Bureau of Mines Report of lnvestigations/l987 

Accurate Directional Borehole Drilling: 

A Case Study at Navajo Dam, 

New Mexico 

By S. J. Kravits, A. Sainato, and G. L. Finfinger 

UNITED STATES DEPARTMENT OF THE INTERIOR 
UNITED STATES DEPARTMENT OF THE INTERIOR 

Donald Paul Hodel, Secretary 

BUREAU OF MINES 

David S. Brown, Acting Director 
Library of Congress Cataloging in Publication Data : 

Kravits, S. J. (Stephen J.) 

Accurate directional borehole drilling. 

(Report of investigations ; 9102) 

Bibliography: p. 18. 

Supt. of Docs. no.: 1 28.23: 9102. 

1. Directional drilling-New Mexico-Navajo Dam. I. Sainato, Albert. 11. Finfinger, 

Gerald L. 111 Title. IV. Series: Report of investigations (United States. Bureau of Mines) ; 

9102. 
CONTENTS 

Page 

Abstract ........................................................................ 1 

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

Acknowledgments ................................................................ 2 

Test site ...................................................................... 2 

Drilling equipment ............................................................. 3 

Hydraulic drill .............................................................. 3 

In-hole motor ................................................................ 3 

Borehole trajectory control devices .......................................... 5 

Surveying equipment and procedures ............................................. 9 

Single-shot survey instrument ................................................ 9 

Surveying accuracy ........................................................... 10 

Planning the borehole .......................................................... 11 

Directional drilling the demonstration borehole ................................ 13 

Effectiveness in controlling borehole trajectory ............................. 13 

Borehole punchout and investigating error in azimuth ......................... 15 

Conclusions .................................................................... 18 

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

Appendix.--Drill and borehole survey log^.........................^............ 19 

ILLUSTRATIONS 

Navajo Dam location map .................................................. 3 

Navajo Dam right abutment ................................................ 4 

Navajo Dam demonstration borehole d r i l l s i t e ............................. 4 

Hydraulic drill and control panel ........................................ 5 

In-hole motor schematic .................................................. 5 

In-hole motor operating parameters ....................................... 6 

Polycrystalline diamond cutter bits ...................................... 6 

In-hole motor equipped with a 2O bent housing ............................ 6 

Side force diagram ....................................................... 7 

Various tool face settings and their effects on borehole trajectory ...... 8 

Single-shot directional survey instrument ................................ 9 

Reading developed survey film disk ....................................... 9 

Survey hardware .......................................................... 10 

Nonmagnetic drill collar and compass spacing selection chart ............. 11 

Vertical section of planned demonstration borehole ....................... 12 

Map view of planned demonstration borehole ............................... 12 

Vertical section of demonstration borehole ....................a.e........ 13 

Plan view of demonstration borehole ..................................... 14 

Various bent housings .................................................... 14 

Borehole punchout ........................................................ 17 

TABLES 

1. Measured deflection rates using 2' bent housing .......................... 16 

A-1 . Log of directional drilling parameters ................................... 19 

A-2 . Demonstration borehole survey log and log of desired departures .......... 22 
UNIT OF MEASURE ABBREVIATIONS USED 

EMU electromagnetic unit Ibf 

f t foot mi n 

ft0lbf foot pound (force) nT 

gal/min gallon per minute psi 

hp horsepower ~sig 

in inch r/min 

in/min inch per minute V ac 

IN THIS REPORT 

pound force 

minute 

nanotesla 

pound per square inch 

pound per square inch, gauge 

revolution per minute 

volt, alternating current 
ACCURATE DIRECTIONAL BOREHOLE DRILLING: A CASE STUDY AT 

NAVAJO DAM, NEW MEXICO 

1 By S. J. Kravits,' A. Sainat~,~ and G. L. Finfinger3 

ABSTRACT 

This report describes a project conducted by the Bureau of Mines in 

which the accurate directional drilling of a borehole was demonstrated 

with the objective of intercepting a designated target. The project was 

conducted at Navajo Dam in northern New Mexico at the request of the Bureau of Reclamation. Borehole survey and drill logs are provided in an 

appendix. 

The trajectory of the demonstration borehole was designed to intercept 

a 5-ft-radius target at the final or "punchout" distance of 885 ft. The 

elevation of the borehole at this distance was within the target; the 

borehole punchout coordinates were 8.81 ft southwest of the target. As 

a result of the demonstrated accuracy, the Bureau of Reclamation has 

contracted the accurate drilling of boreholes as long as 600 ft from the 

inside of a short tunnel, to control water seepage in the right abutment. This resulted in a substantial cost savings compared to the original plan of constructing a longer tunnel and drilling 150-ft boreholes. 

' ~ining engineer. 

2~ining engineering technician. 

3~upervisory geologist. 

Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 
INTRODUCTION 

The Bureau of Reclamation, U.S. Department of the Interior, requested the Bureau of Mines, through Interagency Agreement No. 1409-0070-1212, to demonstrate 

the accuracy of directional drilling a 

near-horizontal borehole to intercept a 

designated target. The Bureau of Reclamation's objective was to determine 

the feasibility of using accurately 

drilled boreholes to control water seepage through open joints in bedrock foundations of embankment dams. 

The Bureau of Mines has researched and 

demonstrated accurate directional drilling as part of its methane control program (1-3).4 -- In 1979, a directional 

surface borehole was drilled using an 

in-hole motor5 to a measured depth of 

1,595 ft, maintaining an arc of 6" per 

100 ft and coming within 3 ft of intercepting the Pittsburgh Coalbed 1,012 ft 

below the surface. Five horizontal methane drainage boreholes were then drilled 

from the surface borehole, totaling 9,544 

ft. 

The Bureau has also demonstrated drilling accuracy in drilling long horizontal 

methane drainage boreholes in underground 

coal mines. Methane drainage boreholes 

have been drilled to depths greater than 

2,000 ft, maintaining vertical borehole 

trajectory within the coalbed (approximately 6 ft) while controlling horizontal 

trajectory as desired to prevent interception by future mining (2-2). - 

ACKNOWLEDGMENTS 

The cooperation of the Bureau of Recla- Navajo Dam maintenance staff for their 

mation was critical in the successful continued support and assistance during 

completion of this project. The authors this project. The authors also thank 

wish to thank Hunter C. Harrel, geolo- Ed J. Blythe, Jr., well planning engigist, Engineering and Research Center, neer, NL Sperry-Sun, Rosenburg, TX for 

Denver, CO; William C. Ehler, geologist, technical assistance provided in improvDurango (CO) Projects Office; Leonard ing surveying accuracy. 

