survey 

is likely to offer the only reliable density information 

(Pritchett, 1980). If the hole is cased, then a BHGM 

is essentially the only way of obtaining a meaningful 

density log. The BHGM is necessary in most unconsolidated sediments because (1) the well has to be cased 

as it is being drilled, and (2) greater mud invasion 

occurs than in more consolidated rocks, because of the 

greater porosity and permeability. The BHGM has 

proven to be very successful in older oil fields where 

the wells were drilled and cased before logging tools 

as sophisticated as those available today were run 

routinely (Bradley, 1976; Gournay and Maute, 1982). 

Exploration Data Consultants Inc. (EDCON) (LaFehr 

and others, 1979) of Lakewood, Colo., has reported 

that about 20 percent of their commercial BHGM 

business is in searching for natural gas behind casing.

The second consideration is the geologic structure and petrophysics of the survey area. In simple 

areas, if the beds are competent and homogeneous, 

and hydrocarbon detection is not a goal, then a conventional density log would suffice. In heterogeneous 

beds, the BHGM is the only means of obtaining density values that can be used to calculate meaningful 

porosities. In studies where porosities are determined, 

saturation percentages can sometimes be calculated 

(Robbins, 1979, p. JJ15). Also, if BHGM surveys are 

repeated in a well over a period of time, saturation 

changes and (or) water/oil/gas percentage changes 

may be observable. For hydrocarbon detection, 

McCulloh (1967) has illustrated what the bulk densities 

should be for various geologic environmental and fluid 

conditions and how BHGM surveys may be of use.

In structurally complex areas, most BHGM 

studies are designed to search for off-hole structures. 

LaFehr and others (1979) stated that 20 percent of 

EDCON's BHGM business is for this purpose. However, few case histories in sedimentary rocks of these 

types of surveys have been published (Bradley, 1976; 

Clark and Hearst, 1983; Hearst and McKague, 1976; 

LaFehr and Dean, 1983; Schmoker, 1977; and 

Schmoker, 1980). There are several underground gravity applications in mining districts that contain anomalous lateral mass distributions; see for example 

Sumner and Schnepfe (1966). True in situ bulk densities can be determined for some strata in complex 

areas if the densities of nearby beds are independently known, the BHGM data are normalized to those 

density values, and no complex structure exists in the 

immediate vicinity of the beds of interest.

Carbonate reservoirs occur in both simple and 

complex areas. LaFehr and others (1979) reported 

that about 60 percent of EDCON's BHGM business 

is in "evaluation of carbonate reservoirs (finding 

oil and gas missed by other techniques)." Consequently, many surveys utilize the simple-area approach 

and some utilize Bradley's (1976) complex-area 

methods.

Data from BHGM surveys can also be useful in 

improving structural interpretations that are determined from surface gravity and (or) seismic data 

(Smith, 1950; LaFehr and Dean, 1983; LaFehr and 

others, 1983).

Most BHGM studies have been related to petroleum exploration and production (Bradley, 1976; 

Parley, 1971; and McCulloh and others, 1968), and 

some surveys have been related to mining studies 

(Robbins, 1979; Schmoker, 1979). Other topic applications are (a) ground-water studies (Head and Kososki, 

1979; Robbins, 1986; and Tucci and others, 1983), 

(b) radioactive waste-disposal site studies (LaFehr and 

Dean, 1983; Robbins, 1986; Robbins and others, in 

press; and Schmoker, 1980), and (c) other research 

studies relating to structurally complex areas (Hearst 

and McKague, 1976; Schmoker, 1977). Chapter C contains references to all BHGM studies and case histories 

presently in the literature (1986).

FUTURE STUDY POSSIBILITIES

There are many areas in which borehole 

gravimetry has yet to be better tested before its full 

potential can be realized. After a review of the 

literature and discussions with several colleagues, a
number of potential study areas are proposed in the 

following discussion:

1. Only one report has been published pertaining to 

the BHGM's use in engineering geology 

(Nichols and Collins, 1986). The BHGM should 

be useful in compaction studies, comparisons 

with conventional logs in rock types where little 

is known about the log responses, remote 

sensing of caverns, measurement of water 

saturation, and subsidence measurements.

2. Very little has been published on use in groundwater problems compared to the potential that 

the instrument offers in this field. Future study 

possibilities include better measurements for the 

calculation of maximum water yields, compaction rates due to water withdrawal, physical 

properties of aquifers and surrounding sediments, silting-in of aquifers, and calculations 

of basin depth and shape.

3. Only 3 of the 39 articles on the use of gravimetry 

in mining environments are related to borehole 

gravimetry. The remaining articles describe 

studies using surface gravity meters in shafts 

and adits. Many more studies are needed in this 

field, including rock-type comparision studies 

with conventional logs (intrusives, volcanics, 

metamorphics, and so forth) and remote sensing of old tunnels, caverns, anomalous masses, 

and structure.

4. Two reports are available on the construction of 

high-temperature sondes with heat sinks for the 

BHGM that would allow its use in very hot wells 

including geothermal wells for short periods of 

time (as long as 30 hours) (Baker, 1977; Black 

and Herring, 1983). The reports conclude that 

such sondes can be and are being made. One 

type of sonde is now in operation by EDCON. 

When further improved, it will increase the 

BHGM's useful capabilities, including the ability to monitor changes in steam-reservoir density through time where geothermal energy or 

thermal recovery techniques are being utilized 

(LaFehr and Nur, 1983).

5. Only one paper (LaFehr and Dean, 1983) has been 

published illustrating the usefulness of borehole 

gravimetry in the interpretation of surface gravity surveys. Robbins and others (in press) is a 

radioactive-waste disposal study where eight 

shallow wells (less than 1,000 feet deep) have 

been logged with the BHGM (Robbins and 

others, 1983) in order to determine the lateral 

changes in the near-surface sediments so that

the top of the basalts' configuration beneath 

these sediments can be determined from the 

surface gravity. (The density contrasts, both 

vertically and laterally, and acoustic impedances 

within and at the base of the sediments are so 

large that reflection seismic surveys have proven 

difficult to run and interpret.) Possible areas of 

study include (a) determining lateral density 

changes within various alluvial basins and 

glacial deposits, (b) interpreting large surfacegravity anomalies when insufficient data are 

available to understand the anomalies, and (c) 

constructing density-with-depth profiles in 

selected young oil-producing basins as starting 

points to aid in gravity stripping for interpretation of the lower oil-producing rocks. 

6. Several areas remain within the oil and gas industry where there apparently has been little 

testing of the BHGM's. In the area of reservoir 

engineering, fluid modeling and changes (Gournay and Maute, 1982), coning (Al-Khafaji and 

Schultz, 1983), pumping-down, compaction, 

and enhanced oil-recovery problems could be 

more completely understood if BHGM surveys 

were repeated over a period of time. As 

previously indicated, more studies are needed 

in complex areas. Studies at sites within high 

fluid-pressure areas, both in and outside the 

Gulf Coast, would help to better understand 

these environments (Pritchett, 1980). BHGM 

surveys could also help in studies of diagenetic 

changes, and secondary porosities. Some oil 

production occurs in atypical rock reservoirs 

(such as volcanics and intrusives); BHGM 

surveys, when compared with conventional logs, 

would aid in gaining a better understanding of 

the conventional log responses in unusual 

environments.

Comparisons between BHGM density profiles 

and borehole acoustic logs (sonic logs) and (or) vertical seismic profiles (VSP) can lead to better 

understanding of the elastic response of sedimentaryrock sections in terms of porosity and lithology. Such 

comparison can also promote understanding of the 

strengths and limitations of the acoustic impedance 

and reflection coefficient determinations of each of the 

different seismic measurements.

Borehole gravimetry's usage in scientific research 

has only begun. Its potential remains large and includes earthquake risk, hazard, and prediction studies, 

crustal studies, regional studies, and heat-flow studies. 

In heat-flow studies, for example, few temperature
measurements are made in deep-sedimentary-basin 

wells because of the uncertainty of the porosity of the 

rocks penetrated and the subsequent effect of incorrect values on the thermal conductivities used in the 

heat-flow calculations. The BHGM should be able to 

provide the needed porosity values used in these 

calculations. This would also allow us to better understand the thermal conditions prevailing in these deepsedimentary basins. As borehole gravimetry becomes 

better understood, more refined, and is used more, 

other areas of use not listed here will become evident.

REFERENCES

Al-Khafaji, S.A., and Schultz, A.K., 1983, Application of 

the borehole gravity meter (BHGM) to hydrocarbon exploration: Society of Exploration Geophysicists, 53rd 

Annual Meeting, Las Vegas, Nevada, Expanded 

Abstracts with Biographies, September 11-15, p. 26-28.

Baker, G.E., 1977, Gravity instrument canister feasibility 

study: San Ramon, California, EG&G Report 

GEB77-57, 63 p.

Beyer, L.A., 1983, Borehole gravity surveys Theory, 

mechanics, and nature of measurements: U.S. Geological Survey Open-File Report 83-76, 87 p.

Black, A.J., and Herring, A.T., 1983, Borehole gravityExpanded operating limits and performance: Society of 

Exploration Geophysicists, 53rd Annual Meeting, Las 

Vegas, Nevada, Expanded Abstracts with Biographies, 

September 11-15, p. 21-23.

Bradley, J.W., 1976, The commercial application and interpretation of the borehole gravimeter, in Jantzen, 

R.E., ed., Tomorrow's oil from today's provinces: 

American Association of Petroleum Geologists, Pacific 

Section, Miscellaneous Publication 24, p. 98-109.

Clark, S.R., and Hearst, J.R, 1983, Determination of subsurface geologic structure with borehole gravimetry: case 

history: Society of Exploration Geophysicists, 53rd Annual Meeting, Las Vegas, Nevada, Expanded abstracts 

with Biographies, September 11-15, p. 35-37.

Parley, D.G., 1971, Application of the downhole gravity 

meter for porosity determination: Preprint, Libyan 

Association of Petroleum Technologists 7th Annual 

Meeting, p. 1-20.

Gournay, L.S., and Maute, R.E., 1982, Detection of bypassed gas using borehole gravimeter and pulsed neutron 

capture logs: The Log Analyst, v. 23, no. 3, p. 27-32.

Head, W.J., and Kososki, B.A., 1979, Borehole gravity: A 

new tool for the ground-water hydrologist [abs.]: Transactions of the American Geophysical Union, v. 60, no. 

18, p. 248.

Hearst, J.R, and McKague, H.L., 1976, Structure elucidation with borehole gravimetry: Geophysics, v. 41, no. 

3, p. 491-505.

LaFehr, Ed, and Nur, Amos, 1983, Application of the 

borehole gravity meter to thermal recovery: Society of 

Exploration Geophysicists, 53rd Annual Meeting, Las 

Vegas, Nevada, Expanded Abstracts with Biographies, 

September 11-15, p. 31-33.

LaFehr, T.R., 1983, Rock density from borehole gravity 

surveys: Geophysics, v. 48, no. 3, p. 341-356.

LaFehr, T.R., and Dean, V.C., 1983, Borehole gravity case 

history of the Mors Salt Dome, Denmark: Society of 

Exploration Geophysicists, 53rd Annual Meeting, Las 

Vegas, Nevada, Expanded Abstracts with Biographies, 

September 11-15, p. 33-35.

LaFehr, T.R., Dean, V.C., Davis, T.L., and Hilterman, 

F.J., 1983, Seismic and gravity modeling of the Mors 

Salt Dome, Denmark: Society of Exploration Geophysicists, 53rd Annual Meeting, Las Vegas, Nevada, Expanded Abstracts with Biographies, September 11-15, 

p. 301-303.

LaFehr, T.R., Merkel, R.H., and Herring, A.T., 1979, 

Evaluation and applications of new LaCoste and 

Romberg borehole gravity meter [abs.]: Geophysics, v. 

44, no. 3, p. 369-370.

McCulloh, T.H., 1966, The promise of precise borehole 

gravimetry in petroleum exploration and exploitation: 

U.S. Geological Survey Circular 531, 12 p.

____1967, Mass properties of sedimentary rocks and 

gravimetric effects of petroleum and natural-gas reservoirs: U.S. Geological Survey Professional Paper 

528-A, 50 p.

McCulloh, T.H., Kandle, J.R., and Schoellhamer, J.E., 

1968, Application of gravity measurements in wells to 

problems of reservoir evaluation: Society of Professional Well Log Analysts 9th Annual Symposium Transactions, p. O1-O29.

Nichols, T.C., Jr., and Collins, D.S., 1986, In situ and 

laboratory geotechnical tests in the Pierre Shale 

near Hayes, South Dakota: U.S. Geological Survey 

Open-File Report 86-152, 24 p., 1 plate, 11 figures, 

1 table.

Pritchett, W.C., 1980, Physical properties of shales and 

possible origin of high pressures: Society of Petroleum 

Engineers Journal, v. 20, no. 5, p. 341-348.

Robbins, S.L., 1979, Density determinations from borehole 

gravity data from a shallow lignite zone within the 

Denver Formation near Watkins, Colorado: Society of 

Professional Well Log Analysts 20th Annual Logging 

Symposium Transactions, p. JJ1-JJ20.

____1981, Reexamination of the values used as constants 

in calculating rock density from borehole gravity data: 

Geophysics, v. 46, no. 2, p. 208-210.

____1986, The use of borehole gravimetry in water well

and waste disposal site evaluations in Proceedings of 

the surface and borehole geophysical methods and 

ground water instrumentation conference and exposition: National Water Well Association, Dublin, Ohio, 

p. 474-486. 

Robbins, S.L., Kunk, J.R., and Bjornstad, B.N., in press,
Three-dimensional density modeling from borehole 

gravity surveys in late Cenozoic sediments at the 

Hanford Site, Washington: Journal of Geophysical 

Research.

Robbins, S.L., Kunk, J.R., and Clutsom, F.G., 1983, 

Principal facts and density estimates for borehole 

gravity stations in boreholes RRL-3, -4, -5, -6B, -7, 

-8, and -9 at the Hanford Site, Benton County, Washington: U.S. Geological Survey Open-File Report 

83-386, 39 p.

Schmoker, J.W., 1977, Density variations in a quartz diorite 

determined from borehole gravity measurements, San 

Benito County, California: The Log Analyst, v. 18, no. 

2, p. 32-38.

____1979, Interpretation of borehole gravity surveys in 

a native-sulfur deposit, Culberson County, Texas: 

Economic Geology, v. 74, p. 1462-1470.

___1980, Effect upon borehole gravity data of salt structures typical of the WIPP Site (northern Delaware

Basin), Eddy County, New Mexico: U.S. Geological 

Survey Oil and Gas Investigations Chart OC-109.

Sherman, Harold, and Locke, Stanley, 1975, Depth of investigation of neutron and density sondes for 

35-percent-porosity sand: Society of Professional Well 

Log Analysts 16th Annual Logging Symposium Transactions, p. Q1-Q14.

Smith, N.J., 1950, The case for gravity data from boreholes: 

Geophysics, v. 15, no. 4, p. 605-636.

Sumner, J.S., and Schnepfe, R.N., 1966, Underground 

gravity surveying at Bisbee, Arizona, in Mining Geophysics, volume 1, Case histories: Tulsa, Okla., Society of Exploration Geophysicists, p. 243-251.

Tucci, Patrick, Schmoker, J.W., and Robbins, S.L., 1983, 

Density of basin-fill deposits calculated from boreholegravity data in four basins in central and southern 

Arizona: Society of Exploration Geophysicists, 53rd Annual Meeting, Las Vegas, Nevada, Expanded Abstracts 

with Biographies, September 11-15, p. 28-31.
BOREHOLE GRAVIMETRY REVIEWS 

By Stephen L Robbins

Chapter B. Borehole Gravity Measurements, Data

Reduction, and Precision A Review and 

Update of U.S. Geological Survey Methods

CONTENTS

FIGURES

Page

Introduction ........................................................ 10

BHGM equipment ................................................... 10

Data acquisition procedures ........................................... 11

Station locations ................................................ 11

Meter operation ................................................. 11

Data collection .................................................. 12

Data reductions ..................................................... 15

Data precision ...................................................... 16

Data interpretation .................................................. 16

Summary ........................................................... 17

References .......................................................... 18

1-3. Photographs showing:

1. U.S. Geological Survey BHGM's BH-1 and BH-6 .............. 10

2. Control consoles used to operate USGS BHGM's BH-1 and BH-6 12

3. Strip-chart recorder with record segments ...................... 14

4. Null-position determination chart with example .................... 15

5-7. Graphs showing:

5. Standard errors of borehole gravimetric determinations of density, 

assuming no error in A (AG) ................................. 17

6. Standard errors of borehole gravimetric determinations of density, 

assuming no error in A (AZ) ................................. 17

7. Example of effect of a displaced horizontal bed (vertical fault) on 

borehole gravity determined densities .......................... 18
INTRODUCTION

The U.S. Geological Survey (USGS) has been 

conducting borehole gravity meter (BHGM) surveys 

since 1966 (McCulloh, LaCoste, and others, 1967) 

using the first La Coste and Romberg, Inc. borehole 

gravity meter built (BH-1). Equipment (including a 

new smaller-diameter meter), methods of data acquisition and reduction, and data precision have steadily 

improved. The purpose of this report is to describe the 

equipment used, procedures developed, and the precision that the USGS was obtaining at the end of 1982. 

Some background information and recent industry improvements are also included.

BHGM EQUIPMENT

Two types of gravity meter systems have been 

used successfully in making high-precision BHGM 

surveys. The first utilizes a sensing element designed 

around the vibrating-string principle. Operational 

meters were built by Shell Development (Goodell and 

Fay, 1964) and by Esso Production Research Co. 

(Howell and others, 1966). These meters, although successful, have been used very little, apparently because 

of instrumental maintenance problems and slow operation, and this type of meter is not considered further 

here.

The second type employs a zero-length-spring 

suspension, and LaCoste and Romberg, Inc. is the 

only manufacturer, to 1986, that has built a successful 

borehole meter of this type. Their first three BHGM's 

utilized sensors from their land geodetic meters 

(McCulloh, LaCoste, and others, 1967). Two of these 

BHGM's are still in operation (the USGS prototype 

BH-1 with sensor G-95 (fig. 1), and BH-2 operated 

by Amoco Production Co.). They are between 51 and 

6 in. in diameter, are thermostated (maintained) at a 

temperature of about 100 °C, and can be operated in 

a borehole with up to a 6° deviation from vertical. In 

1975, LaCoste and Romberg started development of 

a new "slimhole" BHGM that is 41 in. in diameter

o

(fig. 1) and utilizes a redesigned sensor two-thirds the 

previous size. Their thermostated temperature is between 120 and 125 °C, and they can be operated in 

a borehole deviated up to 141°. Nine of these secondgeneration instruments are currently in operation (including USGS's BH-6). Black and Herring (1983, 

p. 21) are now (1986) operating these meters in boreholes at temperatures as high as 200 °C with the use 

of a new high-temperature (larger diameter) sonde.

Figure 1. U.S. Geological Survey Borehole Gravity Meters 

BH-1 (left) and BH-6 (right) built by LaCoste and Romberg, 

Inc.

The electronic control and power systems used 

on LaCoste and Romberg meters are not supplied by 

the manufacturer, although LaCoste and Romberg did 

supply electronic packages for the original three 

BHGM's. The first package, however, required a special 

13-conductor wireline and could not be operated from 

a standard 7-conductor cable. As a result, several different electronic systems have been designed and built 

by owners of these meters. The USGS meter BH-1 

employs an FM system developed by F.G. Clutsom 

(1984a). A quasi-digital system, also developed by F.G. 

Clutsom (1984b), has been installed on BH-6 because 

of the increased number of control functions on the 

"slimhole" meters. Amoco Production Co. developed 

its own independent control system. EDCON of Lakewood, Colo., has purchased the Amoco design and has 

made extensive modifications to it (I.E. Seibert, oral 

commun., 1980). Amoco and EDCON meters contain 

microprocessors for speedier leveling of the meters. 

Amoco has developed a new automated beam nulling 

system for operation of their meters (Lautzenhiser, 

1983).

10
Maintenance on BHGM's is expensive because 

mechanical and electronic components associated with 

the sensor are susceptible to high-temperature fatigue, 

corrosion from well fluids that can occasionally 

damage components, and electrical arcing in cable or 

tool connectors. Fluid leaks into the tool sondes have 

occurred several times and were the cause of the destruction of Amoco's BH-3. Periodic high-temperature 

lab tests, and cleaning and lubricating of the sensor 

components are also necessary.

BHGM surveys can be run from most of the logging trucks that the commercial logging service companies own. Many of the BHGM surveys run by 

EDCON were from other commercial logging service 

company trucks, although now EDCON uses their own 

truck whenever possible. The USGS has its own logging truck (Robbins, 1979), which has allowed acquisition of better quality data at less expense than when 

commercial companies were used prior to the completion of the truck in 1977. Problems encountered while 

employing the services of some commercial wireline 

units included the following: (1) generator fluctuations 

and failure, (2) poor gamma-ray equipment, (3) difficulty in finding seven good conductors within the 

cable, (4) resistances or capacitances too high for the 

BHGM in some cables, (5) trouble providing or finding adaptors to match the cablehead to our tool, 

(6) time and effort required in instructing the truck 

operator in the unusual techniques needed for logging 

with our tool, (7) the logistics of locating an available 

truck when and where needed, (8) inadequate care in 

the handling of electronic consoles by the airline companies during shipment to and from a wellsite location, and (9) in one instance, the parting of a logging 

cable which almost destroyed BHGM BH-1. Cities 

Service Co. put into operation a research logging truck 

that is completely computerized including winch operations for gravity and vertical seismic profiling surveys 

(Caton and others, 1983).

A new downhole clamping device, built by SIE 

of Fort Worth, Texas, is now allowing EDCON to log 

from floating drilling platforms (Black and Herring, 

1983, p. 21).

DATA ACQUISITION PROCEDURES

Gravity data collected by the USGS utilized 

LaCoste and Romberg BHGM's BH-1 and BH-6 

(fig. 1). All boreholes logged by the USGS since early 

1977 were run from the USGS logging truck, and its 

operation is discussed in Robbins (1979). For the

acquisition of the gravity data, the BHGM has to be 

stationary. Therefore, the procedures for the acquisition of data are divided into three subsections: 

(a) selection of station (meter reading) locations, (b) 

mechanical operation of the meter before and at a 

station location, and (c) data recorded and system of 

station occupations and reoccupations.

Station Locations

The objective in choosing station locations is to 

end up with intervals between the stations that are lithologically homogeneous. To this end, the locations of 

tops and bottoms of formations and lithologic units 

were used.

In identifying these locations:

1. All available logs were first studied and preliminary locations chosen.

2. A natural gamma-ray (G-R) log was then obtained 

using the same truck and cable that was to be 

used for the BHGM survey.

3. This G-R log was then used to adjust for any 

datum and (or) cable differences that might have 

existed between the earlier logs and this one.

4. If any new lithologic information was evident on 

this G-R log, station locations were added, subtracted, or moved, and the final location depths 

chosen.

It cannot be stressed enough that picking the 

proper locations (intervals of homogeneous densities) 

for the gravity stations is essential and will determine 

the usefulness of the BHGM survey. Surveys with 

poorly picked station locations may be almost useless. 

LaFehr (1983) has suggested that, for surveys where 

anomalous masses are present (geologically complex 

areas), the station locations be both "just outside as 

well as just within the zone of interest" from which 

a calculation of the real density change at the boundary (the "Poisspn jump") can be made.

Meter Operation

Standard meter operation procedures are contained in the manufacturer's operation manual. In 

addition, USGS surveys in the field included:

1. Setting the meter into sonde and into borehole at 

least 12 hours before start of survey (to allow 

for temperature stabilization).

2. Exercising of screw and springs and tune-up 

(check of beam sensitivity and levels) at least 1 

hour before beginning each survey.

11
3. A maximum of 50 feet per minute for movement 

of instrument inside the borehole (to keep tares 

and temperature effects to a minimum).

4. Logging going into the well (to minimize temperature effects).

5. Screw position was preset to the approximate 

(guessed at) next station reading before or during travel to that location (to minimize the effect 

of the mechanical hysteresis of the flat springs 

in the beam lever system).

6. At all base and other station locations to be reoccupied, placing tape and paint on the cable at 

the well head.

7. When reoccupying a station, moving the cable and 

sonde the final 10 to 20 ft always from the same 

direction (usually down).

8. For leveling BH-6, keeping rotation of meter 

within sonde to a minimum (to minimize 

temperature effects).

Data Collection

This section, an extension of the Meter Operation section, describes how the BHGM electronic 

signals at the meter console are converted into 

meaningful gravity values and are recorded, what 

other data are recorded, the procedures for occupying the gravity stations and for repeating bases, and 

what preliminary calculations were done during a 

survey.

The electronic signals to and from the BHGM's 

are controlled from the BHGM consoles (fig. 2). 

Through the use of switches on the console which control electric motors in the meter, one can level the meter 

sensor, rotate the meter (BH-6), change the screw position, unclamp and clamp the beam, and position the 

beam anywhere between its stops. Signals that come 

to a console from the BHGM are displayed on the console face by use of analog meters showing the position 

of the meter sensor relative to level, the rotation orientation of BH-6, the sonde temperature, and the position of the sensor beam. The screw position is shown 

through a combination of a numerical counter and an 

analog meter (the large one, fig. 2). The BHGM beam 

output voltage signal at the console is a function of 

the beam's position relative to null (that position where 

the suspension spring is zero-length). Zero voltage 

means the beam is in the null position; a negative 

voltage is outputted when the beam is on the low side 

(low gravity) of null; and a positive voltage is outputted 

when the beam is on the high side. By inputting this

Figure 2 (above and facing page). Control consoles used 

to operate USGS BHGM's: A, BHGM BH-1; B, BHGM BH-6.

beam signal into a constant-speed strip-chart recorder, 

an analog record of the BHGM beam position relative 

to time can be made. The angles of the recorded line

12
e*

s

segments (slopes) relative to the horizontal axis of the 

strip chart (fig. 3) represent excursion velocities of the 

beam away from the null position (the beam is placed 

at the null position by a control switch on the console) 2. 

when the counter-screw is not at the null setting (null 

is 0° slope). Because the beam is damped, the excursion rate (slope) varies as a linear function of the screw 3. 

setting relative to null when the screw setting is within 

40 or 50 /ugal (microgals) of null.

The procedures which follow were developed 

so that the data collected would contain as few errors 

as possible and the data precision would be at a 4. 

maximum:

1. Three or more slopes and counter readings were 

obtained which reveal the null position even if 

null was not occupied directly. Most of 

EDCON's surveys (J.E. Seibert, oral commun., 

1980) were run using only the null readings that 

apparently took almost as much time as when 

we took three or more non-null readings. I 

believe that the multiple reading method produces better quality data because the beams on 

these meters occasionally stick, usually around 5. 

the null position. Amoco has a new automated 

system (Lautzenhiser, 1983) which does away 

with the above procedure: in Amoco's system, 

the measuring screw is brought to within 

100 /ugal of null, an electrostatic force and feed- 6. 

back system is used to null the beam, and the

resultant voltage output is converted into an 

electrostatic correction, which is added to the 

measuring screw reading.

Station location depths were recorded to the nearest 0.1 ft or to hundredths when station intervals were small (less than 20 ft).

A separate record was kept containing only 

occupied station depths. Adjustments to the 

chosen location depths were made during the 

survey based on reoccupation depth differences 

caused by cable stretch and (or) shrinkage.

Starting at a primary base station (usually deep 

enough to be a quiet station), 5 to 7 stations were 

read with the last station being a new base station. The meter was then returned to the primary 

base station thus creating a loop. If the meter 

reading closure was good (±30 /ugals or less after 

tidal corrections), then a new loop was started 

at the new base station. This procedure was continued to the bottom of the well. If a loop 

closure was not good, then the stations were 

repeated and a possible tare located.

Loops were not used in some early surveys (surveys 

in 1975-1976). Instead, stations were read from 

the top directly to the bottom of the borehole 

and about every fifth-to-seventh station was 

reoccupied coming back out.

Stations directly above and below the water table 

were occupied at least twice. The change in the

13
Figure 3. Strip-chart recorder with record segments.

8.

temperature gradient on and within the sonde 

can be fairly abrupt when it transits the air to 

water boundary and can sometimes cause some 

temperature effects, especially if the meter 

temperature setting has shifted a little (the optimum temperature at which any LaCoste and 

Romberg gravity meter should be set is dependent on the metallographic makeup of the sensor materials and the only accurate way of 

checking for this shift is in a temperature 

chamber in the laboratory).

At shallow depths or when it was windy, a clamp 

was attached to the cable at the well head and 

tension was released between the clamp and 

the truck, thus reducing oscillations at the 

meter.

Two separate records of the data were made during the survey:

a. The first set was recorded on the analog 

strip-chart paper and included the date, 

the tune-up information, the station

depth, the slopes and their corresponding 

meter counter readings and times of observation, the sonde temperature, and any 

other information pertaining to the quality 

of the data.

b. The second listing on a separate sheet includes the date, the station depth, a visual 

estimate (eyeballing the slopes on the stripchart record) of the meter counter reading 

at 0° slope (null) (these estimates were 

usually good to better than ± 5 jttgal), the 

time, and the gravity tide corrections 

(taken from tide tables that had been 

prepared before leaving for the field). 

From these data, a preliminary density 

value was calculated. If this value appeared unusual (when compared to 

gamma-gamma logs and (or) knowledge 

of the lithology), then the interval stations 

were reocccupied and checked for possible reading errors or tares.

14
DATA REDUCTIONS

Data reductions consist of determining the meter 

null counter reading, converting this number into 

milligal values, adding in tide corrections, determining instrument drift and tare corrections, making 

terrain corrections, calculating the measured gravity 

gradients between adjacent stations, and calculating 

density values. These reductions were normally done 

in the office except for the preliminary calculations 

discussed in 8b, p. 14. The procedure used in the 

reduction of the borehole gravity field data is as 

follows:

1. The slope angles of the beam excursions on the 

strip-chart record were measured using a 

protractor.

2. The angles for a given station were then plotted 

against the counter-screw readings (fig. 4) for 

that station which then revealed the null counter 

reading at the 0° slope position.

3. The null position meter counter readings were converted into arbitrary milligal values using the 

BHGM's calibration tables (it was found that 

the small differences between the factorydetermined calibration values and subsequently determined calibration values, although 

significant in large surface gravity surveys, do 

not measurably change the density calculations 

of borehole data).

4. Tidal gravity corrections were added in.

5. The resultant values for the base stations and any 

other repeated stations were plotted against time 

in order to determine the drift and tare behavior 

of the meters during the surveys and these corrections were added in.

6. Terrain corrections were calculated, in accordance 

with the methods and principles described by 

Hammer (1939), or Swick (1942), and Hearst 

and others (1980). When the terrain within the 

first 100 ft or so of the borehole had slopes 

greater than 5 °, the terrain was sketched so that 

the correction could be later calculated in the 

office. Many of the surveyed boreholes had surface terrain corrections calculated out at least 

to a distance of 72,000 ft (22.9 km), corresponding to zone M of Hammer's (1939) terrain correction chart; others had corrections computed 

out through Hayford-Bowie zone O (167 km). 

These terrain correction values were then 

entered into a computer program by Beyer 

and Corbato (1972) for the calculation of the

BOREHOLE GRAVITY READING-SLOPE COMPUTATION

Well

Sta#

V7

.740

.720

.700

-30° -20° -10° 10° 20° 30°

.680

Well

Sta#

.460

.440

420

.400

-30° -20° -10° 0° 10° 20° 30° 

Figure 4. Null-position determination chart with example.

terrain corrections at the different station depths 

within the borehole.

7. The terrain corrections were added in, thus 

creating corrected observed gravity values.

8. These observed gravity values were then subtracted from the adjacent stations' observed 

values (AG) and the result divided by the 

vertical intervals (AZ), thus giving the measured gravity gradients between each station 

(AG/AZ).

9. Bulk density values (pB) were calculated using the 

formula:

F-AG

AZ (1)

where F is the free-air gradient, and k is the Newtonian gravitational constant (Robbins, 1981; Smith, 

1950); F is discussed further in the Data Interpretation section.

15
DATA PRECISION

Questions commonly asked about BHGM 

surveys pertain to data precision. Typical questions 

are, "How accurate is the survey?" and "How thin 

a bed can be measured?"

McCulloh and others (1967b) suggested from 

early tests with meter BH-1 that a reading precision 

of ±8 /igal is obtainable because they obtained an 

average precision of ± 16 /igal for each pair of stations 

A(AG), based on 20 gravity readings (including both 

meter readings and depth measurements). Their depth 

measurement accuracy ranged between 0.05 and 0.2 ft. 

