bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Well Spacing and Drawdown on Recovery From Internal Gas Drive Reservoirs
Authors: Loper Raymond G. , Calhoun John C.
Published: April 2012

Theoretical calculations for the decline of pressure and the variation ofinstantaneous producing gas-oil ratio with increased cumulative production havebeen made for reservoir systems under various producing drawdown values and forvarious spacings. These variables have been included by a modification of previously published techniques. Thisconsists essentially of utilizing a radial system flowing gas and oil in asuccession of steady state calculations. The results of the calculations do notshow any variation in the predicted behavior of the internal gas drivereservoir when either the drawdown or the spacing are changed.

Introduction

The prediction of performance on an internal gas drive reservoir has beenpresented by various authors. These predictions are in the form of a pressuredecline and an instantaneous producing gas-oil ratio as a function ofcumulative oil withdrawal. In making these predictions a basic assumption hasbeen that the saturation of the reservoir is uniform throughout at any time, orthat the pressure differential imposed on the reservoir system is zero. Becauseof these assumptions the validity of such predictions has been questioned.Their application to actual systems, where saturations are not uniform andwhere producing differentials exist, has been a hazardous procedure.

The authors cited have used different methods of approach to the derivation ofequations for making their predictions and for arriving at a solution of bothequations, but basically the same relationships are utilized in each case. Inall instances the instantaneous producing gas-oil ratio is calculated from theequation:

(Equation 1)

In utilizing this equation an average reservoir pressure and an averagereservoir saturation must be known. Predictions can be made, therefore, onlyfor the conditions of a uniform reservoir saturation and a uniform reservoirpressure.

This restriction of requiring a uniform oil saturation can be resolved byapplying two-phase steady state flow for the radial system to the reservoir'shistory. Radial steady state flow is defined when the ratio of phases flowing, the pressures imposed, and the dimensions of the system are fixed.

T.P. 2592
The Relation Between Electrical Resistivity and Brine Saturation in Reservoir Rocks
Authors: Dunlap Henry F. , Bilhartz Harrell L. , Shuler Ellis , Bailey C.R.
Published: April 2012

In connection with electric log interpretation it is important to know thevalue of the saturation exponent. For example, if in a given reservoir it isfound that the resistivity is three timcs the resistivity observed when thereservoir is 100 per cent saturated with water, this fact would be interpretedas indicating a water saturation of 33 per cent if the saturation exponent were1 and a water saturation of 64 per cent if the saturation exponent were2.5.

Experimental Method

In the work to be described it was assumed that reservoir conditions aremost nearly obtained when core plugs are desaturated by the capillary pressuretechnique referred to in numerous places in the literature, as for example, inBruce and Welge's paper. In this technique the core, saturated 100 per centwith brine, is placed in contact with a ceramic disc permeable to brine but notto the displacing medium for the displacement pressures used. Pressure is thenapplied to the displacing medium and brine forced out of the core through theceramic disc. Fig. 1 shows the core plug in place in the cell in whichresistivity and saturation measurements are made. Fig. 2 shows the schematicelectrical diagram used to make resistivity measurements on the core plug. Afour-electrode type circuit is used, employing a Hewlett-Packard model 400A, ACvacuum tube voltmeter. The 60-cycle AC current through the core is adjusted to1 milliampere and measured by noting the voltage drop across the calibrated100-ohm resistor. The voltages appearing at probes 1, 2, 3, and 4 are thensuccessively measured. Voltage drops across the top, center, and bottomportions of the core are obtained by subtracting the voltages appearing atsuccessive probes. This technique avoids any polarization or other high contactresistance phenomena which may develop at the current input electrodes.Resistances which may develop between the core and the probes, and which aresmall compared to the 1-megohm input impedance of the vacuum tube voltmeterwill obviously not affect the measurements appreciably. Any very appreciableresistances which may develop at any of the probe wires are detected andallowed for by inserting a 1-megohm resistor in series with the voltagemeasuring probe. If the probe resistance is actually zero, the new voltagemeasured after insertion of the 1-megohm resistor will be approximatelyone-half of that previously measured- since the input impedance of the vacuumtube voltmeter is itself 1 megohm. If any appreciable probe resistance hasdeveloped, the new voltage is found to be appreciably greater than one-half ofthe previously measured voltage.

T.P. 2711
Fundamental Forces Involved in the Use of Oil Well Packers
Authors: Webber Jack C.
Published: April 2012

Introduction

The successful use of oil well packers requires, in part, an understanding ofthe pressures which exist at the packer in various applications and anunderstanding of the characteristics of the various types of packers. It iswith these pressures, the resultant forces, and the characteristics of packers, that this paper is primarilyconcerned.