Trujillo, Navajo Dam superintendent; and 

TEST SITE 

Navajo Dam is a zoned embankment structure in northern New Mexico, 39 miles 

east of Farmington, NM, and about 35 

miles southeast of Durango, CO (fig. 1). 

It is one of the key structures of the 

Colorado River Storage Project, regulating the flows of the San Juan River 

and providing storage for Navajo Indian 

Irrigation Project. It also provides 

a facility for recreation and fish and 

wildlife conservation. Navajo Dam, 

'underlined numbers in parentheses refer to items in the list of references 

preceding the appendix. 

constructed from 1958 to 1963, is approximately 400 ft in structural height, 

3,600 ft in crest length, 30 ft in top 

width, and 2,500 ft in maximum base width 

(6). The right abutment of the dam was 

chosen for the loaction of the demonstration borehole, with designed punchout 

occurring near the top of the spillway 

(figs. 2-3). 

5~he term in-hole is synonymous with 

downhole. The authors feel in-hole is 

more descriptively accurate when borehole 

trajectory is near horizontal. 
DRILLING EQUIPMENT 

A Diamant ~oart~ DBH 700 hydraulic core 

drill and a 2-7/8-in-OD high-torque, nonmagnetic in-hole motor manufactured by 

Slimdril, Inc., were used to drill the 

borehole. The in-hole motor was equipped 

with a bent housing and two 3-1/2-in-OD 

polycrystalline diamond cutter bits (used 

separately), one manufactured by Longyear 

and one by Slimdril, Inc. 

'~ef erence to specific equipment does 

not imply endorsement by the Bureau of 

Mines. 

Key mop 

COLORADO 

u MEXICO 

I 

1 LEGEND 

@ U. S. highway 

@ State highway 

- Unpaved road 

---- State boundary 

County boundary 

o Townorcity 

0 10 20 

Scale, miles 

FIGURE 1.-Navajo Dam location map. Adapted from 

Bureau of Reclamation map. 

HYDRAULIC DRILL 

The main components of the Diamant 

Boart DBH 700 unit are the drill itself, 

control panel, and power unit (fig. 4). 

To drill the demonstration borehole, the 

drill was positioned horizontally. The 

power unit is equipped with two hydraulic 

radial piston pumps, one for thrust and 

one for rotation, both powered by a single 40-hp, 440-V ac electric motor. 

IN-HOLE MOTOR 

The 2-7/8-in-OD high-torque in-hole motor is a positive-displacement hydraulic 

motor that rotates the drill bit without 

rotating the drill string. The in-hole 

motor converts the hydraulic horsepower 

generated by the flow of the drilling 

fluid (water) under pressure into torque 

and into the rotational speed or mechanical power that drives the drill bit (5). 

The components of the high-torque motor 

are identified in figure 5. 

When d r i l l i n g f l u i d is pumped through 

the drill string and the in-hole motor at 

rates of 30 to 70 gal/min at differential 

pressures of 250 to 625 psig, the helical 

stainless steel rotor rotates inside the 

rubber molded stator. The range of Slimdril operating parameters is shown in 

figure 6; the actual parameters applied 

are listed in table A-1 (appendix). Rotation of the drive shaft, positioned 

within the bearing package, is transmitted by the flex-coupling, converting 

the eccentric rotary motion of the helical rotor to concentric motion. The 

drive sub is connected to the drive shaft 

and is the only rotating external component of the in-hole motor. The drill bit 

is fastened to the drive sub. Two 3-1/2- 

in-OD polycrystalline diamond cutter 

bits, one each from Longyear and Slimdril, Inc., were equally used to drill 
FIGURE 3.-Navajo Dam demonstration borehole drill site. 
, y; , p

Bearing package NW rod box threa 

NQ rod Crossover sub 

box thread 

Not to scale 

FIGURE 5.-In-hole motor schematic. Stator, rotor and exterior nousing are nonmagnetic. Bearing package and drive sub 

are magnetic. 

the demonstration borehole (fig. 7). BOREHOLE TRAJECTORY CONTROL DEVICES 

Polycrystalline diamond cutter bits are 

recommended for use with in-hole motors Various types of devices can be used 

because they are designed to operate at with in-hole motors to control borehole 

high rotating speeds for extended peri- trajectory. These include bent housings, 

ods. The demonstration borehole's hori- bent subs, eccentric subs, and deflection 

zontal and vertical borehole trajectories shoes. An in-hole motor equipped with a 

were controlled during in-hole motor 2' bent housing is shown in figure 8. 

drilling by using control devices. 
- Scale, in 

FIGURE 7.-Polycrystalline diamond cutter bits. 

While drilling, there is continuous FIGURE 8.-In-hole motor equipped with a 2' bent housing. 

contact between the convex side of the 

bent housing and the wall of the bore- is called tool face direction and is 

hole; this is commonly called side force. the direction borehole trajectory will 

The resultant reaction of the side force follow. Various tool face settings and 

exerted on the wall of the borehole is a their effects on borehole vertical and 

force exerted on the bit in the opposite horizontal trajectories are shown in 

direction or 180' away (fig. 9). The di- figure 10. 

rection of the force exerted on the bit 
Tool face at 180° 

(low s~de) Dlrect~on of force exerted 

on b~t resulting in vertlcal 

drop of hole trajectory 

FIGURE 9.-Side force diagram. Above in-hole motor equipped with bent housing; below, side force 

schematic. 

Deflection rates pertaining to known 

tool face settings are rates at which 

borehole inclination and azimuth (bearing) change or deflect during drilling. 

