bluuebunny/crossref_metadata_2025 huggingface dataset:
Bottom Hole Flow Surveys for Determination of Fluid and Gas Movements in Wells
Authors: Dale C.R.
Published: April 2012

The need for instruments to measure the movement of fluids and gas in wellshas been recognized by engineers for many years. Information regarding flow inthe producing interval has a direct bearing on completion practices in newwells and also provides information on the production characteristics of thewell. Many hours of engineering time are spent in planning and completing wellsbut knowledge as to whether or not the original planning has produced thedesired results has not always been complete. Many questions such as thefollowing often arise: Why is it that two wells are completed under supposedlyidentical conditions, yet one well is a good one and the other is a poor one. Are the sands that look the best on the electric log contributing to theproduction? These and many other conditions in the producing well need to beunderstood in order to develop more efficient production practices and toimprove on methods of completing new wells. It is the purpose of this paper tobriefly describe one type of instrument, outline the methods of running theequipment and show the results of surveys made under various conditions. Withan understanding of the use of this type of survey its importance can beevaluated in relation to the problems encountered by the operator.

Description of Instrument

The instrument is a velocity recorder employing a clock-controlled 16mm filmfor recording the rpm of an extremely sensitive rotor which is rotated by theflow of fluids or gas in a well. The helical-vaned rotor and shaft, weighingone-half of one ounce are an integral unit exposed to the well fluids and arethe only moving parts not enclosed in the fluid-tight housing. No packing orfluid seal of these parts is necessary and the shaft is mounted top and bottomon special jeweled bearings. Fig. A is the lower part of the instrument showingrotor and shaft with the protecting housing sleeve removed. The rpm of therotor is recorded on the moving film by a combination electrical and opticalsystem. The record is a series of dashes on the film, each dash and spacerepresenting twenty (20) revolutions of the rotor.

T.P. 2644
A New Compressibility Correlation for Natural Gases and Its Application to Estimates of Gas-In-Place
Authors: Elfrink E.B. , Sandberg C.R. , Pollard T.A.
Published: April 2012

This paper presents an evaluation of compressibility factor data and adiscussion of their application to the estimation of gas reserves.

A correlation is presented which provides compressibility factors for use inboth two-phase and single-phase hydrocarbon systems. Accuracies comparable tothose obtained previously for single-phase systems only can be expected. Asimple means of predicting the presence or absence of a liquid phase in acondensate system of known composition is illustrated.

The correlation is based on 1,030 compressibility determinations from 21hydrocarbon samples taken from eight oil fields. Of the data used, 75 per centwere from California, 15 per cent were from the Mid-Continent area, and 10 percent were from South America. The average numerical deviation of theexperimental data from this compressibility chart is 1.22 per cent.

Charts and tables are included and discussed which illustrate the errorsinvolved through the misuse or nonuse of compressibility factors in estimatesof gas-in-place.

Introduction

The compressibility factor is a coefficient which expresses the deviation ofa gas of given composition from the Perfect Gas Laws. A factor such as this isnecessary in any calculation involving volumes of gaseous mixtures, and findsextensive application in the estimation of natural gas and condensate reserves.It is used in the decline curve, the volumetric, and the material balancemethods of gas reserves estimation.

The behavior of gases at high pressures has been investigated extensively inrecent years and considerable data have been assembled on the compressibilitycharacteristics of a number of gases. Notable among the investigators of highpressure gas relationships are Kvalnes and Gaddy, Kay, Sage and Lacey, andBrown, Standing, and Katz. Other contributors are Smith and Watson, Roland andKaveler, and Stevens and Vance. The data on compressibility factors assembledby these investigators have been presented and correlated in numerous ways;particularly noteworthy is the method first presented by Kay which relatescompressibility factor ?Z? to pseudo-reduced temperature and pseudo-reducedpressure. Other investigators have used this empirical relationshipsuccessfully and numerous charts covering a large number of gases have beenconstructed on this basis.

It is the purpose of this paper to evaluate compressibility factor data and toillustrate the importance of their proper use in the estimation of gas-in-placefor both gas and condensate reservoirs.