Brown and others (1975) obtained a standard deviation error of ±18 /igal from 150 repeated A(AG) 

readings with BH-2, and Schmoker (1978), using 132 

interval measurements from BH-1, obtained a standard deviation of ± 19 /igal and a standard error of 

13.4 /igal. This suggests a reading precision of 

±7 /igal. Schmoker (1978, p. 541) also found that, by 

restricting the intervals to less than 70 ft and the time 

between readings to less than 0.6 hours, a reading 

precision of ±5 /-igal could be obtained.

For slimhole meters, LaFehr and others (1979) 

reported that EDCON under most operating conditions achieved average A(AG) repeats of ±10-20 /igal 

from BH-4. Caton (1981), in analyzing seven BHGM 

surveys run using BH-10, did not calculate any A(AG) 

errors. However, he did conclude that he was able to 

achieve a ±5 /igal reading precision at the 90-percent 

confidence level if three or more independent readings 

per station were made. Black and Herring (1983), after 

making some heat-compensation adjustments to the 

EDCON BHGM's thermostating circuitry, obtained, 

in a test survey of over 200 gravity readings at 20 stations, a standard deviation error of ±2.6 /igal per 

reading.

Interpretation of the above reports and of 

data that I have personally worked with leads me to 

believe:

1. Most BHGM surveys, with only one reading per 

station and repeats of every few stations, will 

achieve standard deviation errors for A(AG) of 

± 14 to 20 /igal, or better.

2. If maximum care is taken (that is, allowing a 

longer time for temperature stabilization before 

and during the survey, keeping the internal 

meter rotation to a minimum, making repeats 

at least every 1 to 2 hours, and so forth), then 

A(AG) errors will be ± 10 to 14 /igal.

3. If multi-readings are made, an optimum error of 

±6 /igal per A(AG) can be achieved. Beyer

(1983) believed that this error optimally should 

approach ±2 to 4 /-igal.

Interval depth errors are believed by 

McCulloh, Schoellhamer, and others (1967), 

Beyer (1971), Schmoker (1978), Caton (1981), 

and myself to be minimal (usually less than 

±0.1 ft). In checking for errors in our cable 

system, I have found that we were within 2 ft 

over a 10,000-ft interval of cased hole. This is 

an error of 0.1 ft in 500 ft. Moreover, most 

depth errors are reflected in the A(AG) error. 

That is, if a station location is lower by 0.1 ft 

than is believed, then the measured A(AG) for 

the interval above the station will be higher by 

3 to 5 /igal depending on the density of the rocks 

and too low by the same amount for the interval below the station.

Although depth errors are usually minimal and 

are usually part of the A(AG) error, figures 5 and 6 

show that it is necessary to keep these depth measurements as accurate as possible (especially when logging 

thin beds). It should also be noted that the density 

error for a given depth error is also a function of the 

density of the surrounding rocks. The USGS truck has 

two cable measuring systems (Robbins, 1979), and one 

displays the cable depth to the nearest hundredth of 

a foot, values that were used in surveys where the intervals logged were less than 15 ft thick.

The minimum bed thickness (AZ) that one can 

measure with a BHGM is dependent on the accuracy 

of the density data needed and on the accuracy of the 

BHGM data obtained. Figure 6 can be used to determine this minimum bed thickness and shows that optimally, for a required density precision of ±0.02 g/cm3 , 

a 15-ft bed can be surveyed. If less density precision 

is acceptable, then thinner beds can be surveyed.

For a more complete discussion on gravimetry 

repeatability and errors, see Beyer (1983).

DATA INTERPRETATION

Density values (pB) that are determined from 

BHGM surveys using formula 1 (p. 15) are known as 

interval densities. These values in areas of complex 

geology become apparent bulk densities (Beyer, 1983; 

LaFehr, 1983). In order to understand and utilize these 

values, the question, "Do the lithologic beds dip more 

than about seven degrees and (or) is there structural 

complexity in the area (for example, faults, salt domes, 

facies changes, reefs, or caverns)?" needs to be 

answered.

16
100

80

60

40

20

EXPLANATION

For A (A Z) of 0.5 feet for p between 1.5 and 3.0 g/cm3 , 

where density increases to 

right

For A (A Z) of 0.1 feet for p between 1.5 and 3.0 g/cm3 , 

where density increases to 

right

0.10 0.05

STANDARD ERROR OF DENSITY MEASUREMENT 

p. IN GRAMS PER CUBIC CENTIMETER

Figure 5. Standard errors of borehole gravimetric determinations of density as a function of AZ, assuming no error 

in measurement of A(AC).

100

80

60

N

< 40

20

Gravimeter Precision 

(Standard deviation)

+0.005 mgals 

±0.010 mgals 

±0.015 mgals

0.20 0.10 0.05 0.00

STANDARD ERROR OF DENSITY MEASUREMENT, 

IN GRAMS PER CUBIC CENTIMETER

Figure 6. Standard errors of borehole gravimetric determinations of density as a function of AZ, assuming no errors in measurement of A(AZ) (from McCulloh and others, 

1968, p. 8).

When the answer to both parts of the question 

is "no" (simple area; that is, horizontally homogeneous density values with all density variations in the vertical sense), the pB values, if not exact, are very close 

to being true bulk densities and F is not likely to vary 

much from the normal value of 0.09406 mgal/ft 

(0.3086 mgal/m), unless the borehole is located within 

a large graben or horst-like structure. A wrong value 

of F changes the computed absolute densities, causing a dc shift, but does not affect density differences 

between intervals. Also, in many cases, the surveys 

were normalized against accurate core analyses or 

gamma-gamma density logs.

In structurally complex areas, not only are the 

PB values different for the interval horizontally opposite an anomalous structure, but the structure also 

affects pB values for some distance above and below 

the structure (example, fig. 7; LaFehr, 1983). Also, 

local surface geologic effects can cause/7 to vary more 

than 10 percent from the normal value (McCulloh, 

1966, p. 2-3). These effects will also cause F to vary 

over the length of a borehole. Therefore, in order to 

understand and interpret the differences between 

BHGM pB values and true values, good core analyses 

and (or) gamma-gamma density logs are necessary.

One way of interpreting apparent BHGM pB 

values in complex areas is to compare these values with

the density values that have been determined by other 

methods and have been averaged over the BHGM 

survey intervals. The BHGM pB values are then normalized against the above averaged values, and differences are taken. The measured differences can now 

be compared and matched with calculated difference 

curves for simple-body models. Figure 7 is an example 

for a vertical fault (displaced horizontal bed) with 100 

ft of displacement. By making assumptions based on 

knowledge of the local geology such as having a 100-ft 

displacement fault as in figure 7, curves can be calculated and matched to the measured differences for subsurface structural models that are reasonable to the area 

of the survey. The paper by Clark and Hearst (1983) 

is an excellent example of a study in a complex area.

SUMMARY

This chapter ha$ provided a brief introduction 

to the equipment and procedures, used by the USGS, 

in conducting borehole gravity surveys over a 16-year 

period. For a detailed discussion of the fundamentals 

of borehole gravimetry, including theory of operation, 

basic well-measurement procedures, data reductions 

and corrections, measurement errors, and repeatability of measurements, see Beyer (1983).

17
1000

Gravity station m surface

2

1t -1

\

,

2 P1 J

J

3

 

< Pz

Pi

.

« X >

,r Pi

L

Pi

_

2

J

1

500

-500

4.07x

7r+tan-1 XEffect where po=P2~Pi =1 g/cm3

t=100 feet 

Displacement (Z2 - 2^=100 feet

X=100 feet

-.1 -.05 .05

ACTUAL MINUS BHGM DENSITIES 

(PB ). IN GRAMS PER CUBIC CENTIMETER

Figure 7. Example of effect of a displaced horizontal bed (vertical fault) on borehole gravity determined densities.

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Open-File Report 71-42, 229 p.

____1983, Borehole gravity surveys Theory, mechanics, 

and nature of measurements: U.S. Geological Survey 

Open-File Report 83-76, 87 p.

Beyer, L.A., and Corbato, C.E., 1972, A Fortran IV computer program for calculating borehole gravity terrain 

corrections: U.S. Geological Survey Open-File Report, 

27 p.

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18
Analysts 22nd Annual Logging Symposium Transactions, p. RR1-RR44.

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79-1511, 67 p.

____1981, Reexamination of the values used as constants 

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Geophysics, v. 46, no. 2, p. 208-210.

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Smith, N. J., 1950, The case for gravity data from boreholes: 

Geophysics, v. 15, no. 4, p. 605-636.

Swick, C.A., 1942, Pendulum gravity measurements and isostatic reductions: U.S. Coast and Geodetic Survey Special 

Publication 232, 82 p.

19
BOREHOLE GRAVIMETRY REVIEWS 

By Stephen L. Robbins

Chapter C. Bibliography with Abridged Abstracts of 

Borehole (Subsurface) Gravimetry and 

Corresponding In-place Rock Density 

Determinations

CONTENTS

FIGURES

Page

Introduction ........................................................ 22

Bibliographic list with abridged abstracts ............................... 23

Theory, methods, data reduction, and applications .................. 23

Instrumentation, data accuracy, and precision ....................... 39

Case histories ................................................... 43

Reports containing only basic gravity data and reductions with some

preliminary density and porosity determination .................... 56

Author index ....................................................... 59

Title index .......................................................... 61

1. Histogram showing number of reports and abstracts on subsurface gravimetry 

published per year between 1937 and 1987 ........................... 23

2. Histogram showing number of subsurface gravity reports by publisher .. 24

21
INTRODUCTION

This compilation lists 246 reports that contain 

information pertaining to subsurface gravity and the 

corresponding in situ rock density determinations. 

Most of the reports are on borehole gravimetry. 

However, 55 reports listed discuss gravity measurements in mine shafts and underground diggings, such 

as coal, copper, and salt mines.

A little more than half the reports were published 

with abstracts that are reproduced here; many 

abstracts are abridged because of their length. 

Asterisks represent ellipses in original abstracts. For 

other reports, short abstracts have been added. Several in foreign languages have only a translation of the 

title.

The reports are divided into four categories: 

theory, instrumentation, case histories, and basic 

data. Author and title indexes are provided at the 

end. A report pertaining to more than one category is referenced in each section, and its abstract 

appears only in the first section in which it is 

referenced.

I compiled this list by searching the reference lists 

in the borehole gravimetry reports already known to 

me and then by checking the references in these 

reports, and so forth. Cumulative indexes for Geophysics and the Society of Professional Well Log 

Analysts (SPWLA) publications were searched. Colleagues were asked if they knew of any reports. This 

list is quite comprehensive, although a few papers may 

have been overlooked.

I wish to acknowledge L.A. Beyer's (of the U.S. 

Geological Survey) assistance in locating many of these 

references.

Reports on subsurface gravimetry started appearing with regularity about 30 years ago. Only four 

reports (1, 5, 89, and 191) predate 1947. Figure 1, a 

graph showing the number of reports published each 

year, shows three progressively larger periods of 

activity. The first peak was in the late 1940's to 

mid-1950's, and a number of good theoretical papers 

were published, including report 105, which is considered by some to be the classic in the fundamentals 

of borehole gravimetry. The second period was in the 

mid-1960's when several good reports that can be used 

as basic references were written. These include reports 

80 and 82. The third period started in the mid-1970's

and continues to the present. This group contains 

some good case history studies.

Over half of the reports were published in U.S. 

Geological Survey (USGS) publications and in publications of SEG (Society of Exploration Geophysicists). 

Figure 2 shows the distribution of the bibliography by 

publisher.

The first category contains reports that pertain 

to theory, methods, data reduction, and applications. 

Several reports in this section are noteworthy; namely 6, 80, 82, and 105. Reports 10 and 11 are good 

beginning references. A good set of literature now 

exists on terrain corrections; this includes reports 9, 

10, 12, 45, 59, and 103. The following reports contain discussions on deducing structure away from the 

borehole (remote sensing): reports 26, 46, 49, 50, 53, 

56, and 106.

The second section contains 30 reports that pertain to instrumentation. Within borehole gravimetry, 

two types of instruments have been developed: 

(1) vibrating filament, and (2) astatized spring. Instruments of the first type have been built by Esso Production Co., Exxon, and Shell Development and are 

discussed in reports 132, 133, 135, 137, and 146. 

LaCoste and Romberg, Inc. makes the only borehole 

gravity meters (BHGM) of the second type. Reports 

6, 11, 121, 122, 123, 124, 126, 138, 139, 142, 143, and 

149 describe these meters.

The third section lists 74 reports that contain 

only case histories. Thirty-seven reports listed in the 

first two sections are also listed in this section. Case 

histories are given for surveys run in boreholes and 

in underground mines in the following States and 

countries: Arizona, California, Colorado, Florida, 

Michigan, Missouri, Nevada, New Mexico, Ohio, 

South Dakota, Texas, Washington, West Virginia, 

Wyoming, Australia, Austria, Canada, Czechoslovakia, Denmark, England, Germany, Hungary, India, 

Libya, New Zealand, Poland, Russia, and Scotland.

The last section lists reports that contain only 

basic gravity data with reductions and corrections. Additionally, reports 225 through 232, 235, 236, 238, 239, 

243, 244, and 246 contain preliminary density and (or) 

porosity determinations,and gamma-ray logs are included in reports 233, 234, 236, 237, 238, 241, 242, 

243, and 245. Data are from the following States: 

California, Colorado, Florida, Michigan, Montana, 

Nevada, New Mexico, Texas, Washington, West 

Virginia, and Wyoming.

22
30

25

20

15

10

YEARS

Figure 1. Number of reports and abstracts on subsurface gravimetry published per year between 1937 and 1987.

BIBLIOGRAPHIC LIST WITH 

ABRIDGED ABSTRACTS

Theory, Methods, Data Reduction, and 

Applications

1. Airy, G. B. , 1 856, Account of pendulum experiments undertaken in the Harton Colliery for the purpose of determining the mean density of the Earth: London, Royal Society 

Philosophical Transactions, v. 146, nos. 14,15, p. 297-355.

This report is a very detailed step-by-step account of the events that occurred in the author's 

attempts to determine the mean density of the 

Earth by measuring the different periods of a 

pendulum swing at the top and bottom of a vertical mine shaft.

This report is also referenced in Case Histories.

2. Khafaji, S.A. and Schultz, A.K., 1983, Application of the 

borehole gravity meter (BHGM) to hydrocarbon exploration: Society of Exploration Geophysicists 53rd Annual 

Meeting, Las Vegas, Nevada, Expanded Abstracts with 

Biographies, September 11-15, p. 26-28. 

The capability of the BHGM in determining accurate bulk 

densities for a large radius of investigation makes it a powerful tool to locate porosity zones around a borehole and 

analyze reservoir properties. The remote sensing capabilities 

of the BHGM need to be considered before converting the 

gravity values to density, and hence porosity, and integrating 

it with other open-hole logs. In general, the BHGM faithfully 

maps and confirms porous zones indicated by other tools in 

a given borehole. In more than one case, it also pointed out 

other areas of interest in a given reservoir which were missed 

by the other tools either because of their limitations or the 

conditions of the wellbore. The case history examples which 

are presented demonstrate the application of the BHGM to 

a carbonate reservoir where matrix porosity is enhanced by 

fractures. There were sufficient density contrasts for the high

23
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sensitivity of the BHGM to detect. An opening of a zone 

based BHGM in one well increased the rate of flow to make 

the well commercial, and perforation of zones in other wells 

resulted in large quantities of hydrocarbons which otherwise 

might have been completely missed.

Use of the BHGM as a density logging tool suggests that 

a reservoir might be monitored for redistribution of fluids 

as a result of pressure gradients induced by pumping. This 

fluid movement is sometimes referred to as "coning." A gas 

zone may intrude downward toward a perforation and a water 

zone may intrude upward toward a perforation resulting in 

production problems. The difference between densities of gas, 

oil, and water should be reflected in altered gravity data due 

to their redistribution from the prepump to the postpump 

stage. A theoretical study was done of a real world reservoir 

using prepump and postpump models. Measurable density 

differences occurred between the two configurations. 

However, the density differences are of such a subtle nature

that it is imperative to collect data initially in the prepump 

configuration as well as in the postpump stages.

3. ____1984, Application of the borehole gravity meter 

(BHGM) to hydrocarbon exploration [abs.]: Geophysics, 

v. 49, no. 5, p. 596.

Same abstract as report 2.

4. Alien, W.A., Jr., 1956, The gravity meter in underground 

prospecting: American Institute of Mining Engineering 

Transactions, v. 205, p. 293-295.

Gravity meter surveys have been used for underground prospecting in the copper mines at Bisbee, 

Ariz. Evaluation of results indicates definite 

potentialities under proper conditions. Equipment, procedures, and methods of handling data 

are described.

24
5. Benfield, A.E., 1937, Note on the variation of gravity with 

depth: Zeitschrift fur Geophysik, v. 13, p. 157-158. 

A table and curve showing the value of "g" at different 

distances from the centre of the earth have been computed 

from the latest density distribution data. Gravity is shown 

to be remarkably uniform over a large distance.

6. Beyer, L.A., 1971, The vertical gradient of gravity in vertical and near-vertical boreholes: U.S. Geological Survey 

Open-File Report 71-42, 229 p.

A detailed presentation of the theory of borehole gravimetry and how to reduce and interpret 

borehole data is given, including appendices of 

all pertinent formulae.

*** observed vertical gradients from high-precision detailed 

gravity surveys made in seven shallow oil wells that penetrate 

a late Cenozoic sequence of marine and nonmarine rocks in 

the Midway-Sunset oil field, California, are interpreted to 

obtain vertical density profiles. ***.

The unadjusted density profiles of six wells are on the average systematically greater than core densities by .05 g/cm3 . 

Adjusted profiles for the same wells agree with core densities 

to within .01 g/cm3 on the average. Densities of an adjusted 

profile of a seventh well are .15 g/cm3 less than those of the 

unadjusted profile and are in better agreement with core densities by that amount. However, residual systematic discrepancies between core and gravimetric densities for this seventh 

well indicate a measurable variation of the anomalous vertical gradient with depth and (or) lack of representative core 

density data.

Topographic effects and anomalous vertical gradients in 

boreholes are usually small and change slowly with depth but, 

in some instances, may be comparatively large and change 

rapidly with depth. In the former case, gravimetric density 

profiles unadjusted for these effects can be in error by as much 

as about .05 g/cm3 and, in the latter case, by as much as several tenths of a g/cm3 . In both cases, relative errors between 

neighboring parts of the density profiles are much smaller.

In cases where the anomalous vertical gradient changes appreciably with depth, it cannot be reliably estimated in the 

borehole from surface gravity measurements or from tower 

gradient measurements, which are especially sensitive to very 

shallow local density irregularities. At any borehole depth 

the anomalous gradient can be estimated from the difference 

between core and gravimetric densities of the same borehole 

interval. The core densities must be highly accurate and 

representative of the interval and the gravimetric density must 

be adjusted for topographic effects.

Measured borehole vertical gradients have precisions of 

.00025 to .00050 mgal/ft (8 to 16 Eotvos units) for vertical 

intervals as small as 10 ft (3 m); ***.

This report is also referenced under Instrumentation and Case Histories.

7. ____1977, The interpretation of borehole gravity surveys

[abs.]: Geophysics, v. 42, no. 1, p. 141.

Borehole gravity measurements are responsive primarily 

to the vertical density variations in the rocks traversed by 

the survey and, secondarily, to lateral rock density variations 

(mass anomalies) of detectable magnitudes that may occur 

in the region surrounding the surveyed well.

In many cases, a uniform and horizontally layered earth 

can be assumed because the formations surrounding the 

borehole are level or nearly so and possess relatively uniform 

densities in lateral directions. In such areas, borehole gravity data are easily converted to highly accurate and unique 

vertical density profiles. Principal interpretation efforts involve the application of the vertical density profiles to formation evaluation, reservoir engineering, well-log and core 

analysis evaluation, surface gravity and seismic studies, or 

engineering and rock property investigations.

Lateral density variations may be significant where folded 

strata, faults, unconformities, intrusions, or lateral variations 

in lithology, porosity or pore fluids (due to selective depositional or postdepositional processes) intersect or occur within 

detectable distances of the borehole. Analysis of the borehole 

gravity data in these cases is more difficult because isopycnic (equal density) surfaces generally are not known and may 

be complex in shape. Separation of borehole gravity effects 

due to vertical and to lateral density variations is possible 

if independent and reliable vertical rock density information 

can be obtained from well logs, core analyses, or other 

sources. Interpretation of borehole gravity effects due to 

remote lateral density variations is influenced heavily by independent geologic and geophysical data from which the 

structural and stratigraphic setting of the well can be inferred. 

Interpretations are not unique and by necessity usually are 

simple.

Interpretations are presented of borehole gravity surveys 

made (1) in a steeply dipping section, (2) in axial and flank 

locations on a narrow anticline, (3) through an overthrust, 

(4) through a prominent unconformity, (5) through a carbonate reservoir with irregularly distributed porosity, and (6) 

at equivalent subsurface elevations in neighboring wells. 

Analysis techniques and practical limitations are discussed.

8. ____1979a, Terrain corrections for borehole and tower 

gravity measurements: U.S. Geological Survey Open-File 

Report 79-721, 17 p.

Terrain corrections were calculated for borehole gravity and tower gravity surveys made in 

a variety of topographic settings. The effect of 

terrain corrections on vertical density profiles 

calculated from borehole measurements also is 

shown.

9. _____1979b, Terrain corrections for borehole gravity 

measurements: Geophysics, v. 44, no. 9, p. 1584-1587.

This note discusses terrain corrections only for 

borehole gravity measurements and is a condensed version of report 8.

10. ____1982, The interpretation and application of borehole 

gravity surveys: Society of Exploration Geophysicists 

Course Notes, 226 p.

This course [see entry 108] is designed to provide an introductory yet up-to-date description of borehole gravity logging and how it can be used to enhance formation/reservoir 

evaluation and subsurface exploration.

This report accompanies the course described 

in entry 108 and contains discussions of the: 1) 

mechanics of borehole gravity surveys, 2) nature 

of BHGM measurements, 3) density and porosity

25
of sedimentary rocks, 4) conventional methods 

for estimating formation density and porosity, 

5) formation and reservoir evaluation with 

BHGM surveys, 6) systematic and analysis of 

borehole gravity anomalies, 7) studies of borehole gravity anomalies, 8) other uses of BHGM 

surveys, 9) planning and management of BHGM 

surveys, 10) applications and future directions, 

11) exercises, and 12) reprints of several reports 

on borehole gravimetry including reports 20, 53, 

60, 80, 105, 209, 211, and 216.

Successful use of borehole gravity surveys more often than 

not requires knowledge of the strengths and weaknesses of 

conventional open-hole logs and the factors that control density and porosity fluctuations in sedimentary rocks. The joint 

effort of the area or well geologist, a geophysicist, a well log 

analyst, and possibly a reservoir engineer or petrophysicist 

may be necessary to derive the maximum information from 

the survey.

11. ___1983, Borehole gravity surveys; theory, mechanics, 

and nature of measurements: U.S. Geological Survey 

Open-File Report 83-76, 87 p.

The theory, historical development, mechanics and nature 

of borehole gravity survey are presented here for the reader 

who is unfamiliar with these surveys or the gravity method 

of exploration geophysics.

This report contains much of the same material that is presented in entry 10.

12. Beyer, L.A., and Corbato, C.E., 1972, A Fortran IV computer program for calculating borehole gravity terrain corrections: U.S. Geological Survey Open-File Report, 30 p.; 

available as report PB-208-679 from National Technical 

Information Service, Springfield, VA 22161. 

The program calculates terrain corrections at equally or 

unequally spaced gravity stations in a vertical borehole (or 

on a tower above ground) and also calculates vertical gradients and density corrections over intervals between stations 

for analysis of borehole gravity measurements. Terrain must 

be described by a standard scheme (e.g., Hayford-Bowie, 

Hammer) or a special zone and compartment scheme. Terrain density may be specified as constant for all zones or as 

variable by compartment. An approximate correction for the 

earth's curvature is included.

This program presents an improved algorithm 

to the one offered in entry 45.

13. Beyer, L.A., Brune, R.H., and Schmoker, J.W., 1975, Application of borehole gravity to exploration for petroleum 

[abs.]: Program 50th Annual Pacific Section Meeting, 

American Association of Petroleum Geologists-Society of 

Economic Paleontologists and Mineralogists-Society of 

Exploration Geophysicists, Long Beach, California, April 

23-25, p. 29.

Gravity measurements in boreholes provide direct bulkdensity estimates of the formations penetrated by the well. 

These density estimates are highly accurate (.005 to 

.03 g/cm3) and are based on the integrated effect of large 

volumes of rock. The technique is especially well suited to 

evaluation of fracture or vugular porosity, to detection of

oil or gas sands behind casing, and to any situation where 

hole conditions make conventional open-hole porosity and 

density logs unreliable. In special circumstances downhole 

gravity measurements extend mapping of the anomalous 

gravity field into the subsurfaces for purposes of remote 

sensing of anomalous masses.

A reliable smaller diameter borehole gravimeter (tool O.D. 

of 4.25 inches versus existing 5.5 inches and larger tools) is 

under development for the USGS and research is underway 

to study the feasibility of developing a continuous reading 

borehole gravity gradiometer.

14. Black, A. J., 1985, Application of well log density data from 

borehole gravity and gamma-gamma measurement to 

geophysical exploration: Society of Exploration Geophysijists, 55th Annual Meeting, Washington, D.C., Expanded 

Abstracts with Biographies, October 6-10, p. 280-281. 

Density measurements obtained from well logging tools 

are used in the interpretation of gravity surveys recorded both 

on the surface and downhole. Density information is also 

used to calculate reflection coefficients for use in seismic 

modeling. The greatest demands for well log density accuracies are made when they are used for downhole gravity 

structural interpretations.

The vast majority of well log density information is provided by the gamma ray back-scattering technique which is 

often referred to as the gamma-gamma density method.***.

15. ____1986, Application of well log density data for borehole 

gravity and gamma-gamma measurements to geophysical 

exploration [abs.]: Geophysics, v. 51, no. 2, p. 468.

Same abstract as report 14.

16. Black, A.J., and Herring, A.T., 1983, Offset of borehole 

gravity densities due to geologic structures: Preprint, Canadian Society of Exploration Geophysicists, Annual Meeting, Calgary, Alberta, April, 20 p.

This report was written to enlarge on two 

discussions on the usefulness of borehole gravity density logging that were published in the 

July, 1981, issue of Geophysics.

[This report] start [s] by briefly describing the current state 

of the art of instrumentation, surveying methods, and derivation of densities from the gravity measurements. [Then,] computer modelled density logs from some typical petroleum 

exploration environments [are presented, which] serve to illustrate the anomalous density patterns which must be accounted for in order to arrive at good formation densities.

17. Bli&ovsky, M., 1979, Processing and applications in

microgravity surveys: Geophysical Prospecting, v. 27, no.

4, p. 848-861.

An economic and precise processing system for microgravity surveys is presented. Three computer processing modes 

covering areal ground and underground measurements, 

measurements in vertical shafts, and measurements of vertical gravity gradients with a 3 m high tower are dealt with.

Diagrams for manual calculation of gravity effects of 

prismatic walls, vertical shafts, and horizontal galleries, as 

well as programs for calculation of accurate terrain corrections and corrections for gravity effects of bodies with complicated ground-plan are proposed.

The method of processing microgravity data is two to three 

times quicker than any traditional way, with maximum

26
accuracy preserved in resulting gravity micro-anomalies. Applications from the field of mining geophysics and archaeology are included.

18. Bodemiiller, H., 1954, Der schwereunterschied in korrespondierenden punkten iiber und unter tage: Stuttgart, 

Zeitschrift fur Vermessungswesen v. 79, no. 8, p. 263-268. 

[The gravity difference between corresponding points above 

and below ground.]

19. Bradley, J.W., 1974, The commercial application and interpretation of the borehole gravimeter, in Contemporary 

geophysical interpretation, a symposium: Geophysical 

Society of Houston, December 4-5, 14 p., 11 figs.

Basic theory and the data and experience, from 

several of the approximately 50 wells that Amoco 

Production Company has surveyed with the 

borehole gravimeter using the results for reservoir analysis, are presented here. Case history 

areas are (1) Miocene fresh-water dry gas sands 

in the Gulf Coast, and (2) carbonate rocks in 

Grand Traverse and Kalkaska Counties, Mich.

This report is also referenced in Case Histories.

20. ____1976, The commercial application and interpretation 

of the borehole gravimeter, in Jantzen, R.E., ed., Tomorrow's oil from today's provinces: American Association 

of Petroleum Geologists, Pacific Section, Miscellaneous 

Publication 24, p. 98-109.

See report 19 for abstract. This report also 

referenced in Case Histories.

21. Brown, A.R., and Lautzenhiser, T.V., 1982, The effect of 

dipping beds on a borehole gravimeter survey: Geophysics, 

v. 47, no. 1, p. 25-30.

We study the effects of dipping beds on a borehole 

gravimeter (BHGM) survey. A dipping bed solution is 

presented which uses an anomalous bed density in a regional 

framework. A method of application is shown which provides an estimate of the regional framework density and dip 

angle of the beds. The method of application requires measuring local formation density independently.

22. Brown, A.R., Rasmussen, N.F., Garner, C.O., and Clement, 

W.G., 1975, Borehole gravimeter logging fundamentals: 

Preprint, Society of Exploration Geophysicists 45th Annual Meeting, Denver, Colorado, 9 p., 20 fig.

See report 23 for abstract.

23. 1976, Borehole gravimeter logging fundamentals

[abs.]: Geophysics, v. 41, no. 2, p. 345.

The borehole gravimeter (BHGM) gives us the capability 

of determining accurate bulk densities from measurements 

of the earth's gravity field in cased or open holes. Effective 

use of the BHGM as a practical logging tool in the petroleum 

industry requires feasibility studies, careful survey planning, 

and strict attention to survey procedures, as well as theoretically sound interpretation techniques. The interpretation 

of gravity data, based on the assumption of a parallel layered 

earth model, is augmented by incorporating measurements 

from other logging tools and direct gravity modeling. This 

integrated approach requires the combined skills of both a 

geophysicist experienced in gravity interpretation and a log 

analyst.

24. Casten, Uwe, 1984, Subsurface gravity measurements to 

demonstrate mining-induced changes in rock density: 

Geofizikai Kozlemenyek, Geophysical Transactions of the 

Eotvos Lorand Geophysical Institute of Hungary, 

Budapest, v. 30, no. 3, p. 227-236. 

Because of the underlying workings, subsurface mining 

results in deformation of the top layers. Within certain zones 

around working faces and accompanying roads changes in 

density and stress distribution are of interest because rock 

bursts may occur there. Gravity measurements were performed in the base roads and the main road of longwall 

retreat coal faces in a deep mine of the Ruhr coal district. 

Time dependent differences with amplitudes up to 0.1 mgal 

were observed by repeated observations at fixed points. The 

induced anomalies could be correlated with the advance of 

working faces and with de-stressing activities carried out by 

miners. Negative anomalies were interpreted by positive 

changes in density within the top layers, in good accordance 

with a zone of clastic deformation in front of the faces.

This report is also referenced in Case Histories.

25. Caton, P.W., 1981, Improved methods for reducing 

borehole-gravity data Applications and analyses of reduced gravity plots: Society of Professional Well Log Analysts 

22nd Annual Logging Symposium Transactions, v. 2, 

p. RR1-RR44.

*** Precise BHGM density estimates can be obtained from 

numerous repeated measurements, but due to time considerations, the data are necessarily sparse. Existing analysis procedures identify data precisions and errors from density and 

instrument drift plots; however, these approaches are cumbersome, and several factors affecting the measurements are not 

always obvious. A new presentation, the "reduced gravity 

plot," has been developed which illustrates data precisions 

and errors, instrument drift and tares, and the nonlinear 

effects due to temperature stabilization. The plot can be constructed on site, during data collection, to evaluate survey 

and instrument performance before coming out of the hole.

*** Results [from two 1980 BHGM surveys and older data] 

indicate significant temperature influence on slim tool BHGM 

measurements, and the effects due to magnetized sondes and 

operator reading errors are obvious. Additionally, two to 

three instrument tares seem common during BHGM 

surveys. ***. Fortunately, from reduced plot analyses of 

repeated measurements, [these] anomalous [effects] can be 

identified and subsequently removed.

Improved analyses of BHGM data require three independent readings per station. The total BHGM survey time needed 

for three measurements per station is increased 15-20 percent when compared to two per station; however, density 

resolution of 0.02 g/cm3 can be achieved at the 90 percent 

confidence level after compensating for anomalous instrument responses. ***.

26. Coyle, L.A., 1976, The application of borehole gravimetry 

to remote sensing of anomalous masses: Lafayette, Ind., 

Purdue University M.S. thesis, 89 p. 