The rate of change in borehole inclination is the vertical deflection rate; 

the horizontal deflection rate is the 

rate of change in azimuth. Established 

deflection rates would be used to periodically project or estimate bit position 

16 ft ahead of the current survey depth 

and to decide what tool face setting 

should be applied to the next drilling 

interval in order to maintain desired 

borehole trajectory. Vertical and horizontal deflection rates are determined by 
observing the change in inclination and 

azimuth from the previous to the current 

borehole survey depth. For example, referring to the third page of table A-2, 

the vertical and horizontal deflection 

rates observed from survey depths 449 to 

459 ft were 0.09"/ft (0.9" during 10-ft 

interval) and 0.19"/ft (east is positive), respectively. A tool face setting 

of 60" to 80" right was applied using a 

2" bent housing while drilling from 445 

to 475 ft. When the survey was conducted 

at 459 ft, the bit depth was 475 ft. To 

project the inclination at the bit depth 

of 475 it, the established vertical deflection rate of 0.09"/ft was multiplied 

by 16 ft and added to the surveyed inclination at 459 ft. This resulted in a 

projected inclination of 101.8". The 

azimuth at the bit depth was projected to 

be 343.0" by multiplying the horizontal 

deflection rate of 0.19"/ft by 16 ft and 

adding the azimuth surveyed at 459 ft of 

340.0". The projected inclination and 

azimuth at 475 ft were close to the actual results surveyed later at 479 ft 

(table A-2). Angle averaging, which is a 

surveying calculation method, was used to 

calculate projected coordinates and elevation at the bit (2, 6). Established 

deflection rates pertaining to tool face 

settings and bent housing used are provided later in the text. 

Tool face directions are changed by 

turning the drill string clockwise with 

pipe wrenches to a position O0 to 180" 

left or right from the centerline along 

the top of the boring. Borehole inclination, azimuth, and tool face direction 

were continuously monitored and adjusted 

to achieve directional control or to 

maintain the desired horizontal and vertical borehole trajectories. 
FIGURE 12.-Reading developed survey film disk. 
Compass units measure magnetic north and 

require a declination correction to obtain true north. Wolff and deWardt suggest that declination corrections obtained from charts may be incorrect to 

'0.5. The National Geophysical Data Center, Boulder, CO, or the U.S. Geological 

Survey, Reston, VA, can supply an accurate declination correction if provided 

with drill site (collar) coordinates and 

elevation. The declination correction at 

Navajo Dam drill site was 12" E '13 min. 

Random misalignment of the survey hardware and instrument within the drill 

lection charts as guides for estimating 

compass spacing based on geographical 

location (horizontal component of the 

earth's magnetic field intensity varies 

with location), borehole inclination, and 

bearing, as indicated in figure 14 (9). 

Based on the selection chart shown for 

the Navajo Dam location, uncorrected 

bearing of N 10" W, and inclination of 

90°, the compass should be located 20 ft 

from the bottom of the NMDC. While conducting a borehole survey, the NL SperrySun single-shot was placed 13 ft from the 

bottom of the NMDC, or 16 ft from the 

FIGURE 13.-Survey hardware. A, snubber; 19, centralizing pumpdown washers; C, muleshoe. 
BEARING FROM MAGNETIC 

NORTH OR SOUTH, deg 

(Uncorrected for decl inat ion) 

F 

ing 

'IGURE 14.-Nonmagnetic drill collar and compass spacselection chart. 

bit. Although this spacing was 7 ft less 

than the estimated compass spacings, having the compass closer to the bit enhanced the accuray in projecting the current position of the bit from the survey 

position. 

Two related factors that affect borehole surveying accuracy are surveying 

frequency and the surveying calculation 

technique used to determine borehole coordinates and elevation. It is generally 

accepted that regardless of calculation 

technique applied, short survey intervals 

will result in increased accuracy (10). 

Borehole surveys were conducted at 10-ft 

drilling intervals at Navajo Dam. Of the 

dozen or so surveying calculation techniques available, balanced tangential, 

radius of curvature, minimum curvature, 

and angle averaging are generally accepted as providing similar and acceptable results (10). A radius of curvature 

program adapterfor a Hewlett Packard 15C 

calculator was used to calculate borehole 

coordinates and elevation. Angle averaging was used periodically to check the 

radius of curvature results. 

PLANNING THE BOREHOLE 

The borehole starting coordinates were 

N 19,567.69, E 52,697.69; elevation at 

the collar was 5,933.53 ft. The designated "punchout" was to occur within a 

5-ft radius of N 20,447.31, E 52,709.41 

at an elevation of 6,049.03 ft (figs. 15- 

16). The location of the borehole was 

determined after considering the geology 

of the right abutment and the constraints 

that specific geologic features would impose on the placement of the borehole. 

The abutment in the vicinity of the borehole consists predominantly of coarse-tomedium-grained sandstone with interbedded 

shale and siltstone (fig. 15). The sandstone is comprised mostly of very hard 

angular quartz grains weakly to moderately cemented having an unconfined compressive strength of less than 6,900 psi (4). 

The weak nature of the sandstone's intergranular material indicated that the rock 

would probably drill easily even though 

the sandstone's quartz grains were very 

and horizontal joints. Unfortunately, 

the exact locations of the joints could 

not be determined because of thin soil 

cover, and thus the borehole trajectory 

could not be planned to avoid intercepting them. However, the borehole was designed to avoid intercepting the sandfilled joint shown in figure 15. The 

elevation at the bottom of the sandfilled joint was estimated to be 5,950 

ft, or about 16.5 ft above the collar of 

the borehole. To prevent drilling into 

the joint, the first 250 ft of the demonstration borehole was to be drilled keeping borehole elevation near the elevation 

of the collar, or 5,933 ft. Drilling was 

to continue from 250 to 340 ft, by applying maximum build and tool face directions of 0" to 20" right and left (fig. 

10). A desired increase in borehole inclination from 90.0" (horizontal inclination) to 101.0" (11.0" above horizontal) 

would result at 300 to 340 ft. Borehole 

hard and abrasive. Rock outcrops within inclination was then to be maintained at 

the right abutment contain both vertical or near 101.0" to borehole completion in 

order to intercept the target eleva- straight-line collar to punchout trajection. While maintaining desired verti- tory having a bearing of N 0"-45'-00" E 

cal trajectory as mentioned, an attempt was calculated and appears in appendix 

was to be made to maintain departure table A-2. This information would be 

within 2 ft east or west from the planned used continuously during drilling to 

straight-line collar to punchout trajec- monitor deviation from the desired boretory (fig. 16). The departure of the hole departure. 