T.P. 2642
A Calculation of the Effect of Production Rate Upon Ultimate Recovery by Solution Gas Drive
Authors: Miller Charles C. , Brownscombe E.R. , Kieschnick W.F.
Published: April 2012

The possibility has been mentioned that large pressure gradients in asolution gas driven field caused by high production rates might lead to areduction in the ultimate recovery obtainable compared to that which would beobtained by a very slow rate of production. In the present study the reservoirconditions accompanying a high rate of production and the correspondingultimate recovery were compared with those obtained if the reservoir wereproduced at some marginal rate throughout its entire life. The method ofcalculation involved the application of fluid flow - material balance analysisto a series of successive steady state conditions in the reservoir. In the casestudied very little difference in recovery was obtained at the abandonmentpressure. An analysis of the basic factors involved indicates that the sameresults would hold for considerable variation in properties of reservoirfluids, permeability of the formation or well spacing. Even if the reservoirhas a water drive it appears that no harm will be done by open flow productionif the rate is cut back before any appreciable free gas is produced. However, any condition which leads to disproportionate withdrawal rates and which causeslarge pressure differences over large areas might result in substantial loss inultimate recovery.

Introduction

When the pressure declines in a reservoir, gas is evolved from solutioncausing a shrinkage in the reservoir oil so that a stock tank barrel of oilwith its residual dissolved gas occupies a smaller volume than originally. Fora given reservoir oil saturation, therefore, stock tank oil content will behigher at the lower pressure. At the same time the evolved gas which remains inthe reservoir reduces the reservoir oil saturation, and this would be expectedperhaps to cause a reduction in stock tank oil content. However, around thewell the shrinkage occurs so rapidly that stock tank oil may actuallyaccumulate in this region in spite of the simultaneous reduction in reservoiroil saturation. If this accumulation should continue, spreading into a largerzone, the loss might be appreciable and because larger pressure gradientsaccompany higher rates the accumulation might possibly be large if wells areproduced at too high a rate. It is the purpose of this paper to determine theeffect of rate of flow on ultimate recovery by solution gas drive.

T.P. 2565
Correction of Gas Volumes for Compressibility and Temperature
Authors: Brokaw Albert D.
Published: April 2012

The accompanying charts are presented to extend and improve a chartpublished under the title "A Chart to Provide Approximate Correction forTemperature and Deviation from Boyle's Law.'' The applicability of this earlierchart was limited by the fact that it was based on the work of Burke and Keyesand Kvalnes and Gaddy whose experiments were conducted with pure methane, theadjustments suggested for natural gases of higher specific gravity wereunsatisfactory except within limited ranges of temperatures and pressures, andprecise interpolation was difficult.

The extensive work of G. G. Brown, D. L. Katz and their associates on theheavier natural gases has provided better bases for the needed corrections, andthe present charts, which are based largely on their work, are intended tosimplify the computations involved.

The design of the charts has been changed by plotting temperatures as afunction of pressure and correction factor, on a semilogarithmic or"ratio" grid, which gives fairly even spacing of the graphs andsimplifies interpolation. Charts have been prepared for natural gas withspecific gravities of.60,.65,.70,.75 and.80.

T.P. 2698
Multiple Condensed Phases in the Decane-Tetralin-Bitumen System
Authors: Billheimer J.S. , Reamer H.H. , Sage B.H.
Published: April 2012

The influence of pressure, temperature, and relative quantity of decane on theseparation of plastic or solid phases rich in bitumen from thedecane-tetralin-bitumen system has been investigated in a restricted range ofcomposition. Measurements were made at atmospheric pressure and at 8000 psi fortemperatures of 70, 160, and 220'F. Behavior similar to that of then-pentane-tetralin-bitumen system was found except that the influence ofpressure upon the separation of bitumen was radically different in thedecanetetralin-bitumen system than that found in any of the earlierstudies.

Introduction

The separation of solid asphaltic or bituminous material from hydrocarbonliquids has been noted in petroleum operations and studied in the laboratory.Publications relating to the separation of bitumen from naturally occurringhydrocarbon mixtures were reviewed in a recent publication. Earlyinvestigations of these mixtures showed a relatively complex behavior, with thequantity of separated bitumen increasing with increased weight fraction of thelighter hydrocarbons until a state was reached at which the separation of asecond liquid phase (liquid II) began. Further increase in the weight fractionof the lighter component caused a decrease in the amount of solid bitumen.However, the total quantity of bitumen in liquid II and in the separated solidphase continued to increase in a regular fashion. This type of behavior wasalso found in the n-pentane-tetralin-bitumen system.

Because of this similarity in behavior of the simpler system and more complexnaturally occurring hydrocarbon mixtures, it became desirable to extend thestudy to aliphatic hydrocarbons of higher molecular weight. As a part of thisstudy an investigation of the decane-tetralin-bitumen system was carried out at70, 160, and 220'F. The details of the techniques employed in the preparationof a purified bitumen from the natural product have already been described. Anadequate quantity was prepared from a crude bitumen obtained from the SanJoaquin Valley by leaching, solution, and precipitation processes. The purifiedmaterial was similar in all measured respects to that employed in the earlierinvestigation of the n-pentane-tetralin-bitumen system.