The potential of the borehole gravimeter as a remote 

sensing tool is investigated by analyzing the gravity distribution in a vertical cross section caused by five ideal masses 

approximating specific geologic features. The gravitational 

attraction of these bodies will cause perturbations in the normal free-air-Bouguer anomaly curves through the geologic

27
section if they are near enough for detection. This distance 

is a function of the physical size and shape of the anomalous 

mass and the density contrast involved.

The gravity-depth profile, after corrections are made for 

nonstandard conditions, the free-air effect, and the Bouguer 

component, will indicate the presence or absence of a remote 

mass. If a local positive or negative perturbation exists in 

the profile, the cause is a layer of density unaccounted for 

in the reduction of the Bouguer effect. If a local positive and 

negative perturbation exists in the profile, the cause may be 

due to a remote body. The separation distance of the maximum and minimum values is the maximum thickness of the 

remote mass; and the zero gravity value depth is the depth 

of the center of mass of the remote body. The geometrical 

shape of the body cannot be deduced uniquely from the 

gravity-depth profile.

The distance to the remote body can be determined within 

certain limits from the analysis of the Aaa curve, the difference between the densities recorded by the BHGM log and 

FDC log or from the direct modeling of the gravity-depth 

profile. The actual position of a remote body cannot be determined from the measurements in a single drill hole. However, 

by superimposing the circular rings defined by the maximum 

and minimum distance limits as determined from the observations from more than one drill hole, it is possible to decrease 

the potential area in which the anomalies mass is located.

27. Domzalski, W., 1954, Gravity measurements in a vertical 

shaft: London, Bulletin of Institute of Mining and Metallurgy Transactions 571, v. 63, p. 429-445. 

After a short introduction on the application of gravity 

measurements in a shaft and the description of such a survey 

carried out in the shaft at Snowdown Colliery, Kent, 

[England,] the factors affecting the vertical distribution of 

gravity are discussed. The results *** are analyzed and the 

effects of errors in the measurements of gravity and distance 

are discussed.

This report is also referenced in Case Histories.

28. ____1955, Relative determination of the density of surface 

rocks and the mean density of the earth from vertical gravity measurements: Geophysical Prospecting, v. 3, no. 3, 

p. 212-227.

The gravity difference between two stations, one at the surface and the other underground vertically below the former 

and at a given distance from it, depends on the mean density of the earth, am, as well as on the density of the layer of 

rock contained between the two stations. When one of these 

densities is known, the other can be computed from this gravity difference. The reliability of this determination depends 

on the relative accuracies with which a and a can be m

obtained.

These accuracies are discussed***. The mean density of 

the earth has been determined with an accuracy of approximately 0.01 gm/cm3 . The determination of the density of 

a layer of rock depends on density determinations of rock 

samples which are not representative of the layer as a whole. 

Thus the accuracy of the value of a based on a number of 

sample determinations will depend on many factors, including 

the method of averaging the density values obtained from 

the samples and the degree of uniformity in the geology.

To investigate the problem discussed above, three sets of 

gravity measurements were made under differing conditions 

[at Godstone Quarries and at Cumberland, England]. ***

This report is also referenced in Case Histories.

29. EDCON, 1977, Borehole gravity meter manual: Lakewood, 

Colorado, Exploration Data Consultants Inc., 44 p.

This manual was put together for the benefit 

of EDCON's customers and contains a complete 

introduction to the principles of borehole 

gravimetry including theory, data acquisition, 

data reduction, and interpretation.

30. Egyed, Lazlo, 1960, Zur frage der Schweremessungen in 

Bohrlochern: Freiburger Forschungshefte C81, Geophysik, 

p. 167-170 (in German). [On the question of gravity measurements in boreholes.]

With the determination of various physical parameters in 

boreholes, the ability to determine the background density 

is made possible. We can make a density profile, provided 

we have a method for the determining the average vertical 

gradient

where lX =

then g2 - gl = a=Ca.

a is the average density between the points 1 and 2, A" is 

dependent on the ratio d/h (d = borehole diameter, h = 

measurement interval). The determination of the average gradient seems to be feasible with the presently available 

technology. The author has designed some fundamental and 

practical aspects of the construction of such instruments.

This report is also referenced in Instrumentation.

3 1 . Fajklewicz, Zbigniew, 1966, Effect of roof fall zones on the 

accuracy of underground microgravity measurements: 

Bulletin de 1'Academie Polonaise des Sciences, Serie-des 

Sciences Geologiques et Geographiques, v. 14, no. 1, 

p. 13-15.

[This report examines the effect of roof fall zones near 

where subsurface gravity stations are located and concludes] 

that minor roof fall zones in the hanging layer of mine workings cannot exert any essential influence on the results of 

underground microgravity measurements.

32. ____ 1973, Grawimetria Poszukiwawcza: Skrypty Uczelniane nr. 335, Warszawa, Wydawnictwa Geologiczne, 

416 p. [Gravimetric explorations.]

This report contains a complete discussion on 

land gravimetry. This includes instrumentation, 

data reduction, and qualitative and quantitative 

interpretation including examples. Also included 

are discussions on borehole and subsurface gravity, deep crustal interpretations, and rock density.

33. ____ 1980, Mikrograwimetria gornicza: Katowice, Poland, 

Slask Publishing Co., 264 p. (in Polish). [Mining 

micr ogr avimetry . ]

In this book are described the basic theory and methods 

of surveying and interpretation of microgravimetric research 

performed for the needs of mining and engineering geology.

28
Special attention has been given to problems of discovering cavities after exploitation, research of discontinuous tectonics, karst and erosion landforms, investigations of ground 

conditions disturbed by underground exploitation, and detecting useful mineral deposits.

***

Discussions on both borehole and subsurface 

gravity are included.

34. Fajklewicz, Zbigniew, and Duda, Wladyslaw, 1964, Proba 

zastosowania pomiarow mikrograwimetrycznych dla potrzeb 

gornictwa weglowego: Technika Poszukiwan, rok 3, zeszyt 

9, p. 1-7. [Test of the application of microgravimetric measurements for coal mining requirements.]

The article deals with the experimental works concerning 

application of microgravimetric measurements in coal mining industry. Technique and results of microgravimetric 

measurements carried out to detect the Carboniferous faults 

and mine workings, and to trace erosional forms occurring 

at the top of the Carboniferous strata are discussed, as well.

35. Fajklewicz, Zbigniew, Glinski, A.L.R., and Sliz, Janusz,

1982, Some applications of the underground tower gravity

vertical gradient: Geophysics, v. 47, no. 12, p. 1688-1692.

Underground tower gravity vertical gradient (UTGVG)

measurements made in mine workings have been applied to

the detection of caverns, old mine workings, dislocations,

and erosive or karstic forms. Since UTGVG measurements

are subject to large errors, Kotelnikov's criterion can be used

to determine the probability of isolation of the useful

anomalies.

The properties of the UTGVG reduce the ambiguity of interpretation of underground gravity surveys.

Simultaneous Ag and UTGVG measurements carried out 

in the same underground profile frequently replace a threedimensional or multilevel gravity survey.

The paper presents some applications of the UTGVG [in 

three mines in Poland].

This report is also referenced in Case Histories.

36. Garland, G.D., 1981, Discussion on "Densities determined 

from surface and subsurface gravity measurements" by 

B.A. Sissons with reply by author: Geophysics, v. 47, no. 

10, p. 1460.

This paper contains a brief discussion on B.A. 

Sissons' report (no. 99) and a brief reply by B.A. 

Sissons.

37. Glinski, A.L.R., 1974, Sposob uwzgledniania grawitacyjnego 

wplywu wyrobisk gorniczych w podziemnych pomiarach 

mikrograwimetrycznych: Technika Poszukiwan rok 13, 

zeszyt 1/49, p. 1-7.

Method of allowance of the gravitational effect of mining diggings in underground microgravimetric measurements.

38. ____1978, Podziemne wielopoziomowe zdjecia mikrograwimetryczne i ich zastosowanie w badaniu budowy 

geologicznej g6rotworu: Polska Akademia Nauk, Oddziol 

w Krakowie, Komisja Nauk Geologicznych, Prace 

Geologiczne 109, 60 p. (in Polish). 

Underground multi-level microgravity surveys and their 

application to the study of the geologic structure of the rock

39. Gournay, L.S., 1983, Detection of bypassed gas using 

borehole gravimeter and pulsed neutron capture logs [abs.]: 

The Log Analyst, v. 24, no. 3, p. 27.

Same abstract as report 42. This report also 

referenced in Case Histories.

40. Gournay, L.S., and Lyle, W.D., 1984, Determination of 

hydrocarbon saturation and porosity using a combination 

borehole gravimeter (BHGM) and deep investigating electric log [abs.]: The Log Analyst, v. 25, no. 2, p. 59-60. 

The BHGM measures the change in gravity with depth at 

discrete points or stations along a borehole. Formation bulk 

density between stations is then calculated from the change 

in gravity with depth. As a first approximation the volume 

sensed by the BHGM and for which the bulk density is 

calculated is a cylinder centered on the borehole of height 

equal to the station separation and radius equal to five times 

the station separation. The bulk density equation for this 

volume contains terms corresponding to porosity, fluid densities, matrix density, and fluid saturations. Since the fluid 

saturations must sum to one the equation can be reduced to 

an equation containing these density and porosity parameters, 

and with water saturation the only saturation term present. 

Assuming the component densities in the equation are known, 

the bulk density equation can then be viewed as an equation 

containing two unknown parameters porosity and water 

saturation.

Archie's equation relates water saturation, formation 

resistivity, water resistivity, and porosity. An equivalent 

resistivity obtained as a properly weighted average of the 

resistivities measured by a deep investigating resistivity log 

such as the induction or older electric log can be calculated 

such that the equivalent resistivity closely approximates the 

resistivity of the cylinder described above. Using this equivalent resistivity Archie's equation becomes a bulk equation 

applying to the same volume as that sensed by the BHGM. 

Assuming that the cementation factor, saturation exponent, 

and water resistivity are known the bulk Archie equation contains the unknown quantities porosity and water saturation. 

Solving the Archie equation and bulk density equations 

simultaneously results in estimates of bulk porosity and bulk 

water saturation. Hydrocarbon saturation is then known since 

the sum of water saturation and hydrocarbon saturation 

equals one.

The advantage of this approach is that the porosity and 

saturation estimates obtained are not severely affected by 

wellbore damage and drilling filtrate invasion, and are therefore estimates of the formation undisturbed by the drilling 

operation. Actual field test results for five wells are presented 

to illustrate the technique. Conditions under which the technique can be applied to the problem of detection of by-passed 

oil and gas in old wells are also presented.

This report is also referenced in Case Histories.

41. ____1984, Determination of hydrocarbon saturation and

porosity using a combination borehole gravimeter (BHGM)

and deep investigating electric log: Society of Professional

Well Log Analysts, 25th Annual Logging Symposium

Transactions, v. 2, p. WW1-WW14.

Formation bulk density over a radius of at least 50 feet

from the wellbore is routinely obtained using the BHGM.

The bulk density equation for this volume of rock contains

terms for porosity, fluid densities, matrix density, and fluid

29
saturations. Assuming the component densities are known, 

the bulk density equation can be reduced to one containing 

only two unknown parameters porosity and water 

saturation.

Archie's equation relates water saturation, formation 

resistivity, water resistivity, and porosity. By properly 

weighting the formation resistivities measured by a deep investigating resistivity log, one can obtain an equivalent 

resistivity for a bulk Archie's equation that applies to the 

same volume that is sampled by the BHGM. If the cementation factor, saturation exponent, and water resistivity are independently known, Archie's equation reduces to one 

containing two unknowns porosity and water saturation.

A simultaneous solution of the bulk density and Archie 

equations is possible, and this solution provides values of 

porosity and water saturation within the volume sampled by 

the BHGM and resistivity log. Hydrocarbon saturation is then 

easily obtained, since it plus water saturation must equal one.

It is important to note that porosity values are obtained 

from this approach alone and are not required from any other 

external source such as logs or cores.

One advantage of this technique is that the computed 

porosities and saturations are very insensitive to wellbore conditions, filtrate invasion, and other drilling disturbances. 

Another advantageous result is the investigation of a large, 

representative volume of reservoir rock that is not normally 

accessible by conventional logging methods.

Actual field results for several wells are presented. Applications include the detection of bypassed hydrocarbons and the 

determination of residual oil saturation.

This report is also referenced in Case Histories.

42. Gournay, L.S., and Maute, R.E., 1982, Detection of bypassed gas using borehole gravimeter and pulsed capture 

logs: The Log Analyst, v. 23, no. 3, p. 27-32. 

A method is described where the Borehole Gravimeter 

(BHGM) and Pulsed Neutron Capture (PNC) logs are used 

together to identify bypassed gas. The technique was tested 

in a 40 year-old oil field. Five wells were logged; four potential sands were identified and tested. Two of these produced 

933 MCFD and 940 MCFD each with no oil or water. Fluid 

redistribution due to production was revealed by the BHGM 

in a third well.

A case is examined where the BHGM alone could unambiguously detect gas. A field example is also given where BHGM 

data would negate useless testing of a tight zone that showed 

gas potential on neutron and resistivity logs.

This report is also referenced in Case Histories.

43. Hammer, Sigmund, 1950, Density determinations by

underground gravity measurements: Geophysics, v. 15, no.

4, p. 637-652.

Gravimeter observations, in a vertical shaft 2,247 feet deep 

of the Pittsburgh Plate Glass Company's limestone mine at 

Barberton, Ohio, for the purpose of determining the densities of the subsurface rock strata, are reported. The survey 

was made with a standard-type gravimeter to simulate the 

data which would be obtained by a borehole gravimeter to 

aid in the anticipation and formulation of problems in the 

development and application of a borehole gravimeter for 

gravity prospecting.

Density measurements on many selected core drill rock 

samples are compared with the densities determined from the

gravimeter data. The individual sample measurements show 

large scatter and systematically low values. Attempts to 

restore the samples to initial conditions underground were 

unsuccessful. It appears that density determinations of finite 

intervals of underground rock strata can be done better with 

the gravimeter than by laboratory measurements of rock 

samples.

See references 134 and 196 for discussion of 

instrument calibration error in this study. This 

error negates some of the above conclusions.

This report is also referenced in Case Histories.

44. ____1963, Rock densities and vertical gradient of gravity 

in the earth's crust: Journal of Geophysical Research, v. 

68, no. 2, p. 603-604.

This is a discussion of the feasibility of obtaining gravity measurements in the Mohole project.

45. Hearst, J.R, 1968, Terrain corrections for borehole 

gravimetry: Geophysics, v. 33, no. 2, p. 361-362.

This report describes the method and formulas 

used in a computer program written for the application of terrain corrections to borehole 

gravimetry measurements. See report 12 for an 

improved procedure.

46. ____1977a, On the range of investigation of a borehole 

gravimeter: Society of Professional Well Log Analysts 18th 

Annual Logging Symposium Transactions, p. E1-E12. 

Concepts of the range of investigation of a borehole 

gravimeter are reviewed. It is shown that the maximum sensitivity to a mass point at a horizontal distance R from a 

borehole occurs at a vertical distance Z = R/J2~. Thus, the 

angle of maximum sensitivity is about 55 ° from the vertical. 

It is also shown that the absolute value of the gravitational 

effect decreases with increasing R. There are two maxima 

of the vertical gradient of gravity (at Z=0 and at Z= 

.J3/2 R). The minimum distance required between gravimeter 

stations to obtain a usable measurement can be determined. 

The slab radius R for which the gravitational effect of a 

horizontal slab is equal to 45%, 90%, and etc., of that of 

an infinite horizontal slab is a function of the measurement 

spacing. The closer the measurement spacing, the more information obtained.

47. ____1977b, Estimation of dip and lateral extent of beds with 

borehole gravimetry: Geophysics, v. 42, no. 5, p. 990-994. 

Simple expressions for the estimation of dip or lateral extent of a bed whose extent is large compared to its thickness 

have been developed. ***. Numerical solutions are obtained 

and graphed.

48. ____1978, BIFUR II, a program for calculating borehole 

gravity caused by two-dimensional structure: Lawrence 

Livermore Laboratory Interdepartmental Letter 17852, 

AG78-54, 22 p.; available from National Technical Information Service, U.S. Department of Commerce, 

Springfield, VA 22161.

A revised computer program, BIFUR II has been written 

to compute the gravitational effect of structures describable 

in two dimensions by straight line segments. The primary application is to borehole gravimetry, but surface gravity problems can also be investigated. Input is *** not limited to 

structures bounded by vertical sides.

30
This program has been superseded by BIFUR 

III. See report 49 for reference.

49. ____1981, BIFUR HI, a program for calculating borehole 

and surface gravity caused by two-dimensional structure 

in Cartesian or cylindrical coordinates: Lawrence Livermore Laboratory Report UCID-19030, 100 p.; available 

from National Technical Information Service, U.S. Department of Commerce, Springfield, VA 22161. 

[BIFUR III is] an interactive computer program***. It 

computes the gravitational effect of two-dimensional structures bounded by planes (Program BIFUR3) or co-axial cylindrical surfaces (Program BIFURC). The calculated 

gravimetric density can be compared to density calculated 

from measurements of gravity in a borehole and from a density log. The user can change the structure online and compare the results of different change. The primary application 

is to borehole gravimetry, but surface gravity problems can 

also be investigated.

50. ____1983, Revealing subsurface structure with borehole 

gravimetry: Energy and Technology Review, 

UCRL-52000-83-9, September, p. 18-29; available from 

National Technical Information Service, U.S. Department 

of Commerce, Springfield, VA 22161. 

In recent years, computational methods comparing 

hypothetical models of subsurface structure at NTS with data 

obtained from borehole gravimetry and other geophysical logs 

have greatly reduced the need for exploratory drilling.

51. Hearst, J.R, and Carlson, R.C., 1977, The gravimetric density formula for a spherical shell: Geophysics, v. 42, no. 

7, p. 1469.

This short note derives the formula for the 

change in gravity through a spherical shell.

52. ____1982, Measurement and analysis of gravity in 

boreholes, in Fitch, A.A., ed., Developments in geophysical exploration methods 3: Essex, England, Applied 

Science Publishers LTD., p. 269-303. 

This paper discusses the history of the development of borehole gravimetry and the borehole gravimeter. Important 

aspects of field operations are described and the corrections 

necessary for data reduction are explained. The several 

methods of analysing the data to attempt to infer subsurface structure from borehole gravity and density log data are 

outlined. Finally, a number of applications of the method 

are listed.

53. Hearst, J.R, and McKague, H.L., 1976, Structure elucidation with borehole gravimetry: Geophysics, v. 41, no. 3, 

p. 491-505.

The observed densities, assuming infinite homogeneoushorizontal beds, computed from borehole gravimetry were 

as much as 15 percent greater than those derived from 

gamma-gamma density logs in the lower portion of several 

clustered boreholes at the U.S. Energy Research & Development Administration (USERDA) Nevada Test Site. A model 

having a single high- density buried scarp to the west of the 

holes was constructed, the gravimetric density calculated, and 

the model varied in an attempt to improve agreement between 

measurement and calculation. Only slight improvement was 

obtained. Newly acquired geologic information made it possible to construct a more complex multiscarp model, providing 

much better agreement between measurement and calculation. In turn, this more complete model was refined with the 

help of the calculations.

This method permits one to choose between qualitatively 

different models and, given a qualitatively correct model, to 

improve it quantitatively.

This report is also referenced in Case Histories.

54. Hearst, J.R, and Nelson, P.H., 1985, Well logging for 

physical properties: New York, McGraw-Hill Book Co., 

571 p.

[This book's] aim is to teach basic understanding of the 

[well log] methods [and the] large number of pitfalls in obtaining data from the [well] logs. [Also discussed are] the 

physical principles behind the logging methods and the 

assumptions used in the conversion of the signals obtained 

from the logging equipment into values of the properties of 

the formation being logged.

Included in this book are two sections of 

borehole gravimetry. The first is a general introduction to the methods, and the second is an 

application of the method used in inferring 

geologic structure at the Nevada Test Site.

This report is also referenced in Case Histories.

55. Hearst, J.R, Carlson, R.E., and Clark, S.R., 1986a, Calculation of gravimetric density caused by three-dimensional 

structure [abs.]: The Log Analyst, v. 27, no. 1, p. 78-79. 

For many years we have been comparing measured and 

calculated gravimetric density to density from a gammagamma density log to infer subsurface structure. We have 

used two-dimensional models, usually geologists' cross sections, to provide input for calculation of corrected gravimetric 

density for comparison with measured gamma-gamma density. Often the real structures could be better described in 

three dimensions.

The difficulty with calculating the gravitational effect of 

three-dimensional structure is not in the calculation itself, 

but in the description of the structure such that it fills all space 

and does not contain voids. We have solved this problem by 

using contour maps of subsurface boundaries between media 

of different density. The contour lines are digitized, and the 

digitized data are used to construct a function that is then 

evaluated over a fine grid surrounding the borehole. The 

algorithm used to construct the approximating function is 

a modification of Hardy's multiquadric method for interpolating scattered data. ***.

The gravity calculation uses an algorithm by Banerjee and 

Gupta for the calculation of the gravitational effect of a right 

rectangular prism. For each rectangle of the grid, the depth 

of the corners is averaged and used for the depth of one end 

of the prism. At each grid rectangle there are two prisms: 

one with the top at the top surface and the bottom at the 

contact surface, the other with the top at the contact surface and the bottom at the bottom surface. Two contact surfaces (describing three layers) can be used, in which case a 

third prism, with its ends on the two contact surfaces, is 

calculated. Gravimetric density is then calculated from the 

vertical gradient of gravity.

The method has been checked against structures [at the 

Nevada Test Site] for which analytical solutions are available 

and agrees within the error of digitization. When applied to 

real structures, the input is simple and the results plausible. 

Consequently, three-dimensional geologic models are now 

practical.

31
56.

This report is also referenced in Case Histories.

_1986b, Calculation of gravimetric density caused by

three- dimensional structure: Society of Professional Well 

Log Analysts, 27th Annual Logging Symposium Transactions, v. 1, p. F1-F22.

Same abstract as report 55. This report also 

referenced in Case Histories.

57. Hearst, J.R, Kasameyer, P.W., and Owen, L.B., 1978, 

Potential uses for a high-temperature borehole gravimeter: 

Lawrence Livermore Laboratory, California, CRL-52421, 

8 p.; available from National Technical Information Service, U.S. Department of Commerce, Springfield, VA 

22161.

It is possible to design a canister to cool a borehole 

gravimeter for use in geothermal and high-temperature (up 

to 350 °C) gas wells. Repeat surveys with such a gravimeter 

could (1) help estimate the extent of reservoir plugging in 

geothermal injection well after one year of operation and (2) 

detect compaction of a geothermal aquifer if the change in 

thickness of the aquifer exceeds 1 m. The instrument could 

be used together with conventional logging tools to evaluate 

radial dependence of density around a well, or to estimate 

gas-filled porosity around wells drilled with mud. A hightemperature borehole gravimeter could also be used to 

evaluate structure and stratigraphy around geothermal and 

high-temperature gas wells.

58. Hearst, J.R, Schmoker, J.W., and Carlson, R.C., 1979, Effects of terrain on borehole gravity data [abs.]: Geophysics, 

v. 44, no. 3, p. 370-371.

The effect of terrain on gravity measurements in a borehole 

and on formation density derived from borehole gravity data 

is studied as a function of depth in the well, terrain elevation, terrain inclination, and radial distance to the terrain 

feature. ***.

59. ____1980, Effects of terrain on borehole gravity data: 

Geophysics, v. 45, no. 2, p. 234-243.

Same abstract as report 58.

60. Jageler, A.H., 1976, Improved hydrocarbon reservoir evaluation through use of borehole gravimeter data: Journal of 

Petroleum Technology, v. 28, no. 6, p. 709-718. 

A brief review of lateral and vertical response characteristics of various logging devices indicates that correction of 

logging responses for borehole and near-borehole effects is 

inadequate when rock heterogeneity and (or) filtrate invasion characteristics approach or exceed the bulk resolution 

of conventional logging devices.

The lateral response of borehole gravimeters is shown to 

be a function of the geometry of density contrasts along a 

lateral plate of infinite extent resulting in bulk volume porosity measurements compatible with deep investigating resistivity 

devices.

The development of special logging techniques and the 

evaluation of tool characteristics of the borehole gravimeter 

have resulted in successful applications of borehole gravimetry

to reservoir analysis. 

***

61. ____1980, New well logging tools improve formation 

evaluation: World Oil, March, p. 89-103. 

Downhole equipment that provides better information 

about reservoir rock and fluid characteristics is being

developed by Amoco. Thus far, an improved density device 

[(BHGM)] has reached commercial acceptance. Other tools 

that show promise include a borehole televiewer, hard rock 

sidewall coring systems, and a new wireline formation tester.

62. ____1983, New techniques in well logging [abs.]: The Log

Analyst, v. 24, no. 3, p. 27.

Well logging, one of the oldest measuring techniques in 

petroleum geology, is being enhanced by recently developed 

methods and equipment. The presentation will detail the new 

tools in well logging along with their applications and limitations. Of special interest will be the down-hole gravity meter.

This report is also referenced under Instrumentation.

63. Jones, B.R., 1972, The use of downhole gravity data in formation evaluation: The Log Analyst, v. 13, no. 6, p. 15-21.

***

The high precision and large rock-volume measurement 

capabilities of the borehole gravity meter [are discussed. These 

capabilities] make it especially useful in measuring low 

porosities, as for example, that of a fractured quartzite in 

Libya; and fluid density behind casing, for example, gas in 

Texas.

64. Karl, J.H., 1983, The normal vertical gradient of gravity: 

Geophysics, v. 48, no. 7, p. 1011-1013.

This paper proposes a new value for the 

normal vertical gradient of gravity which is about 

14 percent lower than the value which has been 

assumed for the past several decades.

See reports 72 and 112 for disagreements with 

this article.

65. Kazinskii, V.A., 1963, The means of development and 

methods of solving problems of underground gravimetry: 

Bulletin (Izvestiya) Academy of Sciences, U.S.S.R., 

Geophysics Series; translated and published by American 

Geophysical Union, Washington, D.C., no. 5, p. 463-472.

The article presents the results of the development of underground gravimetry, which was fora long time considered a little-studied area of 

geophysics.

66. Labo, J.A., 1987, Borehole gravimeter principles, in A practical introduction to borehole geophysics: Society of Exploration Geophysicists Geophysical References no. 2, 

chapter 9, p. 179-195.

This paper discusses: (1) gravity formationdensity relationships and measurement, (2) 

EDCON borehole gravimeter tool, (3) depth of 

investigation, (4) measurement technique, 

(5) manual corrections, (6) formation evaluation, 

and (7) remote sensing.

67. LaFehr, Ed, and Nur, Amos, 1983, Application of the 

borehole gravity meter to thermal recovery: Society of Exploration Geophysicists, 53rd Annual Meeting, Las Vegas, 

Nevada, Expanded Abstracts with Biographies, September 

11-15, p. 31-33.

Thermal techniques have become increasingly important 

in enhanced oil recovery and in extracting heavy crude 

from reservoirs. Of interest to the petroleum engineer and

32
development geophysicist is a better understanding of the 

shape, rate, and direction of propagation of a thermal front 

as these parameters bear directly on production. Many logging and seismic methods have been used in studying thermal flooding and have met with varying success. For example, 

the extremely shallow depth of penetration of standard logging devices prohibits a study of thermal processes at great 

distances from the borehole.

This paper will evaluate the possibility for monitoring thermally produced low-density zones by the borehole gravity 

meter (BHGM). The BHGM is a nonstandard logging device 

with a theoretically infinite lateral depth of penetration. For 

this reason, detecting density contrasts away from the well 

bore can be accomplished by the BHGM. A thermal recovery 

process produces a low density body which is precisely the 

situation to employ the BHGM.

From BHGM measurements one can calculate an apparent 

density contrast produced by the actual density contrast at 

the leading edge of the low-density zone. It is this 

measurement-calculation of apparent density contrast that 

determines distance to the front. We analyzed a hypothetical 

tar-sand formation flooded by fire and steam, first examining the case for the BHGM and thermal process in the same 

hole. Secondly, we studied the BHGM response in a 

peripheral well to the thermal process.

68. ___1984, Application of the borehole gravity meter to 

thermal recovery [abs.]: Geophysics, v. 49, no. 5, p. 595.

Same abstract as report 67.

69. LaFehr, T.R., 1980, Gravity method: Geophysics, v. 45, no.

11, p. 1634-1639.

Developments in the field of gravity exploration have been 

significant from Galileo to the recent adaptation of inertial 

navigation systems. ***.

Gravity meters have been made to operate remotely on the 

water bottom, on the sea surface, in the air, and in boreholes. 

The final accuracies are generally limited by errors in positioning data rather than the precision of gravity instruments. 

The achievement of microgal precision (a few parts per 

billion) is one of the most remarkable engineering 

developments.

Interpretation has nearly kept pace with instrument development, but reports on methods and successes seriously lag 

(by at least 10 years) in the literature. The problem of ambiguity with respect to mass distributions has been clearly 

reported. This problem, however, is not adequately treated 

with respect to anomaly separation. Nonetheless, many excellent papers dealing with anomaly resolution are scattered 

throughout the literature, from ring operators to fast Fourier 

transforms. Much discussion also exists on forward and inverse calculations, but little attention has been given in the 

literature to practical interpretation, especially in the integration of gravity with seismic, magnetic, and borehole 

geophysical data.

70. ____1982, Apparent density from borehole gravity survey 

[abs.]: Geophysics, v. 47, no. 4, p. 447-448. 

The formula widely used for determination of rock density between two gravity stations in a well bore yields apparent 

density, not bulk density or average density as so often stated. 

Apparent density equals bulk density only if the earth is 

composed of horizontal, infinitely wide, uniformly thick, constant density beds. Although departures from these assumptions are sometimes too insufficient to cause concern, 

borehole gravity meter (BHGM) surveys can be better planned

71.

and more effectively interpreted by a deeper understanding 

of the apparent density measurement.

When the borehole intersects an anomalous mass, the controlling mathematical relationship changes from LaPlace's 

to Poisson's equation. Because the horizontal derivatives are 

continuous across the density boundary and the vertical 

derivative is discontinuous, an abrupt change ("the Poisson 

jump") in apparent density which approximates the actual 

density contrast of the anomalous mass with respect to the 

host rocks is measured by the BHGM. Within the anomalous 

mass, the apparent density anomaly is some fraction of the 

actual density contrast and for some conditions is independent of the size of the anomalous mass and the station depth 

in the hole.

Significant distortions in BHGM densities can occur outside the zone containing anomalous masses, and appreciable 

departures from formation bulk density can occur within the 

zones of interest because of the influence of the vertical gravity gradient. A simple understanding of the phenomenon 

significantly improves the interpretability of BHGM data, 

but even more useful exploration results can be obtained by 

quantitatively integrating the BHGM data with other geophysical or geological data.

At least two gravity stations should be occupied just above 

as well as just within the geologic formation or zone of interest to enhance the determination of the Poisson jump. 

Much thinner beds can be studied with the BHGM than 

generally believed, perhaps as thin as 3 ft, even with much 

wider station spacing. In many cases, formation bulk density can be derived, not by computing the difference between 

the 77 log and BHGM densities, but by applying corrections 

based on the available data.

A geologic case history is presented from two wells surveyed 

in a salt dome in Denmark. These surveys, together with extensive other information, yield interesting and informative 

results about salt, salt dome behavior, and BHGM apparent 

density anomalies.

This report is also referenced in Case Histories. 

___1983, Rock density from borehole gravity surveys:

Geophysics, v. 48, no. 3, p. 341-356.

The borehole gravity meter (BHGM) is recognized as an 

important logging tool for obtaining formation bulk density. In general, however, the difference between two gravity 

observations vertically separated in a well leads to an apparent 

and not the actual bulk density. BHGM-derived apparent 

densities are equal to the formation bulk densities when the 

instrument passes through beds which are horizontal, infinitely extended laterally, uniformly thick, and constant in density. For many applications, departures from these assumed 

conditions are so slight that their effects can be ignored, and 

the BHGM essentially yields bulk density with a large radius 

of investigation.

In the presence of anomalous masses, significant distortion in formation bulk density is possible. The apparent density anomaly produced in the well by an elongated, offset 

density contrast is proportional to the angle subtended by 

the density-change interface. For a density-change boundary 

having circular symmetry with respect to the well, the apparent density anomaly at the center of the bed is proportional to the sine of the subtended angle.

Because the distortion in bulk density is the same above 

a horizontal boundary as it is just below (in the limit, at the 

boundary, for a normally incident well), an abrupt change

33
in apparent density is equal to the real density change at the 

boundary. This change in density, termed "the Poisson 

jump," is independent of geometry; our ability to measure 

it, however, is a function of station location with respect to 

the geologic bodies.