DIRECTIONAL DRILLING THE DEMONSTRATION BOREHOLE 

Several bent housings were used to 

drill the demonstration borehole; the 2" 

bent housing was the most effective in 

controlling vertical and horizontal trajectories (fig. 8). Before discussing 

the effectiveness of the bent housings, 

the drilling of the borehole's vertical 

and horizontal trajectories is briefly 

described. 

The first 250 ft of the borehole were 

drilled maintaining elevation near the 

collar elevation as planned (fig. 17). 

Drilling continued to a depth of 495 ft 

without developing the necessary increase 

in vertical borehole trajectory. Consequently, the borehole was abandoned in 

order to start a new borehole within the 

initial borehole at a depth of 289 ft. 

After the new borehole was started at 289 

ft, drilling continued to borehole completion at 885 ft, maintaining desired 

vertical trajectory. 

Horizontal borehole trajectory during 

the first 250 ft of the borehole was 

maintained to within 2.5 it of the desired departure. (Table A-2 gives the 

actual borehole survey log and desired 

borehole departures. ) As drilling continued from 250 ft to 495 ft, horizontal 

borehole trajectory deviated from the desired course. After the new borehole was 

started at 289 ft, horizontal trajectory 

of the new borehole was maintained close 

to the desired course to borehole completion, according to borehole surveys (fig. 

18). 

EFFECTIVENESS IN CONTROLLING 

BOREHOLE TRAJECTORY 

The 112" bent housing with pad was used 

to drill the initial borehole to a depth 

of 455 f t (fig. 19). Although the desired vertical and horizontal borehole 

Target elevation. 

1301 11 11 1111 IIII 1111 1111 IIII 1111 , , 6.0?;6.0? 

HORIZONTAL DEPTH. ft 

FIGURE 17.-Vertical section of demonstration borehole. 