An oil well packer may be defined as a mechanical device for blocking thepassage of fluids in an annular space. In the more usual case, the annularspace is that between the tubing or drill pipe in a well and the casing, andpackers which block such an annular space are broadly referred to as casingpackers. In the other case, the annular space is that between the tubing ordrill pipe and the walls of an open hole, and packers for blocking this spaceare generally called formation packers. While the hydraulics involved areessentially the same for casing and formation packers, a greater variety of conditions areencountered in the use of casing packers and only casing packers will bediscussed.

After a packer has been set and a pressure seal effected between tubing andcasing, the packer is comparable to a piston in a cylinder. Pressures actingupon a piston result in forces which will move the piston unless some means isprovided to prevent such movement.

In the same manner, pressures acting upon a packer will move the packer unlessthere is present a sufficiently great restraining force.

Packer Classifications

Packers may be classified according to the pressure conditions under which theyare capable of blocking the annular space between tubing and casing. Fig. 1shows schematically two types of packers in common use. These packers arecapable of blocking the annular space against the passage of fluids under adifferential pressure of significant magnitude only when the pressure in theannular space above the packing element is greater than the pressure below. Itmay be seen that in Fig. 1-a, slips with teeth which bite into the casing andprevent downward movement are provided. In Fig. 1-b, an anchor preventsdownward movement. In each case, there is only the tubing to prevent upwardmovement when differential pressures act to move the packers upwardly. Packerswhich hold only a significant differential pressure acting downwardly have beenin use since the early days of the oil industry and will hereafter be referredto as conventional type packers.

T.P. 2710
Multiple Condensed Phases in the N-Pentane-Tetralin-Bitumen System
Authors: Billheimer J.S. , Sage B.H. , Lacey W.N.
Published: April 2012

A restricted ternary system made up of n-pentane, tetralin, and a purifiedbitumen was investigated at 70, 160, and 220'F. Most of the experimentalobservations were at atmospheric pressure or at 200 psi. However, someexperimental measurements were carried out at a pressure of approximately 8000psi.

It was found that the purified bitumen was precipitated from its solution ordispersion in tetralin by the addition of n-pentane and that the separationoccurred at lower weight fractions of n-pentane at the lower temperatures. Thebitumen-tetralin solutions show some colloidal characteristics at temperaturesbelow 160'F when near compositions at which the bitumen separates as a solidphase. At states remote from the phase boundaries and at temperatures above160'F these characteristics become less evident. Under these lattercircumstances the mixtures tend to follow the behavior of true solutions, particularly in regard to the approach to heterogeneous equilibrium. Anincrease in pressure appears to increase the solubility of bitumen intetralin-n-pentane solutions. This effect is more pronounced at temperaturesabove 160'F than at lower temperatures.

Introduction

Asphaltic phases of plastic or solid nature have appeared in numerous instancesduring the recovery of petroleum from underground reservoirs. Such depositionsoccurring underground appear to have caused adverse production histories forparticular wells or zones. Because of this field experience, it is desirable tounderstand the factors which influence the formation or separation of theasphaltic phases from petroleum. The problem is unusually complex because thenumber of true components involved is very large and the details of the phasebehavior encountered are difficult to ascertain experimentally.

The literature relating to asphalts, asphaltines, and bitumen is voluminous andwidespread. Only those references which are directly pertinent to the work athand are cited. The separation of an asphaltic phase, hereinafter calledbitumen, from naturally occurring hydrocarbon mixtures has been the subject ofseveral investigations. It has been found that as many as four phases may beproduced from a crude oil by the solution of a natural gas and propane at apressure of 1500 psi and a temperature of 70'F. The separation of bitumen fromsuch naturally occurring mixtures results in at least one liquid phase which issubstantially free of high molecular weight components. The influence of thesolution of lighter hydrocarbons on the separation of bitumen from a Santa FeSprings crude oil has been investigated.

T.P. 2730
Wave Forces Computed for a Typical Offshore Drilling Site
Authors: Horrer Paul L.
Published: April 2012

Costly damage by severe wave attack to many engineering structures hasillustrated the need for a consideration of the nature of wave action in plansfor offshore drilling operations. Using wave data it is possible to answerquestions pertaining to engineering problems such as platform elevation, structure orientation, and expected wave forces. For locations where waverecords are not available a technique can be used to obtain information aboutwave characteristics from past meteorological data and near shore submarinetopography. Forces exerted on structures by waves may be divided into fourparts. A completed study is given in which frequencies of various wave heightsand maximum frictional drag forces are computed for a typical offshore drillingsite.

Introduction

Waves of tremendous proportions accompanying hurricane winds crash againstbreakwaters and other offshore structures causing untold damages. Wave forcesexerted on structures at these times are enormous, as shown by past records ofincidents where massive portions of breakwaters have been broken off and movedby waves. On other similar occasions, whole structures have been unloosed andsmashed or floated away. These incidents, which seem almost incredible, serveto illustrate the great amount of energy contained in large waves, and to showthat this energy results in powerful forces destructive to offshoreinstallations which are not designed sufficiently strong to withstand waveattack.