Two methods are suggested for obtaining bulk densities 

from BHGM apparent densities: (1) by obtaining two stations just outside as well as just within the zone of interest, 

the Poisson jump can be approximated and added to an independent density source (e.g., the gamma-gamma log), and 

(2) the apparent density anomaly within the formation of interest can be derived by modeling (perhaps based on seismic 

or well data) and added to the BHGM-determined densities.

Thinner beds can be studied with the BHGM than generally 

believed, even with much greater station spacing.

72. LaFehr, T.R., and Chan, K.C., 1986, On "The normal 

vertical gradient of gravity," by J.H. Karl (Geophysics, 

48, 1011-1013, July, 1983): Geophysics, v. 51, no. 7, 

p. 1505-1508.

In this paper, the authors dispute the conclusions of J.H. Karl in his paper on the normal 

vertical gradient of gravity. In disputing Karl's 

discussion, LaFehr and Chan refer to the extensive data from borehole gravity surveys for support of their disagreement.

Report 64 is the paper disputed in this article. 

Also see report no. 112 for a disagreement to 

report 64.

73. Laurin, P.J., Black, A.J., LaFehr, T.R., and Bichara, M., 

1981, Borehole gravimetry; an application example to 

engineering: Societ6 pour L'Avancement de L'lnterpretation des Diagraphies, 7th European Logging Symposium 

Transactions, no. 27, 10 p. (in French). 

The aim of this paper is, after a review of some theoretical

aspects of BHGM, to present an example in engineering where

its use was found very useful. 

The case concerned a well drilled in a salt dome [in the

Texas gulf coast]. There were two objectives for this logging.

(1) determining the proximity of edge of salt from the well

(2) determination of the extension of high density formations (probably anhydrite blocks) within the salt 

which were encountered in drilling.

This well was planned to be used in leaching the salt in 

order to create a natural reservoir for petroleum.

Whereas, due to a low density contrast between the salt 

and sedimentary formation, the first point was inconclusive, 

it was possible to assert that there was no extension to the 

high density formations. This permitted the well to be planned 

for a leaching operation.

This report is also referenced in Case Histories.

74. Lindner, Harold, Hanemann, K.-D., and Schubert Heinz, 

1981, Methodik zur Bestimmung der Streckenreduktion 

in der Untertagegravimetrie: Neue Bergbautechnik, seiten 

257, bis 312, Heft 5, p. 271-276. [Method of determination of the space reduction in underground gravimetry.]

75. Lukavchenko, P.I., 1948, K voprosu ob izmereniyakh sily 

tyazhesti v burovykh skvazhinakh: Applied Geophysics, 

v. 4, Gostoptekhizd, p. 159-167. [The problem of gravity 

measurements in wells.]

76. ___1955, Gravity measurements in boreholes: Prikladnaya 

Geopizika, no. 12, p. 157-176; Translated August 1959, 

Liaison Office, Technical Information Center, MCLTD, 

Wright-Patterson Air Force Base, Ohio, MCL-20/V, 

24 p.

In this paper, the fundamental theoretical 

questions of gravitational logging are discussed.

77. McCalpin, G.A., 1985, Operational and technical results 

from a multi-well borehole gravity survey [abs.]: Unconventional Methods in Exploration for Petroleum and 

Natural Gas, Symposium IV, Institute for the Study of 

Earth and Man, Dallas, Texas, May 1-2, p. 32. 

[Unpublished manual for symposium participants.] 

Restated in report 78. This report is also 

referenced in Case Histories.

78. ___1986, Operational and technical results of a multiwell 

borehole gravity survey, in Davidson, M.J., ed., Unconventional methods in exploration for petroleum and natural 

gas IV: Dallas, Texas, Institute for the Study of Earth and 

Man, Southern Methodist University Press, p. 313-320.

A twelve-well borehole gravity meter survey was conducted 

for Sun Exploration and Production Company in August, 

1983, in South Texas in temporarily abandoned wells ***. 

The twelve wells were logged in a period of nineteen days, 

including moving days and off-days. Average "hole time" 

for the surveys was slightly over eight hours, with rig-up and 

rig-down time adding an additional two to three hours. The 

time between station readings averaged about ten minutes 

for the 429 stations and repeats in the surveys.

One hundred eighty zones were examined, ranging in depth 

from 890 ft. to 4,950 ft. A porosity, assuming 100% water 

saturation, was computed for each of these zones from the 

gravity-derived density and compared with the porosity determined from a compensated neutron log. On the basis of this 

comparison approximately 61% of the zones were interpreted 

as water sands, 28% as hard streaks, and 11% as prospective for either oil or gas.

This report is also referenced in Case Histories.

79. McCulloh, T.H., 1966a, Gravimetric effects of petroleum 

accumulations A preliminary summary: U.S. Geological 

Survey Circular 530, 4 p.

Negative gravity anomalies of very local extent and with 

amplitudes of 1.2 milligals or less have been observed over 

some known petroleum and natural gas fields in southern 

California and South Dagestan, U.S.S.R. Field evidence, 

laboratory measurements, and theory indicate that these 

anomalies are mainly the result of hydrocarbon pore fluids 

of densities significantly lower than that of water. Gravity 

meters already available have the precision necessary to detect 

some of these anomalies from surface measurements. In addition, a high-precision borehole gravity meter has been 

developed, by the industrial firm of LaCoste and Romberg, 

Inc., that can be used ***. ***These observations and the 

new gravimeter should aid in the search for new petroleum 

fields and for new reservoirs in known fields that are incompletely explored.

80. ____1966b, The promise of precise borehole gravimetry 

in petroleum exploration and exploitation: U.S. Geological 

Survey Circular 531, 12 p.

34
The underground vertical gravity gradient is related to rock 

density in situ, gravimetric effects of nonlevel surfaces of 

equal rock density beneath and around the borehole (including topographic effects), and the free-air vertical gravity gradient.

Accurate determinations of average rock density in situ 

underground could be calculated from properly interpreted 

precise borehole gravimeter measurements. Such determinations would be relatively free from the effects of rock damage 

due to drilling or invasion by mud filtrate. The measurements 

could be made in cased wells, and they would be based on 

much larger volumes of rock than are sampled by any other 

method. Such measurements would be independent of coreanalysis data and would therefore provide a standard against 

which to judge the core-analysis data as well as to evaluate 

conclusions drawn from gamma-gamma or other logs.

Conversely, independent knowledge of rock density at a 

borehole would permit separation of the gravitational effects 

of rocks beneath and around the surveyed borehole from 

other effects naturally integrated in the borehole gravimeter 

measurements and thereby offer unique opportunities for 

geological exploration.

*** Instrumental and operational characteristics of an experimental prototype borehole gravimeter are considered.

81. ___1967a, Borehole gravimetry New developments and 

applications, in Origin of oil, geology and geophysics: 

London, Elsevier, 7th World Petroleum Congress, Mexico City, April 2-8, Proceedings, v. 2, p. 735-744. 

Announcements in late 1965 and early 1966 of successful 

independent developments of two dissimilar borehole 

gravimeters having precisions close to 0.01 milligals began 

a new era of subsurface geophysical research. ***

Full use of such high precisions requires various 

corrections. ***.

Heavy dependence of underground vertical gravity gradients upon rock density encourages the use of borehole 

gravimetry for studies of density, porosity, and fluid 

character. However, the partial dependence of gravity and 

gradients on nonlevel isopycnic surfaces below the borehole 

forces caution on the interpreter while also providing a tool 

of value in geological exploration.

A borehole gravimetric density and porosity profile of a 

marine clastic Pleistocene-Pliocene section is in excellent 

agreement with laboratory measurements of conventional 

cores. Underground and surface gravity and geologic data 

for the residual gravity minimum of Santa Fe Springs oil field 

illustrate the potential exploration value of borehole 

gravimetry.

This report is also referenced in Case Histories.

82. ___1967b, Mass properties of sedimentary rocks and 

gravimetric effects of petroleum and natural-gas reservoirs: 

U.S. Geological Survey Professional Paper 528-A, 50 p. 

Relatively negative gravity anomalies of very local extent 

and with amplitudes of 1.2 milligals or less have been observed over some known petroleum and natural-gas fields 

in southern California and in South Dagestan, Azerbaijan, 

U.S.S.R. These anomalies indicate that such productive 

hydrocarbon reservoirs are lower in density than surrounding strata. The hypothesis that the low densities result importantly from hydrocarbon pore fluids that have densities 

significantly lower than the density of water suggests that 

most petroleum and natural-gas reservoirs should produce

negative gravimetric effects, although such effects may be 

small enough in many instances to be obscured or hidden 

by other anomalies. This hypothesis and its practical prospecting consequences and limitations are examined and 

analyzed in detail.

***_

Hypothetical gravimetric effects computed from density 

models based on selected well-drilled California oil fields of 

small to moderate size illustrate the kinds and magnitudes 

of effects expectable. ***.

The hypothetical gravimetric effects computed from the 

density models were utilized also for an examination of the 

subsurface gravimetric effects that would be obtainable 

through use of a borehole gravimeter ***. Underground 

(borehole) gravity measurements should be of particular value 

in exploration for deep and small hydrocarbon accumulations in extensively explored basins, where much is already 

known about the rocks and structures and their densities, 

by extending to depth the technique of detection of the 

relatively negative gravimetric effects of petroleum and 

natural-gas reservoirs. Bore-hole gravimeter measurements 

should also prove of great value in exploration for deeper 

pools and lateral extensions of known pools in partly developed oil fields, thereby lowering development risks and costs. 

Because of the prounounced gravimetric effects of variations 

in porosity and pore fluid composition, borehole gravity 

measurements could be utilized also with advantage in 

evaluating reservoir properties and monitoring reservoir performance in a developing and producing field.

This report is also referenced in Case Histories. 

83. McCulloh, T.H., Kandle, J.R., and Schoellhamer, I.E., 

1968, Application of gravity measurements in wells to problems of reservoir evaluation: Society of Professional Well 

Log Analysts, 9th Annual Logging Symposium Transactions, p. O1-O29.

***

Novel borehole gravity meters suitable for logging formation density consist of single high-sensitivity gravity sensors 

operated on conventional multiconductor well logging 

wireline. Discontinuous logs of gravity versus depth result. 

Average interval formation densities are calculated from vertical gradients of gravity by simple inverse proportionality. 

Gravity sensors now available are sufficiently precise to 

measure the differences in formation density caused by the 

presence in the pores of most crude oils rather than water. 

Intervals should be about 30 feet thick or more for such 

measurements. Complicating effects of surface topography 

or nonlevel underground surfaces of equal rock density can 

be evaluated. Borehole irregularities, or variable mudcake, 

filtrate invasion, casing, and cement produce practically

negligible effects.

***_

A deep well in Santa Fe Springs oil field, California, was 

surveyed during tests of the U.S. Geological Survey-LaCoste 

and Romberg borehole gravimeter. Unsuccessful and successful recompletion attempts in a nearby well confirmed that 

the technique has the professed capability of detecting 

anomalously low density undepleted oil- and gas-bearing 

zones. Careful interpretation permits distinguishing between 

these, more dense water-saturated zones, and less dense 

depleted secondary gas caps. Net oil production of 14,000+ 

barrels in 10 months attests to the method's potential value.

35
Entry 83 is also referenced in Case Histories.

84. Miller, A.H., and Innes, M.J.S., 1953, Application of 

gravimeter observations to the determination of the mean 

density of the Earth and of rock densities in mines: Canada 

Dominion Observatory, Ottawa Pubs., v. 16, no. 4, 

p. 3-17.

Subterranean observations of gravity can be 

employed to determine the densities of rock 

layers beneath the surface. This paper demonstrates this application in connection with the 

results at Lake Shore Mine, Kirkland Lake, Ontario, and Home Mine, Noranda, Quebec.

This report is also referenced in Case Histories.

85. Mudrecova, E.A., 1960, Underground gravity surveys in copper sulphide deposits in the Central Ural Mountains: 

Geofizicheskaia Razvedka, no. 2, p. 31-59 (in Russian).

This report also referenced in Case Histories.

86. Murty, B.V.S., and Chandra Reddy, P., 1983, The problem 

of hollow space correction in subsurface gravity surveys: 

Geophysics, v. 48, no. 10, p. 1406-1408. 

When correcting for the effect of hollow spaces in subsurface gravity surveys, a three-dimensional assumption is 

advantageous because the entire hollow space can be fully 

accounted for and also knowledge of the density of the 

material removed can be properly utilized.

The approach suggested here is equally applicable for 

manual or computer estimation.

Very accurate reading of distances is essential or else the 

estimated hollow space effect can be erroneous.

87. Oelsner, Christian, 1960, Schweremessungen unter Tage: 

Zeitschrift fur Angewandte Geologic, v. 4, p. 172-177. 

[Underground gravity measurements.]

Measurements were made at the OttoBrosowski mine, Germany. 

This report is also referenced in Case Histories.

88. Overton, A., 1975, Borehole gravimetry, in Dyck, A. V., ed., 

Borehole geophysics applied to metallic mineral 

prospecting a review: Canadian Geological Survey Paper 

75-31, p. 31-33.

This report is a brief description of the uses 

to which borehole gravimetry can be put and of 

available meters and their limitations.

89. Poynting, J. H., 1894, The mean density of the Earth:

London, Charles Griffin and Co., 156 p., 9 diagrams.

This Essay, ***, gives an account of the various experiments, including one by the author, which have been 

made to determine the mean density of the earth.

The First Part consists of an introductory discussion of 

the problem and an account of the experiments hitherto made 

on the subject. ***.

The Second Part contains an account of my own 

experiments,***.

I have prefixed a bibliography of works and papers containing important or noteworthy contributions to the subject. ***.

A few of these works and papers contain accounts of subsurface gravity measurements.

90. Pritchett, W.C., 1982, Physical properties of shales and possible origin of high pressures: Society of Exploration 

Geophysicists, 52nd Annual Meeting, Dallas, Texas, Expanded Abstracts with Bibliographies, October 17-21, 

p. 504-505.

It is commonly thought that all high-pressure shales in the 

U.S. Gulf Coast have low density and have never undergone 

normal compaction. But these shales are easily altered and 

much of the density data for these shales may not be accurate. 

The scatter gamma ray density log has an extremely shallow 

depth of investigation and would not see through a zone of 

altered shale surrounding the borehole. The borehole 

gravimeter tools would be ideal for measuring the in-situ density of these shales, but we do not have such data. Neutron 

lifetime logs have a moderate depth of investigation. Studies 

of these logs in three wells indicate that the high-pressure 

shales encountered had undergone normal compaction and 

have normal densities or possibly higher than normal 

densities. 

***.

It might be important to oil and gas exploration to determine to what extent each of the two theories for generating 

high pressures (dewatering or continuous undercompaction) 

accounts for the high-pressure shales in a given basin. The 

best and most reliable method for making such determinations is by bulk density measurements with the borehole 

gravimeter. Alternatively, or in addition, neutron lifetime logs 

should be run to measure total water content (pore water plus 

interlayer water). Data should be acquired for shales with 

both high and normal pressures and from shallow to great 

depths.

This report is also referenced in Case Histories.

91. ____ 1983, Physical properties of shales and possible origin 

of high pressures [abs.]: Geophysics, v. 48, no. 4, p. 483.

Similar abstract as in report 90. This report is 

also referenced in Case Histories.

92. Rasmussen, N.F., 1973, Borehole gravity survey planning and 

operations: Society of Professional Well Log Analysts 14trr 

Annual Logging Symposium Transactions, p. Q1-Q28. 

The borehole gravity meter survey provides a unique advantage to the log analyst. This is the capability of determining accurate bulk densities for a large radius of 

investigation in cased or open boreholes. The accuracy requirements for formation evaluation are exacting, and 

established survey procedures must be strictly observed to 

obtain accurate results. A comparison of survey results using 

the LaCoste Romberg borehole gravity meter shows that 75% 

of the interval gravity measurements repeat to 10 microgals 

or better. These results are taken from a number of surveys 

conducted under ideal conditions. Prior to the survey, the 

feasibility of attaining the survey objectives and the economics 

of success can be reasonably assured. A number of corrections are needed and should be considered during the planning phase. If proper data are obtained, most corrections 

can be combined into a single vertical gradient correction.

93. ____1975, Borehole gravimeter finds bypassed oil, gas: Oil 

and Gas Journal, v. 73, no. 39, p. 100-104. 

A new logging tool is being successfully applied in original 

completions and old wells to find production bypassed with 

conventional formation-evaluation equipment and techniques. ***. [Basic principles and interpretation techniques

36
are presented along with] successes [which range] from 

shallow gas plays in South Texas to the reef play in northern 

Michigan.

94. ____1977, Gravity logs promise new applications: Petroleum Engineer International, July, p. 21-24.

Borehole gravimetry promises two theoretical 

uses for enhanced recovery applications. One is 

determination of gas saturation and the other is 

determination of sweep efficiency.

95. ____1984, Borehole gravity used together with surface gravity, in Davidson, M. J., and Gottlieb, B.M., eds., Unconventional methods in exploration for petroleum and natural 

gas III: Dallas,Texas, fcstitutefor the Study of Earth and 

Man, Southern Methodist University Press, p. 90-103. 

Structural interpretation is one of the uses of borehole 

gravity surveys. The effectiveness of structural interpretation 

is enhanced by including high resolution gravity and airborne 

magnetic surveys. All types of data that can be used to improve the interpretation should be included. While the use 

of subsurface and seismic data is obvious, the use of surface 

gravity and airborne magnetic surveys is not.

Prior to conducting and interpreting the borehole gravity 

survey, geological and geophysical data are used to create 

a detailed computer model. This model is used to calculate 

the predicted structural effects curve for the borehole gravity survey. This curve can be used as part of a feasibility study 

to determine whether or not a borehole gravity survey can 

resolve the detail needed for interpretation.

Once the feasibility is demonstrated and the survey is conducted, the predicted structural effects curve is compared with 

the actual structural effects curve. Significant differences between the two indicate the existence of structural configurations not previously interpreted. The resulting changes in the 

interpretation are incorporated as changes in the computer 

model used. The theoretical effects calculated from the model 

must agree with both the surface and the borehole gravity 

data.

The theoretical applications include the interpretation of 

structures and reservoirs below the total depth of the borehole. Distances to basement, the presence of deep faults, and 

the presence of potential reservoirs are some of the significant factors that can be determined by this method.

96. Rische, Hans, 1957, Dichtebestimmungen im Gesteinsverband 

durch Gravimeter- und Drehwaagemessungen unter Tage: 

Freiberger Forschungshefte, C35, 84 p. 

Density determinations in the rock assemblage through

gravity-meter and torsion-balance measurements made

underground.

Case histories are in central Germany. 

This report is also referenced in Case Histories.

97. Robbins, S.L., 1980, Bibliography with abstracts of subsurface gravimetry (especially borehole) and corresponding in 

situ rock density determinations: U.S. Geological Survey 

Open-File Report 80-710, 47 p.

This Open-File is superseded by the present 

report.

98. ____1981, Reexamination of the values used as constants 

in calculating rock density from borehole gravity data: 

Geophysics, v. 46, no. 2, p. 208-210.

This report examines the accuracy and values 

of the constants F (free-air gradient) and k 

(Newtonian gravitational constant) used in the 

formula for determining in situ bulk density from 

borehole gravity data.

99. ____1986a, The use of borehole gravimetry in water well 

and waste disposal site evaluations [abs.], in Surface and 

borehole geophysical methods and ground water instrumentation A conference and exposition: National Water Well 

Association Program, Denver, Colorado, October 15-17. 

For the past 20 years the U.S. Geological Survey has been 

a pioneer in the development and application of borehole 

gravimetry. During this time, borehole gravity surveys for 

water well and waste disposal site evaluation have been conducted in more than 40 wells in Arizona, Colorado, Florida, 

Montana, Nevada, New Mexico, South Dakota, Washington 

and Wyoming.

Borehole gravity measurements are converted directly to 

the in situ bulk density value of the rocks that surround the 

borehole. The resulting densities are averages for rocks which 

extend a large distance from the borehole (the actual rock 

volume is dependent on the vertical spacing between stations 

within the borehole). In areas where there is no complicating 

subsurface structure and where lithologic beds are nearly 

horizontal, the measured densities are assumed to be true 

values. In structurally or stratigraphically complex areas, an 

"apparent" bulk density is determined. When this is compared with density values determined by other methods, 

elucidation of the subsurface structures is possible.

All the water-well studies and some of the waste-disposal 

evaluations were conducted in areas of near horizontal beds 

with no complicating structure. Many of the density values 

were used to calculate porosities for use in water yield and 

potential storage calculations. In the waste disposal evaluations where complex structure existed, the borehole gravity 

density data were used for structural analyses.

The advantages of borehole gravimetry in water well evaluations are: (1) the density values represent the formation for 

some distance from the borehole; whereas, a more conventional method such as a gamma-gamma density log only 

"sees" the first few inches, and (2) many water wells are in 

alluvial sediments that need to be cased quickly, and a more 

conventional log run in a cased hole is not meaningful; whereas, casing does not affect a borehole gravity measurement.

This report is also referenced in Case Histories.

100. ___1986b, The use of borehole gravimetry in water well 

and waste disposal site evaluations, in Proceedings of the 

surface and borehole geophysical methods and ground 

water instrumentation conference and exposition: Dublin, 

Ohio, National Water Well Association, p. 474-486.

Same abstract as report 99. This report is also 

referenced in Case Histories.

101. ___1989a, What is borehole gravimetry? A summary: 

This report, chapter A.

This paper defines borehole gravimetry, examines the capabilities of the BHGM, relates 

already successful or nonsuccessful uses of the 

meter and suggests other areas of possible use for 

the BHGM.

37
102. ____1989b, Borehole gravity measurements, data reduction, and precision A review and update of U.S. 

Geological Survey methods: This report, chapter B.

This paper discusses the equipment used in 

making a BHGM survey, field and office procedures developed and used in the reduction of 

the gravity data, and the precision that the U.S. 

Geological Survey obtained before 1983.

103. Schmoker, J.W., 1980, Terrain effects of cultural features 

upon shallow borehole gravity data: Geophysics, v. 45, no. 

12, p. 1869-1871.

This report presents four figures that can be 

used to simplify making terrain corrections due 

to cultural features (like water tanks) when obtaining borehole gravity data at shallow depth.

104. Sissons, B.A., 1981, Densities determined from surface and 

subsurface gravity measurements: Geophysics, v. 46, no. 

11, p. 1568-1571.

A least-squares method for the direct inversion of surface 

and subsurface gravity measurements to obtain in situ density estimates is presented. The method is applied to a set 

of measurements made in a tunnel through the flank of 

[Tihia] andesitic volcano [in central North Island, New 

Zealand]. Densities obtained are 2.14 g/cm3 for material in 

the top 100 m increasing to 2.32 g/cm3 at about 200 m 

depth. The average density for rocks penetrated by the tunnel is, from laboratory measurements, 2.42 g/cm3 , i.e., 

about 4 percent higher. The difference is ascribed to joints 

and voids present in situ and not sampled in the laboratory 

specimens.

A brief discussion on this report by G.D. 

Garland and a reply by B.A. Sissons are listed 

as report 36.

This report is also referenced in Case Histories.

105. Smith, N.J., 1950, The case for gravity data from boreholes:

Geophysics, v. 15, no. 4, p. 605-636.

The immediate urge for gravity meter surveys in boreholes 

is the desire to improve the gravity method itself but there 

are other potential uses for data so obtained. Borehole gravity 

surveys, through the influence of density, would be related 

to numerous important rock properties such as the velocity 

of seismic waves, the coefficient of reflection, the electrical 

resistivity, lithology, porosity, and the kinds and states of 

fluids in the rock. Therefore, in addition to improvement 

in gravity prospecting, the data would bear upon seismic 

techniques and, depending on accuracy and detail, upon the 

interpretation of lithologic and electric logs. The more obvious of the possible uses are indicated and some of the problems and inherent limitations holding up development are 

discussed.

106. Snyder, D.D., 1976, The borehole Bouguer gravity

anomaly Application to interpreting borehole gravity

surveys: Society of Professional Well Log Analysts, 17th

Annual Logging Symposium Transactions, p. AA1-AA20.

When employing the borehole gravity meter for remote

sensing applications, it is useful to reduce the borehole gravity

data to the Bouguer anomaly before interpretation. This

paper deals with the calculation and subsequent quantitative

interpretation of the borehole Bouguer anomaly. Numerical 

modeling of lateral density contrasts such as reefs and salt 

domes are shown to illustrate the effect that these mass 

distributions have on the bulk density calculated from 

borehole gravity measurements. The borehole Bouguer anomaly data for several borehole gravity surveys dramatically indicate the presence of inhomogeneities which do not intersect 

the borehole.

107. Snyder, D.D., and Merkel, R.H., 1977, Generalized correction for dipping beds for the borehole gravity meter: The 

Log Analyst, v. 18, no. 2, p. 41-43.

Formulas expressing the relationship between 

dipping beds of differing densities and borehole 

vertical gravity gradients are presented for both 

two-dimensional and three-dimensional 

problems.

108. Society of Exploration Geophysicists, 1986, Focusing on SEG 

continuing education; borehole gravity surveys: The 

Leading Edge of Exploration, v. 5, no. 4, p. 62-63.

This article contains a brief description of 

SEG's continuing education course "Borehole 

gravity surveys." This course is usually offered 

one or more times a year and is taught (to 1988) 

by Larry A. Beyer.

109. Stacey, F.D., and Tuck, G.J., 1981, Geophysical evidence 

for non-Newtonian gravity: Nature, v. 292, no. 5820, 

p. 230-232.

Measurements of the variation of gravity with depth in 

mines and boreholes permit the densities of intervening rock 

strata to be inferred. In the few cases in which reliable absolute values of density have been independently determined, 

the calculations can be used to check the value of the Newtonian gravitational constant, G. Such large-scale measurements 

of G are important because the validity of the inverse square 

law of gravity at short range is being questioned. We have 

made such a series of measurements and have found four 

other data sets in the literature that suffice for the estimation of G. We also report here a statistical analysis of 

1,100 km2 of overlapping sea floor and sea surface gravity 

data from the Gulf of Mexico (made available by Exxon). 

All these estimates of G give values that are higher then the 

conventional, laboratory-determined one. While the possibilities of systematic errors in these data sets preclude a 

definite conclusion that Newton's law of gravity fails at short 

range, the strong circumstantial evidence suggests that well 

controlled large-scale experiments on the inverse square law 

are urgently required.

110. Stacey, F.D., Tuck, G.J., Holding, S.C., Maher, A.R., and 

Morris, D., 1981, Constraint on the planetary scale value 

of the Newtonian gravitational constant from the gravity 

profile within a mine: Physical Review D, v. 23, no. 8, 

p. 1683-1692.

Measurements of gravity down a 950-m vertical line within 

the mine at Mount Isa, Queensland, [Australia,] are used to 

estimate the value of the Newtonian gravitational constant 

G on a geophysical scale. The value obtained is (6.71± 

0.13)xlO~n m3kg" 1 sec"2. The assigned uncertainty is the 

possible (but not probable) systematic error arising from density inhomogeneity and indicated by local variations in gravity

38
gradient, and is several times as large as the formal error of 

a least-squares fit to the gravity-depth data. A dramatic improvement in accuracy can be anticipated if measurements 

can be made in a flat-lying sedimentary basin, or even better 

within the sea in a gravitationally featureless area.

111. Stewart, R. M., 1949, Gravity in the interior of the Earth:

Royal Astronomical Society of Canada Journal, v. 43, no.

4, Whole 379, p. 129-137.

General formulae are developed which show the manner 

in which the existence of maxima and minima of gravity in 

the interior of the earth is dependent on the variation of density with distance from the earth's center.

Several special cases are discussed among which is the 

assumed approximation of a succession of layers, each of 

uniform density, separated by definite surfaces.

In an added note, an article by Benfield [report 5], listing 

values of density and gravity at various depths, is compared 

with the conclusions of this paper.

112. Swain, C. J., 1984, On "The normal vertical gradient of gravity," by J.H. Karl (Geophysics, 48, 1011-1013): Geophysics, v. 49, no. 9, p. 1563.

This paper disputes the conclusions of J.H. 

Karl in his paper on the normal vertical gradient 

of gravity. Report 64 is the paper disputed in this 

article.

Also see report 72 for a disagreement to report 

64.

113. Thyssen-Bornemisza, Stephen, 1 963, The vertical gravity gradient in borehole exploration: Geophysics, v. 28, no. 6, 

p. 1072-1073.

This short note discusses theoretically what information could be derived from a borehole 

gravity survey.

114. ___1963, Determination of Bouguer density in shallow 

holes: Geophysics, v. 29, no. 3, p. 445-446.

This short note suggests that a borehole gravity meter could be used in shallow holes for obtaining density data for surface gravity studies.

115. ___1965a, Determination of the vertical density gradient 

in a borehole: Geophysics, v. 30, no. 3, p. 439-440.

This short note presents formulas for the determination of the vertical density gradient for 

borehole gravity data.

116. ___1965b, The anomalous free-air vertical gradient in 

borehole exploration: Geophysics, v. 30, no. 3, p. 441-443.

The average vertical gradient of gravity 

generated by a buried vertical cylinder is noted.

117. ___1966, Possible application of the anomalous free-air 

vertical gradient to marine exploration: Geophysics, v. 31, 

no. 1, p. 260-263.

This short note presents the concept that a 

borehole gravity meter could be used in measuring anomalous free-air vertical gravity gradients 

above a marine well site.

118. Vaschilov, U.N., 1964, Oochye vliyaniya ryelyefa myestnosti

pri gravimyetrichyeskikh nablviyeniyakh v podeyemnekh 

gornekh verabotkakh i skvazhnakh: Razvedochnaya i 

Promyslovaya Geofizika, v. 51, p. 71-75 (in Russian). 

[Allowance for the effects of the relief of the locality in 

gravimeter observations in underground workings and 

boreholes.]

119. Zagonov, A.V., and Lukavchenko, P. I., 1974, Opryedyelyeniye izbetochnoe plotnosti vozmooshchaushchikh 

obyektov po danne'm nazemnoe i skvazhinnoe gravirazvedki s pomoshchu lineenogo programmirovaniya: Prikladnaia Geofizka, v. 75, p. 158-165 (in Russian). [The excess 

density estimation of disturbing bodies from surface and 

borehole gravimetry observations with the use of linear 

programming.]

Instrumentation, Data Accuracy, and Precision

120. Baker, G.E., 1977, Gravity instrument canister feasibility 

study: San Ramon, Calif., EG&G Report GEB77-57, 63 p. 

A feasibility study was made for a canister to contain a 

gravity instrument used for well logging. The canister will 

protect the gravity instrument for a typical 30-hour logging 

cycle in an environment of 350 ^C and 17,000 psi. The internal canister temperature will be maintained at a nominal 

100 °C. The canister has a diameter of 5 in. and a length 

of 18 ft. The housing for the gravity instrument has a diameter 

of 5- in. and a length of 6 ft.

This report describes: (1) preliminary specifications for the 

canister, (2) methods of absorbing heat, and (3) a survey of 

suppliers for a super- insulated dewar. It also presents the 

preliminary calculations justifying a detailed study for the 

building and testing of the canister.

121. Beyer, L.A., 1968, Recent tests of the U.S. Geological 

Survey-La Coste and Romberg borehole gravimeter system 

[abs.]: Geophysics, v. 33, no. 6, p. 1030. 

Repeatability tests using the La Coste and Romberg 

borehole gravimeter No. 1 and established depth measuring 

techniques suggest that interval gravity gradients in boreholes 

can be reproduced to about 0.00025 mgal/ft, depending on 

the magnitude of the vertical interval between measurements 

and the number of repeated gravity observations at each 

station. The conversion of interval gravity gradients in 

boreholes to absolute values of in situ rock densities may require careful reduction of the borehole gravity measurements 

in conjunction with surface gravity observations, subsurface 

geologic data, and well history information. These factors 

are considered in the analysis of borehole gravity 

measurements in the Lakeview area of the Midway-Sunset 

Oil field, California.

6. ___1971, The vertical gradient of gravity in vertical and 

near-vertical boreholes: U.S. Geological Survey Open-File 

Report 71-42, 229 p.

This report is referenced under Theory and 

Case Histories. The abstract is located under 

Theory.

122. Black, A. J., 1983, Performance characteristics of the LaCoste 

and Romberg borehole gravity meter [abs.]: Program, 36th 

Annual Midwest Meeting, Society of Exploration 

Geophysicists, Denver, Colorado, March 6-9, p. 50.