120 

110- 

loo90- 

.I- C 

80- 

i 70- 

0 

F 60- P 

50- W 

40 

30 

20- 

-I0 

0 

- 

- 

- KEY 

Surveyed elevation station - 

of Initial borehole - 

- A Surveyed elevation station - 

of new borehole, sidetracked 

- from initial borehole - 

- 

- Collar elevation, 5,933.53 f t - 

o.*-f .- .---- ---= -.- 

~~~~~~~~'~~'~'~~~

100 200 300 400 500 600 700 800 900 
FIGURE 19.-Various bent housings. Top to bottom: 2' bent housing on in-hole motor, slip-on shoe, lo bent housing with pad, 

112" bent housing with pad. 

trajectories were maintained to a depth 

of 250 ft, the vertical and horizontal 

deflection rates were inconsistent and 

unpredictable. Drilling continued to a 

depth of 455 ft without success in bringing the vertical and horizontal borehole 

trajectories to the desired course. The 

inconsistent deflection rates causing 

poor trajectory control resulted from a 

lack of sufficient side force being generated while using the 112' bent housing. 

The weak nature of the sandstone's intergranular material is believed to have negated any potential side force generated 

by the 112' bent housing. At a depth of 

455 ft, the drill string and in-hole motor were pulled out of the borehole to 

replace the 112" housing with a lo bent 
housing, after it became apparent that 

the necessary increase in elevation of 

112 ft and change in departure of 14 ft 

east required to intercept the target 

could not be accomplished using the 112" 

bent housing. 

Drilling continued from 455 ft to a 

depth of 495 ft using the 1" bent housing 

with pad (fig. 19). Even though the vertical deflection rates were more consistent when compared to the 112" bent housing, the horizontal borehole trajectory 

continued west instead of east. At the 

survey depth of 479 ft (bit depth of 495 

ft), the borehole was calculated to be 

16.8 ft west of the target departure and 

96.0 f t below target elevation. Consequently, it was decided to abandon the 

borehole and to sidetrack or start a new 

borehole from within the initial borehole 

at a depth of 289 ft. As with the 112" 

bent housing, the 1' bent housing apparently failed to generate sufficient side 

force to control borehole trajectory. 

To accommodate the sidetrack at a depth 

of 289 ft, enough drill rod was removed 

from the borehole to position the drill 

bit at a depth of 275 ft, to begin the 

sidetrack. The sidetracking procedure 

has been described in a previous Bureau 

of Mines publication (2). - Using the inhole motor equipped with the 1" bent 

housing, the sidetrack was started at a 

depth of 275 ft and completed at a borehole depth of 289 f t (fig. 17). The initial borehole was also resurveyed from 

89 to 289 ft, primarily for bearing, after replacing a defective muleshoe and 

centralizing pumpdown washers that were 

believed to have caused error in measuring borehole bearing (table A-2, figure 

13). 

Drilling of the new borehole resumed 

from 289 ft to a depth of 385 ft after 

the 1' housing was replaced with a 2" 

housing equipped with a slip-on shoe (positioned on the in-hole motor at the apex 

of the 2' bent housing) (fig. 19). Desired borehole inclination and elevation 

were attained at a depth of 329 ft after 

only 40 ft of drilling with the 2' housing and slip-on shoe and were maintained 

thereafter. By referring to the actual 

borehole survey log and the desired 

borehole departures in table A-2, it can 

be seen that horizontal trajectory was 

returned to and controlled within 2 ft of 

the desired borehole departure (fig. 18). 

Control on both vertical and horizontal 

borehole trajectories was accomplished 

for the first time because the tool face 

settings resulted in predictable and consistent deflection rates. While drilling 

with the 2" housing and slip-on shoe, 

compared to the previous bent housings, 

the side force generated was great enough 

to overcome the weak nature of the sandstone's intergranular material. Although 

directional control had improved, the 

slip-on shoe frequently got stuck in the 

borehole while drilling, causing the 

average penetration rate to decrease to 

7 in/min from 21 in/min with the previous 

housings. Therefore, at a depth of 385 

ft, the drill rods and in-hole motor were 

removed from the borehole to remove the 

slip-on shoe from the 2" bent housing. 

The demonstrat ion borehole was completed to the final borehole depth of 

885 ft using the 2' bent housing without 

the slip-on shoe (figures 8 and 19). Actual deflection rates were consistent and 

predictable for directional control with 

the 2" housing (table 1). The horizontal 

borehole trajectory was maintained within 

2 ft east or west of the designed trajectory except for a short interval around 

500 ft (fig. 18). Borehole elevation or 

vertical trajectory increased at an average rate of 1.98 ft per 10 ft drilled, 

maintaining an average borehole inclination of approximately 101.0" to successfully intercept the designated target 

elevation (fig. 17). 

BOREHOLE PUNCHOUT AND INVESTIGATING 

ERROR IN AZIMUTH 

The actual demonstration punchout depth 

was 885 ft at elevation 6,047.53, 1.50 ft 

below target center and 8.81 ft southwest of the target perimeter or 13.81 ft 

southwest of target center (fig. 20). 

The targeted punchout was to occur within 

a 5-ft radius with center coordinates 

of N 20,447.31, E 52,709.41 at elevation 

6,049.03 ft. The calculations from the 

NL Sperry-Sun surveys showed the punchout 
TABLE 1. - Measured deflection rates using 2" bent housing, 

degrees per foot 

Tool face setting 

Right: 

20" to 40°..... 

40" to 60°..... 

60" to 80°..... 

80" to 100°.... 

100" to 120°... 

120" to 140°... 

140" to 160°... 

Left: 

00 to 20 o~..... 

40" to 60°..... 

60" to 80°..... 

80" to 100°.... 

100" to 120°... 