In the past the expected frequencies of waves having various characteristicshave rarely been considered in the design of structure affected by wave action.As a result, many structures have failed to accomplish the purpose for whichthey were designed or have collapsed under wave attack. Others have beenconstructed to withstand greater wave energy than is ever encountered, withresulting waste of material and construction time.

In this study an analysis is made of the frequencies of waves having differentcharacteristics which affect the plans for offshore drilling installations.After such an analysis the erection of these structures can proceed with lessrisk involved and with more efficiency and economy.

T.P. 2767
The Application of the Laplace Transformation to Flow Problems in Reservoirs
Authors: Van Everdingen A.F. , Hurst W.
Published: April 2012

For several years the authors have felt the need for a source from whichreservoir engineers could obtain fundamental theory and data on the flow offluids through permeable media in the unsteady state. The data on the unsteadystate flow are composed of solutions of the equation

(Equation).

Two sets of solutions of this equation are developed, namely, for "theconstant terminal pressure case" and "the constant terminal ratecase." In the constant terminal pressure case the pressure at the terminalboundary is lowered by unity at zero time, kept constant thereafter, and thecumulative amount of fluid flowing across the boundary is computed, as afunction of the time. In the constant terminal rate case a unit rate ofproduction is made to flow across the terminal boundary (from time zero onward)and the ensuing pressure drop is computed as a function of the time.Considerable effort has been made to compile complete tables from which curvescan be constructed for the constant terminal pressure and constant terminalrate cases, both for finite and infinite reservoirs. These curves can beemployed to reproduce the effect of any pressure or rate history encountered inpractice.

Most of the information is obtained by the help of the Laplacetransformations, which proved to be extremely helpful for analyzing theproblems encountered in fluid flow. The application of this method simplifiesthe more tedious mathematical analyses employed in the past. With the help ofLaplace transformations some original developments were obtained (andpresented) which could not have been easily foreseen by the earliermethods.

Introduction

This paper represents a compilation of the work done over the past few yearson the flow of fluid in porous media. It concerns itself primarily with thetransient conditions prevailing in oil reservoirs during the time they areproduced. The study is limited to conditions where the flow of fluid obeys thediffusivity equation. Multiple-phase fluid flow has not been considered.

T.P. 2732
A Note on the Theoretical Description of Wetting Liquid Relative Permeability Data
Authors: Rose Walter , Wyllie M.R.J.
Published: April 2012

In a recent technical note, Owen Thornton suggests that wetting liquidrelative permeability may be derived from the relationship:

(Equation 1)

where Pd/Pc is the ratio of displacement pressure to capillary pressure atthe wetting liquid saturation Sw, and I is the resistivity index at thissaturation. Thornton shows that this expression gives values for relativepermeability in good agreement with those experimentally determined byLeverett. We have recently developed another expression for krw, which seemspreferable to Equation 1 since it requires fewer experimental data for itsverification. This equation may be derived in the following manner. Making useof the analogy between mass transfer of fluid in a porous medium and electricalconductivity through the fluid in the same medium, we can postulate a hydraulicformation resistivity factor analogous to an electrical formation resistivityfactor. From Poiseuille's Law the resistivity to flow in a tube of radius R isof the form 8'/R', where ? is the viscosity of the fluid. Similarly, theresistivity to flow in a porous medium of the same dimensions as the tube isgiven by D'Arcy's Law as ?/k, where k is the permeability of the medium. Thehydraulic formation resistivity factor, Ff is thus the quotient of these tworesistivities, or:

(Equation 2)
Gas Hydrates of Carbon Dioxide-Methane Mixtures
Authors: Unruh Carl H. , Katz Donald L.
Published: April 2012

Experimental data are presented for hydrate formation conditions for gasmixtures of carbon dioxide and methane. Equilibrium constants for carbondioxide, defined as the mole fraction of carbon dioxide in the gas phase (drybasis) divided by the mole fraction of carbon dioxide in the hydrate (drybasis), were calculated using the equilibrium constants for methane developedin an earlier paper.

Introduction

A series of papers have been written on gas hydrates, giving temperaturesand pressures at which hydrates would form. Vapor-solid equilibrium constantshave been developed for methane, ethane, propane and iso-butane by which it ispossible to compute for a specific gas mixture the temperature and pressure atwhich hydrates will form.

Carbon dioxide is present in many natural gases in concentrations usuallyfrom 0.1 to 2.0 per cent. It also forms a gas hydrate with water and presumablyenters the solid solution when present with a natural gas which is forming ahydrate. The equilibrium constant giving the ratio of the concentration ofcarbon dioxide in the gas phase to the concentration in the solid phase isrequired for including the effect of the carbon dioxide when computing theconditions for hydrate formation.