39
Recent application of Borehole Gravity surveys to determination of reservoir fluid saturations have emphasized a 

need for higher than usual gravity reading accuracies. To ensure these accuracies could be realized in the well environment a close study of the Borehole Gravity Meter's (BHGM) 

reading accuracy as a function of environmental and temporal changes was made. Temperature change emerged as 

the largest cause of reading disturbance. Implementation of 

electronic controls suggested by Dr. L. LaCoste and the 

development of a down-hole Dewar flash have both decreased 

temperature disturbances and allowed surveys at temperatures 

at 400 °F. A survey strategy involving multiple repeat station occupations minimizes drift error and provides improved 

statistical accuracies. An example data set shows that apparent density calculations accurate to ± .01 g/cc over 10 

foot station intervals are routinely available with these 

improvements.

123. ____1986, Improved accuracy of a computer controlled 

borehole gravity system and applications to reservoir flood 

monitoring: Preprint, Center for Potential Field Studies 

Symposium, Colorado School of Mines, Golden, September 17, 9 p.

A new computer controlled system for LaCoste and 

Romberg Borehole Gravity meters has been used for field 

surveys since January 1986. The system uses an amplitude 

modulated electrostatic force feedback system in combination with the measuring screw. Repeatable, operator independent gravity readings with accuracies on the order of ± 1 

to 2 microgals are obtainable under field conditions. Under 

laboratory conditions, reading noise levels are less than 0.3 

microgals. The system can be operated in environments with 

noise levels of about 1.5 milligals.

An application of this instrument is to monitor reservoir 

floods. A flood front approaching an observation well may 

be detected by observing differences between repeated gravity 

measurements in an observation well at appropriate intervals as a flood front approaches. After the flood has passed 

the well, density changes corresponding to changes in the 

reservoir fluid composition may be measured and estimate 

of fluid saturation changes may be made. The largest of these 

effects will be seen in steam and CO2 floods.

This report is also referenced in Case Histories.

124. Black, A. J., and Herring, A.T., 1983, Borehole gravity; expanded operating limits and performance: Society of Exploration Geophysicists, 53rd Annual Meeting, Las Vegas, 

Nevada, Expanded Abstracts with Biographies, September 

11-15, p. 21-23.

Borehole gravity meter (BHGM) surveys have been applied 

to numerous petroleum exploration and engineering projects 

in North America, Europe, and the Middle East. The highest 

percentage of surveys were for petroleum exploration within 

the United States, where the majority of applications used 

the BHGM's ability to provide a density log over a wide radius 

investigation.

High temperature boreholes and wells drilled from floating 

platforms were inaccessible to the BHGM until recently. 

(Thermoshield , PDA Engineering) suggests that the 

design criteria of an operating temperature of 200 ^C (400 °F) 

at 25,000 psi have been met. A downhole clamping device 

that couples to the BHGM sonde was tested and will enable 

routine logging from floating drilling platforms. Application of the BHGM to a wide radius of investigation

density-porosity measurements requires higher accuracy than 

required by most structural modeling problems. To achieve 

such high accuracy, optimum survey planning, meter operation, and meter preparation are essential. Change in the 

gravity meter's thermal environment is now recognized as 

generally the most important source of BHGM error. Progress in controlling the BHGM's thermal environment resulted in improved accuracy. Further stabilization of the 

BHGM's thermal environment will result from the use of the 

Thermoshield.

125. ____1984, Borehole gravity: expanded operating limits and 

performance [abs.]: Geophysics, v. 49, no. 5, p. 594.

Same abstract as report 24.

126. Byerley, K.A., 1977, A field test for borehole gravity meter

precision in shallow wells: Boulder, Colo., University of

Colorado M.S. thesis, 78 p.

Three water wells located in Douglas County, Colorado, 

were logged using a LaCoste and Romberg gravity meter ***. 

The purpose of the survey was to study the field precision 

of the instrument in shallow wells. Data [were] collected and 

reduced using standard techniques.

A total bulk density error relationship was developed as 

well as a nomogram that graphically interprets some of the 

error levels involved. Lithologic interpretation of the relative 

density variation is attempted although it involves numerous 

uncertainties.

127. Caton, P.W., Clement, W.G., and Witterholt, E.J., 1983, 

Borehole gravity logging developments; a status report: 

Society of Exploration Geophysicists, 53rd Annual Meeting, Las Vegas, Nevada, Expanded Abstracts with Biographies, September 11-15, p. 23-26. 

During the 1960s, LaCoste and Romberg developed the 

first successful borehole gravity meter (BHGM) in cooperation with the USGS (Beyer, 1968). ***. In the late 1970s, Edcon and Amoco added microprocessors in order to speed 

leveling of the LaCoste and Romberg meters, but since that 

time, there have been few hardware improvements or new 

approaches to speed data collection.

***. This paper reviews recent developments for improving BHGM survey performance by discussing a new special 

purpose logging truck designed for "slow" tool operations 

and a digital telemetry system which has the flexibility to add 

other tools to the BHGM sonde. Also discussed are new 

borehole gravity sensors, of standard and unconventional 

designs, that are anticipated to have increased latitude and 

temperature ranges, with improved accuracy, and those with 

fewer mechanical parts, which should improve instrument 

ruggedness.

The quality of a BHGM density survey depends on two 

factors: first is instrument performance, which determines 

gravity measurement precisions and accuracies, and the 

second is depth control. Thus, the ability to locate the tool 

accurately and to reoccupy instrument depth positions 

becomes an integral part of quality control during a 

survey. ***

128. ___1984, Borehole gravity logging developments; a status 

report [abs.]: Geophysics, v. 49, no. 5, p. 594.

Same abstract as report 127.

129. Clutsom, F.G., 1984a, U.S. Geological Survey borehole 

gravimeter no. 1 electronic system schematics: U.S. Geological Survey Open-File Report 84-337.

40
This report contains the schematics for the 

electronic circuitry used on BHGM no. 1.

130. ____1984b, U.S. Geological Survey borehole gravimeter 

electronic system borehole gravimeter no. 6 mechanical 

drawings: U.S. Geological Survey Open-File Report 84-338.

This report contains the schematics for the 

electronic circuitry used on BHGM no. 6 (a 

slimline meter). This system, much newer than 

the one in report 129, is also better.

131. Dolbear, D.W.N., 1959, Design considerations of a borehole

gravimeter: Geophysical Prospecting, v. 7, no. 2,

p. 196-201.

Due weight must be given to three factors (1) its purpose, 

(2) the limitations imposed by nature, industry and environment, (3) the effect of errors in auxiliary measurements. 

Together the last two factors give an estimate of the accuracy 

which can be achieved. If this is sufficient for the instrument 

to fulfil its purpose, design and construction can proceed. 

If it is not, a detailed survey of the last two factors is necessary 

in order to estimate the research effort that will be required 

when directed into the most effective channels. If the project is considered worth the effort it can proceed. These factors are discussed in relation to a borehole gravimeter. *** 

30. Egyed, Lazlo, 1960, Zur Frage der Schweremessungen in

Bohrlochern: Freiburger Forschungshefte C81, Geophysik,

p. 167-170.

This report is referenced under Theory, where 

the abstract is also located.

132. Gilbert, R.L.G., 1952, Gravity observations in a borehole: 

Nature, v. 170, no. 4523, p. 424-425.

This report describes a vibrating filament borehole gravity meter along with some preliminary 

tests.

133. Goodell, R.R., and Fay, C.H., 1964, Borehole gravity meter 

and its application: Geophysics, v. 29, no. 5, p. 774-782. 

The Shell Development borehole gravimeter is an instrument which utilizes as a measure of gravity the frequency 

of a chosen mode of vibration of a string supporting a freely 

suspended mass. The instrument, which is capable of determining differences in gravity between stations to one milligal 

or better, has been in semiroutine use by Shell for over two 

years. The most common application of such a meter, the 

determination of average densities for intervals of the order 

of one thousand feet, is illustrated by data from several wells.

Errata for article appears in Geophysics, v. 30, 

no. 2, p. 337.

134. Hammer, Sigmund, 1965, Density determinations by underground measurements Sequel: Geophysics, v. 30, no. 6, 

p. 1133-1134.

This report confirms report 196 finding that 

the gravity meter used in Hammer's earlier report 

39 had a calibration error of about 12 percent.

135. Heintz, K.O., and Alexander, M., 1979, Sulfur exploration 

with core hole and surface gravity [abs.]: Geophysics, v. 

44, no. 3, p. 370.

In 1968 a major sulfur exploration play was touched off 

in the Texas Permian basin. Both the geologic setting and

operational logistics were particularly favorable for gravity 

method use, and it was adopted as the optimum geophysical 

technique for West Texas sulfur exploration. The typical 

sulfur prospect was relatively shallow and areally compact, 

with light-density ore filling fractures and vugs in a dense 

carbonate or sulfate host rock. Since the ore body could be 

irregularly shaped, with sulfur concentrations varying widely within the zone of deposition, prospect analysis required 

high-resolution gravity data and good density control. The 

usual stages of prospecting included: definition of the surface gravity anomaly, preliminary core hole program planning, density measurement, gravity modeling, and finally, 

revision of the core hole program.

Exxon added downhole remote sensing capabilities through 

development of a miniaturized version of its EPR vibrating 

string borehole gravity meter. This new core hole meter 

operated successfully in 4-inch holes to a depth of almost 

3000 ft. Comparisons between densities derived from meter 

measurements, gamma-gamma logs, and core samples indicate the meter provided the most consistently useful 

data.***. A plunge in sulfur prices abruptly ended the West 

Texas play before several indicated anomalies were fully 

evaluated.

This report is also referenced in Case Histories.

136. Howell, L.G., Heintz, K.O., and Barry, A., 1965, The development and use of a high-precision downhole gravity meter 

[abs.]: Geophysics, v. 30, no. 6, p. 1237. 

The vibrating-string downhole gravity meter is described 

which has a precision of about 0.01 mgal in gravity measurement. With measurements of this precision, density of a 30-ft 

section in the subsurface can be determined with an accuracy 

of .02 gm/cm3 . These density measurements are useful in 

gravity interpretation, in computing acoustic impedance for 

use in seismology, and in estimating porosities of formations. 

Examples of density profiles measured in boreholes are given.

137. ___1966, The development and use of a high-precision 

downhole gravity meter: Geophysics, v. 31, no. 4, 

p. 764-772.

Same abstract as report 136.

62. Jageler, A.H., 1983, New techniques in well logging [abs.]: 

The Log Analyst, v. 24, no. 3, p. 27.

This report is referenced under Theory, where 

the abstract is also located.

138. LaFehr, T.R., Merkel, R.H., and Herring, A.T., 1979, 

Evaluation and applications of new LaCoste and Romberg 

borehole gravity meter [abs.]: Geophysics, v. 44, no. 3, 

p. 369-370.

The new (41 inch) LaCoste and Romberg BHGM has been 

operational for about one year. Its limitations are minimum 

cased hole inside diameters of 4l inches, maximum hole 

deviations where readings are made of 141 degrees, and maximum pressure of 12,000 psi. BHGM no. 4 has a nominal 

drift rate of about 0.5 /igal per minute.

Laboratory measurement repeatability of 3 /igal is routinely 

achieved. Well bore repeatability depends upon differential 

sticking in the hole (with resultant errors in depth determination), seismic noise (both natural and man-made), fluid movement in the well, and wind noise in the surface rigging. 

Average interval difference repeats of 6 /igal have been 

achieved under optimal conditions. Average repeatability of

41
10-20 /xgal is normally achievable under most operating conditions. Although adverse well environments can degrade 

repeatability to 20-60 /xgal, poorer repeatability is very rare. 

Statistical methods can identify poor stations and improve 

accuracy.

The tools are now being used approximately as follows: 

(1) finding natural gas behind casing; about 20 percent; (2) 

remote sensing (salt overhang, missed reefs and edges of 

thrust sheets, etc.); about 20 percent; and (3) evaluation of 

carbonate reservoirs (finding oil and gas missed by other 

techniques); about 60 percent.

139. Lautzenhiser, T.V., 1983, Amoco/LaCoste and Romberg 

automated borehole gravity meter: Society of Exploration 

Geophysicists, 53rd Annual Meeting, Las Vegas, Nevada, 

Expanded Abstracts with Biographies, September 11-15, 

p. 20-21.

The LaCoste and Romberg borehole gravity meter 

(BHGM) with Amoco electronics proved to be a highly 

reliable and precise instrument. However, use of the BHGM 

required a high level of training for the operators as well as 

extended concentration for long periods from the operators. 

Even good operators become less effective as time passes in 

real field situations. Consequently, there was a need to 

automate the reading process of the BHGMs. In Block and 

Moore (1966), the use of linearized electrostatic forcing and 

feedback to control the beam position of a LaCoste and 

Romberg gravity meter is described. Their use of the system 

was for long period measurements for use in tide measurements and related work. Electrostatic feedback is utilized in 

the control and in the calculation of the resultant data for 

the automated borehole gravity meter.

140. ____1984, Amoco/LaCoste and Romberg automated borehole gravity meter [abs.]: Geophysics, v. 49, no. 5, p. 594.

Same abstract as report 139.

141. Lukavchenko, P.I., 1962, NabliQdeniiS s gravimetrami v 

burov'ykh skvazhina i shakhtakh: Razvedochnaia i 

Promyslovaia Geofizika, no. 43, p. 52-64 (in Russian). 

Observations with gravity meters in wells and mine shafts.

142. McCulloh, T.H., LaCoste, L.J.B., Schoellhamer, I.E., and 

Pampeyan, E.H., 1967, The U.S. Geological SurveyLaCoste and Romberg precise borehole gravimeter 

system Instrumentation and support equipment, in 

Geological Survey research 1967: U.S. Geological Survey 

Professional Paper 575-D, p. D92-D100. 

A special modification of the LaCoste and Romberg 

astatized spring-type geodetic meter is the gravity sensor of 

the precise borehole gravimeter system. The sensor and certain support components are insulated and operate normally at a thermostatically controlled 101 °C. ***. Heavy 

damping of the gravimeter beam and the generally quiet conditions in the borehole permit the gravimeter to be leveled 

and read remotely, [at a stationary point in the hole,] in the 

unanchored sonde. When gravity and depth measurements 

are carefully made and reduced, the usual overall precision 

of gravity determinations is better than 0.016 mgal for all 

depths. A single gravity reading requires less than 10 and 

generally 3-5 minutes.

143. McCulloh, T.H., Schoellhamer, I.E., Pampeyan, E.H., and 

Parks, H.B., 1967, The U.S. Geological Survey-LaCoste 

and Romberg precise borehole gravimeter Test results, 

in Geological Survey research 1967: U.S. Geological Survey 

Professional Paper 575-D, p. D101-D112.

The U.S. Geological Survey and LaCoste and Romberg, 

Inc., have developed a borehole gravimeter system and components characterized by precision of (1) depth measurements 

in the range of 0.05 to 0.2 ft between the surface and 9,500-ft 

depth, and (2) downhole gravity measurements ranging from 

a high of 0.008 mgal to a low of 0.02 mgal. An average precision of 0.016-mgal is attainable at all depths and includes 

both precision of gravimeter readings and of depth measurements. Time tests suggest that, during normal routine operation, detailed (one station every 100 ft) and precise (±0.01 

mgal) gravimeter surveys of wells less than 10,000 ft deep 

may be made at 300 to 500 ft per hour (including base checks 

for drift control) by a skilled three-man crew. In the laboratory, an increase or decrease in environment temperature of 

60 °C on the gravity sensor produces a maximum change in 

apparent gravity reading of 0.1 mgal. ***.

144. Mobil Oil Corp., 1986, Continuous gravity gradient logging:

U.S. Patent 4,602,508, August 29.

A continuous gravimetry survey is carried out with a gravity 

logging tool having a column of fluid * within the tool. First 

and second pressure sensors *,* are located at spaced-apart 

axial positions within an upper portion of the fluid column. 

Third and fourth pressure sensors *,* are located at spacedapart axial positions within a lower portion of the fluid column. The outputs from the first and second pressure sensors are differenced to produce a first pressure difference 

signal. The outputs of the third and fourth pressure sensors 

are also differenced to produce a second pressure difference 

signal. The difference between these first and second pressure 

difference signals is related to the gravity gradient along the 

earth formation adjacent the fluid column. Such a gravity 

gradient is a continuously moving gradient that is insensitive 

to acceleration effects from unsteady motions of the logging 

tool as it traverses the earth formation during the gravimetry 

survey.

145. Nieto, M.N., Goldman, T., and Gutschick, V.P., 1983, An 

electronic gravimeter to measure g(r): Geophysics, v. 48, 

no. 1, p. 39-41.

We point out that a battery may be designed so that in 

a gravitational field it will have a gravitationally induced emf 

in addition to an electrochemical one. The gravitationally induced emf of a battery with a small "effective" electrochemical potential and a long "effective" length can readily 

be measured to very high precision by means of any precise 

voltmeter, and in particular by a Josephson junction. Such 

a device may be employed to measure any component of the 

gravitational acceleration vector. It can be constructed compactly enough to be placed down a borehole. Thus, in principle it is an extremely precise and adaptable tool for 

geophysical exploration.

146. Oil and Gas Journal, 1966, Esso licenses downhole gravity 

meter: Oil and Gas Journal, v. 64, no. 26, p. 101-102.

This report describes a vibrating-wire gravity 

meter which Esso Production Research Co. was 

testing.

147. Robbins, S.L., 1979, Description of a special logging truck 

built for the U.S. Geological Survey for borehole gravity 

surveys: U.S. Geological Survey Open-File Report 79-1511, 

67 p.

The U.S. Geological Survey has developed a logging truck 

designed specifically for the operation of borehole gravity

42
meters. The truck is self-contained for most logging operations and can accommodate most conventional wireline 

tools. ***. 

***

148. ____1980, Display of features on the U.S. Geological 

Survey's logging truck built especially for borehole gravity surveys [abs.]: Geophysics, v. 45, no. 4, p. 552.

Same abstract as report 147.

149. Schmoker, J.W., 1978, Accuracy of borehole gravity data:

Geophysics, v. 43, no. 3, p. 538-542.

Repeated subsurface gravity measurements, obtained with 

the U.S. Geological Survey-LaCoste and Romberg borehole 

gravity meter, were studied to determine the accuracy of the 

borehole gravity data, the dependence of accuracy upon 

elapsed time and vertical separation, and the precision of bulk 

densities calculated from borehole gravity measurements. The 

likelihood of poor interval gravity measurements increases 

sharply for vertical intervals greater than 150 ft, and increases 

approximately linearly with increasing time between readings. 

After a brief warmup period, data quality does not improve 

with the passage of time from the beginning of the survey. 

If the stations of a borehole gravity survey are separated by 

less than 70 ft, and the time between readings is less than 

18 minutes, the gravity difference between two points in a 

borehole can be measured to ± 10 /igals. For intervals greater 

than 20 ft, this is equivalent to a density error of ±.02 

g/cm3 or less.

Case Histories

1. Airy, G.B., 1856, Account of pendulum experiments undertaken in the Harton Colliery for the purpose of determining 

the mean density of the Earth: London, Royal Society 

Philosophical Transactions, v. 146, nos. 14,15, p. 297-355.

This report is referenced under Theory, where 

the abstract is also located.

150. Algermissen, S.T., 1961, Underground and surface gravity 

survey, Leadwood, Missouri: Geophysics, v. 26, no. 2, p. 

158-168.

A surface gravity survey consisting of 214 stations covering approximately four square miles was conducted over and 

adjacent to the North Leadwood Mines at Leadwood, 

Missouri. A corresponding survey of 278 stations was carried out in the mine workings. A method of reducing 

underground gravity observations is outlined. The principal 

factors limiting the accuracy of the underground observations are given. Methods for determining rock densities are 

described. A comparison of the surface and underground 

gravity maps shows that major Precambrian knobs were 

revealed by both surveys. Smaller structures not shown on 

the surface map were revealed by the underground survey. 

Anomalous density areas between the level of the two surveys 

were easily located.

6. Beyer, L.A., 1971, The vertical gradient of gravity in vertical and near- vertical boreholes: U.S. Geological Survey 

Open-File Report 71-42, 229 p.

This report is referenced under Theory and

under Instrumentation. The abstract is located 

under Theory.

151. ____1977, Interpretation of borehole gravity in the 

southern San Joaquin Basin [abs.]: Geophysics, v. 42, no. 

5, p. 1100.

Borehole gravity measurements are responsive primarily 

to the vertical density variations in the rocks traversed by 

the survey and secondarily to lateral rock density variations 

(mass anomalies) of detectable magnitudes that may occur

in the region surrounding the surveyed well.

***

Variations in lateral density may be significant where folded 

strata, faults, unconformities, intrusions, or lateral variations 

in lithology, porosity or pore fluids (due to selective depositional or postdepositional processes) intersect or occur within 

detectable distances of the borehole. Analysis of the borehole 

gravity data in these cases is difficult because isopycnic (equal 

density) surfaces generally are not known and may be complex in shape. Separation of borehole gravity effect due to 

vertical and to lateral density variations is possible if independent and reliable information about vertical rock densities can be obtained from well logs, core analysis, or other 

sources.

In a well that penetrates the steeply dipping section at the 

Santiago area of the Midway-Sunset oil field, borehole gravity effects due to lateral density variations are calculated, with 

the aid of core analysis and known subsurface structure, to 

be as great as 25 percent of the gravity effects due to the vertical density variations. In other areas of the Midway-Sunset 

oil field and in the Kern River oil field where lateral density 

variations are believed to be small, density and porosity profiles calculated from borehole gravity surveys are compared 

to core analyses and conventional open-hole logs in order 

to maximize formation evaluation. Borehole gravity measurements made at equivalent subsurface elevations in a series 

of wells across the Thirty-Five Anticline in the MidwaySunset oil field illustrates the change in form of a gravity 

anomaly with increasing depth.

152. ____1979, Borehole gravity study of the density and porosity of selected Frontier, Tensleep, and Madison reservoirs 

in the Bighorn Basin, Wyoming [abs.]: American Association of Petroleum Geologists Bulletin, v. 63, no. 5, p. 822. 

Borehole gravity surveys in the Gebo, Garland, and Big 

Polecat oil fields of Wyoming uniquely assess the density and 

porosity of the reservoir and associated rocks. ***.

Interval density and porosity profiles determined from the 

Bighorn basin surveys were compared with gamma-gamma 

density logs, neutron porosity logs, and density and porosity measurements of core samples. Discrepancies between the 

density and porosity methods arise because borehole gravity, owing to its large radius of investigation, measures an 

average porosity that includes the irregularly distributed component (e.g., vugular porosity of reservoir rocks in the 

Madison Limestone at Garland) which is less effectively 

evaluated by conventional shallow-penetration logs or core 

samples. Other discrepancies are usually due to the inherent 

limitations of one or several of the methods and are mostly 

dependent on the composition and coherence of the rocks. 

Variations in the contribution of fracture porosity to total 

porosity in the Tensleep Sandstone reservoir at Gebo are 

masked by much larger fluctuations in intergranular porosity caused by differences in the cementation and abundance

43
of dolomite. Whatever the cause, the magnitude of fracture 

porosity is probably below the threshold of detection with 

borehole gravity. High-porosity (>15 percent) and (or) gasfilled sandstone units, principally in the Frontier Formation, 

were easily detected behind casing in the three oil fields. An 

abrupt and possibly widespread downward increase in porosity in the upper part of the Frontier Formation may (1) reflect 

lithologic and mineralogic variations owing to changes in the 

depositional environment, (2) be related to a previously proposed unconformity, and (3) have exploration significance.

153. ____1980, Benefits of borehole gravity studies in the San 

Joaquin Basin, and suggested future work [abs.]: Geophysics, v. 45, no. 8, p. 1330.

Seventeen borehole gravity surveys and related studies 

made by the Geological Survey in five oil fields in the southern 

San Joaquin basin have yielded the following results. Confirmation of high precision borehole gravity measurements 

and detection of dry gas and oil sands behind casing were 

first demonstrated in 1968. Borehole gravity measurements 

were analyzed in structurally complex sections, where anomalous vertical gravity gradients are significant, in three separate 

studies in the Twenty-five Anticline and Santiago areas of 

the Midway-Sunset oil field and the Lost Hills oil field between 1969 and 1975. Comparisons of density and porosity 

profiles, calculated from borehole gravity surveys, with conventional core analyses and open-hole logs in shallow, poorly 

consolidated rocks were completed in 1976. Results not 

previously shown of a borehole gravity survey in a northeast 

flank well at Elk Hills reveal shallow gas sands and generally low porosity in the uppermost Miocene section at this 

location.

Future uses of borehole gravity in the San Joaquin Basin 

may profitably focus on (1) confirmation of subtle porosity 

changes associated with diagenesis and facies changes, (2) 

evaluation and calibration of conventional open-hole porosity 

logs in cases where they are insufficiently precise or unreliable, 

(3) monitoring of fluid conditions in high porosity reservoirs, 

and (4) in special cases, detection of laterally adjacent reservoirs missed by the drill. ***.

154. ____1983a, Density and porosity changes with depth, Sisquoc and Monterey Formations, Santa Maria-Point Conception region, California [abs.]: Program, 58th Annual 

Pacific Section Meeting, American Association of 

Petroleum Geologists-Society of Economic Paleontologists 

and Mineralogists-Society of Exploration Geophysicists, 

Sacramento, California, May 18-21. 

Borehole gravity, well log, and core data from selected locations of the onshore Santa Maria Basin and adjacent offshore area show that bulk density of Tertiary siliceous rocks 

increases sharply with increasing depth. Borehole gravity 

surveys indicate that saturated bulk density increases in the 

Sisquoc and Monterey Formations from about 1.8 to 

2.4 g/cm3 *** at Casmalia, from about 1.65 to 2.4 g/cm3 

*** at Orcutt, and from about 2.2 to 2.55 g/cm3 *** at West 

Cat Canyon. ***. [At] offshore Point Conception ***, log 

interpretations suggest that bulk density increases from about 

1.95 to 2.5 g/cm3 ***. The rates of increase of bulk density 

with depth are atypically high, exceeding all rates observed 

in studies of comparably aged California marine sandstones 

and clay shales.

Large-scale, sharp increases of bulk density and concomitant decreases of porosity of siliceous rocks in the Santa Maria

region are caused primarily by burial diagenesis (as reported 

in papers by Isaacs, Pisciotto, and others) aided by higher 

than average subsurface temperature gradients. Transitions 

between silica phases, ***, are evident in the interval density profiles from the borehole gravity surveys at Casmalia, 

Orcutt, and West Cat Canyon. More locally, interval density fluctuations within the Monterey are related partly to 

various recognized zones or facies and, on a smaller scale, 

partly to variations of the abundance of such rock constituents as silica, calcite, dolomite clay, or organic matter.

Interval density profiles from the borehole gravity surveys 

are converted to porosity profiles by assignment of grain densities based on silica phase or phases present and estimated 

abundances of rock constituents. Generalized density and 

porosity variations of the Sisquoc and Monterey Formations 

are presented for the range of depths investigated.

155. ____1983b, Estimation of reservoir porosities from 

borehole gravity surveys, Long Beach Unit, Wilmington

011 Field, California [abs.]: Program, 58th Annual Pacific 

Section Meeting, American Association of Petroleum 

Geologists-Society of Economic Paleontologists and 

Mineralogists-Society of Exploration Geophysicists, Sacramento, California, May 18-21.

Borehole gravity measurements made from the uppermost 

Tar zone through the lowermost 237 zone of the Long Beach 

unit are interpreted as vertical profiles of interval (total) 

porosity. Calculated porosities range from as much as 35 percent in upper zones to about 20 percent in deep zones and 

have uncertainties, due to gravity measurement errors, that 

range from less than 1 to about 2 porosity percent. Additional uncertainties in porosity depend on the reliability of 

independent estimates of grain and pore-fluid densities and 

may be as large as 1 to 2 porosity percent. Where reservoirs 

consist of thinly interbedded sand, silt, and clay, porosity 

analysis of sands is improved by knowledge of the relative 

compaction behavior of these sediments which can be inferred 

from the borehole gravity measurements. Discrepancies between porosities determined from core measurements, 

gamma-gamma density logs, and borehole gravity measurements are largest for shallow producing zones that consist 

of unconsolidated to poorly consolidated sands. Apparently open-hole density and porosity logs are strongly affected 

by drilling-induced formation damage in these shallow zones 

and samples recovered by coring are so physically altered that 

laboratory measurements, indicative of reservoir porosity, 

are difficult or impossible to make. Porosity estimates from 

borehole gravity measurements are also preferable in the deep 

fractured shale (237) zone because these measurements examine volumes of reservoir rocks that are about four to seven 

orders of magnitude greater than volumes examined by conventional well logs or coring processes.

156. ____1987, Porosity of unconsolidated sand, diatomite and 

fractured shale reservoirs, South Belridge and West Cat 

Canyon oil fields, California, in Meyer, R.F., ed., Exploration for heavy crude oil and natural bitumen: American 

Association of Petroleum Geologists Studies in Geology, 

no. 25, p. 395-413.

157. Beyer, L.A., and Clutsom, F.G., 1978a, Borehole gravity 

survey in the Dry Piney Oil and Gas Field, Big PineyLaBarge area, Sublette County, Wyoming: U.S. Geological 

Survey Oil and Gas Investigations Chart OC-84, 2 sheets,

12 p.

44
This report analyzes rock density and porosity changes through 3,000 ft of Paleozoic rocks 

and 2,000 ft of underlying Cretaceous rocks, 

separated by the Hogback thrust in western 

Wyoming in terms of lithology, age, and possible structural effects.

Comparisons with open-hole logs are made, 

and a comprehensive explanation for the reduction and precision of the borehole gravity measurements is given.

158. ____1978b, Density and porosity of oil reservoirs and 

overlying formations from borehole gravity measurements, 

Gebo Oil Field, Hot Springs County, Wyoming: U.S. 

Geological Survey Oil and Gas Investigations Chart 

OC-88, 3 sheets, 16 p.

This report interprets rock density and porosity 

changes through 5,083 ft of Pennsylvanian to 

Upper Cretaceous rocks in the Big Horn Basin 

in terms of lithology, age, depth of burial, facies 

changes and probable pore-fluid content.

Comparisons with open-hole logs are made, 

and a comprehensive explanation for the reduction and precision of the borehole gravity measurements is given.

159. ___1980, Density and porosity of Upper Cretaceous 

through Permian formations from borehole gravity measurements, Big Polecat oil and gas field, Park County, 

Wyoming: U.S. Geological Survey Oil and Gas Investigations Chart OC-103, 3 sheets.

This report analyzes rock density and porosity changes through 5,359 ft of Permian to Upper Cretaceous rocks in the northern Big Horn 

Basin in terms of lithology, age, depth of burial, 

facies changes, presence of coal, and probable 

pore-fluid content. Comparisons with open-hole 

logs are made and a comprehensive explanation 

for the reduction and precision of the borehole 

gravity measurements is given.

160. Bhattacharji, J.C., 1963, Investigation of the vertical gradients of gravity measured inside the Earth, in Geophysical 

exploration, a symposium, Baroda, India, 1959: Proceedings Council of Scientific and Industrial Research, New 

Delhi, India, p. 39-46.

Vertical gradients of gravity have been reduced from observations carried out with the Frost gravimeter at various depths 

inside the Nundydroog mine in the Kolar Gold Field in 

Mysore, in 1948. These results have been found to be in 

general agreement with those derived on theoretical 

consideration.

Densities of finite intervals of underground rock strata have 

been determined from the measured vertical gradients. 

Though the results have shown slight discordance with the 

measured densities, yet these are likely to be more representative and as such may prove more adequate for the purpose 

of gravity prospecting than what are ordinarily obtained from 

measurements of rock samples.

123. Black, A.J., 1986, Improved accuracy of a computer controlled borehole gravity system and applications to reservoir flood monitoring: Preprint, Center for Potential Field 

Studies Symposium, Colorado School of Mines, Golden, 

September 17, 9 p.

This report is referenced under Instrumentation, where the abstract is also located.

19. Bradley, J.W., 1974, The commercial application and interpretation of the borehole gravimeter, in Contemporary 

geophysical interpretation, a symposium: Geophysical 

Society of Houston, December 4-5, 14 p., 11 figs.

This report is referenced under Theory, where 

the abstract is also located.

161. ___1975, The application of the borehole gravimeter to 

the evaluation and exploration of oil and gas reservoirs: 

Preprint, Society of Exploration Geophysicists, 45th Annual Meeting, Denver, Colorado, 8 p., 7 fig. 

In recent years, Amoco Production Co. has evaluated approximately 80 wells with the LaCoste-Romberg borehole 

gravimeter. A large number of these surveys have been in 

the search for and evaluation of commercial hydrocarbon 

reservoirs. Additional surveys have provided background density information for geophysical and geological evaluations, 

including surface gravity interpretation and seismic modeling. 