120" to 140°... 

140" to 160°... 

NAp Not applic 

Change in inclination 

(vertical) l 

Range 

Change in bearing 

I (horizontal) 

Average 

-003 to +.09 

-001 to +.06 

-012 to +.06 

-012 to +.04 

NAp 

-.07 to -020 

NAp 

Range I Average 

I 

-003 

+. 05 

-002 

-004 

-013 

-012 

-. 16 

.30L- .11R 

.52L- .OOR 

m4OL- .02L 

m13L- .59L 

NAP 

m53L- 00 1R 

NAp 

ble. ' + Increase (buildup) ; - decrease (drop). 

'R Right (east); L Left (west). 

3~eftool face settings were applied from 805- to 885-ft 

borehole depth. During that drilling interval, the necessary 

bit thrust of >7,000 lb was not readily available. Consequently, drilling penetration rates and deflection magnitudes 

decreased. 

to be at elevation 6,047.14 ft 1.89 f t 

below the target center, and at coordinates N 20,439.96, E 52,710.80, 1.4 ft 

northeast of the target center. The elevation error between the actual and calculated punchout was 0.39 f t, which was 

well within the accuracy of the survey 

instrument. The coordinate error between 

the actual and calculated punchout was 

15.20 ft (figures 18 and 20), which was 

within the 1" accuracy of the survey instrument in measuring bearing. 

Investigation into calculating systematic compass error caused by drill string 

interference has indicated that a possible error of 0.30" E was imposed on the 

compass (11). Applying the equation developed by~l~the and Callas (11) - for est imat ing compass spacing, 

C = sin-' ((F/H)(sin (1) sin (EN), 

where C = compass correction, ", 

F = net forces affecting compass, 

EMU, 

H = horizontal component of 

earth's magnetic field intensity (23,300 nT or 0.0233 EMU 

at Navajo Dam, according to 

the National Geophysical Data 

Center), 

I = borehole inclination, 95", 

and E = compass reading, 350". 
FIGURE 20.-Borehole punchout. 

where PL = lower pole strength, estimated at 100 EMU, 

PU = upper pole strength, estimated at 1,000 EMU, 

DL = compass distance from lower 

pole, 400 cm, 

and DU = compass distance from upper 

pole, 3,020 cm. 

C = -0.30' (correction of 0.30° W). 

A final punchout departure of 52,706.16 E 

was calculated by applying the compass 

error correction to the previously surveyed borehole bearings. This departure 

is 4.61 ft closer to the actual punchout 

as compared to not applying the compass 

correction. Although caution must be 

used when calculating compass correction 

caused by drill string interference, because pole strengths cannot be measured 

precisely and are not constant, the calculation in this application' would have 

increased borehsle punchout accuracy. 
CONCLUSIONS 

The demonstration borehole was direc- instrument. The 2" bent housing was the 

tionally drilled to a final depth of 885 most effective in maintaining directional 

ft, where punchout occurred. Final bore- control of the vertical and horizontal 

hole elevation was well within the tar- borehole trajectories. 

get; borehole punchout coordinates were As a result of the demonstrated bore8.81 ft southwest of the target. Bore- hole drilling accuracy, the original plan 

holes can only be directionally drilled of constructing a long tunnel under the 

within the accuracy of the borehole sur- right abutment of Navajo Dam and drilling 

vey system used. The NL Sperry-Sun type 150-ft boreholes from inside the tunnel 

B 120" single-shot directional survey in- to control water seepage was abandoned. 

strument is accurate to within 1" bearing The Bureau of Reclamation has instead 

and 0.24" inclination. The borehole- contracted the construction of a shorter 

surveyed punchout, relative to the land- tunnel and the accurate drilling of boresurveyed actual punchout, was within the holes as long as 600 ft, resulting in a 

accuracy of the NL Sperry-Sun survey substantial cost savings to the taxpayer. 

REFERENCES 

1. Oyler, D. C., and W. P. Diamond. 

Drilling a Horizontal Coalbed Methane 

Drainage System From a Directional Surface Borehole. BuMines RI 8640, 1982, 

50 PP. 

2. Kravits, S. J., A. Sainto, and 

G. L. Finfinger. Comparison of Rotary 

and In-Hole Motor Techniques for Drilling 

Horizontal Boreholes in Coal. BuMines 

RI 8933, 1985, 33 pp. 

3. . The Advantages of In-Hole 

Motor Drilling. Coal Min., v. 21, No. 

11, 1984, pp. 44-46. 

4, Ehler, W. C. Final Report on Investigations for Seepage Control Navajo 

Dam. U. S. BuReclamation (Dep. Interior), 

1983, 48 pp. 

5. Pittard, F. High Torque 2-718-inOD In-Hole Motor Performance Data. Slimdril Inc., Houston, TX, 1984, 21 pp. 

6. American Petroleum Institute. Directional Drilling Survey Calculation 

Methods and Terminology. Bull. D20, Dec. 

1985, 31 pp. 

7. NL Sperry-Sun (Oklahoma City, OK). 

Magnetic Directional Single-shot Operating Instructions. 1972, 12 pp. 

8. Wolff, C. J. M., and J. P. 

deWardt. Borehole Position Uncertainty 

Analysis of Measuring Methods and Derivation of Systematic Error Model. J. Pet. 

Technol., v. 33, 1981, pp. 2339-2350. 

9, Blythe, E. J., Jr. Estimating 

Compass Spacing Inside Nonmagnetic 

Collars. Drilling - DCW, v. 36, 1975, 

pp. 44-47. 

10. Fitchard, E. E. Randomly Simulated Borehole Tests Accuracy of Directional Survey Methods. Oil and Gas J., 

v. 79, No. 26, 1981, pp. 140-150. 

11. Blythe, E. J., Jr, , and N. P. Callas. Procedure Improves Platform Well 

Location Technique. Oil and Gas J., v. 

75, No. 18, 1977, pp. 224-232. 
APPENDIX.--DRILL AND BOREHOLE SURVEY LOGS 

TABLE A-1. - Log of directional drilling parameters 

Date. I Borehole I Intake water I Bi t I Bit 

1985: 1 de;;h, 

Sept.. 

19.... 

Oct. : 

4.b.. 

4.b.. 

7.b.. 

7.b.. 

8.... 

11.b.. 

19.... 

19.... 

20. . . . 20.... 

20.b.. 

20.... 

22. . . . 22r 

22.b.. 

22.b.. 

23.... 

23.. . . 23.... 

23.... 

23.... 

23.... 

23.,.. 

23.... 

23.,.. 

24.... 

24.,.. 

24.... 

24.... 