T.P. 2731
An Electrical Computer for Solving Phase Equilibrium Problems
Authors: Muskat M. , McDowell J.M.
Published: April 2012

Introduction

In both production and refining operations of the oil industry manyprocesses are controlled by the gas-liquid phase relationships of thehydrocarbon mixtures of interest. The quantitative behavior of fractionating ordistillation columns and stills depends on the changes in the equilibriumdistributions of the hydrocarbon components between the gas and liquid phasesas the pressure or temperature conditions may vary along the length of thecolumn or as the gross operating parameters and compositions are varied. In oilproducing operations the nature and amount of gas phase developed within anunderground reservoir as it is being depleted and its pressure declines alsoinvolve the basic equilibrium gas-liquid phase interactions. The influence ofsurface conditions of temperature and pressure and various separationprocedures on the nature and amount of stock tank oil and natural gas recoveredfrom a given well stream is likewise determined by the same basic phaseequilibrium characteristics of the hydrocarbon systems. Such equilibriumseparation of the gas and liquid phases in a well stream is of importance bothin establishing optimum separator conditions for obtaining maximum stock tankoil yields and in the general problem of crude stabilization.

The phenomena involved in these problems and their quantitative aspects can, of course, be established in each individual instance by appropriate laboratoryexperimentation. It has been found, however, that by associating with theindividual hydrocarbon components functional characteristics describing theirindividual gas-liquid phase equilibrium behavior, the phase properties of thecomposite mixtures can be predicted by mathematical computation.

T.P. 2733
Phase Equilibria in Hydrocarbon-Water Systems
Authors: Culberson O.L. , Horn Albert B. , McKetta J.J.
Published: April 2012

The Solubility of Ethane in Water at Pressures to 1200 Pounds Per SquareInch

Since water is present in natural gas and petroleum reservoirs, it is ofengineering value to have accurate experimental data regarding the behavior ofwater in hydro-carbon systems. Since experimental data of this nature are soscarce in literature, a program is under way at the University of Texas toobtain experimental data regarding the distribution of water in petroleum hydrocarbons.

This initial paper is subdivided into three parts:The apparatus and analytical procedure are discussed.The equipment has been checked by comparing the experimental data with dataof literature on the solubility of methane in water at 77'F and pressures to10,000 psia.Experimental data are presented at 100, 160, 220, 280, and 340'F on thesolubility of ethane in water at pressures to 1200 psia. As the temperature isincreased the solubility of ethane in water first exhibits a minimum and then amaximum solubility. The range of applicability of Henry's Law is discussed.

Introduction

Although considerable experimental data have been published onwater-hydrocarbon systems in the hydrate region, the information on thesesystems in the vapor-liquid and the vapor-liquid-liquid regions at elevatedpressures is extremely scarce. A survey of the literature on hydrocarbon-watersystems at elevated pressures was presented by McKetta and Katz showing thesystems and phases investigated. In addition to these existing published data, Poettman and Dean have reported the water content of propane in the three-phaseregion (only the propane-rich liquid and the vapor phases were studied) andMichels, et al. have reported the solubility of methane in water at pressuresto 6800 pounds per square inch at 77?F and at pressures to 1500 psia attemperatures to 300'F.

It has been shown, that the presence of water will materially affect thephase equilibrium of hydrocarbon systems. In order to make experimental studieson the quantitative effect of the presence of water in naturally-occurringhydrocarbon systems, it is desirable to have data available on binaryhydrocarbon-water systems.

T.P. 2778
Squeeze Cementing Operations
Authors: Howard George C. , Fast C.R.
Published: April 2012

Laboratory and field testing of various squeeze cementing techniques andmaterials revealed that many improvements could be made in squeeze cementingoperations. The use of a slow-pumping squeeze cementing procedure permitted thecontrol of the quantity of cement displaced into a formation and aided inobtaining a high final squeeze pressure. Field testing indicated thedesirability of obtaining high final squeeze pressures, the need for improvedformation breakdown fluids, and the necessity of controlling the pressuredifferential during testing after a squeeze job.