There are two primary applications in which the BHGM 

has been run routinely with economic success. The first takes 

advantage of the BHGM's capability to operate in the 

presence of casing, distinguishing between shallow dry gas 

and fresh water sands in the Gulf Coast. The second application involves reservoir definition in lime reef environments. 

Fracture porosity, as well as porosity in proximity to the well 

bore, has successfully been isolated where normal logging 

procedures have failed. This application has been especially

successful economically.

***

162. ____1976a, The application of the borehole gravimeter to 

the evaluation and exploration of oil and gas reservoirs 

[abs.]: Geophysics, v. 41, no. 2, p. 344.

Same abstract as report 161.

20. ____1976b, The commercial application and interpretation

of the borehole gravimeter, in Jantzgen, R.E., ed., Tomorrow's oil from today's provinces: American Association 

of Petroleum Geologists, Pacific Section, Miscellaneous 

Publication 24, p. 98-109.

This report is referenced under Theory. The 

abstract is also located under Theory, in entry 19.

24. Casten, Uwe, 1984, Subsurface gravity measurements to 

demonstrate mining-induced changes in rock density: 

Geofizikai Kozlemenyer, Geophysical Transactions of the 

Eotvos Lorand Geophysical Institute, Budapest, Hungary, 

v. 30, no. 3, p. 227-236.

This report is referenced under Theory, where 

the abstract is also located.

163. Clark, S.R., and Hearst, J.R, 1983a, Determination of subsurface geological structure with borehole gravimetry 

[abs.]: Abstracts, 2nd Symposium on Containment of 

Underground Nuclear Explosions, Albuquerque, New 

Mexico, August 2-4, p. 15.

45
Conventional gamma-gamma and gravimetric density 

measurements are routinely gathered for most holes used for 

underground nuclear tests. The logs serve to determine the 

subsurface structural geology near the borehole. The gammagamma density log measures density of the rock within about 

15 cm of the borehole wall. The difference in gravity 

measured at two depths in a borehole can be interpreted in 

terms of the density of an infinite, homogeneous, horizontal bed between those depths. When the gravimetric density 

matches the gamma-gamma density over a given interval it 

is assumed that the bed actually exists, and that rocks far 

from the hole must be the same as those encountered adjacent to the borehole. Conversely, when the gravimetric density differs from the gamma-gamma density, it is apparent 

that the gravimeter is being influenced by a rock mass of different density than that at the hole wall. This mismatch can 

be a powerful tool to deduce the local structural geology. 

The geology deduced from gravity measurements in emplacement hole, U4al, and the associated exploratory hole UE4al, 

is an excellent example of the power of the method.

164. ____1983b, Determination of subsurface geological structure with borehole gravimetry: Proceedings of the 2nd 

Symposium on Containment of Underground Nuclear 

Explosions, Albuquerque, New Mexico, August 2-4, v. 1, 

p. 205-211.

Same abstract as report 163.

165. ____1983c, Determination of subsurface geologic structure

with borehole gravimetry; case history: Society of Exploration Geophysicists, 53rd Annual Meeting, Las Vegas, 

Nevada, Expanded Abstracts with Biographies, September 

11-15, p. 35-37.

Same abstract as report 163.

166. ____ 1984, Determination of subsurface geologic structure 

with borehole gravimetry; case history [abs.]: Geophysics, 

v. 49, no. 5, p. 596.

Same abstract as report 163.

167. Cook, A.H., and Thirlaway, H.I.S., 1951, A gravimeter survey 

in the Bristol and Somerset Coalfields: Geological Society of London Quarterly Journal, v. 107, pt. 3, p. 255-286. 

Gravity measurements in the Bristol and Somerset 

coalfields are described and discussed. Accounts are given 

of the methods of measuring gravity, of calculating the gravity 

anomalies and estimating the densities of rocks. It is shown 

that the variations of gravity correspond in a general way 

to the geological structure of the coalfields but that discrepancies in detail indicate that the anomalies are partly due to 

structures lying below the coalfields which may have controlled the development of sedimentation and deformation 

in the region. Detailed studies were made in the neighborhoods of Bitton, Chew Stoke, Ston Easton and Avonmouth 

with a view to assisting the planning of a boring programme 

for the development of the coalfields in these areas. 

27. Domzalski, W., 1954, Gravity measurements in a vertical 

shaft: Bulletin of the Institute of Mining and Metallurgy 

Transaction 571, v. 63, p. 429-445.

This report is referenced under Theory, where 

the abstract is also located.

168. ____1955a, Three dimensional gravity survey: Geophysical 

Prospecting, v. 3, no. 1, p. 15-55.

The paper describes and discusses the results of an experimental gravity survey which was carried out underground 

on different levels of a mine, in the mine shafts, and on the 

surface above the mine workings [in Cumberland, England]. 

***. *** gravity measurements in the shaft give attention 

to the particular problem of the terrain corrections 

underground ***. The interval densities from gravity 

measurements in the shafts are computed and adjusted in 

accordance with known geology and compared with the 

stratigraphical columns of the shafts. The effect of the ore 

body on the stations in the shaft is derived theoretically and 

compared with the observed one.

The gravity contours are constructed on different levels 

in the mine workings [and on the surface] and are discussed 

in relation to the known extent of the ore body [and known 

geology including faulting]. ***.

The densities computed from the gravity measurements are 

compared with the laboratory determinations of the densities, 

carried out on samples from different parts of the mine. 

The contours on the top of the base formation are constructed from the information obtained from the boreholes, 

and are compared with the gravity contours on the surface 

above.

A simple method of computation of the effects of slabs 

and blocks is presented as applied to the calculation of the 

corrections for underground drifts and faults. ***. 

28. ____1955b, Relative determination of the density of surface 

rocks and the mean density of the Earth from vertical gravity measurements: Geophysical Prospecting, v. 3, no. 3, 

p. 212-227.

This report is referenced under Theory, where 

the abstract is also located.

169. Drake, R.E., 1967, A surface-subsurface measurement of an 

anomaly in the vertical gradient of gravity near Loveland 

Pass, Colorado: University of California at Riverside M.S. 

thesis, 41 p.

The validity of using the theoretical normal value of the 

vertical gradient of gravity in the free-air correction of gravity 

data is questionable due to the magnitude of local variations 

in this value.

Surface-subsurface measurements of the actual vertical gradient along an 8,300-foot tunnel line at an approximate elevation of 12,000 feet near Loveland Pass, Colorado, were made 

using a gravimetrically determined density of 2.76 gm/cm3 

for the intervening mass of rock. The results show an anomaly 

in the normal vertical gradient of gravity ranging from +0.4 

to +3.7 percent.

It is concluded that the magnitude of observed anomalies 

in the vertical gradient in the area are too great to be ignored. 

This is particularly true at high elevations, and errors introduced by these anomalies in the vertical gradient may be 

minimized by reducing gravity data to a local datum rather 

than sea-level, and by making individual vertical gradient 

measurements at each gravity station.

170. Facsinay, Laszlo, and Haaz, R.H., 1953, Kozetsiirusegmeghataroz6s a fetszin alatt kulonbozo melysegekben vegzett 

gravimeter-meresek alapjan: Magyan Allami Eotvos 

Lorand Geofizikai Intezet, Geofizikai Kozlemenyek, v. 2, 

no. 4, p. 41-49 (in Hungarian).

Density determinations of rocks, based on subsurface gravimeter measurements at different depths.

46
Gravimeter measurements were made by the authors on 

different levels of a mine in Hungary. The density variations 

resulting from these measurements, are in good agreement 

with the geological log. The computed values for the densities are higher than the densities determined in laboratory. 

It is suggested that calculations of gravitational effects should 

be based on density values resulting from gravimeter 

measurements made in mine-shafts or in boreholes. For this 

purpose a gravimeter with 0.1 mgal precision is sufficient.

171. Fajklewicz, Zbigniew, 1956, O podzienmych Pomiarach 

grawimetrycznych w zastosowaniu do gornictwa weglowego. Wyniki prac w kopalni Miechowice: Archiwum 

G6rnichwa, torn I, zeszyt 4, p. 345-355 (in Polish with 

English abstract). [Underground gravity measurements applied to coal mining results at the Miechowice Mine.] 

Underground gravity measurements were carried out at the 

Miechowice mine in order to determine the actual density 

of the rocks. ***.

The influence of shafts and excavations was taken into account in the treatment of experimental data ***.

The mean density obtained *** is 2.589 g/cm3 . This value 

is greater by 4.00% than the value used, p = 2.50 g/cm3 . 

As the error is 0.111 mgl, the densities are determined with 

the following error: 

1. The complex strata

from surface to 370 m level dp = 0.4% 

The complex strata

from 370 m level to 520 m level dp=0.9% 

The complex strata

from 520 m level to 620 m level dp = 1.34% 

The complex strata

from 620 m to 720 m level dp = 1.32% 

Laboratory measurements provide an error of the order of 

10-15%. The actual density p being known and the velocities 

the seismic waves V and Vs , the Young modulus, the 

Poisson constant, the Lame constants and derived values may 

be determined. The gravity measurements of the densities 

enable maps of isodenses to be drawn and these may serve 

for the analysis of the gravimetric image of Silesia in order 

to investigate the tectonics. The gravimetric method may help 

to discover faults and hollow spaces in mines.

172. ____1957, Podziemne pomiary grawimetryczne w 

kopalniach G6rnego Slaska: Geodezja i Kartografia, torn 

6, zeszyt 3, p. 161-173. [Subsurface gravimetry measurements in the mines of the Upper Silesia.]

173. ____1957, Underground gravity measurements in the mines 

of Upper Silesia: Academic Polonaise des Sciences, Comite 

de Geodesic, Vasovie, Toronto, Canada, September 3-14, 

16 p.

174. ____1963, Detection of fault in the BD Coal Mine by means 

of microgravity measurements: Bulletin de I'Acad&nie 

Polonaise des Sciences, Serie des Sciences Geologiques et 

Geographiques, v. 11, no. 4, p. 197-200.

This report describes the use of a gravimeter 

along mine workings at 5 m intervals in a coal 

mine in Upper Silesia, Austria. The purpose of 

the study was to detect from gravity anomalies, 

faults that cross the carboniferous layer. Maximum detectable change in the gravity anomalies 

caused by the faults was about 0.20 mgal. The

175.

study was able to detect and follow some of the 

faults.

____1972, Pustki poeksploatacyjne i odksztalcenia

objetosciowe gorotworu w swietle pomiar6w gradientu 

pionowego sily ciezkos"ci i jej mikroanomalii: Przeglad 

Gorniczy, v. 10, p. 425-431 (in Polish). [Post-exploitation 

cavities and volumetric deformation of the rock mass in 

the light of measurement of the gravity vertical gradient 

and gravity anomalies.]

176. ____1975, Pionowe przekroje pola sily ciezkosu i ich 

zwiazek z odksytalceniami gorotworu: Krak6w, Akademia 

Gorniczo-Hutniczej, Zeszyty Naukowe, G6rnictwo z. 76, 

nr. 522, p. 185-195 (in Polish with English summary). [Vertical sections of gravity field and their relation with orogen 

strains.]

In the work there are presented results of periodical 

microgravimetric investigations carried on in two sections 

located under coal stratum deposited on depths 120-160 

meters. These sections each 1,100 meters long were situated 

perpendicularly to extent of the wall, mining of which was 

planned for the nearest future. Measuring points in each of 

them were situated in intervals of 10 to 20 meters. On so 

prepared traverse before mining starting there were made 

measurements of gravity microanomalies and were determined with great accuracy heights of each measuring point. 

These measurements set was repeated after 3,9, 19 and 25 

months from the moment of mining end. As time passed there 

was observed decrease of measured values of gravity microanomalies corresponding with terrain surface lowering. 

Values of changes of measured values of gravity microanomalies in comparison with vertical movements of terrain 

surface show quicker manifestation, in measured values of 

gravity microanomalies, after-mining changes in orogen mass 

distribution in relation to formation time of settlement basin. 

To determine sources of changes of gravity microanomalies 

field in time, there was made analytical prolongation of 

measured distribution of gravity force microanomalies to 

depth exceeding the mining depth. Analytical prolongations 

were also made for intermediary levels, what enables drawing of vertical sections of gravity anomalies field. These sections allow to determine singular points of gravity potential 

and its derivatives and to determine their shifts as time passes. 

We ought to add, that the mentioned singular points are 

treated as sources generating the measured fields of gravity 

microanomalies.

The investigations results show origining of local disturbances of gravity anomalies field occurring on different depths, 

specially in place of old mining headings, lying over the mined 

stratum, or along fault planes. The above investigations show 

places of occurrence of the strongest volumetric strains of 

orogen and may be useful in investigation of orogen strain 

mechanism in its mining effect.

177. ____1982, Neue Perspektiven der Mikrogravimetrie Teil 

der Gebirgsschlagprognose: Neue Bergbautechnik, seiten 

121, bis 176, heft 3, p. 140-143. [New perspectives in 

microgravimetry part of the rock burst problem.]

178. ____1983, Rock-burst forecasting and genetic research in 

coal mines by microgravity method: Geophysical Prospecting, v. 31, no. 5, p. 748-765.

Microgravity can be used for predicting rock bursts. For 

the first time gravity anomalies related to rock bursts have

47
been recorded. The methodology developed has led to 

the first successful predictions. The depth of the rock-burst 

focus might be determined on the basis of analytical downward continuation of related gravity anomalies: the focus 

is treated as a singular point of the gravity potential and its 

derivatives.

The rock-burst gravity anomalies might be explained on 

the basis of the assumed dilatancy process that causes the 

rock burst. The mean density change of the rock mass 

threatened with rock bursts can be estimated from the corresponding rock-burst gravity anomalies.

34. Fajklewicz, Zbigniew, and Duda, Wladyslaw, 1964, Proba 

zastosowania pomiarow mikrograwimetrycznych dla potrzeb gornictwa weglowego: Technika Poszukiwan, rok 3, 

zeszyt 9, p. 1-7. [Test of the application of microgravimetric measurements for coal mining requirements.]

This report is referenced under Theory, where 

the abstract is also located.

179. Fajklewicz, Zbigniew, Duda, Wladyslaw, and Rejman, T., 

1966, Geophysical measurements of density in closely 

neighboring mine shafts: Bulletin de 1'Academic Polonaise 

des Sciences, Series des Sciences Geologiques et Geographiques, v. 14, no. 1, p. 7-11.

This report presents and discusses density 

calculations from gravity measurements in three 

mine shafts in the Upper Silesian Coal Mines.

35. Fajklewicz, Zbigniew, Gliriski, A.L.R., and Sliz, Janusz, 

1982, Some applications of the underground tower gravity 

vertical gradient: Geophysics, v. 47, no. 12, p. 1688-1692.

This report is referenced under Theory, where 

the abstract is also located.

180. Farlay, D.G., 1971, Application of the downhole gravity 

meter for porosity determination: Preprint, Libyan 

Association of Petroleum Technologist 7th Annual 

Meeting, p. 1-20.

A high precision downhole gravity meter developed by Esso 

Production Research Co. has been run in a number of Esso 

Libya wells in an attempt to improve the reliability and accuracy of porosity determinations in vuggy limestone and 

fractured quartzite reservoirs. In general, porosities determined from the gravity meter were higher than those determined previously from sonic logs using conventional 

interpretation relationships. When a relationship between 

porosity values and sonic log readings established with density data was used in calculating the sonic logs, porosities 

for specific intervals sometimes gave poor agreement with 

those from the downhole gravity meter, but the average

thickness-weighted values gave good agreement.

***

181. Fausset, N.E., and Butler, David, 1979, Computer modeling of the theoretical borehole gravity response in the vicinity of the Aneth Field, Paradox Basin [abs.]: Geophysics, 

v. 44, no. 3, p. 370.

Borehole gravimetry has proven useful as a petroleum 

reservoir evaluation tool in that calculations from precise 

gravimeter measurements yield accurate determinations of 

average rock density in situ. However, independent knowledge of rock densities throughout a penetrated section may 

permit separation of gravitational effects due to rocks

intersecting the borehole and rocks remote from the borehole. 

In this manner, the borehole gravimeter may be used as a 

remote sensing tool and provide unique opportunities in 

geophysical exploration.

By adapting Talwani's algorithm for computer use, the 

gravitational effects of various shaped 3-D bodies may be 

easily calculated.

The Aneth field of the Paradox basin was chosen as a 

model because of the sharp lateral density contrast between 

the reservoir and the surrounding country rock. ***.

Due to the small relief and the large areal extent of the 

reservoir, it was modeled as two abutting semi-infinite sheets. 

The vertical component of attraction was then calculated in 

hypothetical boreholes at various distances from the reservoir edge. Results from this idealized model indicate the 

Aneth field may be detected by borehole gravimetry up to 

450 ft from its boundary. ***.

Although these results show that the borehole gravimeter 

is not significantly affected by bodies at large distances from 

the wellbore, they also show that the remote sensing of 

anomalous masses is possible for concise bodies marked by 

large density contrasts. ***.

182. Gibb, R.A., and Thomas, M.D., 1980, Density determinations of basic volcanic rocks of the Yellowknife supergroup 

by gravity measurements in mine shafts Yellowknife, 

Northwest Territories: Geophysics, v. 45, no. 1, p. 18-31. 

Gravity measurements were made in two gold mine shafts 

sunk in the Archean Yellowknife greenstone belt to determine the in situ densities of basic volcanic rocks of the Kam 

formation, Yellowknife supergroup. ***. Densities were computed using the terminology of borehole gravimetry with appropriate corrections for surface terrain and underground 

voids such as shafts, drifts, and slopes. [These values are compared to values from rock samples.] 

***

39. Gournay, L.S., 1983, Detection of bypassed gas using 

borehole gravimeter and pulsed neutron capture logs [abs.]: 

The Log Analyst, v. 24, no. 3, p. 27.

This report is referenced under Theory, where 

the abstract is also located.

40. Gournay, L.S. and Lyle, W.D., 1984a, Determination of 

hydrocarbon saturation and porosity using a combination 

borehole gravimeter (BHGM) and deep investigating electric log [abs.]: The Log Analyst, v. 25, no. 2, p. 59-60.

This report is referenced under Theory, where 

the abstract is also located.

41. ____1984b, Determination of hydrocarbon saturation and 

porosity using a combination borehole gravimeter (BHGM) 

and deep investigating electric log: Society of Professional 

Well Log Analysts, 25th Annual Logging Symposium 

Transactions, v. 2, p. WW1-WW14.

This report is also referenced under Theory. 

The abstract is under Theory in entry 40.

183. Halley, R.B., and Schmoker, J.W., 1983, High-porosity 

Cenozoic carbonate rocks of south Florida; progressive loss 

of porosity with depth: American Association of Petroleum 

Geologists Bulletin, v. 67, no. 2, p. 191-200. 

Porosity measurements by borehole gravity meter in subsurface Cenozoic carbonates of south Florida reveal an 

extremely porous mass of limestone and dolomite which is

48
transitional in total pore volume between typical porosity 

values for modern carbonate sediments and ancient carbonate 

rocks. A persistent decrease of porosity with depth, similar 

to that of chalks of the Gulf Coast, occurs in these rocks. 

[No attempt is made] to differentiate depositional or 

diagenetic facies which produce scatter in the porosity/depth 

relationship; the dominant data trends thus are functions of 

carbonate rocks in general rather than of particular carbonate 

facies. Carbonate strata with less than 20% porosity are absent from the rocks studied here.

Aquifers and aquicludes cannot be distinguished on the 

basis of porosity. ***.

Dolomites [are equally] porous or slightly less porous than 

[the] limestones [they replace] *** [suggesting] dolomitization does not take place by a simple ion-for-ion replacement 

of magnesium for calcium. ***.

The great volume of pore space in these rocks serves to 

highlight the inefficiency of early diagenesis in reducing carbonate porosity and to emphasize the importance of later 

porosity reduction which occurs during the burial or late nearsurface history of limestones and dolomites. 

43. Hammer, Sigmund, 1950, Density determinations by underground gravity measurements: Geophysics, v. 15, no. 4, 

p. 637-652.

This report is referenced under Theory, where 

the abstract is also located.

184. Head, W.J., and Kososki, B.A., 1979, Borehole gravity a 

new tool for the ground water hydrologist [abs.]: Transactions American Geophysical Union, v. 60, no. 18, p. 248. 

The basic principles that have made the BHGM useful to 

the energy industry can also be applied to ground water 

investigations. ***.

The results of borehole-gravity surveys in the Madison 

Limestone of northeast Wyoming and in an alluvial aquifer 

at the Nevada Test Site provide two examples that illustrate 

the value of BHGM logging techniques. In the Madison 

Limestone, the neutron log recorded zones of relatively high 

porosity, which borehole televiewer logging indicated were 

the result of secondary porosity development. In some instances, on the basis of borehole gravity data, the authors 

concluded that this secondary porosity was only of local extent and did not represent zones of high water production. 

This conclusion was subsequently supported by flow tests. 

In the alluvial aquifer, the invasion of drilling fluids and 

hole rugosity seriously degrade the quality and hence the interpretation of conventional wire-line logs. In this case, the 

BHGM with its relatively large radius of investigation, which 

minimizes the effects of near-borehole conditions, proved to 

be a superior logging tool.

185. Healey, D.L., 1970, Calculated in situ bulk densities from

subsurface gravity observations and density logs, Nevada

Test Site and Hot Creek Valley, Nye County, Nevada, in

Geological Survey research 1970: U.S. Geological Survey

Professional Paper 700-B, p. B52-B62.

At the Nevada Test Site and Hot Creek Valley a borehole

gravity meter was used to log four holes, and standard gravity

meters were used to log five 48-inch-diameter holes and a

vertical shaft. Three holes (Ue2y, test well B, and UCe-18)

and the U5i shaft penetrated alluvium, and six holes

penetrated Tertiary volcanic rocks on Pahute Mesa. The

weighted average densities determined in the holes and shaft

in alluvium are 1.94, 1.69, 2.22, and 2.05 g/cc, respectively; 

the density determined in five of the six holes in Tertiary 

volcanic rocks ranged from 1.98 to 2.06 g/cc. One hole 

(UE19n) penetrated a thick ash-flow tuff that averaged 

1.51 g/cc. Density logs were taken in 10 additional holes. 

In Yucca Flat the mean density of more than 7,000 feet of 

alluvium is 2.01 g/cc, and in Hot Creek Valley the mean of 

more than 18,000 feet is 2.18 g/cc.

53. Hearst, J.R, and McKague, H.L., 1976, Structure elucidation with borehole gravimetry: Geophysics, v. 41, no. 3, 

p. 491-505.

This report is referenced under Theory, where 

the abstract is also located.

54. Hearst, J.R, and Nelson, P.H., 1985, Well logging for 

physical properties: New York, McGraw-Hill Book Co., 

571 p.

This report is referenced under Theory, where 

the abstract is also located.

55. Hearst, J.R, Carlson, R.E. and Clark, S.R., 1986a, Calculation of gravimetric density caused by three-dimensional 

structure [abs.]: The Log Analyst, v. 27, no. 1, p. 78-79.

This report is referenced under Theory, where 

the abstract is also located.

56. ____1986b, Calculation of gravimetric density caused by 

three-dimensional structure: Society of Professional Well 

Log Analysts, 27th Annual Logging Symposium Transactions, v. 1, p. F1-F22.

This report is also referenced under Theory. 

The abstract is under Theory in entry 55.

135. Heintz, K.O., and Alexander, M., 1979, Sulfur exploration 

with core hole and surface gravity [abs.]: Geophysics, v. 

44, no. 3, p. 370.

This report is referenced under Instrumentation, where the abstract is also located.

186. Hinze, W.J., Bradley, J.W., and Brown, A.R., 1978, 

Gravimeter survey in the Michigan Basin deep borehole: Journal of Geophysical Research, v. 83, no. B12, 

p. 5864-5868.

Borehole gravimetric measurements were made at major 

Phanerozoic formation contacts and within the Precambrian 

sedimentary rocks to a depth of 4 km in the McClure-Sparks 

No. 1-8 drill hole. The inplace densities of these units were 

calculated from the corrected observations. The densities of 

the Phanerozoic rocks vary considerably owing to the 

presence of evaporites contrasting with the clastic and carbonate rocks, and the mean density of the Phanerozoic rock 

column is 2.61 g/cm3 . The borehole gravimeter density of 

the Precambrian clastic rocks is 2.77 g/cm3 , 0.05 g/cm3 

greater than the density obtained from sample cuttings. The 

source of this discrepancy is unknown, but one possible explanation is the gravimetric effect of mafic igneous rocks, 

which may be more common within the Precambrian 

sedimentary rocks than is indicated by intersection of these 

rocks in the drill hole.

187. Hussain, A., 1979, Untertagegravimetrie in alpinen Gebieten 

mit besonderer Berucksichtegung des Blei-Zink-Bergbaus 

Bleiberg-Kreuth (Karnten): Leobon, Mining and Metallurgy University, Ph. D. thesis, 176 p.

49
[Underground gravimetry in alpine regions with specific 

consideration of the lead-zinc mine Bleiberg, Carinthia.]

188. ____1983, Underground gravity surveys, in Fitch, A.A., 

ed., Developments in geophysical exploration methods 5: 

Essex, England, Applied Science Publishers LTD, p. 35-63. 

The gravimeter used in underground mines is a threedimensional exploration device which provides very valuable 

information about the density distribution around the measurement level. In this article we will examine its application 

for density determination in situ and for 'anomalous zone' 

definition in the mines. Practical examples of subsurface 

gravity surveys carried out in the shafts of a coal mine and 

in different levels of a lead-zinc mine will be presented. Gravity anomaly maps and profiles were constructed from different levels and compared with the known geology. The 

results demonstrate that gravity studies are the best first phase 

of study for defining drilling targets.

189. Hussain, A., and Walach, G., 1980, Subsurface gravity measurements in a deep intra-Alpine Tertiary basin: Geoexploration, v. 18, p. 165-175.

This paper is concerned with an underground gravity survey 

carried out in the Fohnsdorf-Knittelfeld basin, Styria, 

Austria. The measurements were made in three vertical shafts, 

reaching to a depth of 833 m, within the Fohnsdorf coal 

mines. The in situ densities, calculated from the corrected 

gravity values, furnished information about the threedimensional density distribution within the basin which was 

helpful in interpreting other geophysical data from this area. 

The density profiles from each shaft were compared with one 

another and with the surrounding geology. About 50 m thick 

coal formation (6 m thick coal seam and remaining light marl) 

provided a significant density contrast with the upper lying 

marl and the lower lying sandstone. The accuracy achieved 

in the in situ density determinations was better than 

0.01 g/cm3 . The gravimetric densities agree well with the 

hand sample densities collected from outcrops and the shaft 

surroundings.

190. Hussain, A., Walach, G., and Weber, F., 1981, Underground

gravity survey in Alpine regions: Geophysical Prospecting,

v. 29, no. 3, p. 407-425.

An underground gravity study was carried out under extreme conditions of the Alpine regions. The lead-zinc mine 

Bleiberg, Carinthia, [Austria,] was selected as an example 

to show the possibilities and limitations of the subsurface 

gravity method. For in situ density determinations, gravity 

measurements were made in two vertical mine shafts passing through Triassic sedimentary rocks of the Bleiberg Unit. 

The main problem in gravity data reduction in extremely 

rugged topography is the accurate calculation of the terrain 

effect on underground stations. A general discussion of the 

various corrections required for the gravity measurements 

in the mine is presented. The mean interval densities in the 

two shafts, in limestone, dolomite, and schists formations, 

were determined as 2.76 and 2.77 g/cm3 , respectively, with 

an accuracy of better than 0.01 g/cm3 for depth interval of 

50 m. The interval densities provide valuable information 

about the lithological and structural changes in the shaft surroundings and also agree well with the representative hand 

sample densities.

In the second part, the applications of subsurface horizontal gravity surveys in exploration are discussed. Since the influence of topography is less underground because of the

greater distance to the surface, subsurface surveys have 

definite advantages over surface surveys and can be very 

helpful in locating anomalous density zones in the mines. An 

example of gravity survey with a station spacing of 10 m at 

a depth of about 540 m is presented. 

191. Jung, Heinrich, 1939, Dichtebestimmung in anstehenden

Gestein durch Messung der Schwerebeschleunigung in

verschiedenen Tiefen unter Tage: Zeitschrift fur Geophysik, v. 15, p. 56-65.

Density determinations in the solid rock from measurement of the gravity acceleration at differing depths beneath 

the surface.

Measurements were made in the Wilhelms 

Shaft near Clausthal, Germany.

70. LaFehr, T.R., 1982, Apparent density from borehole gravity surveys [abs.]: Geophysics, v. 47, no. 4, p. 447-448.

This report is referenced under Theory, where 

the abstract is also located.

192. LaFehr, T.R., and Dean, V.C., 1983, Borehole gravity case 

history of the Mors Salt Dome, Denmark: Society of Exploration Geophysicists, 53rd Annual Meeting, Las Vegas, 

Nevada, Expanded Abstracts with Biographies, September 

11-15, p. 33-35.

Two wells (Erslev 1 and 2) were drilled and logged (conventional and BHGM) in the Mors salt dome, Denmark. A 

third well was drilled and conventionally logged (no BHGM) 

about 10 km north-northeast of the dome. Surface seismic 

and gravity data were acquired, modeled (LaFehr et al, 1983, 

[report 194]), and used as a geologic constraint for this 

borehole gravity study. We expect, and see, in the Erslev 1 

and 2 BHGM logs three responses within the MORS salt 

dome: (1) the structural effect of the salt dome, (2) the 

primary effect of pure halite, and (3) the effects of impurities 

in the salt and its internal structure. The mean density of the 

salt dome is about 2.2 g/cm3 , or close to that of pure halite. 

Observed BHGM structural effects of the Mors salt dome 

are compared with the calculated density from seismic 

models. The two models produce significantly different 

BHGM density curves; a deeper base of salt beneath the 

overhang, together with the seismic interpretation with less 

overhang is supported by the BHGM data. The cap rock and 

deeper anhydrite zones produce very strong BHGM 

anomalies. Modeling of the deeper zones suggests their offwell connection and through-the-well dip. However, a more 

quantitative interpretation must await a better modeling 

capability. Smaller high frequency variations in the BHGM 

data suggest variations in the anhydrite concentrations in the 

rock salt, fluctuating between 0-5 percent.

193. ____1984, Borehole gravity case history of the Mors Salt 

Dome, Denmark [abs.]: Geophysics, v. 49, no. 5, p. 595-5%.

Same abstract as report 192.

194. LaFehr, T.R., Dean, V.C., Davis, T.L., and Hilterman, F.J., 

1983, Seismic and gravity modeling of the Mors Salt Dome, 

Denmark: Society of Exploration Geophysicists, 53rd Annual meeting, Las Vegas, Nevada, Expanded Abstracts 

with Biographies, September 11-15, p. 301-303. 

Seismic and gravity modeling are used to investigate salt 

domes located in Denmark. ***. An extremely diverse and 

impressive array of geologic, geochemical, geophysical, and 

engineering disciplines has been engaged ***.

50
Each individual discipline, certainly the seismic and gravity 

methods, requires high specialization to understand their application and limitations fully, but it is equally important to 

have the general view of contributions from the disciplines 

to fully utilize the information at hand. Viewed from the 

perspective of integrated geophysics and geology, the surface and borehole seismic and gravity data have important 

roles. They respond to changes in rock density, which is one 

of the most important of rock properties. In addition to its 

effect on gravity anomalies, density influences seismic wave 

speeds, (whether compressional or shear), acoustic impedance 

(whose changes are required for the occurrence of seismic 

reflections) and is influenced by porosity development, fluid 

density, mineralogy, and compaction.

Different combinations of geologic structures and rock densities can give rise to the same gravity observations, so the 

incorporation of independent seismic and geologic information is critical in the evaluation of gravity data. ***. 

195. ____1984, Seismic and gravity modeling of the Mors

Salt Dome, Denmark [abs.]: Geophysics, v. 49, no. 5,

p. 629-630.

Same abstract as report 194.

73. Laurin, P.J., Black, A.J., LaFehr, T.R.,and Bichara, M., 

1981, Borehole gravimetry; an application example to 

engineering: Societd pour 1'Avancement de 1'Interpretation 

des Diagraphies, 7th European Logging Symposium Transactions, no. 27, 10 p. (in French).

This report is referenced under Theory, where 

the abstract is also located.

77. McCalpin, G.A., 1983, Operational and technical results 

from a multi-well borehole gravity survey [abs.]: Unconventional Methods in Exploration for Petroleum and 

Natural Gas, Symposium IV, Institute for the Study of 

Earth and Man, Dallas, Texas, May 1-2, p. 32.

This report is also referenced under Theory. 