24.... 

24.. .. 

rotation, 

r/min 

torque, 

ftblbf 

NAp I NAp I NAp 1 NAp 1 3-l/Z-in re

Survey 

time, 

mi n 

Lost circu

C

Completed 

Regained c

Lost parti

Do. 

Do . Do. 

Do . Do . Do. 

Do . Do. 

Do . Return wa

Do. 

Do . 

NAp Not applicable. '~hrust force = Thrust pressure (bars) x 14.7 psig/bar x 1.268 in2 (piston area). 
TABLE A-1. - Log of directional drilling parameters--Continued 

Return wat

Output flow 

Output flow 

80-gpm out

Installed 

Sidetracke

Installed 

Surveying 

100-gpm ou

Removed sl

Conducted 

Date, 

1985 

Oct.: 

24.. . . 24. ... 25.... 

25.. . . 25. .. . 25.. .. 25. .. . 25.. .. 25. ... 25. ... 25.... 

26.... 

30... . 30.... 

30.... 

30. ... Nov. : 

l.... 

4.... 

5.... 

6.... 

6.... 

6. .. . 7.... 

7.... 

7.... 

7.... 

7.... 

8.... 

8.... 

go... 

9.... 

9.. .. 9.... 

9.... 

9. ... 9.... 

9.... 

9.... 

Borehole 

depth, 

f t 

355 

365 

375 

385 

395 

405 

415 

425 

435 

445 

455 

NAp 

465 

475 

485 

495 

NAp 

NAp 

NAp 

305 

315 

325 

335 

345 

355 

365 

375 

385 

NAp 

395 

405 

415 

425 

435 

445 

455 

465 

475 

Intake 

gpm 

67 

67 

67 

67 

67 

67 

65 

65 

68 

68 

68 

NAp 

63 

62 

62 

68 

NAp 

NAp 

NAp 

65 

66 

67 

66 

66 

65 

69 

65 

67 

NAp 

68 

66 

65 

66 

65 

66 

67 

66 

66 

Bit 

rotation, 

r/min 

813 

813 

813 

813 

813 

813 

785 

785 

825 

825 

825 

NAP 

746 

7 30 

7 30 

825 

NAP 

NAP 

NAP 

785 

800 

8 13 

800 

800 

785 

839 

785 

813 

NAP 

825 

800 

785 

800 

785 

800 

8 13 

800 

800 

water 

psig 

600 

600 

600 

600 

575 

500 

550 

500 

550 

625 

625 

NAp 

650 

600 

700 

700 

NAp 

NAp 

NAp 

650 

650 

650 

650 

550 

600 

600 

600 

550 

NAp 

500 

525 

550 

500 

550 

510 

510 

600 

550 

Bit 

torque, 

ft0lbf 

110 

110 

110 

110 

100 

90 

95 

90 

95 

110 

110 

NAP 

115 

110 

125 

125 

NAP 

NAP 

NAP 

170 

176 

178 

176 

176 

156 

166 

156 

148 

NAP 

90 

90 

95 

90 

95 

90 

90 

110 

95 

Thrust 

pressure, 

bars 

245 

245 

235 

245 

250 

255 

255 

250 

250 

250 

250 

NAP 

250 

250 

250 

250 

NAP 

NAP 

NAP 

250 

250 

250 

230 

250 

260 

250 

250 

260 

NAP 

260 

275 

295 

290 

305 

300 

295 

310 

300 

Thrust' 

force, 

lbf 

4,567 

4,567 

4,380 

4,567 

4,660 

4,753 

4,753 

4,660 

4,660 

4,660 

4,660 

NAP 

4,660 

4,660 

4,660 

4,660 

NAP 

NAP 

NAP 

4,660 

4,660 

4,660 

4,287 

4,660 

4,846 

4,660 

4,660 

4,846 

NAP 

4,846 

5,126 

5,499 

5,406 

5,685 

5,592 

5,499 

5,778 

5,592 

Drill time, 

10-ft rod, 

mi n 

3 

4 

3 

4 

4 

4 

5 

6 

3 

3 

4 

NAP 

3 

3 

3 

3 

NAP 

NAP 

NAP 

2 1 

28 

13 

9 

13 

8 

31 

2 1 

25 

NAP 

5 

5 

4 

5 

6 

5 

5 

6 

5 

Survey 

time, 

mi n 

31 

33 

139 

5 7 

49 

50 

35 

67 

31 

40 

31 

NAP 

42 

39 

3 1 

36 

NAp 

NAp 

NAp 

32 

47 

19 

30 

30 

2 1 

32 

3 2 

30 

NAp 

23 

42 

28 

45 

59 

22 

26 

19 

22 
NAp Not applicable. '~hrust force = Thrust pressure (bars) 

Surveying p

Conducted 

Do. 

Do. 

Do. 

Do. 

Repaired s

Used a win

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

14.7 psig/bar x 1.268 in2 (piston area). 
TABLE A-2. - Demonstration borehole survey log and log of desired departures 

Borehole 

depth, 

ft 

NAP 

NAP 

NAP 

NAP 

NAP 

65 

75 

85 

95 

105 

115 

125 

135 

145 

155 

165 

175 

185 

195 

205 

215 

225 

235 

245 

255 

265 

275 

285 

Azimuth 

(uncorrected), 

degl 

NAP 

NAP 

350.81 

NAP 

NAP 

349.50 

348.25 

348.50 

350.50 

351.50 

352.86 

350.70 

351.20 

351.00 

348.90 

349.50 

348.47 

350.36 

347.70 

347.90 

348.40 

348.70 

348.00 

345.70 

347.00 

345.50 

346.30 

344.80 

Survey 

depth, 

ft 

0 

6 

16 

26 

36 

49 

59 

69 

79 

89 

99 

109 

119 

129 

139 

149 

159 

169 

179 

189 

199 

209 

219 

229 

239 

249 

259 

269 

Borehole 

inclination, 

deg 

90.0 

87.9 

88.0 

87.5 

88.9 

88.9 

89.5 

90.0 

90.4 

90.9 

91.0 

91.4 

91.0 

90.5 

90.6 

90.7 

91.0 

91.5 

89.7 

89.2 

89.5 

89.9 

90.0 

90.1 

90.0 

90.0 

90.5 

91.1 

Change 

in 

departures , ft 

NAP 

NAP 

0.39 

NAP 

NAP 

1.24 

.15 

.06 

.26 

.52 

.73 

.66 

.51 

.54 

.31 

.17 

.17 

.25 

.18 

-.03 

.03 

.lo 

.06 

-.20 

-.29 

-.31 

-.37 

-.43 

Latitude, 

ft 

19,567.69 

NAp 

19,583.68 

NAp 

NAp 19,616.64 

19,626.64 

19,636.64 

19,646.63 

19,656.62 

19,666.59 

19,676.57 

19,686.55 

19,696.54 

19,706.53 

19,716.53 

19,726.53 

19,736.52 

19,746.52 

19,756.52 

19,766.52 

19,776.51 

19,736.51 

19,796.51 

19,806.51 

19,816.50 

19,826.50 

19,836.48 

Change 

in 

latitudes , ft 

NAP 

NAP 

15.99 

NAP 

NAP 

32.96 

9.99 

9.99 

9.99 

9.98 

9.97 

9.97 

9.98 

9.98 

9.99 

9.99 

9.99 

9.99 

9.99 

9.99 

9.99 

9.99 

9.99 

9.99 

9.99 

9.99 

9.99 

9.99 

Change 

in true 

vertical 

depth, 

ft 

NAp 

0.11 

.36 

.39 

.3 1 

019 

.14 

004 

-003 

-011 

-017 

-021 

-.21 

-. 13 

-. 10 

-011 

-.15 

-. 22 

-. 10 

.lo 

.11 

.05 

.01 

-.01 

-.01 

.OO 

-004 

-014 

True 

vertical 

depth, 

ft2 

-5,933.53 

-5,933.42 

-5,933.06 

-5,932.67 

-5,932.36 

-5,932.17 

-5,932.03 

-5,931.99 

-5,932.02 

-5,932.14 

-5,932.30 

-5,932.51 

-5,932.72 

-5,932.85 

-5,932.95 

-5,933.06 

-5,933.21 

-5,933.43 

-5,933.53 

-5,933.44 

-5,933.33 

-5,933.27 

-5,933.26 

-5,933.27 

-5,933.28 

-5,933.28 

-5,933.32 

-5,933.46 

Departure, 

ft 

52,697.79 

NAP 

52,698.18 

NAP 

NAP 

52,699.42 

52,699.57 

52,699.64 

52,699.90 

52,700.42 

52,701.15 

52,701.81 

52,702.33 

52,702.87 

52,703.18 

52,703.35 

52,703.52 

52,703.77 

52,703.95 