Direct determination of the concentration of carbon dioxide in solid hydraterequires a difficult separation to be made. Therefore, this research resortedto the measurement of the temperature and pressure at which specific mixturesof methane and carbon dioxide would form hydrates. From the equilibriumconstants previously mentioned for methane, it is possible to compute theequilibrium constant for carbon dioxide, without measurement of the compositionof the solid phase.

Fig. 1 shows the conditions at which methane and carbon dioxide formhydrates.

T.P. 2578
Relative Permeability To Gas
Authors: Leas W.J. , Jenks J.H. , Russell Charles D.
Published: April 2012

A detailed description is given of an experimental method for determiningrelative permeability of porous media to gas. Results are presented for naturaland synthetic cores. The experimental data for two and three phase systems arecompared. The reproducibility of the equilibrium gas saturation is demonstratedand the effects due to a variation in rate of gas flow are discussed. Anattempt is made to correlate total permeability and rock textural factors withrelative permeability to gas. Capillary pressure curves obtained simultaneouslywith the relative permeability curves are shown to be equivalent to thoseobtained in conventional displacement cells.

Introduction

The advances in petroleum reservoir technology during the past decade havemade increasingly apparent the desirability of a simple, rapid, reliable methodfor obtaining relative permeability data on small cores. Such data are neededin order to study fluid mechanics in porous media and for the more refinedreservoir behavior prediction calculations now under development.

T.P. 2810
Performance Characteristics of a Volumetric Condensate Reservoir
Authors: Allen F.H. , Roe R.P.
Published: April 2012

The performance history of a volumetric gas condensate reservoir ispresented. Curves depict the pressure-production relation and illustrate thephase behavior of the reservoir fluid. This performance is compared tocalculated performance.

This Bacon Lime Reservoir was discovered in 1941 and has been produced tofield separators and gas sales. Reservoir performance has been observed byperiodic bottom hole pressure surveys and companion sample analysis of welleffluents, in addition to gas and condensate production data.

The pressure-production history demonstrates that the reservoir has producedunder volumetric control. The "retrograde" behavior of the reservoirfluid is illustrated by decreasing butanes-plus content of the well effluent, followed by revaporization as the reservoir pressure approaches abandonment.Calculated performance predictions are compared to actual performance and somediscussion offered on apparent discrepancies.

Introduction

Since the late 1930's, many gas condensate reservoirs have been developed, the retrograde theory of phase behavior has been generally accepted, and anumber of cycling programs have been initiated. Numerous technical papers havesince appeared in the literature dealing with the theory and application ofcycling the gas condensate reservoirs. Some cycling operations have nowadvanced to a stage where it is possible to determine performancecharacteristics to a fair degree of accuracy.

Field performance data for gas condensate reservoirs operated by pressuredepletion have not been so extensively reported in the literature, althoughtheir probable behavior has been discussed in explanation of the retrogradetheory. It is the purpose of this paper to compare calculated theoreticalreservoir performance with field observations and well stream analyses whichhave been obtained throughout the practical producing life of a smallvolumetric gas condensate reservoir.

The reservoir under study is the Bacon Lime Zone of a field located in EastTexas. The Bacon Lime occurs in the Lower Glen Rose Formation of CretaceousAge.

T.P. 2708
The Estimation of Permeability and Reservoir Pressure From Bottom Hole Pressure Build-Up Characteristics
Authors: Miller C.C. , Dyes A.B. , Hutchinson C.A.
Published: April 2012

This paper presents a simple and practical method for the estimation ofeffective permeability and reservoir pressures from the rise in bottom holepressure when a well is shut in. The equations on which the method is basedconsider a stabilized well producing from a uniform formation when flow is shutoff at the sand face followed by the unsteady state flow of a compressibleliquid from regions far from a well to points closer in during the build-upperiod. An approximation for extending the method for two-phase flow in thereservoir is also presented.

In order to compare the effects of extremes in the conditions existing atthe external boundary of the reservoir, two general equations defining thebuild-up characteristics of the reservoir are shown: first, for a reservoirwith constant pressure maintained at the radius of drainage, and second, for areservoir with no influx over the radius of drainage. These equations definethe build-up characteristics for the shut-in well as functions of time, thepermeability and porosity of the drainage area, the viscosity andcompressibility of the fluid flowing, the production rate prior to shut-in, andthe radius of drainage of the well.

When a well is shut in at the surface, rather than at the sand face, flowwill continue into the well bore after shut-in due to the compressibility ofthe fluids in the bore. The effect upon the build-up characteristics of thisflow into the well after shut-in has been studied by means of the electricalanalyzer. From the basic relationships and consideration of the limitations dueto continued flow after shut.in, methods have been developed for the estimationof the effective permeability of an area from the plot of the build-upcharacteristics of the well producing that area.