Introduction

During the past few years, squeeze cementing operations have beeninvestigated, both from the theoretical as well as the practical point of view, in an effort to arrive at some solution to the many and varied problems thatarise with this type of operation. A review of well files indicated that inmany instances, wells were being squeeze cemented four and five times before asatisfactory pressure buildup was obtained. There seemed to be considerablevariation in opinion as to the proper method of squeeze cementing, as well asdisagreement as to the proper breakdown agent, the quantity of cement thatshould be used, type retainer and length of WOC time that was necessary.Consequently, it was deemed advisable to approach this problem theoretically, field testing each idea developed in hopes of eventually arriving at a squeezecementing procedure that would give reasonable assurance of a successful jobafter one squeeze cementing operation. This investigation was, therefore, divided into two broad headings:Preliminary studies, which include boththeoretical and laboratory studies, andField investigations to determinethe proper squeeze cementing methods.

Preliminary Studies

Overburden Pressure Studies

Squeeze cementing problems are so intimately related to the earth'soverburden pressure that solutions to them are very difficult, if notimpossible, without an understanding of the nature and magnitude of theoverburden pressures encountered at the depths of producing wells. It was thusfelt that the first approach to research on squeeze cementing should be madethrough a study of these pressures.

T.P. 2795
Some Theoretical Considerations Related To The Quantitative Evaluation Of The Physical Characteristics Of Reservoir Rock From Electrical Log Data
Authors: Wyllie M.R.J. , Rose Walter D.
Published: April 2012

Introduction

The use of electrical well logs for the quantitative determination of suchreservoir parameters as connate water saturation, formation permeability andconnate water salinity has recently been attracting the attention of a numberof workers.

While the theory of the determination of connate water salinity from theself potential S.P. log has received rather detailed treatment, relativelylittle attention has been paid to the theoretical aspects involved in thequantitative interpretation of resistivity data. It is clear that if electricalwell logs can be used for the quantitative evaluation of physicalcharacteristics of reservoir rock, they will provide a valuable tool tosupplement cheaply information obtained by more laborious core analysis. Incertain cases it is conceivable that the coring program could be considerablycurtailed if the electric log could be relied upon to give reasonably accuratequantitative information.

It is our object in this paper to examine the theoretical basis ofquantitative log interpretation as expressed in such well-established loggingconcepts as formation factor and cementation factor. It is also our object toinvestigate the physical aspects of the relationship which is presumed to existbetween resistivity index and brine saturation in reservoir rock. Inparticular, we will endeavor to draw attention to the fact that it is possibleto express these logging concepts in terms of capillary pressure-saturationrelationships, permeability and tortuosity parameters which we will consider inthis paper to be fundamentally indicative of rock texture. The probability ofbeing able to obtain from log recordings alone the data theoretically essentialto permit quantitative log interpretation will be examined, and considerationwill also be given to the problem of formulating simple semiempiricalrelationships for use in the field.

Theoretical Considerations

The concept of formation resistivity factor, or as it is now commonlycalled, formation factor, appears to have been introduced by G. E. Archie.Formation resistivity factor as defined by Archie is the resistivity of a rock100 per cent brine-saturated divided by the resistivity of the brine. Thisrelationship had previously been used by physical chemists and the concept is, for example, implicit in an early treatment by Fricke of the conductivity of aqueous slurries.

T.P. 2852
The Coexistence of Liquid and Vapor Phases at Pressures Above 10,000 Psi
Authors: Rzasa Michael J. , Katz Donald L.
Published: April 2012

With greater effort being devoted to the discovery of new oil and gasreserves and a consequent increase in bottom hole pressures due to greaterdrilling depths, the phase relationships of hydrocarbon fluids at pressuresabove 10,000 lb psi are becoming increasingly important.

The present paper discusses the results of research with a windowed cell ona methane-Kensol 16 system to pressures of 25,000 lb psi and temperatures to260'F. Kensol 16 is a commercial high narrow-boiling-range oil.

It is shown that for the temperature range of 60'F to 260'F, this particularsystem exists in two phases to pressures of approximately 14,000 Ib psi, anddata are presented giving the relative amounts of liquid and vapor phasescoexisting under these conditions. Partial phase diagrams are shown for sixdifferent mixtures of methane and Kensol 16, three of which include thecritical region.

In contrast to mixtures composed of substances of fairly close volatility, critical opalescence was noted for as much as ?200'F of the criticaltemperature.

The critical locus of the methane-Kensol 16 system was estimated and theconventional pressure-composition and temperature-composition diagrams were prepared. From these, the equilibriumvaporization factors for methane and Kensol 16 were estimated for temperaturesfrom 60'F to 700'F and to pressures above 12,000 Ib psi.

The relations of this study to petroleum production problems and other phaseequilibria research are discussed.

Introduction

A knowledge of the physical behavior of naturally-occurring hydrocarbonmixtures is fundamental to a thorough treatment of nearly all operationsinvolved in the recovery, refining, and transportation of petroleum.