52,703.91 

52,703.94 

52,704.04 

52,704.10 

52,703.90 

52,703.61 

52,703.30 

52,702.94 

52,702.51 
See footnotes at end of table. 
TABLE A-2. - Demonstration borehole survey log and log of desired departures--Contin

Borehole 

depth, 

ft 

345 

355 

365 

375 

385 

395 

405 

4 15 

425 

435 

445 

455 

465 

475 

485 

495 

505 

515 

525 

535 

545 

555 

565 

575 

585 

595 

605 

615 

625 

Borehole 

inclination, 

deg 

100.9 

100.4 

99.9 

98.2 

100.3 

103.5 

102.9 

100.9 

101.0 

100.0 

100.0 

100.0 

100.4 

101.3 

101.9 

103.1 

102.8 

102.1 

102.9 

103.5 

103.5 

102.5 

100.9 

101.0 

100.3 

100.7 

100.8 

101.4 

101.0 

Survey 

depth, 

ft 

329 

339 

349 

359 

369 

379 

389 

399 

409 

419 

429 

439 

449 

459 

469 

479 

489 

499 

509 

5 19 

529 

539 

549 

559 

569 

579 

589 

599 

609 

Azimuth 

(uncorrected), 

degl 

347.90 

352.55 

349.60 

344.40 

347.50 

351.20 

352.50 

346.70 

346.70 

346.80 

346.50 

343.30 

338.14 

340.00 

341.20 

344.80 

346.30 

347.60 

348.70 

350.00 

354.90 

353.30 

352.20 

355.00 

355.10 

353.80 

353.80 

Change 

in 

departures , ft 

-0.46 

.38 

.53 

-.I7 

-.35 

.23 

.65 

.27 

-.22 

-.21 

-.23 

- . 53 

-1.25 

-1.52 

-1.26 

-.85 

-.42 

-.I8 

.03 

.23 

.75 

1.04 

.81 

-96 

1.21 

1.10 

.99 

.94 

350.50 

Change 

in 

latitudes , ft 

9.81 

9.82 

9.83 

9.87 

9.86 

9.78 

9.71 

9.78 

9.81 

9.83 

9.84 

9.83 

9.76 

9.70 

9.71 

9.72 

9.74 

9.76 

9.76 

9.73 

9.69 

9.69 

9.76 

9.77 

9.75 

9.77 

9.77 

9.77 

9.79 

Change 

in true 

vertical 

depth, 

ft 

-1.72 

-1.85 

-1.76 

-1.57 

-1.61 

-2.06 

-2.28 

-2.06 

-1.90 

-1.83 

-1.75 

-1.74 

-1.77 

-1.88 

-2.01 

-2.16 

-2.24 

-2.16 

-2.16 

-2.28 

-2.33 

-2.25 

-2.03 

-1.90 

-1.85 

- 1.82 

-1.87 

-1.93 

-1.94 

Departure, 

ft 

52,703.55 

52,703.93 

52,704.46 

52,704.29 

52,703.93 

52,704.16 

52,704.82 

52,705.09 

52,704.87 

52,704.65 

52,704.42 

52,703.89 

52,702.64 

52,701.11 

52,699.85 

52,699.00 

52,689.58 

52,698.40 

52,698.43 

52,698.65 

52,699.41 

52,700.44 

52,701.26 

52,702.22 

52,703.42 

52,704.52 

52,705.52 

52,706.46 

52,707.12 

Latitude, 

ft 

19,895.93 

19,905.75 

19,915.58 

19,925.45 

19,935.31 

19,945.09 

19,954.80 

19,964.58 

19,974.39 

19,984.22 

19,994.07 

20,003.90 

20,013.66 

20,023.36 

20,033.07 

20,042.80 

20,052.53 

20,062.30 

20,072.06 

20,081.80 

20,091.49 

20,101.18 

20,110.93 

20,120.70 

20,130.46 

20,140.23 

20,150.00 

20,159.77 

20,169.56 

True 

vertical 

depth, 

ft2 

-5,938.48 

-5,940.33 

-5,942.09 

-5,943.67 

-5,945.27 

-5,947.34 

-5,949.62 

-5,951.68 

-5,953.58 

-5,955.41 

-5,952.14 

-5,958.89 

-5,960.64 

-5,962.53 

-5,964.54 

-5,966.71 

-5,968.95 

-5,971.10 

-5,973.26 

-5,975.55 

-5,977.88 

-5,980.13 

-5,982.16 

-5,984.06 

-5,985.91 

-5,987.73 

-5,989.60 

-5,991.52 

-5,993.46 
635 

645 

655 

665 

675 

685 

595 

705 

715 

725 

735 

745 

755 

765 

775 

785 

795 

805 

815 

825 

835 

845 

855 

865 

875 

885 

885 

YAp Not applicable. 

Borehole bearing converted to uncorrected azimuth, radius of curvature calculator program. 

declination (Navajo Dam, add 12' E in NE quadrant). Engineering 40 scale used to eliminate read

*changes to TVD: Up -, Down +. 

3~og of desired departures every 10 ft, collar to 880 ft using azimuth of 0.76O. 

4~epth at which desired departures calculated. 

5~orehole terminated at 495 ft, new borehole sidetracked at 289 ft. Borehole resurveyed 89 

defective survey hardware; used original surveys 0 to 89 ft. 

619 

629 

639 

649 

659 

669 

679 

689 

699 

709 

719 

729 

739 

749 

759 

769 

779 

789 

799 

809 

819 

829 

839 

849 

859 

869 

885 

100.5 

100.2 

100.8 

101.5 

100.9 

100.2 

98.9 

99.5 

100.1 

98.9 

99.5 

100.1 

101.0 

102.1 

101.4 

101.2 

100.0 

100.1 

100.1 

101.2 

102.2 

103.1 

103.3 

103.8 

104.1 

104.1 

103.8 

347.00 

347.90 

348.70 

349.80 

350.10 

350.70 

350.00 

349.50 

348.40 

344.40 

344.20 

345.00 

346.50 

350.60 

352.10 

353.40 

347.50 

348.40 

348.60 

350.10 

352.80 

351.60 

348.60 

349.70 

347.50 

347.00 

345.60 

0.13 

-009 

005 

.2 1 

.33 

.41 

.40 

.30 

.16 

-028 

-064 

-058 

-038 

.09 

.57 

.81 

.42 

.OO 

-009 

.23 

.59 

.71 

.36 

-19 

.lo 

-018 

-035 

-1.86 

-1.80 

-1.82 

-1.93 

-1.94 

-1.83 

-1.66 

-1.60 

-1.70 

-1.65 

-1.60 

-1.70 

-1.83 

-2.00 

-2.04 

-1.96 

-1.84 

-1.74 

-1.75 

-1.85 

-2.03 

-2.19 

-2.20 

-2.34 

-2.41 

-3.41 

-2.89 

9.82 

9.84 

9.83 

9.81 

9.80 

9.82 

9.80 

9.87 

9.85 

9.86 

9.85 

9.84 

9.82 

9.79 

9.77 

9.77 

9.82 

9.84 

9.84 

9.82 

9.77 

9.73 

9.73 

9.72 

9.70 

3.68 

1.64 

52,707.24 

52,707.15 

52,707.20 

52,707.42 

52,707.75 

52,708.16 

52,078.57 

52,708.87 

52,709.03 

52,708.76 

52,708.12 

52,707.53 

52,707.15 

52,707.24 

52,707.81 

52,708.63 

52,709.05 

52,709.04 

52,709.13 

52,709.37 

52,709.45 

52,710.60 

52,711.02 

52,711.22 

52,711.32 

52,711.14 

52,710.80 

20,179.38 

20,189.21 

20,199.05 

20,208.85 

20,218.67 

20,228.48 

20,238.33 

20,248.20 

20,258.05 

20,267.91 

20,277.76 

20,287.60 

20,297.42 

20,307.22 

20,316.99 

20,326.76 

20,336.58 

20,346.42 

20,356.27 

20,366.09 

20,375.86 

20,385.60 

20,395.32 

20,405.04 

20,414.75 

20,428.32 

20,439.96 

-5,955.33 

-5,997.12 

-5,998.95 

-6,000.88 

-6,002.82 

-6,004.65 

-6,006.31 

-6,007.91 

-6,009.61 

-6,011.26 

-6,012.86 

-6,014.56 

-6,016.39 

-6,018.40 

-6,020.43 

-6,022.39 

-6,024.23 

-6,025.98 

-6,027.73 

-6,029.58 

-6,031.61 

-6,033.80 

-6,036.08 

-6,038.42 

-6,040.83 

-6,044.24 

-6,047.14