T.P. 2849
The Microlog - A New Electrical Logging Method for Detailed Determination of Permeable Beds
Authors: Doll H.G.
Published: April 2012

A new electrical logging method is described which measures the resistivity ofsmall volumes of material near and behind the wall of the bore holes. The verysmall electrode systems used are supported in the face of the flexibleinsulator pad of appropriate dimension maintained in contact with the wall. Themeasurements are recorded simultaneously with two different electrodespacings.

This method provides a very detailed record of the formations and particularlyof the permeable beds traversed by the bore holes.

The application of MicroLog to the location of permeable zones within compactformations, such as limestone, and to the determination of the amount of sandexisting in sequences of thin shale and sand streaks is discussed.

The possibility of quantitative determination, providing a step toward theevaluation of formation porosity and mud cake thickness, is also examined.

Field examples illustrate the essential features of the method.

Introduction

In conventional electrical logging, the spontaneous potential (SP) log is usedto delineate the permeable beds, and the resistivity logs are used primarily toprovide indications concerning the fluid content of the beds.

When the formations are much more resistive than the mud, as happens, forexample, in limestone fields, the SP currents are short-circuited by the moreconductive mud column, with the result that the SP log is quite rounded. Inthat case, the SP log generally gives the approximate location of the permeableformations but it cannot be used for an accurate determination of theboundaries of each permeable bed.

Solutions for the problem of obtaining a better determination of the permeablebeds in limestone fields were developed from two angles. One approach consistedin improvements to the logging of the SP, as given by Selective SP logging andStatic SP logging. These new methods, which have been described in an earlierpaper, give good results when the mud is not too salty, but they are still in asomewhat experimental stage, mostly because the development efforts have latelybeen concentrated on another approach to the problem, i.e., the MicroLog.

T.P. 2880
Improvements in the X-Ray Saturation Technique of Studying Fluid Flow
Authors: Morgan F. , McDowell J.M. , Doty E.C.
Published: April 2012

Improvements in the X-ray method of measuring liquid saturation and saturationdistribution are presented. Two identical direct current amplifiers have beenadded to measure continuously the intensities of the X-ray tube output and thebeam which has passed through the core under test. The ratio of theseintensities is automatically recorded on a modified Brown Electronik Recorder.Arrangements have been made to drive the core automatically and in synchronismwith the recorder chart so as to give a continuous curve showing the variationof liquid saturation along the length of the core. By determining the ratio ofthe two X-ray beam intensities simultaneously the measurements are madeessentially independent of small fluctuation in voltage and current supplied tothe tube. This improved technique has been used for investigating the fluiddistribution along the length of cores and core assemblies when one fluid isdisplaced by another. Typical results of these studies are shown.

Introduction

In a previous publication a method was described for measuring the oilsaturation in cores which was based on the absorption of X-rays by the fluidcontent of the core. While that technique is capable of yielding accurateresults, the original apparatus was not especially convenient for determiningthe fluid distribution along the length of a core. This was primarily due tothe slow response of the amplifier and galvanometer and the necessity of makinga point by point survey of the material under investigation. It was, therefore, not only possible for sections of the core having a variable or unusualsaturation distribution to escape observation entirely, but changes in outputof the X-ray generator between readings on the unknown and the monitorintroduced errors in the measurements that could be avoided only by furtherstabilization of the source or by taking a large number of readings.

This paper describes a method and apparatus for recording continuously andautomatically the intensity of the X-ray beam that is transmitted by a core.The variation of saturation with time at a given section of the core may thusbe found, or by scanning the core by driving it in synchronism with therecorder the saturation distribution may readily be determined.

T.P. 2881
Pore Size Distribution of Petroleum Reservoir Rocks
Authors: Burdine N.T. , Gournay L.S. , Reichertz P.P.
Published: April 2012

An investigation of equivalent pore entry radii in typical samples of petroleumreservoir rock and the pore volume associated with each value of pore entryradius has been made. Theoretical discussions together with experimentalprocedures for obtaining pore entry radii and the distribution of pore volumewith pore entry radii are presented. Experimental results on a number of coresamples, along with typical distribution curves, are shown. Data on the percent of the pore volume filled by mercury at a pressure of 1500 psi areincluded. The results of re-runs of samples, made possible by regenerativeapparatus, show the repeatability of the data and indicate the amount ofphysical change in the samples by mercury penetration. Theoretical equationsfor calculating permeability from pore size distribution data were derived andthe results of such calculations are compared with measured gas permeabilitydata. The effect of the shape, surface area, and weight of the sample on thepore size distribution of reservoir rocks was investigated experimentally.Mercury capillary pressure curves are compared with those obtained by theporous diaphragm method using gas to displace water.