The abstract is under Theory in entry 78.

78. ____1986, Operational and technical results of a multiwell 

borehole gravity survey, in Davidson, M.J., ed., Unconventional methods in exploration for petroleum and natural 

gas IV: Dallas, Texas, Institute for the Study of Earth and 

Man, Southern Methodist University Press, May 1-2, 1985, 

p. 313-320.

This report is referenced under Theory, where 

the abstract is also located.

196. McCulloh, T.H., 1965, A confirmation by gravity 

measurements of an underground density profile based on 

core densities: Geophysics, v. 30, no. 6, p. 1108-1132. 

Accurate laboratory measurements of dry bulk densities 

of 79 samples of Paleozoic sedimentary rocks from a 2,851-ft 

deep core hole near Barberton, Ohio, are the basis of a vertical profile of "natural" density which differs on the average 

0.013 gm/cm3 or less from a profile of in situ density 

calculated from gravity variations observed using a LaCoste 

and Romberg gravimeter in an adjacent 2,247-ft-deep vertical mine shaft. Both profiles agree well with the most meaningful Barberton core sample densities reported by Hammer 

(1950, Fig. 3 [report 39]), but are significantly lower than 

in situ interval densities calculated by Hammer from gravity 

variations observed in the shaft using a Gulf gravimeter. The

0.13 gm/cm3 average discrepancy between the old and new 

in situ density profiles is probably attributable to a 12-percent 

error in calibration of the Gulf gravimeter.

The close agreement between the new profiles of "natural" 

and in situ density suggests that changes in bulk volume of 

compact sedimentary rocks that occur during or following 

the coring process are probably ordinarily so small that properly constructed core sample density profiles are reproducible and reliable even when small numbers of samples of aged 

cores are used. ***.

81. ____1967a, Borehole gravimetry New developments and 

applications, in Origin of oil, geology and geophysics: London, Elsevier, 7th World Petroleum Congress, Mexico 

City, April 2-8, Proceedings, v. 2, p. 735-744.

This report is referenced under Theory, where 

the abstract is also located.

82. ____1967b, Mass properties of sedimentary rocks and 

gravimetric effects of petroleum and natural gas reservoirs: 

U.S. Geological Survey Professional Paper 528-A, 50 p.

This report is referenced under Theory, where 

the abstract is also located.

83. McCulloh, T.H., Kandle, J.R., and Schoellhamer, I.E., 

1968, Application of gravity measurements in wells to problems of reservoir evaluation: Society of Professional Well 

Log Analysts 9th Annual Logging Symposium Transactions, p. O1-O29.

This report is referenced under Theory, where 

the abstract is also located.

197. McLean, A.C., 1961, Density measurements of rocks in 

southwest Scotland: Royal Society of Edinburgh Proceedings, sec. B, v. 68, pt. 2, p. 103-111. 

A large number of density measurements of the more important rock-types exposed at the surface in Ayrshire and 

certain neighboring areas provide information for the interpretation of gravity measurements. The three methods 

employed of determining density are (1) laboratory measurements of rock samples, (2) gravimeter measurements in mineshafts, and (3) gravimeter measurements over topographic 

features.

The first method, the most widely used is the only one applicable to many of the geological formations. A total of 600 

specimens measured cover all the common rock types of the 

Lower and Upper Palaeozoic systems and their associated 

igneous rocks. Use of the second method is restricted to 

Carboniferous rocks, in which records from four mineshafts Littlemill 5, Mauchline 1, Auchincruive 1, and 

Houldsworth cover much of the Carboniferous succession 

in south Ayrshire. The third method was seldom applied as 

there are few suitable topographic features, independent of 

geological structure, in Ayrshire.

The results of the measurements are summarized, and their 

reliability discussed. Two contrasts of rock density of regional 

importance occur in the sedimentary succession of south 

Ayrshire the first at the plane of unconformity between Upper and Lower Old Red Sandstone, and the second between 

Lower Old Red Sandstone and the Lower Palaeozoic greywackes. A marked contrast of local importance occurs between the Permian sandstones of the Mauchline Basin and 

the underlying lavas and Carboniferous rocks. In north 

Ayrshire the most important density contrast lies between

51
the Upper Palaeozoic sediments and the associated dense igneous rocks the Clyde Plateau Lavas, the Millstone Grit 

lavas, and the thick dolerite intrusions.

198. Miles, D.R., 1977, A gravity survey in the haulage tunnel 

of the Henderson Mine near Berthoud Pass, Colorado: 

Golden, Colo., Colorado School of Mines M.S. thesis, 

37 p., 2 plates.

A gravity survey was conducted in the haulage tunnel of 

the Henderson Mine, followed by the reduction and interpretation of the data and analysis of errors. The gravity survey 

consisted of 64 stations in the tunnel and five stations on the 

surface ***.***. The computed bulk densities show a slightly 

higher than average density implying that the country rock 

is a mixture of granite and metasediment.

The uncertainties in the complete Bouguer-corrected data 

are as large (±1.30 mgals) as most of the anomalies. The 

large relief (y 2,500 feet to 3,300 feet or ~0.75 km to 1.0 km) 

caused usually trivial errors in the terrain correction to account for most of the uncertainty in the data. Thus, a criterion 

utilizing the surface gravity survey and the deviation from 

the regional gradient was developed.

Four anomalies based on the criteria appear to be caused 

by granite or metasediment pods in the mixed granitemetasediment country rock, rather than uncertainties in the 

data. Models of the source of the anomalies range in size 

from between 500 ft. (152 m) and 3,000 ft. (914 m.) from

the tunnel.

***

84. Miller, A.H., and Innes, M.J.S., 1953, Application of 

gravimeter observations to the determination of the mean 

density of the Earth and of rock densities in mines: Canada 

Dominion Observatory, Ottawa Publications, v. 16, no. 

4, p. 3-17.

This report is referenced under Theory, where 

the abstract is also located.

85. Mudrecova, E.A., 1960, Underground gravity surveys in copper sulphide deposits in the Central Ural Mountains: 

Geofizicheskaia Razvedka, no. 2, p. 31-59 (in Russian).

This report is referenced under Theory, where 

the abstract is also located.

199. Murty, B.V.S., Chandra Reddy, P., Venkat Reddy, P., and 

Ghyasuddin, Mohd., 1984, Subsurface gravity survey in 

aid of mine planning and development; a case study from 

Mailaram Copper Mines, Andhra Pradesh, India: Society of Exploration Geophysicists, 54th Annual Meeting, 

Atlanta, Georgia, Expanded Abstracts with Biographies, 

December 2-6, p. 226-228.

Toward demonstrating the usefulness of the subsurface 

gravity technique in mine planning and development, a gravity survey was conducted in the different levels, shafts, and 

crosscuts in the Mailaram copper mines of Andhra Pradesh, 

India. The authors report the results of the investigation 

which helped decipher the geometry of the chalcopyrite ore, 

the zones of its probable extension, structural features like 

faults, and the extent of the ore available in the mine. It is 

suggested that accurate gravity measurements, attention 

toward necessary corrections to obtain the subsurface 

Bouguer anomalies, and due weightage to surface and subsurface geologic information could help using the successful 

subsurface gravity technique toward solving mining geophysical problems.

200. ____1985, Subsurface gravity survey in aid of mine planning and development; a case study from Mailaram Copper 

Mines, Andhra Pradesh, India: Geophysics, v. 50 , no. 

2, p. 293.

Same abstract as report 199.

201. Murty, B.V.S., Ghyasuddin, Mohd., and Venkat Reddy, P., 

1982, Subsurface gravity measurements and density mapping in the Mailaram Copper Mines, Andhra Pradesh, 

India: Geophysical Prospecting, v. 30, no. 4, p. 444-453. 

Gravity measurements were made in the Mailaram copper 

mines, Andhra Pradesh. The observations were distributed 

between the two shafts situated about 220 m apart and in 

the three levels up to a maximum depth of 100 m. Assuming 

a normal free-air gradient, average densities for the three 

layers were determined as 2.631, 2.604, and 2.823 g cm~3 , 

respectively. Upon incorporating the weighted mean density values from measurements on samples, the free-air gradients were found to be 0.315 mGal m" 1 for the second layer 

(i.e. between the first and second levels) and 0.2978 mGal 

m~' for the third layer (i.e. between the second and third 

levels). The density variation map obtained from the gravity data, the deduced anomalies, the weighted mean density 

values from measurements on rock samples, and the varying free-air coefficients all suggest correspondence with the 

concentration of ore lodes.

202. Nichols, T.C., Jr., and Collins, D.S., 1986, In situ and laboratory geotechnical tests in the Pierre Shale near Hayes, 

South Dakota: U.S. Geological Survey Open-File Report 

86-152, 24 p.

A geotechnical investigation of the Pierre Shale near Hayes, 

S. Dak., was conducted by the U.S. Geological Survey. The 

physical and mechanical properties of the shale were determined through use of four core holes and several supplementary holes, drilled to a maximum depth of 184 m. In situ 

borehole determinations included a gravimeter survey, 

pressuremeter testing, thermal profile measurements, and 

borehole velocity measurements of shear and primary waves. 

Onsite laboratory measurements included geologic logging 

of cores, bulk density determinations, moisture content determinations, and rebound measurements. Offsite laboratory 

measurements included sonic velocity measurements of shear 

and primary waves, X-ray mineralogy and major element 

determinations, size analyses, fracture analyses, fabric 

analyses, and determination of thermal properties.

203. Nichols, T.C., Jr., Collins, D.S., and Davidson, R.R., 1986, 

In situ and laboratory geotechnical tests of the Pierre Shale 

near Hayes, South Dakota A characterization of engineering behavior: Canadian Geotechnical Journal, v. 23, 

no. 2, p. 181-194.

The abstract for this report is similar to report 

202. The report itself is an expanded version of 

report 202.

87. Oelsner, Christian, 1960, Schweremessungen unter Tage: 

Zeitschrift fur Angewandte Geologic, v. 4, p. 172-177.

This report is referenced under Theory, where 

the abstract is also located.

204. Picha, Jan, 1953, Tihove' zrychleni pod povrchem zemsk^m 

v dole "Anna" na Brezovych Horach: Geofysikalni 

Sbornik, no. 9, p. 119-129 (in Czechoslovakian).

52
[Underground gravity surveys in the "Anna" shaft in 

Brezowe Gory.]

205. Plouff, Donald, 1961, Gravity profile along Roberts Tunnel, Colorado: U.S. Geological Survey Professional Paper 

424-C, p. C263-C265.

This report discusses density determinations 

from gravity data collected in and above the 

Harold D. Roberts Tunnel east of Dillon, Colo. 

This study is part of a regional gravity survey of 

the Colorado Rocky Mountains.

206. Pritchett, W.C., 1980, Physical properties of shales and possible origin of high pressures: Society of Petroleum Engineers 

Journal, v. 20, no. 5, p. 341-348. 

Laboratory and borehole measurements of shale properties may be unreliable because of modification during or after 

drilling or coring. The borehole gravimeter is an ideal tool 

for measuring the bulk density of thick shale units because 

of its great depth of investigation and negligible sensitivity 

to shale in the vicinity of the borehole, which may have been 

modified in drilling. By contrast, the scatter gamma ray density log has an extremely shallow depth of investigation and 

its response may be dominated by modified shale surrounding a borehole. A comparison of bulk densities measured by 

these two methods in both sands and shales was made in three 

U.S. Gulf Coast wells. In all three wells, the two methods 

yielded comparable densities for the sands. But in two wells, 

which were drilled with fresh muds, the density log yielded 

shale bulk densities significantly less than those shown by 

the borehole gravimeter. These data indicate that shale adjacent to the borehole in these two wells had been modified 

by drilling and the modified shale densities had been reduced 

significantly. ***.

High-pressure shales are particularly susceptible to modification during drilling since they are relatively permeable and 

soft. ***. Density log data in high-pressure shales are 

unreliable due to probable shale modification. ***.

90. ____1982, Physical properties of shale and possible origin 

of high pressures: Society of Exploration Geophysicists, 

52nd Annual Meeting, Dallas, Texas, Expanded Abstract 

with Biographies, October 17-21, p. 504-505.

This report is referenced under Theory, where 

the abstract is also located.

91. ____1983, Physical properties of shales and possible origin

209.

See report 209 for abstract.

___1975b, The successful use of the borehole gravity

of high pressures [abs.]: Geophysics, v. 48, no. 4, p. 483.

This report is also referenced under Theory. 

The abstract is under Theory in entry 90.

J07. Prudic, D.E. and Herman, M.C., in press, Ground water 

hydrology and simulated effects of pumping patterns in 

Paradise Valley, a stream dominated basin in Humboldt 

County, Nevada: U.S. Geological Survey Professional 

Paper 1409-F.

Reference is made in this paper to BHGM 

surveys in two shallow wells within the basin. See 

report 238 for the principal facts to these surveys.

208. Rasmussen, N.F., 1975a, The successful use of the borehole 

gravity meter in northern Michigan: Transactions, Canadian Well Logging Society, Fifth Formation Evaluation 

Symposium, paper X.

meter in northern Michigan: The Log Analyst, v. 16, no.

5, p. 3-10.

Borehole gravity surveys have been used in Northern 

Michigan to make producers out of otherwise dry holes. Wells 

which are drilled in thick, tight, salt-plugged reefs may have 

encountered a very restricted, tight facies. The borehole gravity survey can be used to detect nearby porosity. Such porosity 

zones can be entry beds to the main reservoir. The basis for 

qualitative interpretation is to determine the sidewall lithology 

and then evaluate which rock parameters could vary laterally to change bulk density. Porosity changes produce distinct 

low density deflections on gravity log plots. The bases for 

quantitative evaluations are the results of computer models 

or of simple cylindrical models. The maximum distance to 

a porous zone can be calculated using a cylindrical or ringshaped model. 

96. Rische, Hans, 1957, Dichtebestimmungen im Gesteinsverband

durch Gravimeter und Drehwaagemessungen unter Tage:

Freiberger Forschungshefte, C35, 84 p.

This report is referenced under Theory, where 

the abstract is also located.

210. Robbins, S.L., 1979, Density determinations from borehole 

gravity data from a shallow lignite zone within the Denver 

Formation near Watkins, Colorado: Society of Professional Well Log Analysts, 20th Annual Logging Symposium Transactions, p. JJ1-JJ20. 

Two 50- to 55-meter-deep test holes near Watkins, Colorado, penetrate through an 8-meter-thick lignite zone within 

the Upper Cretaceous and Paleocene Denver Formation. 

These test holes were surveyed using a borehole gravity meter 

and the principal facts along with a summary of datainterpretation relationships and data accuracies are presented. 

Conclusions derived from the BHGM data and comparisons 

of these data with gamma-ray and gamma-gamma logs are 

as follows: (1) The lignite densities are in the 1.3- to 

1.4-g/cm3 range, with differences between the BHGM density values and gamma-gamma density values for these zones 

ranging from 0.2 to 0.3 g/cm3 higher for the gamma-gamma 

values. (2) These differences are probably caused by both 

mud invasion into parts of the lignite seams and a (Z/A) ratio 

in the gamma-gamma log reduction that is too low. (3) 

Porosities for the clastic sediments are between 27 and 42 

percent. (4) Water saturation of these sediments above the 

water table at the time of the survey was about 70 percent. 

(5) Since the gamma-ray logs proved to be a poor method 

in this area for ash content determination and the density 

values from the gamma-gamma logs were too high, care must 

be used when interpreting logs from radiation sensitive tools 

in wells containing organic material.

99. ____1986a, The use of borehole gravimetry in water 

well and waste disposal site evaluations [abs.], in Surface 

and borehole geophysical methods and ground water 

instrumentation A conference and exposition: National 

Water Well Association Program, Denver, Colorado, 

October 15-17.

This report is referenced under Theory, where 

the abstract is also located.

100. ____1986b, The use of borehole gravimetry in water well

53
and waste disposal site evaluations, in Proceedings of the 

surface and borehole geophysical methods and ground 

water instrumentation conference and exposition: Dublin, 

Ohio, National Water Well Association, p. 474-486.

This report is also referenced under Theory. 

The abstract is under Theory, entry 99.

211. Robbins, S.L., Kunk, J.R. and Bjornstad, B.M., in press, 

Three-dimensional density modeling from borehole gravity 

surveys in late Cenozoic sediments at the Hanford Site, 

Washington: Journal of Geophysical Research. 

Nine boreholes that penetrate the suprabasalt sediments

at the Hanford Site, Washington, were surveyed by borehole 216.

gravity meters so that accurate densities could be obtained.

The boreholes are in an area designated as the Reference

Repository Location which lies within the Cold Creek syncline

in the western Pasco Basin in the western Columbia Plateau. 

The density layers in the four two-dimensional profiles

presented here were determined by a technique that has not

been previously described. 

Observations about the geologic character of the sediments

based on interpretation of the profiles [are] include[d] ***.

212. Rogers, G.R., 1952, Subsurface gravity measurements:

Geophysics, v. 17, no. 2, p. 365-377.

Gravity data were obtained at approximately 100-foot intervals in a vertical mine shaft 2,916 feet deep [in Arizona]. 

The shaft passed through a region of high positive density 

contrast, and a local anomaly was observed of plus 14.0 gravity units to minus 17.9 gravity units. Calculations for Bouguer 

densities were carried out with the gravity measurements. A 

theoretical sphere that closely approximates the observed data 

and known conditions is derived from the gravity data.

213. Schaefer, D.S., in press, Geophysical techniques to determine hydrologic parameters and specific basin studies in 

the Great Basin, Nevada and Utah: U.S. Geological Survey 

Professional Paper.

Reference is made in this paper to BHGM 217 

surveys in three shallow wells within Nevada. See 

report 238 for the principal facts to these surveys.

214. Schmoker, J.W., 1977a, Density variations in a quartz diorite 

determined from borehole gravity measurements, San 

Benito County, California: The Log Analyst, v. 18, no. 

2, p. 32-38.

In situ bulk densities were determined in the Stone Canyon 

Experimental No. 1 well, San Benito County, California, using the U.S. Geological Survey-LaCoste and Romberg 

borehole gravity meter. The well penetrates granitic rocks 218. 

of the Gabilan Range which are highly fractured, presumably 

from the tectonic effects of the nearby San Andreas fault. 

Densities measured in the well varied by .30 g/cm3 . A particularly disturbed zone between 497 and 673 ft (151-205 m) 

was found. The borehole gravity method for determining in 

situ density variations appears particularly useful in highly 

fractured rocks such as these found in the Stone Canyon well.

215. ____1977b, A borehole gravity survey to determine density variations in the Devonian shale sequence of Lincoln 

County, West Virginia: U.S. Department of Energy, 

Energy Research Center, MERC/CR-77/7, 15 p. 

In situ bulk densities of the Devonian shale section 

penetrated by the Columbia Gas Transmission Corp. 20402 

well, Lincoln County, West Virginia, were determined using

the U.S. Geological Survey-LaCoste and Romberg borehole 

gravity meter. Densities from two gamma-gamma logs, run 

by different companies, were also available. A cumulative 

difference of .034 g/cm3 /l,000 ft (.112 g/cm3 /km) exists 

between the two gamma-gamma logs. The two intervals of 

lowest density derived from the borehole gravity data show 

higher densities on both gamma-gamma logs, possibly indicative of the deeper investigation radius of the borehole 

gravity meter. In most intervals, higher gamma-ray intensity correlates with lower density, indicating that organic content is the primary variable affecting both bulk density and 

uranium concentration.

____1979, Interpretation of borehole gravity surveys in a 

native-sulfur deposit, Culberson County, Texas: Economic 

Geology, v. 74, p. 1462-1470.

Borehole gravity surveys to determine formation densities 

were conducted by the U.S. Geological Survey in four exploratory wells penetrating the native-sulfur deposit at the 

Duval Culberson property, Culberson County, Texas. The 

borehole gravity meter has a depth of penetration comparable 

to the recovery radius of the Frasch process for mining sulfur, 

which is an advantage for evaluating the sulfur content of 

heterogeneous deposits. Mineralized zones are treated as 

three-component systems bioepigenetic limestone, interstitial sulfur, and water-filled pores. A ternary diagram 

relating combinations of these components to borehole gravity densities, together with empirical data relating sulfur content and water-filled porosity, are used to estimate sulfur 

volumes from the borehole gravity data. Estimated sulfur 

contents range from 0 to 33 percent. Comparisons with the 

amount of sulfur observed in core and cuttings from the four 

study wells and from surrounding wells show both the positive 

benefits of a greater range of investigation and the negative 

effects of relying solely on formation density as a measure 

of sulfur volume. Estimates of sulfur content based on 

borehole gravity data can supplement conventional analyses 

of core, as well as standard geophysical surveys of boreholes. 

____1980, Effect upon borehole gravity data of salt structures typical of the WIPP Site (northern Delaware Basin), 

Eddy County, New Mexico: U.S. Geological Survey Oil 

and Gas Investigations Chart OC-109.

This report presents the feasibility of detecting 

and defining salt structures at the WIPP site with 

borehole gravimetry. Since the gravity signal due 

to salt structures is small and falls off rapidly 

with distance, the meter is not very effective here.

Schmoker, J.W., and Halley, R.B., 1982, Carbonate porosity 

versus depth A predictable relation for South Florida: 

American Association of Petroleum Geologists Bulletin, 

v. 66, no. 12, p. 2561-2570.

This study examines the porosity of limestones and dolomites in the South Florida basin. Porosity data are derived 

from borehole-gravity measurements and from suites of 

acoustic, neutron, and density logs. ***. Investigation depths 

range from the surface to about 18,000 ft (5,500 m) and span 

the transition from high-porosity near-surface carbonate 

sediments of Pleistocene age to much denser Mesozoic carbonate rocks with porosities of only a few percent.

Carbonate porosity in the South Florida basin was affected 

by a variety of diagenetic processes. *** The basin contains 

little clastic material; present depths of burial are about equal

54
to maximum depths of burial; the influences of tectonism, 

geopressures, and hydrocarbon accumulations are minimal.

Curves of porosity versus depth, reflecting large-scale 

porosity-loss processes in the subsurface, are derived for a 

composite carbonate section and for carbonate strata of different ages and compositions. The decrease of porosity with 

depth for a composite carbonate section representing a wide 

range of depositional environments and subsequent diagenetic 

histories can be characterized by the exponential function 

0 = 41.73e -z/8197 (ft) [<j> = 41.73e ~z/2498 (m)], where <j> is 

the porosity (%) and z is the depth below ground level (feet 

or meters). Average porosity is reduced by a factor of two 

in a depth interval of about 5,700 ft (1,740 m).

Carbonate strata of different ages that are buried to equal 

depths show no systematic porosity differences. This implies 

that the effect of time on porosity in these rocks is probably 

subordinate to that of burial depth. The data also show a 

faster than expected rate of porosity decrease with depth for 

rocks of Eocene age and younger. If it is assumed that the 

decrease in the volume of evaporites in these rocks indicates 

less saline pore fluids, porosity loss in shallow-water carbonates may be inversely related to the magnesium content 

of pore waters.

Dolomite porosity is lower than limestone porosity in the 

near surface, but does not decrease as rapidly with depth. 

Below about 5,600 ft (1,700 m), dolomite is more porous than 

limestone. It is hypothesized that most dolomitization occurred relatively early and either reduced original porosity 

or selectively favored lower-porosity limestones. With continued burial, dolomite was more resistant than limestone 

to associated porosity-reducing effects. 

104. Sissons, B.A., 1981, Densities determined from surface and

subsurface gravity measurements: Geophysics, v. 46, no.

11, p. 1568-1571.

This report is referenced under Theory, where 

the abstract is also located.

110. Stacey, F.D., Tuck, G.J., Holding, S.C., Maher, A.R., and 

Morris, D., 1981, Constraint on the planetary scale value 

of the Newtonian gravitational constant from the gravity 

profile within a mine: Physical review D, v. 23, no. 8, 

p. 1683-1692.

This report is referenced under Theory, where 

the abstract is also located.

219. Sumner, J.S., and Schnepfe, R.N., 1966, Underground gravity surveying at Bisbee, Arizona, in Mining Geophysics, v. 

1, Case histories: Society of Exploration Geophysicists, 

Tulsa, Oklahoma, p. 243-251.

During the past fifteen years, Phelps Dodge Corporation 

has actively used underground gravity surveying at Bisbee, 

Arizona. The method has proven to be quite useful for purposes of locating and assisting in the development of massive 

sulfide bodies within the district. Host rocks for replacement 

sulfides are fairly uniform in density, being in the range 2.65 

to 2.70 gm/cm3 . Average densities of sulfide bodies reach 

as high as 4.00 gm/cm3 , providing a strong density contrast. 

In development of the gravity station network it was 

necessary to make extensive topographic corrections in order 

to compensate for nearby and overlying mountainous terrain. 

Because of the complex nature of the mine workings, 

results are interpreted quantitatively without regard to corrections for underground openings. ***

Raw gravity readings are corrected and reduced by applying the free air correction, the Bouguer correction, a combined correction, and a "sigma" correction. ***

Residual gravity values are plotted on level plan maps and 

these values are contoured. ***

Vertical sections of gravity data are prepared from level 

maps. These sections are contoured and then interpreted to 

give a measure of "apparent density" by relating vertical 

gravity gradient to density, using the departure from the

assumed Bouguer density value. ***

***

220. Tucci, Patrick, 1981, Density of basin-fill deposits calculated 

from borehole gravity data in four basins in central and 

southern Arizona [abs.]: Eos, v. 62, no. 45, p. 863. 

In situ density values for basin-fill deposits in four basins 

in Arizona were calculated from borehole gravity 

measurements in six wells the first such measurements for 

hydrologic investigations in the State. Density values ranging from 1.73 to 2.46 grams per cubic centimeter were 

calculated from the 300 to 600 meters of basin fill that were 

logged. Density values are similar to those obtained from 

gamma-gamma logs and samples of basin fill in Arizona and 

from borehole gravity data from Nevada. The values obtained 

from borehole-compensated gamma-gamma logs below the 

water table are slightly less than and those above the water 

table slightly more than the borehole gravity values.

From two to four distinct density layers, defined by the 

density plots, are present in the basins. Shape of the plot and 

density range of the layers differ from basin to basin and 

may differ within a basin. A general depth-density curve, 

based on the borehole gravity data, may be used to approximate the depth-density relation in basins where subsurface 

data are sparse.

Porosity calculated from the borehole gravity data depends 

to a large extent on the gain density of the basin fill. Porosity of the saturated density layers ranges from 17 to 33 

percent, assuming a grain density of 2.65 grams per cubic 

centimeter. A comparison between basin-fill density and hydraulic conductivity generally indicates that lithologically similar high-density deposits have a low hydraulic conductivity.

221. Tucci, Patrick, Schmoker, J.W., and Robbins, S.L., 1982, 

Borehole-gravity surveys in basin-fill deposits of central 

and southern Arizona: U.S. Geological Survey Open-File 

Report 82-473, 23 p.

Principal facts and density estimates are provided from borehole gravity surveys in six wells 

in Avra, Butler, and Vekol Valleys and the Tucson basin, Arizona. A brief discussion of density comparisons in basin-fill deposits is provided 

along with some porosity averages and ranges 

below the water table.

222. ____1983, Density of basin-fill deposits calculated from 

borehole gravity data in four basins in central and southern 

Arizona: Society of Exploration Geophysicists 53d Annual 

Meeting, Las Vegas, Nevada, Expanded Abstracts with 

Biographies, September 11-15, p. 28-31. 

In situ density value for basin-fill deposits in four Arizona 

basins were computed from borehole-gravity measurements. 

The measurements were made in the upper 300 to 600 meters 

of six wells, the first such measurements for hydrologic investigations in the State. Calculated density values range from

55
1.73 to 2.46 g/cm3 . These densities are similar to reported 

values derived from conventional gamma-gamma logs and 

samples of basin fill in Arizona, and from borehole gravity 

data in Nevada. Densities obtained from gamma-gamma logs 

in the wells logged here tend to be lower than borehole gravity 

values below the water table, and higher than borehole gravity 

values above the water table.

***. The thicknesses, depths, and densities of the layers 

vary from basin to basin and within basins. In general, densities of the basin fill increase with depth from the surface 

to about 240 m, and then remain approximately constant or 

even decrease with additional depth. A composite plot of 

density versus depth presented here can be used to estimate 

density in basins where subsurface data are lacking.

Porosity values calculated from the borehole gravity data 

range from 17 to 33 percent, assuming a grain density of 

2.65 g/cm3 . In some instances when other geologic factors 

remain approximately constant, porosity shows a positive correlation with hydraulic conductivity and so is related to potential aquifer production.

223. ____1984, Density of basin-fill deposits calculated from 

borehole gravity data in four basins in central and southern 

Arizona [abs.]: Geophysics, v. 49, no. 5, p. 595.

Same abstract as report 222.

224. Whetton, J.T., Myers, J.O., and Smith, R., 1957, Correlation of rock density determinations for gravity survey interpretation: Geophysical Prospecting, v. 5, no. 1, p. 20-43. 

The results of field and laboratory methods of density 

determination on a series of Coal Measure, Permian and 

Triassic rocks are presented and the different methods compared. It is concluded that the most satisfactory method is 

that of measuring the vertical change of gravity in a mine 

shaft. Nettleton's method is unsatisfactory to us, due to 

weathering of the rocks (particularly Magnesian Limestone) 

and possible effects from drift. Laboratory measurements 

are of variable value depending on the lithology and source 

of the samples.

A method adopted to solve the problem of finding the true 

densities for use in a local gravity survey in N.E. England 

is given.

Reports Containing Only Basic Gravity Data and 

Reductions with some Preliminary Density and 

Porosity Determination

225. Beyer, L.A., 1980, Narrative and basic data of the U.S. 

Geological Survey borehole gravity program (1963-1975): 

U.S. Geological Survey Open-File Report 80-903, 76 p.

This report describes the development of the 

first reliable and durable high-precision borehole 

gravity meter. Also included are basic borehole 

gravity data for 21 surveys made in California 

and Wyoming between 1968 and 1975.

226. Beyer, L.A., Robbins, S.L., and Clutsom, F.G., 1985, Basic 

data and preliminary density and porosity profiles for 

twelve borehole gravity surveys made in the Los Angeles, 

San Joaquin, Santa Maria and Ventura Basins, California: U.S. Geological Survey Open-File Report 84-42, 66 p.

This report presents a brief summary of the borehole gravity method, a description of the data reduction and error 

estimate procedures, and preliminary density and porosity 

profiles for twelve borehole gravity surveys made in California by the U.S. Geological Survey. A brief description of the 

geologic setting and petroleum field characteristics for each 

surveyed well is also included.

227. Byerley, K.A., and Schmoker, J.W., 1977, Density and 

porosity estimates from borehole gravity data in the Castle 

Pines #1, 2, and 3 water wells, Douglas County, Colorado: 

U.S. Geological Survey Open-File Report 77-875, 17 p.

This report presents the basic gravity data plus 

reduction corrections and includes density and 

porosity determinations. SP and resistivity curves 

are also presented for the lower sections of wells 

3, and 2.

228. Healey, D.L., Clutsom, F.G. and Glover, D.A., 1984, Borehole gravity meter surveys in drill holes USW G-3, 

UE-25p#l and UE-25c#l, Yucca Mountain area, Nevada: 

U.S. Geological Survey Open-File Report 84-672, 16 p. 

[This report presents the basic BHGM data plus reduction 

corrections and includes the interval densities.] Free-air gradient (FAG) measurements were made at UE-25p#l and 

UE-25c#l. The BHGM data in these two holes were reduced 

using the measured FAG values. *** The measured FAG 

values are 0.8 and 0.97 percent higher and the calculated densities are 0.07 and 0.04 mg/m3 higher than values calculated 

using the "normal" value. These calculated differences in 

density are not insignificant and indicate the need to measure 

the FAG at each logged hole.

229. ____1986, Borehole gravity meter survey in drill hole USW

G-4, Yucca Mountain area, Nye County, Nevada: U.S.

Geological Survey Open-File Report 86-205, 18 p.

Drill hole USW G-4 was logged with the U.S. Geological 

Survey borehole gravity meter (BHGM) BH-6 as part of a 

detailed study of the lithostratigraphic units penetrated by 

this hole. *** USW G-4 is an especially important hole 

because of its proximity to the proposed exploratory shaft 

at Yucca Mountain.

The BHGM data were reduced to interval densities using 

a free-air gradient (F) of 0.3083 mGal/m (0.09397 mGal/ft) 

measured at the drill site. The interval densities were further 

improved by employing an instrument correction factor of 

1.00226. This factor was determined from measurements obtained by taking gravity meter BH-6 over the Charleston Peak 

calibration loop.

The interval density data reported herein should be helpful 

for planning the construction of the proposed shaft.