T.P. 2809
Relative Productivity of Perforated Casing-1
Authors: Howard Robert A. , Watson Marsh S.
Published: April 2012

An electrolytic model study has been made of the relative productivity ofperforated casing. The results show that the relative productivity is roughlyone-half to two-thirds of that predicted from point-sink calculations. Thisdiscrepancy can be satisfactorily explained on the basis of casinginterference. The relative productivity was found to be insensitive to spatialarrangement of the perforations.

Introduction

The relative productivity of wells with perforated casing has been treatedmathematically by Muskat. In his treatment the perforations are represented bysmall spheres, thus enabling him to approximate the flow by that to pointsinks. By neglecting interference between the flow into the various spheresrepresenting the perforations, one may deduce the approximate formula (Equation1).

Fig. 1 is a comparison of values calculated from equation (1) with Muskat'svalues. It will be observed that the approximate values are in error by lessthan 2' per cent.

The disturbing effect of the casing on the flow lines is not explicitly takeninto account by Muskat, but he reasons that interference between the flowpatterns from the various point sinks will result in a negligible flow in theregion within the well radius, and that no appreciable error will result fromnot explicitly excluding flow from this region. This line of reasoning is opento question, however, as the flow impedance, in the immediate vicinity of thewell, of a hemispherical cavity in contact with an opening in the casing istwice that of a spherical sink in a continuous sand layer. There will be adifference, moveover, between the flow into a hemispherical cavity and thatinto a circular hole in the casing. This latter difference can best beappreciated by comparing the flow from a semi-infinite medium into ahemispherical cavity at the edge of the medium with the flow out of a circularopening of the same radius as the hemisphere and which is also on the edge ofthe medium.

T.P. 2851
Liquid-Liquid Displacement in Porous Media as Affected by the Liquid-Liquid Viscosity Ratio and Liquid-Liquid Miscibility
Authors: Everett J.P. , Gooch F.W. , Calhoun John C.
Published: April 2012

The results of two sets of displacement experiments are reported. In the firstset of experiments various solutions of sugar in water were displaced by othersolutions of sugar in water. In the second set oils were displaced by water.Each set of experiments was performed on a linear system made of cementedsilica sand grains.

These displacement tests were made to evaluate the behavior when the ratio offluid viscosities between the displacing and displaced phases was varied. Afurther consequence of the test results is a comparison between displacementbehavior when the displaced and displacing phases are miscible as with sugarsolutions and when they are immiscible as with oil and water.

Introduction

Buckley and Leverett have presented a theory for the displacement of oil by gasor water based upon the relative permeability concept. This theory presents thedisplacement of oil as occurring in two phases, an initial or primary phasepreceding the breakthrough of the displacing phase and a subordinate orsecondary phase during which both oil and the displacing phase flowsimultaneously through the same porous section. These authors gave the resultsof calculations to show that the percentage of oil displaced during the primaryphase by water drive would be dependent upon the ratio of the viscosity of theoil to that of the water. No experimental evidence was reported by theseauthors to substantiate their theory. Qualitatively, however; it has been foundto be in agreement with many observed field results.

Laboratory investigators have been in general agreement in reporting for air orgas drive a small primary phase of production and a large secondary phase.Reported investigations on water drive have shown instances where both primaryand subordinate phases were important, with the former in general being moresignificant.

T.P. 2787
Critical Analysis of the Effect of Well Density on Recovery Efficiency
Authors: Keller W.O. , Callaway F.H.
Published: April 2012

The various theories as to the well spacing-recovery relationship are reviewedin considerable detail and these theories analyzed in terms of theirconsistency with modern reservoir engineering concepts. It is concluded thatthe well spacing problem must be analyzed in terms of recovery efficiency andthat a positive answer to the relation between well density and recoveryefficiency is not available from direct comparisons of the production historiesof wells and fields.

The results of an engineering analysis designed to permit approximatecalculation of recovery efficiencies as a function of well spacing in adepletion type reservoir from basic reservoir data is presented. Results ofthis type analysis indicate that the effect of well spacing on recoveryefficiency in depletion type reservoirs can be expected to be very small.Limitations of this approach are pointed out, particularly with respect to itsapplication in lenticular reservoirs.

Testing techniques are outlined which should indicate whether or not areservoir is continuous between wells and whether or not satisfactory drainageis being obtained with present spacings. A mass of data of this type indicatescontinuity to exist in most fields.