Introduction

Standard core analysis techniques, in general, lead to quantities which arestatistical averages of the varying properties of the samples underexamination. Although such statistical information has real value in predictingthe gross performance of porous bodies, it fails to provide fundamentalinformation concerning the properties of the porous medium itself or anyprocesses which may be occurring in it. For example, a gas permeabilitymeasurement on a core sample is an indirect way of determining an average poreradius for that particular sample. Since there are many combinations of poreradii that will give the same radius, and, hence, the same permeability, noinformation is obtained on the pore size distribution. Furthermore, similarvalues in permeability do not imply similarity in other properties of a porousmedium. For instance, it is possible to have two core samples with identicalpermeability which would have different residual oil contents at the end of anair-oil drive, or even different amounts of interstitial water.

It has been recognized for some time by the petroleum industry that adetermination of pore size distribution for porous reservoir rocks offeredpromise of increased understanding of fundamental flow processes in the porousmatrix, and therefore of petroleum reservoir performance in general.

T.P. 2893
The SP Log in Shaly Sands
Authors: Doll H.G.
Published: April 2012

As a continuation of the earlier paper on the general subject of the SP log, amore complete analysis of certain features of the SP log in shaly sands isgiven. The pseudo-static SP in front of shaly sands is compared, on atheoretical basis, to the static SP in front of clean sands, as a function ofthe respective amount of shale and sand in the formation, and of the relativeresistivities of the shale, of the uncontaminated part of the sand, and of theinvaded zone of the sand.

As a conclusion, the advantage of using reasonably conductive mud in this caseis shown.

The discussion is illustrated by field examples.

Introduction

The discussion reported in the present paper is based on a theoreticalanalysis, and not on experiment. The field examples, joined to the text, areshown only as qualitative illustrations of the essential results of thisanalysis. Although the hypotheses made in the theoretical developments mayperhaps be somewhat improved, it seems, nevertheless, that the results obtainedaccount reasonably well for the actual phenomena, and give a fair approximationof their order of magnitude.

The paper contains a mathematical analysis of a tri-dimensional distribution ofpotentials and current lines, due to spontaneous electromotive forces arisingat the contact of shales and free electrolytes, as a function of the geometryand of the respective resistivities of the different media involved. It isassumed, although this hypothesis is not proven, that the emf's remain the sameeven if the shale occurs in very thin layers or in dispersed particles.

It has already been pointed out that, all other conditions being the same, thedeflection of the SP log in front of a shaly sand is smaller than opposite aclean sand. When the thickness and the conductivity of a clean sand are largeenough, the deflection of the SP log reaches a limiting value which is equal tothe "static SP" of the clean sand. It is generally convenient to takethe static SP of shale as the reference value or "base line." As aconsequence, and for the sake of abbreviation, the expression, "static SPof a clean sand," is often used to designate the difference between thestatic SP of that sand and that of the shales, which difference is a measure ofthe total electromotive forces involved in the chain mud sand-shale.

T.P. 2912
Analysis of Fractured Limestone Cores
Authors: Kelton Frank C.
Published: April 2012

A method is outlined for the analysis of large cores, developed primarily forthe purpose of obtaining reliable data on fractured or vugularlimestones.

Porosity and fluid saturations are determined by a modified Dean-Starkextraction after initially bringing the samples to 100 per cent liquidsaturation by a vacuum-pressure method. Horizontal permeabilities on the wholesamples are determined in two directions, parallel and perpendicular to thedirection of principal fracturing.

Results are presented for various types of formations. A comparison is madebetween data obtained by this special method and the method of conventionalanalysis, and discussion is given of the relative advantages and limitations ofeach. In view of this comparison a modified method for the analysis offractured and vugular formations is proposed, which method retains theadvantages of the previously outlined techniques but gives promise of speedingup the analysis.

Introduction

For many years the greater part of the production in the Permian Basin was fromformations of Permian and Pennsylvanian age. While production from theseformations is still the predominant production, deeper prospecting has broughtto light older formations with oil productive characteristics. Attempts to corethese deeper horizons were at first usually characterized by poor recovery. Theold rule of thumb, "good core recovery - poor well" was originated andremained in effect until recently. With the advent of diamond coring and theincreased efficiency in drilling and coring operations, the old adage has lostits significance. Formations of Devonian, Silurian and Ordovician ages weresuccessfully cored with varying degrees of recovery. The cores thus obtainedwere surprising and in some cases disappointing. Good recovery from theseformations led to speculation as to the feasibility of analysis and the meaningof data obtained from conventional analysis. Commercial laboratories wereengaged to analyze these cores, and their results indicated that data obtainedby conventional methods would be of little value. From visual inspection it wasapparent that in many cases the effective porosity for storage of hydrocarbons, and permeability, were contained largely in fractures and solution cavitiesrather than in the primary crystalline structure of the formation. In othercases the solution cavities augmented the effective porosity of the primarycrystalline structure, or fractures enhanced the permeability of the latter sothat the formation might respond favorably to acidization and becomecommercially productive. Since the spacing of the cavities and fractures wasoften comparable to the core diameter, it was evident that the entire coreshould be analyzed instead of small fragments.