230. Kososki, B.A., and Robbins, S.L., 1979, In situ bulk density and porosity estimates from borehole gravity data in 

the Madison Limestone test well no. 1, Crook County, 

Wyoming: U.S. Geological Survey Open-File Report 

79-1514, 14 p.

This report presents the basic gravity data plus 

reduction corrections for the well and includes 

density and porosity determinations. A generalized stratigraphic section is also included.

231. ____1980a, In situ bulk-density estimates from borehole 

gravity data in the Madison Group test well no. 3, Yellowstone County, Montana: U.S. Geological Survey OpenFile Report 80-784, 11 p.

56
This report presents the basic gravity data plus 

reduction corrections for the well and includes 

density determinations. A generalized stratigraphic section is also presented.

232. ___1980b, In situ bulk-density estimates from borehole 

gravity data from the Madison Group test well no. 2, 

Custer County, Montana: U.S. Geological Survey OpenFile Report 80-982, 11 p.

This report presents the basic gravity data plus 

reduction corrections for the well and includes 

density determinations. A generalized stratigraphic section is also included.

233. Kososki, B.A., Robbins, S.L., and Schmoker, J.W., 1978a, 

Principal facts for borehole gravity stations in stratigraphic 

test well ERDA no. 9, Eddy County, New Mexico: U.S. 

Geological Survey Open-File Report 78-696, 11 p.

This report presents the basic gravity data plus 

reduction corrections for the well. A gamma-ray 

log and a generalized stratigraphic section also 

are reproduced.

234. ___1978b, Principal facts for borehole gravity stations 

in test well Uel9z, exploratory drill hole PM-1, and water 

well 5a, Nevada Test Site, Nye County, Nevada: U.S. 

Geological Survey Open-File Report 78-983, 16 p.

This report presents the basic gravity data plus 

reduction corrections. Gamma-ray curves and 

generalized stratigraphic sections are also 

presented.

235. Robbins, S.L., and Clutsom, F.G., 1983, Principal facts and 

density estimates for borehole gravity stations in exploratory wells Ue7h, Ue4al, and Uella at the Nevada Test 

Site, Nye County, Nevada: U.S. Geological Survey OpenFile Report 83-244, 20 p.

This report presents the basic gravity data plus 

reduction corrections (including instrument drift 

correction curves). Density determinations and 

generalized stratigraphic sections are also 

presented.

236. Robbins, S.L., Kunk, J.R., and Clutsom, F.G., 1983, Principal facts and density estimates for borehole gravity stations in boreholes RRL-3, -4, -5, -6B, -7, -8, and -9 at 

the Hanford Site, Benton County, Washington: U.S. 

Geological Survey Open-File Report 83-386, 39 p.

This report presents the basic gravity data plus 

reduction corrections (including instrument drift 

correction curves). Density determinations, 

gamma-ray curves, and generalized stratigraphic 

sections are also included.

237. Robbins, S.L., Martinez, R.J., and Smith, D.L., 1979, Principal facts for borehole gravity stations in wells DC-3, 

DC-5, and DC-7 at the Hanford Works, Washington, and 

in well RSH #1 on Rattlesnake Hills Ridge, Washington: 

U.S. Geological Survey Open-File Report 79-849, 27 p.

This report presents the basic gravity data plus

reduction corrections (including instrument drift 

correction curves). Gamma-ray and CCL logs are 

also included.

238. Robbins, S.L., Prudic, D.E., Schaefer, D.H., and Clutsom, 

F.G., 1983, Principal facts and density estimates for 

borehole gravity stations in three water wells located in 

Dixie and Paradise Valleys, Nevada: U.S. Geological 

Survey Open-File Report 83-426, 20 p.

This report presents the basic gravity data plus 

reduction corrections (including instrument drifts 

correction curves). Density determinations, 

gamma-ray curves, and generalized lithologic 

sections are also presented.

239. Robbins, S.L., Schmoker, J.W., and Hester, T.C., 1982, 

Principal facts and density estimates for borehole gravity 

stations in exploratory wells Ue4ah, Ue7j, Uelh, Uelq, 

Ue2co, and USW-H1 at the Nevada Test Site, Nye County, Nevada: U.S. Geological Survey Open-File Report 

82-277, 33 p.

This report presents the basic gravity data plus 

reduction corrections (including instrument drift 

correction curves). Density determinations and 

generalized stratigraphic sections are also 

presented.

240. Schmoker, J.W., 1976, Principal facts for borehole gravity 

stations in the Columbia Gas #20402 well, Lincoln County, West Virginia: U.S. Geological Survey Open-File Report 

76-593, 5 p.

This report presents the basic gravity data plus 

reduction corrections for the well.

241. Schmoker, J.W., and Kososki, B.A., 1977, Principal facts 

for borehole gravity stations in the Columbia Gas Transmission Corp. 4771 well, Kanawha County, West Virginia: 

U.S. Geological Survey Open-File Report 77-267, 6 p.

This report presents the basic gravity data plus 

reduction corrections. A gamma-ray log is also 

presented.

242. ___1978, Principal facts for borehole gravity stations in 

test wells UelOj, Ue7ns, and Ue5n, Nevada Test Site, Nye 

County, Nevada: U.S. Geological Survey Open-File Report

78-212, 11 p.

This report presents the basic gravity data plus 

reduction corrections. Gamma-ray curves are 

shown for wells UelOj, and Ue7ns.

243. Schmoker, J.W., and Robbins, S.L., 1979, Borehole gravity surveys in native sulfur deposits, Culberson and Pecos 

Counties, Texas: U.S. Geological Survey Open-File Report

79-361, 22 p.

This report presents the basic gravity data plus 

reduction corrections. Density determinations 

and gamma-ray curves are also included. Temperatures for well C-211 are also listed.

244. Schmoker, J.W., Halley, R.B., Meyer, F.W., and Robbins, 

S.L., 1979, Preliminary porosity estimates of south Florida

57
Cenozoic carbonate rocks based on borehole gravity Virginia: U.S. Geological Survey Open-File Report 77-852, 

measurements: U.S. Geological Survey Open-File Report 10 p.

79-1652, 17 p. jjj-g rep0rt presents the basic gravity data plus

This report presents density and porosity deter- reduction corrections. It also includes gammaminations from five wells situated along a more ray logs for the wells.

or less north-south profile in southern Florida. 246- Secor- G-B" Jr-> Meyer' H-J- and Hinze' W-J- 1963 ' A

Lithologic information is also Summarized. demity d^ermination by underground gravity measurements in Michigan: Geophysics, v. 28, no. 4, p. 663-664. 

245. Schmoker, J.W., Robbins, S.L., Clutsom, F.G., and Martinez, R.J., 1977, Principal facts for borehole gravity sta- This report presents density determinations for

tions in the Columbia Gas Transmission Corp. 4982,5016, three locations in and adjacent to the Detroit Salt

and 6871 wells, Jackson and Kanawha Counties, West Mine, Michigan.

58
AUTHOR INDEX

Author Report number Author Report number

A, B

Airy, G.B. ................... 1

Al-Khafaji, S.A. ............. 2, 3

Alexander, M. ............... 135

Algermissen, S.T. ............ 150

Alien, W.A. '................. 4

Baker, G.E. ................. 120

Barry, A. .................... 136, 137

Benfield, A.E. ............... 5

Beyer, L.A. .................. 6-13, 121, 151-159, 225, 226

Bhattacharji, J.C. ............ 160

Bichara, M. ................. 73

Bjornstad, B.N. .............. 211

Black, A.J. .................. 14,15,16,73,122,123,124, 125

Blizkovsky, M. ............... 17

Bodemiiller, H. .............. 18

Bradley, J.W. ................ 19, 20, 161, 162, 186

Brown, A.R. ................. 21, 22, 23, 186

Brune, R.H. ................. 13

Butler, David ................ 181

Byerley, K.A. ................ 126, 227

C, D

Carlson, R.C. ................ 51, 52, 55, 56, 58, 59

Casten, Uwe ................. 24

Caton, P.W. ................. 25, 127, 128

Chan, K.C. .................. 72

Chandra Reddy, P. ........... 86, 199, 200

Clark, S.R. .................. 55, 56, 163, 164, 165, 166

Clement, W.G. ............... 22, 23, 127, 128

Clutsom, F.G. ............... 129, 130, 157, 158, 159, 226,

228, 229, 235, 236, 238, 245 

Collins, D.S. ................. 202, 203

Cook, A.M. ................. 167

Corbato, C.E. ............... 12

Coyle, L.A. ................. 26

Davidson, R.R. .............. 203

Davis, T.L. .................. 194, 195

Dean, V.C. .................. 192, 193, 194, 195

Dolbear, D.W. ............... 131

Domzalski, W. ............... 27, 28, 168

Drake, R.E. ................. 169

Duda, W. ................... 34, 179

E-G

EDCON ..................... 29

Egyed, Lazlo ................ 30

Facsinay, Laszlo ............. 170

Fajklewicz, Zbigniew ......... 31-35, 171-179

Farlay, D.G. ................. 180

Fausset, N.E. ................ 181

Fay, C.H. ................... 133

Garland, G.D. ............... 36

Garner, C.O. ................ 22, 23

Ghyasuddin, Mohd. .......... 199, 200, 201

Gibb, R.A. .................. 182

Gilbert, R.L.G. .............. 132

Gliriski, A.L.R. .............. 35, 37, 38

Glover, D.A. ................ 228, 229

Goldman, T. ................. 145

Goodell, R.R. ................ 133

Gournay, L.S. ............... 39, 40, 41, 42

Gutschick, V.P. .............. 145

H-J

Haaz, R.H. .................. 170

Halley, R.B. ................. 183, 218, 244

Hammer, Sigmund ........... 43, 44, 143

Hanemann, K.-D. ............ 74

Head, W.J. .................. 184

Healey, D.L. ................ 185, 228, 229

Hearst, J.R .................. 45-59, 163-166

Heintz, K.O. ................. 135, 136, 137

Herman, M.C. ............... 207

Herring, A.T. ................ 16, 124, 125, 138

Hester, T.C. ................. 239

Hilterman, F.J. .............. 194, 195

Hinze, W.J. ................. 186, 246

Holding, S.C. ................ 110

Howell, L.G. ................ 136, 137

Hussain, A. ................. 187, 188, 189, 190

Innes, M.J.S. ................ 84

Jageler, A.H. ................ 60, 61, 62

Jones, B.R. .................. 63

Jung, Heinrich ............... 191

K, L

Kandle, J.R. ................. 83

Karl, J.H. ................... 64

Kasameyer, P.W. ............. 57

Kaziniskii, V.A. .............. 65

Kososki, B.A. ................ 184, 230-234, 241, 242

Kunk, J.R. .................. 211, 236

Labo, J.A. .................. 66

LaCoste, L.J.B. .............. 142

LaFehr, Ed .................. 67, 68

LaFehr, T.R. ................ 69-73, 138, 192-195

Laurin, P.J. ................. 73

Lautzenhiser, T.V. ........... 21, 139, 140

Lindner, H. ................. 74

Lukavchenko, P.I. ........... 75, 76, 119, 141

Lyle, W.D. .................. 40, 41

M

Maker, A.R. ................. 110

Martinez, R.J. ............... 237, 245

Maute, R.E. ................. 42

McCalpin, G.A. .............. 77, 78

McCulloh, T.H. .............. 79, 80, 81, 82, 83, 142, 143, 196

McKague, H.L. .............. 53

McLean, A.C. ............... 197

Merkel, R.H. ................ 107, 138

59
Author Report number Author Report number

Meyer, F.W. ................. 244

Meyer, H.J. ................. 246

Miles, D.R. .................. 198

Miller, A.H. ................. 84

Mobil Oil Corp. .............. 144

Morris, D. ................... 110

Mudrecova, E.A. ............. 85

Murty, B.V.S. ............... 86, 199, 200, 201

Myers, J.O. ................. 224

N-R

Nelson, P.M. ................ 54

Nichols, T.C. ................ 202, 203

Nieto, M.M. ................. 145

Nur, Amos .................. 67, 68

Oelsner, Christian ............ 87

Oil and Gas Journal .......... 146

Overton, A. ................. 88

Owen, L.E. .................. 57

Pampeyan, E.H. ............. 142, 143

Parks, H.B. ................. 143

Picha, Jan ................... 204

Plouff, Donald ............... 205

Poynting, J.H. ............... 89

Pritchett, W.C. .............. 90, 91, 206

Prudic, D.E. ................. 207, 238

Rasmussen, N.F. ............. 22, 23, 92, 93, 94, 95, 208, 209

Rejman, T. .................. 179

Rische, Hans ................ 96

Robbins, S.L. ................ 97-102, 147, 148, 210, 211,

221-223, 226, 230-239, 243-245 

Rogers, G.R. ................ 212

Schaefer, D.H. ............... 213, 238

Schmoker, J.W. .............. 13, 58, 59, 103, 149, 183,

214-218, 221-223, 227, 233, 234, 

239-245 

Schnepfe, R.N. .............. 219

Schoellhamer, J.E. ........... 83, 142, 143

Schubert, H. ................. 74

Schultz, A.K. ................ 2, 3

Secor, G.B. .................. 246

Sissons, B.A. ................ 104

Sliz, Janusz .................. 35

Smith, D.L. ................. 237

Smith, N.J. .................. 105

Smith, R. ................... 224

Snyder, D.D. ................ 106, 107

Society of Exploration

Geophysicists .... 108

Stacey, F.D. ................. 109, 110

Stewart, R.M. ............... Ill

Sumner, J. S. ................ 219

Swain, C.J. .................. 112

T-Z

Thirlaway, H.I.S. ............ 167

Thomas, M.D. ............... 182

Thyssen-Bornemisza, Stephen .. 113, 114, 115, 116, 117 

Tucci, Patrick ................ 220, 221, 222, 223

Tuck, G.J. .................. 109, 110

Vaschilov, U.N. .............. 118

Venkat Reddy, P. ............ 199, 200, 201

Walach, G. .................. 189, 190

Weber, F. ................... 190

Whetton, J.T. ............... 224

Witterholt, E.J. .............. 127, 128

Zagonov, A.V. ............... 119

60
TITLE INDEX

Report 

number

149.

118.

139, 140.

116.

70. 

26.

13. 

84.

83.

161, 162. 

67, 68. 

2, 3. 

180. 

14, 15.

226.

153. 

97.

48.

49.

106.

93.

22, 23. 

66. 

88.

73.

Title

Account of pendulum experiments undertaken in the 

Harton Colliery for the purpose of determining the 

mean density of the earth

Accuracy of borehole gravity data

Allowance for the effects of the relief of the locality in 

gravimeter observations in underground workings and 

boreholes

Amoco/Lacoste and Romberg automated borehole 

gravity meter

(The) anomalous free air vertical gradient in borehole 

exploration

Apparent density from borehole gravity surveys

(The) application of borehole gravimetry to remote 

sensing of anomalous masses

Application of borehole gravity to exploration for 

petroleum

Application of gravimeter observations to the determination of the mean density of the earth and of rock densities in mines

Application of gravity measurements in wells to problems 

of reservoir evaluation

(The) application of the borehole gravimeter to the 

evaluation and exploration of oil and gas reservoirs

Application of the borehole gravity meter to thermal 

recovery

Application of the borehole gravity meter (BHGM) to 

hydrocarbon exploration

Application of the downhole gravity meter for porosity 

determination

Application of well log density data from borehole gravity and gamma-gamma measurements to geophysical 

exploration

B

Basic data and preliminary density and porosity profiles 

for twelve borehole gravity surveys made in the Los 

Angeles, San Joaquin, Santa Maria and Ventura 

basins, California

Benefits of borehole gravity studies in the San Joaquin 

basin, and suggested future work

Bibliography with abstracts of subsurface gravimetry 

(especially borehole) and corresponding in-situ rock 

density determinations

BIFUR II, a program for calculating borehole gravity 

caused by two-dimensional structure

BIFUR III, a program for calculating borehole and surface gravity caused by two-dimensional structure in 

cartesian or cylindrical coordinates

(The) borehole Bouguer gravity anomaly Application 

to interpreting borehole gravity surveys

Borehole gravimeter finds bypassed oil, gas

Borehole gravimeter logging fundamentals

Borehole gravimeter principles

Borehole gravimetry

Borehole gravimetry; an application example to 

engineering

Report 

number Title

81. Borehole gravimetry; new developments and applications 

192, 193. Borehole gravity case history of the Mors Salt Dome,

Denmark

127, 128. Borehole gravity logging developments; a status report 

102. Borehole gravity measurements, data reduction, and

precision A review and update of U.S. Geological

Survey methods

133. Borehole gravity meter and its application 

29. Borehole gravity meter manual 

229. Borehole gravity meter survey in drill hole USW G-4,

Yucca Mountain area, Nye County, Nevada 

228. Borehole gravity meter surveys in drill holes USW G-3,

UE-25p#l and UE-25c#l, Yucca Mountain area,

Nevada 

152. Borehole gravity study of the density and porosity of

selected Frontier, Tensleep, and Madison reservoirs

in the Big Horn Basin, Wyoming 

157. Borehole gravity survey in the Dry Piney Oil and Gas

Field, Big Piney-LaBarge area, Sublette County,

Wyoming

215. (A) borehole gravity survey to determine density variations in the Devonian shale sequence of Lincoln

County, West Virginia

92. Borehole gravity survey planning and operations 

243. Borehole gravity surveys in native sulfur deposits,

Culberson and Pecos Counties, Texas 

11. Borehole gravity surveys; theory, mechanics, and nature

of measurements

95. Borehole gravity used together with surface gravity 

184. Borehole gravity, a new tool for the ground-water

hydrologist

124, 125. Borehole gravity; expanded operating limits and performance 

221. Borehole gravity surveys in basin-fill deposits of central

and southern Arizona

185. Calculated in situ bulk densities from subsurface gravity observations and density logs, Nevada test site and 

Hot Creek Valley, Nye County, Nevada

55, 56. Calculation of gravimetric density caused by threedimensional structure

218. Carbonate porosity versus depth; a predictable relation 

for South Florida

105. (The) case for gravity data from boreholes

19, 20. (The) commercial application and interpretation of the 

borehole gravimeter

181. Computer modeling of the theoretical borehole gravity 

response in the vicinity of the Aneth Field, Paradox 

basin

196. (A) confirmation by gravity measurements of an underground density profile based on core densities

110. Constraint on the planetary scale value of the Newtonian gravitational constant from the gravity profile 

within a mine

144. Continuous gravity gradient logging

224. Correlation of rock density determinations for gravity 

survey interpretation

61
Report 

number

104.

154.

227.

158.

159.

43.

134.

246.

210.

182.

170.

197.

220, 222,

223.

214.

18.

147.

131.

39, 42.

174.

114. 

40, 41.

163, 164.

165, 166.

115.

136, 137.

191.

Title

D

Densities determined from surface and subsurface gravity

measurements 

Density and porosity changes with depth, Sisquoc and

Monterey Formations, Santa Maria-Point Conception

region, California 

Density and porosity estimates from borehole gravity

data in the Castle Pines #3, #2, and #1 water wells,

Douglas County, Colorado

Density and porosity of oil reservoirs and overlying formations from borehole gravity measurements, Gebo

Oil Field, Hot Springs County, Wyoming 

Density and porosity of Upper Cretaceous through Permian Formations from borehole gravity measurements, Big Polecat oil and gas fields, Park County,

Wyoming 

Density determinations by underground gravity

measurements 

Density determinations by underground gravity

measurements Sequel 

(A) density determination by underground gravity

measurements in Michigan 

Density determinations from borehole gravity data in two

shallow lignite wells near Watkins, Colorado 

Density determinations of basic volcanic rocks of the

Yellowknife supergroup by gravity measurements in

mine shafts, Yellowknife, Northwest Territories 

Density determinations of rocks, based on subsurface

gravimeter measurements at different depths 

Density measurements of rocks in southwest Scotland 

Density of basin-fill deposits calculated from borehole

gravity data in four basins in central and southern

Arizona 

Density variations in a quartz diorite determined from

borehole gravity measurements, San Benito County,

California 

Der Schwereunterschied in korrespondierenden punkten

iiber und unter tage 

Description of a special logging truck built for the U.S.

Geological Survey for borehole gravity surveys 

Design considerations of a bore-hole gravimeter 

Detection of bypassed gas using borehole gravimeter and

pulsed neutron capture logs 

Detection of faults in the BD coal mine by means of

microgravity measurements

Determination of Bouguer density in shallow holes 

Determination of hydrocarbon saturation and porosity

using a combination borehole gravimeter (BHGM) and

deep investigating electric log 

Determination of subsurface geologic structure with

borehole gravimetry 

Determination of subsurface geologic structure with

borehole gravimetry; case history 

Determination of the vertical density gradient in a

borehole 

(The) development and use of a high-precision downhole

gravity meter 

Dichtebestimmung im anstehenden Gestein durch

Messung der Schwerebeschleunigung in vershiedenen

Tiefen unter Tage

Report 

number Title

96. Dichtebestimmungen im Gesteinsverband durch 

Gravimeter und Drehwaagemessungen unter Tage

36. Discussion on "Densities determined from surface and 

subsurface gravity measurements" by B.A. Sissons 

with reply by author

148. Display of features on the U.S. Geological Survey's logging truck built especially for borehole gravity surveys

21. (The) effect of dipping beds on a borehole gravimeter

survey 

31. Effect of Roof Fall zones on the accuracy of

underground microgravity measurements 

217. Effect upon borehole gravity data of salt structures

typical of the WIPP site (northern Delaware Basin),

Eddy County, New Mexico 

58, 59. Effects of terrain on borehole gravity data

145. (An) electronic gravimeter to measure g(r)

146. Esso licenses down-hole gravity meter

47. Estimation of dip and lateral extent of beds with borehole 

gravimetry

155. Estimation of reservoir porosities from borehole gravity surveys, Long Beach Unit, Wilmington Oil Field, 

California

138. Evaluation and applications of new LaCoste and 

Romberg borehole gravity meter

119. (Th£) excess density estimation of disturbing bodies from 

surface and borehole gravimetry observations with the 

use of linear programming

F-H

126. (A) field test for borehole gravity meter precision in

shallow wells 

108. Focusing on SEG continuing education; borehole gravity

surveys

12. (A) Fortran IV computer program for calculating borehole gravity terrain corrections 

107. Generalized correction for dipping beds for the borehole

gravity meter

109. Geophysical evidence for non-Newtonian gravity 

179. Geophysical measurements of density in closely neighboring mine shafts

213. Geophysical techniques to determine hydrologic parameters and specific basin studies in the Great Basin, 

Nevada and Utah 

167. (A) gravimeter survey in the Bristol and Somerset coal

fields

186. Gravimeter surveys in the Michigan Basin deep borehole 

51. (The) gravimetric density formula for a spherical shell 

79. Gravimetric effects of petroleum accumulations A

preliminary summary

111. Gravity in the interior of the Earth 

120. Gravity instrument canister feasibility study 

94. Gravity logs promise new applications 

27. Gravity measurements in a vertical shaft 

76. Gravity measurements in boreholes 

4. (The) gravity meter in underground prospecting 

69. Gravity method 

132. Gravity observations in a borehole

62
Report 

number Title

205. Gravity profile along Roberts Tunnel, Colorado

198. (A) gravity survey in the haulage tunnel of the Henderson Mine near Berthoud Pass, Colorado

32. Grawimetria poszukiwawcza

207. Ground-water hydrology and simulated effects of pumping patterns in Paradise Valley, a stream dominated 

basin in Humboldt County, Nevada

183. High-porosity Cenozoic carbonate rocks of South 

Florida

I

123. Improved accuracy of a computer controlled borehole

gravity system and applications to reservoir flood

monitoring 

60. Improved hydrocarbon reservoir evaluation through use

of borehole gravimeter data 

25. Improved methods for reducing borehole-gravity data 

Applications and analyses of reduced gravity plots

202. In situ and laboratory geotechnical tests in the Pierre 

Shale near Hayes, South Dakota

203. In situ and laboratory geotechnical tests of the Pierre 

Shale near Hayes, South Dakota A characterization 

of engineering behavior

230. In situ bulk density and porosity estimates from borehole 

gravity data in the Madison Limestone test well no. 

1, Crook County, Wyoming

232. In situ bulk-density estimates from borehole gravity data 

from the Madison Group test well no. 2, Custer County, Montana

231. In situ bulk-density estimates from borehole gravity data 

in the Madison Group test well no. 3, Yellowstone 

County, Montana

10. (The) interpretation and application of borehole gravity surveys

151. Interpretation of borehole gravity in the southern San 

Joaquin Basin

7. (The) interpretation of borehole gravity surveys

216. Interpretation of borehole gravity surveys in a nativesulfur deposit, Culberson County, Texas

160. Investigation of the vertical gradient of gravity measured 

inside the Earth

K-M

75. K voprosu ob izmereniyakh sily tyazhesti v burovykh

skvazhinakh 

82. Mass properties of sedimentary rocks and gravimetric

effects of petroleum and natural gas reservoirs 

89. (The) mean density of the Earth 

65. (The) means of development and methods of solving

problems of underground gravimetry

52. Measurement and analysis of gravity in boreholes: 

74. Methodik zur Bestimmung der Streckenreduktion in der

Untertage-gravimetrie 

33. Mikrograwimetria gornicza

N, O

141. Nabliudeniiff s gravimetrami v burovykh skvazhina i 

shakhtakh

Report 

number Title

225. Narrative and basic data of the U.S. Geological Survey

borehole gravity program (1963-1975) 

177. Neue Perspektiven der Mikrogravimetri Teil der

Gebirgsschlagprognose 

62. New techniques in well logging 

61. New well logging tools improve formation evaluation 

64. (The) normal vertical gradient of gravity 

5. Note on the variation of gravity with depth 

171. O podziemnych Pomiarach grawimetrycznych w

zastosowaniu do gornictwa weglowego. Wyniki prac

w kopalni Miechowice 

16. Offset of borehole gravity densities due to geologic

structures 

72, 112. On "The normal vertical gradient of gravity" by J.H.

Karl (Geophysics, 48, 1011-1013) 

46. On the range of investigation of a borehole gravimeter

77. Operational and technical results from a multiwell 

borehole gravity survey

78. Operational and technical results of a multiwell borehole 

gravity survey

122. Performance characteristics of the LaCoste and Romberg

borehole gravity meter

90, 91, Physical properties of shales and possible origin of high 

206. pressures 

176. Pionome przekroje pola sily ciezkos'ci i ich zwiazek z

odksztalceniami g6rotworu 

172. Podziemne pomiary grawimetyczne w kopalniach

Gornego S'laska 

38. Podziemne wielopoziomowe zdjecia mikrograwimetryczne i ich zastosowanie w badaniu budowy geologicznej g6rotworu 

156. Porosity of unconsolidated sand, diatomite and fractured

shale reservoirs, South Belridge and West Cat Canyon

oil fields, California 

117. Possible application of the free-air vertical gradient to

marine exploration 

57. Potential uses for a high-temperature borehole

gravimeter 

244. Preliminary porosity estimates of south-Florida Cenozoic

carbonate rocks based on borehole gravity

measurements 

236. Principal facts and density estimates for borehole gravity

stations in boreholes RRL-3, -4, -5, -6B, -7, -8, and

-9 at the Hanford site, Benton County, Washington 

239. Principal facts and density estimates for borehole gravity

stations in exploratory wells Ue4ah, Uelh, Uelq,

Ue2co, and USW-H1 at the Nevada Test Site, Nye

County, Nevada 

235. Principal facts and density estimates for borehole gravity

stations in exploratory wells Ue7h, Ue4al, and Uel la

at the Nevada test site, Nye County, Nevada 

238. Principal facts and density estimates for borehole gravity

stations in three water wells located in Dixie and

Paradise Valleys, Nevada

233. Principal facts for borehole gravity stations in stratigraphic test ERDA no. 9, Eddy County, New Mexico

234. Principal facts for borehole gravity stations in test well 

Uel9z, exploratory drill hole PM-1, and water well 

5a, Nevada Test Site, Nye County, Nevada

63
Report

number Title

242. Principal facts for borehole gravity stations in test wells 

UelOj, Ue7ns, and Ue5n, Nevada test site, Nye County, Nevada

240. Principal facts for borehole gravity stations in the Columbia Gas #20402 well, Lincoln County, West Virginia

241. Principal facts for borehole gravity stations in the Columbia Gas Transmission Corp. 4771 well, Kanawha 

County, West Virginia

245. Principal facts for borehole gravity stations in the Columbia Gas Transmission Corp. 4982, 5016, and 6871 

wells, Jackson and Kanawha Counties, West Virginia

237. Principal facts for borehole gravity stations in wells 

DC-3, DC-5, and DC-7 at the Hanford Works, 

Washington, and in well RSH #1 on Rattlesnake Hills 

Ridge, Washington

34. Proba zastosowania pomiarow mikrograwimetrycznych 

dla potrzeb gornictwa weglowego

86. (The) problem of hollow space correction in subsurface 

gravity surveys

17. Processing and applications in microgravity surveys

80. (The) promise of precise borehole gravimetry in petroleum exploration and exploitation

175. Pustki poeksploatacyjne i odksztalcenia objetosciowe 

gorotworu w s'wietle pomiarow gradientu pionowego 

sily ciezkosci i jej mikro-anomalii

R

121. Recent tests of the U. S. Geological Survey LaCoste and

Romberg borehole gravimetric system 

98. Reexamination of the values used as constants in

calculating rock density from borehole gravity data 

28. Relative determination of the density of surface rocks

and the mean density of the earth from vertical gravity

measurements

50. Revealing subsurface structure with borehole gravimetry 

44. Rock densities and vertical gradient of gravity in the

earth's crust

71. Rock density from borehole gravity surveys 

178. Rock-burst forecasting and genetic research in coal-mines

by microgravity method

S,T

87. Schweremessungen unter tage

194, 195. Seismic and gravity modeling of the Mors Salt Dome, 

Denmark

35. Some applications of the underground tower gravity vertical gradient

37. Sposob uwzgledniania grawitacyjnego wplywu wyrobisk 

gorniczych w podziemnych pomiarach mikrograwimetrycznych

53. Structure elucidation with borehole gravimetry

201. Subsurface gravity measurements and density mapping 

in the Mailaram Copper Mines, Andhra Pradesh, 

India

189. Subsurface gravity measurements in a deep intra-Alpine 

Tertiary basin

Report 

number Title

24. Subsurface gravity measurements to demonstrate mininginduced changes in rock density

212. Subsurface gravity measurements

199, 200. Subsurface gravity survey in aid of mine planning and 

development; a case study from Mailaram Copper 

Mines, Andhra Pradesh, India

208, 209. (The) successful use of the borehole gravity meter in 

northern Michigan

135. Sulfur exploration with core hole and surface gravity

169. (A) surface-subsurface measurement of an anomaly in 

the vertical gradient of gravity near Loveland Pass, 

Colorado

8. Terrain corrections for borehole and tower gravity 

measurements

45. Terrain corrections for borehole gravimetry

9. Terrain corrections for borehole gravity measurements

103. Terrain effects of cultural features upon shallow borehole 

gravity data

211. Three-dimensional density modeling from borehole 

gravity surveys in Late Cenozoic sediments at the Hanford site, Washington

168. Three-dimensional gravity survey

204. Tihove zrychlenf pod povrchem zemskym v dole "Anna" 

na Brezovych Horach

U-Z

130. U.S. Geological Survey borehole gravimeter electronic 

system borehole gravimeter no. 6 mechanical drawings

129. U.S. Geological Survey borehole gravimeter no. 1 electronic system schematics

142. (The) U.S. Geological Survey-LaCoste and Romberg 

precise borehole gravimeter system Instrumentation 

and support exploration

143. (The) U.S. Geological Survey-LaCoste and Romberg 

precise borehole gravimeter system Test results

150. Underground and surface gravity survey, Leadwood, 

Missouri

173. Underground gravity measurements in the mines of 

Upper Silesia

190. Underground gravity survey in Alpine regions

219. Underground gravity surveying at Bisbee, Arizona

85. Underground gravity surveys in copper sulphide deposits 

in the central Ural Mountains

188. Underground gravity surveys

187. Untertagegravimetrie in Alpinen Gebieten mit besonder 

Beriicksichtigung des Blei-Zink-Bergbaus BleibergKreuth (Karnten)

99, 100. (The) use of borehole gravimetry in water well and waste 

disposal site evaluations

63. (The) use of downhole gravity data in formation 

evaluation

6. (The) vertical gradient of gravity in vertical and nearvertical boreholes

113. (The) vertical gravity gradient in borehole exploration

54. Well logging for physical properties

101. What is borehole gravimetry? A summary

30. Zur Frage der Schweremessungen in Bohrlochern

64

 &U.S. GOVERNMENT PRINTING OFFICE: 1989-673-047/86041