Introduction

The purpose of this paper is to review critically the engineering aspects ofthe well spacing problem, both from the standpoint of certain concepts and fromthe standpoint of reservoir mechanics. The well spacing problem is primarily aneconomic problem in which the optimum well density for a particular field isthat density which will yield the greatest oil recovery consistent withjustifiable development costs. The well spacing answer in terms of economicconditions, however, is extremely sensitive to the variation in recoveryefficiency with well density. The variation in recovery efficiency with welldensity is properly an engineering problem. Different opinions as to thecorrect answer to this engineering problem is the basis for most of the widedifference in opinion among various members of the industry as to optimum wellspacing. This paper will be confined to the engineering problem of the relationbetween well density and ultimate oil recovery; economic considerationsnecessary for the evaluation of optimum well density for any particular fieldwill not be discussed.

T.P. 2938
Performance of Limestone Reservoirs
Authors: Craze R.C.
Published: April 2012

During the past 20 years, research and development in the study of reservoirbehavior have dealt principally with flow of oil through sandstones. Manyreservoir studies of sand fields have proved valuable in promoting recoveryefficiency.

This paper discusses fundamental principles governing oil and gas productionfrom sandstone and limestone alike and presents the results of investigationsrelating to the application of analytical techniques used for sandstonereservoir studies to the study of limestone reservoir performance. Thecharacteristics of limestone porous systems, porosity-permeabilityrelationships, distribution and occurrence of oil, and characteristics of flowthrough such systems are discussed. Recognition is made of the similarities ordifferences which these factors exhibit in limestone and sandstone systems. Comparisons between operating data for typical limestone and sand reservoirsare presented. It is indicated that the distribution and movement of fluids inand through porous limestones follow the same fundamental principles underlyingsuch processes in sandstones. This fundamental similarity may readily bediscernible in the performance of many limestone reservoirs.

The volumetric balance and unsteady state radial flow equation, the fluiddisplacement equation, use of electrical analogue devices, and other analyticaltechniques to study the behavior of limestone fields appear fundamentallyapplicable, but do require thorough understanding of the properties of theformation, of the fluids, their behavior during flow, and adequate productionoperating data. Need for more complete coring and comprehensive examination ofcore properties is stressed. The results of "active oil" studies, andof flow and interference tests are presented. Well spacing, well completion, and efficient rates of production in limestone reservoirs are brieflydiscussed.

Introduction

Limestone and dolomite reservoirs constitute the largest source of supply ofcrude oil in the world, an estimated 60 per cent of present production comingfrom carbonate reservoirs. In many large geologic provinces such as Mexico, theMiddle East, and more recently Canada, almost all the oil is found in this typeof rock. In the United States, all of the major oil-producing areas exceptCalifornia and Pennsylvania contain oil-bearing carbonate formations. Thediscovery in recent years of large oil reserves in the Silurian, Devonian, andOrdovician formations in West Texas, in addition to the large reserves in thePermian, has accentuated the interest of operators, geologists, and engineersin limestone formations and in the many problems associated with understandingthe performance of these reservoirs. The rapid increase in discovery of oil inlimestone formations and the present-day position of prominence held by thesefields in the production and reserve picture in all parts of the worldemphasize the horizons opened to the reservoir technologist in the field ofgeological and production research.

T.P. 2935
Anomalies in the Measurement of Wetting Liquid Pressure Gradients
Authors: Rose Walter , Greifer Bernard
Published: April 2012

The purpose of this note is to call attention to a source of difficultywhich can be responsible for inaccurate estimates of wetting liquid pressuregradients in mixture flow experiments of the Hassler type. It has been ourexperience occasionally to observe what were indicated to be negative pressuregradients, and these were regarded as anomalous in the sense that physicallythey seemed to contradict the requirement that the flux be in the direction ofthe potential field.

At first it was thought that our scheme of assembling barriers and coresample led to such asymmetry in the distribution of isobars that the manometricleads at each end of the core were responding to internal pressures (within thecore sample) which could be either positive or negative with respect to eachother, and which in fact might tend to reflect on different effective corelengths in an unpredictable fashion as the wetting liquid saturation waschanged. However, no compelling evidence of this possibility has beenestablished. In addition, we were cognizant of the requirements to be satisfiedin selecting manometric instrumentation to minimize the delay in response ofthe manometer to the differential pressures being measured, and were thusassured that our observations of anomalous pressure gradients could not beexplained by faulty instrumentation.

What we suggest is that if a leak sink occurs in the fluid lines connecting thecore to either side of the differential manometer, errors exceeding 100 percent may result in the estimation of wetting liquid pressure gradient, eventhough the leak is of such small magnitude that its existence would tend to beobscured by evaporation effects. This is because in a system with leaks at thespecified places, the manometer records at steady state the pressure dropacross the manometer barrier elements in addition to the pressure drop acrossthe core sample.