T.P. 2913
Vapor-Liquid Equilibrium Data on the System Natural Gas-Water-Triethylene Glycol at Various Temperatures and Pressures
Authors: Porter Joe A. , Reid Laurance S.
Published: April 2012

Gas dehydration plays an important part in the production of natural gas.Effective dehydration prevents formation of gas hydrates and the accumulationof water in transmission systems, insuring uninterrupted gas deliveries atmaximum efficiency under the most adverse weather conditions. At the presenttime, most gas companies require a maximum water vapor content of seven lb permillion standard cu ft of gas, so that virtually all gas tendered for sale mustbe dehydrated to meet this specification.

For a number of years it has been common practice to produce gas and gather itat a common point for dehydration prior to discharge into the transmissionsystem. However, higher transmission line pressures, long gathering lines andrelatively low ground temperatures have made it necessary to dehydrate gas at, or near, individual wells in order to gather gas from a number of newlydeveloped fields without unusual difficulty. Where gas has been dehydrated atpressures ranging from 300 to 800 psi in the past, future trends indicate thatthese processes may be operated at pressures as high as 2,000 psi.

Economics of gas dehydration are of great importance, particularly wherefacilities must be provided to process relatively small quantities of gas, suchas the production from an individual well. Although the adsorption of watervapor from gas on a granular sorbent material such as activated bauxite, activated alumina, or one of the alumina-silica gels is highly effective andproduces virtually "bone dry" gas, the cost of a small unit of thistype is substantially greater than that of an absorption process which, throughproper selection of the absorbing liquid, will dehydrate the gas sufficientlyto meet pipe line specifications. For this reason, a great deal of emphasis hasbeen placed on the development of small, inexpensive dehydration units and thesearch for more effective absorbent liquids has been intensified.

T.P. 2848
Volumetric Behavior of Oil and Gas From a Louisiana Field I
Authors: Reamer H.H. , Sage B.H.
Published: April 2012

An experimental investigation was conducted upon five different pairedsamples of oil and gas from a field in Louisiana. The study, with each pair ofsamples, included the measurement of the formation volume and the volume of theliquid phase for three mixtures of the oil and gas. The gas-oil ratio variedfrom approximately 200 to over 40,000 cu ft per bbl and measurements were madeat temperatures between 40' and 250'F. The gravity of the tank oil for the fivesamples under investigation varied between 38.0? and 55.8? API.

The composition of the oil and gas samples and their mixtures is submitted intabular form. A number of diagrams depicting the effect of temperature andgas-oil ratio upon retrograde dew-point pressure are presented.

Introduction

During the past two decades a fairly large number of investigations were madeof the volumetric behavior of naturally occurring hydrocarbon mixtures. Theearlier work of Beecher and Parkhurst and a more recent report on samples fromDominguez Field are typical of research of this nature. Such studies have beenused in estimating the volumetric behavior of fluids in producing fields otherthan those from which samples were taken. Progress has been made in correlatingthe influence of pressure, temperature, and composition upon the specific andformation volume of hydrocarbon mixtures of relatively low gas-oil ratios, butattempts to extend this correlation to higher ratios have not been particularlysuccessful. The influence of composition upon the volumetric behavior of suchsystems cannot be simply related to a single parameter such as gas-oil ratio.In order to aid in the extension of the correlation, of the volumetric behaviorof mixtures of oil and gas to higher ratios, a rather complete study was madeof five different pairs of samples from a Louisiana field. The complexity ofthe influence of composition upon the volumetric and phase behavior of suchsystems in the regions of retrograde condensation was indicated by earlierwork, and it is doubtful if simple correlations can be established in theseregions with the information currently available. The terminology employed inthis paper is identical to that utilized earlier.

T.P. 2950
The Kobe Porosimeter and the Oil Well Research Porosimeter
Authors: Beeson Carrol M.
Published: April 2012

Reasons are given for using a Boyle's-law porosimeter in conducting coreanalysis for either routine or research purposes. Among other things, it ispointed out that such a porosimeter permits the measurement of all basicproperties on the same sample, thereby eliminating the sources of errorinherent in the use of adjacent samples. References are made to investigationsof gas adsorption on various porous materials, to show that the use of heliumin Boyle's-law porosimeters reduces to negligible proportions the error due tothe adsorption or desorption of the operating gas.