This possibility will be illustrated below analytically and by numericalexample for the special case where the leak occurs on the high pressure side ofthe core, since we are especially desirous to explain the significance of ourobservations of the so-called negative pressure gradients. It will beindicated, however, that leak sinks on the low pressure side of the core canaccount for observations of anomalously high values of pressure gradient, andthat multiple leaks on both sides of the core can provide for some compensationso that the errors in pressure estimation are reduced. However, the major pointto be emphasized is the fact that the impracticality of detecting the smallleak sinks which give rise to the difficulties makes it a complicated task forthe experimenter in a particular case to know with certainty that hisestimation of pressure gradient lies within the limits of error which can betolerated.

T.N. 57
Influence of Different Types of Formation Waters on Disintegration of Cements
Authors: Clark Roscoe C.
Published: April 2012

A study of the effect of various corrosive waters on five different types ofcements indicated that those cements containing less than 5 per cent tricalciumaluminate were the most resistant to corrosion.

Introduction

Oil field experience indicates that some formation waters are excessivelycorrosive to some cements. A study has been made to determine the mostcorrosive waters and the relative resistance of various types of cement tothese corrosive waters.

Procedure

This study of the corrosion of cement was limited to an evaluation of theeffect of various corrosive waters on five different types of cements. Adetermination was made of the types of cements which offer the greatestresistance to corrosion and of the chemical contents of waters found to be themost destructive to cements.

The laboratory tests were conducted by immersing small cylinders of 20 samplesof set cement in various corrosive waters. The initial mixing of most of thecement slurries was done using Tulsa tap water as the mixing water; however, afew of the slurries were mixed using a sulfate water as the mixing water. Whenthe 20 samples had been immersed for a period of nine months, they were removedfrom their corrosive baths, inspected and photographed.

The field tests were conducted by placing ten cement specimens, each containedin a screen wire thimble, in the gas anchors of insert pumps in wells in sixdifferent fields. The specimens were observed whenever it was necessary to pullthe pumps and were returned to the laboratory when deterioration had reached aserious state.

Experimental Results

In both the field and laboratory tests the resistance of the different cementsto corrosion was determined by the condition of the samples and the number ofsamples of each that were in good condition at the end of the immersion period.Table I lists the various cements tested in the order of their resistance tocorrosion with the most resistant at the top and the least resistance at thebottom.

T.N. 59
Carter Reservoir Analyzer Timing Circuit
Authors: Baldwin W.F.
Published: April 2012

The timing circuit generally employed in Carter Reservoir Behavior Analyzersconsists of a synchronous motor driven cam which actuates a microswitch. Amechanically actuated timer of this type has several inherent disadvantages, among which are the following:The first time interval may not be of uniform length, depending on the exactposition of the cam at the conclusion of a previous run.The positioning adjustments on the microswitch lever arms are critical andrequire periodic readjustment.The mechanical system is subject to wear which will ultimately impair itsaccuracy.

It was therefore considered desirable to devise an alternate method which wouldeliminate these difficulties without introducing others that would be equallytroublesome. This note describes the design of an electronic timing devicewhich has been incorporated in the analyzer constructed by the Field ResearchLaboratories of Magnolia Petroleum Co.

The electronic timer circuit is built around a simple neon glow tube relaxationoscillator, the complete circuit diagram of which is shown in Fig. 1. Theoperation of the circuit is as follows: Condenser C1 is charged to the criticalfiring voltage of the neon glow tube VR-75 by battery B, through resistors R1and R2. When the neon glow tube fires, the condenser C1 is discharged.

T.N. 63
Pressure Behavior in the Woodbine Sand
Authors: Bell John S. , Shepherd J.M.
Published: April 2012

A pressure difference of 280 psi measured initially on opposite sides of themajor fault in the Hawkins Field led to pressure determinations in the Woodbinesand throughout the East Texas basin. Considering the large area, there isunusually good correlation between pressure losses and points of majorwithdrawals, these losses indicating that the basin pressure has beenmaterially reduced by withdrawals, primarily from the East Texas Field andsecondarily from the old fault-line fields of Limestone and Navarro counties, with the pressure loss varying inversely with the log of the distance fromthese two main areas of basin withdrawals to the measurement points. Apparentlyfaults located throughout the basin serve as local blocks to continuouspressure gradients.