Two Boyle's-law instruments are described, which permit accurate and rapidmeasurements of porosity. Schematic sketches and explanations are included, along with derivations of equations required in performing precisedeterminations.

Summaries of data obtained during calibration are tabulated and analyses of thedata are presented as indications of the precision and accuracy of each device. Comparisons are also shown for measurements made with each of the instrumentson the same test pieces and cores.

Introduction

An accurate porosimeter, operating on the principle of Boyle's law, is ofconsiderable value in the analysis of cores for either routine or researchpurposes. This is due primarily to the fact that the measurement of porositywith such an instrument leaves the sample free of' contamination by anyliquid.

When used in conjunction with an extraction apparatus for determining oil andwater saturations, a Boyle's-law porosimeter permits the measurement of allbasic properties on the same sample. This eliminates the sources of errorinherent in the use of adjacent samples, or the necessity of determiningporosity after all other properties have been obtained.

Large errors may result from combining measurements made on adjacent samples inorder to obtain a single property. This type of error is definitely involvedwhen oil and water are measured with one sample and the pore volume is measuredwith an adjacent one. Furthermore, the source of error would be present to someextent, even if the analyst could choose the samples so they were trulyadjacent from a geological standpoint.

T.P. 2953
Relative Productivity of Perforated Casing - II
Authors: Howard Robert A. , Watson Marsh S.
Published: April 2012

The effect of depth of formation penetration by casing perforations has beenstudied by means of an electrolytic model. It is found that the relativeproductivity of perforated casing is profoundly affected by the depth to whichthe formation is penetrated. The first in. of penetration is of especialimportance. A scaling equation which was shown to agree with experimentalresults at zero penetration is used to calculate the relative productivity of ascaled down casing with scaled down perforations.

Introduction

In an earlier paper the authors showed that the point sink representation ofcasing perforations is inadequate. It was pointed out at that time that whilethe electrolytic model results were a marked improvement over point-sinkcalculations, they still left a great deal to be desired in that theelectrolytic model represented a case not realizable in practice, namely, aclean hole through the casing but undisturbed formation on the other side ofthe casing. Obviously, to be effective, the perforation must penetrate a finitedistance into the producing formation. It was the purpose of the presentinvestigation to find how the relative productivity of perforated casing varieswith depth of penetration.

The term "depth of penetration" as used in this paper refers to thedistance which the perforation penetrates the producing formation. The amountof casing and cement penetrated is not taken into account, a fact which isdiscussed more fully later. The "casing radius," therefore, is to beinterpreted as the radius of the boundary between cement and formation wall, incases where the casing is not in contact with the formation wall.

Apparatus

The electrolytic model experimental setup was identical with that describedin the previous paper except that the platinum electrodes were now allowed toproject from the lucite cylinder by varying amounts. When fewer than eightelectrodes were used, the unused ones were covered with a coat of insulatingmaterial to minimize disturbances to the current flow-lines.

T.P. 2933
High Pressure Water Injection for Maintaining Reservoir Pressures, New Hope Field, Franklin County, Texas
Authors: Trube Albert S. , DeWitt Sam N.
Published: April 2012

This paper presents a discussion of the pressure maintenance operations whichwere begun in the New Hope Field, Franklin County, Texas, in 1944. The projecthas required the injection of extraneous waters at depths from 7,300 to 8,00'Ft with intake well-head pressures up to 4,000 psi in three differentreservoirs - the Bacon, Hill, and Pittsburg.

Records of oil and water production, water injection and the GOR have been keptfor each reservoir and reservoir pressures were taken at regular intervals.These data indicate that the Bacon Reservoir had no apparent water encroachmentup to the time of water injection. However, the Pittsburg and Hill reservoirshad some natural water influx but not sufficient to prevent pressures fromdeclining below the bubble point. The Bacon and Hill reservoirs respondedalmost immediately to water injection, while the Pittsburg, which is the leastpermeable, has shown good pressure response only since August, 1948.

The principle objective of the project has been to increase ultimate recovery.Success of the project to date also has resulted in reduced lifting costs.Estimates based on the initial water breakthrough patterns indicate that theprimary objective of substantial additional recovery will be accomplished, andthere is a possibility that the original estimates of oil recovery withpressure maintenance will be exceeded.

Introduction

This pressure maintenance project was one of the earliest primary pressuremaintenance programs to be attempted on a multiple zone field. There are threeproducing reservoirs into which water is being injected for the purpose ofmaintaining pressure and increasing the ultimate recovery from each. This paperis limited in scope to all account of the development of the project, thepressure production relationship prior to the injection of water and the effectof water injection on the producing reservoirs. Also discussed are the natureof the injection system and the indicated results on initial waterbreak-through in the Bacon Reservoir.

T.P. 2939