Introduction

The pressure anomalies found in the Hawkins Field, Wood County, Texas, shortly after discovery have led to an area-wide investigation of the pressuredistribution within the Woodbine sand of the East Texas basin. These pressureswere obtained by drill-stem tests made for that sole purpose while drillingwildcat wells to deeper horizons. The Woodbine sand of Gulf Cretaceous Age isor has been productive of oil and gas in 42 different fields, with the 28 oilfields currently active having produced 118,000,000 bbl of oil during 1949.With one exception, producing energy for all Woodbine reservoirs has been from water drive provided predominantly by expansion of the tremendousvolume of water contained in the Woodbine sand. This producing mechanism wasrecognized at an early date and was described mathematically by Muskat and bySchilthuis and Hurst in 1934, and these principles were applied to the EastTexas Field performance by Buckley in 1938.

Factual data on the pressure behavior in the Woodbine sand, especially inareas non-productive of oil, have been generally lacking, making estimates ofpressures at various points within the basin dependent upon mathematicalanalyses involving numerous assumptions. Such factual data have been gatheredand are now presented as possible aid to the industry in further analysis ofthe producing mechanism in tile Woodbine sand.

T.P. 3000
Low Temperature Dehydration of Natural Gas
Authors: Records Louis R. , Seely Dwight H.
Published: April 2012

A process for low-temperature dehydration of natural gas utilizingJoule-Thomson effect in expansion through a throttling orifice has been testedin a full-scale field installation. The results of these tests are presented inthe form of performance curves from which the process may be easilyevaluated.

The effect of separation temperature on condensate recovery from the processis also shown.

Introduction

The transportation of natural gas from producing well to the consumer hasalways encountered the problem of hydrate prevention. This problem has becomeincreasingly important in the past ten years due to the rapid increase inproduced gas volumes, production pressures, transportation pressures anddistance from producing wells to consumer.

Natural gas, as normally produced from gas or gas-condensate wells, issaturated with water vapor at well-head conditions of temperature and pressure.The solution of the hydrate problem requires but one basic process -dehydration of the gas to a water content which will result in a waterdew-point below the minimum temperature to be encountered from the producingwell to the point of consumption.

Much of the recent development of gas and gas-condensate reserves in theGulf Coast Area has been in locations which are accessible only by water. Highwell-head pressures, pipeline construction and maintenance costs and thedesirability of final central gas-condensate separation facilities havestimulated the development of dehydration equipment which can be installed ateach well and which will permit hydrate-free transportation of both gas andcondensate in the same line to central facilities.

There are four types of natural gas dehydration processes now used:Adsorptive processes.Absorptive processes.Chemical reaction processes.Refrigeration processes.

The first three of these processes are indirect in that they require use ofadsorbents, absorbents or reactive chemicals. These materials requireregeneration and part of the total gas stream is consumed in the regenerativeprocess. Indirect processes have a wide range of flexibility as defined byallowable operating pressure and temperature, but most are not easily adaptedto automatic operation.

The refrigeration process described in this paper was designed forinstallation at the producing well-head. It requires no regenerative cycle andwith normal well-head temperatures no external source of heat. The flexibilityof this process is limited only by the pressure drop which may be allowedbetween well-head and transportation line.

T.P. 3022
Carrying Capacity of Drilling Muds
Authors: Williams C.E. , Bruce G.H.
Published: April 2012

The trend toward deeper drilling, together with the attendant increase inpower requirements for circulation of the drilling fluid, has emphasized theneed for a critical examination of the factors affecting the removal of bitcuttings from the hole by the drilling fluid. The ability of drilling fluids tolift cuttings is called their carrying capacity.

A series of laboratory and field experiments has been conducted to determinethe minimum annular velocity necessary to remove cuttings, and to investigatethe effects of properties of drilling fluids on their carrying capacities.

Consideration of the results of these experiments led to the followingconclusions:Turbulent flow in the well annulus is most desirable from the standpointof cutting removal.Low viscosity and low gel are advantageous in removing cuttings.Increase in mud weight is effective in increasing carrying capacity.The carrying capacity is higher when the pipe is rotated than when it isnot.If turbulent flow can be maintained, an annular velocity slightly higherthan the slip velocity of the largest cuttings to be transported should keepthe bore hole clean. This implies velocities of 100 to 125 ft per minute ratherthan the presently used 175 to 225 ft per minute.

Introduction

Power Savings by Reduction of Annular Velocities

A large portion of the power expended in drilling operations is consumed incirculating the drilling fluid. An important factor in establishing the rate ofmud circulation is the minimum velocity in the annulus necessary to remove bitcuttings. Empirically, it has been found that average annular mud velocities ofabout 200'Ft per minute will remove cuttings. It was not definitely known, however, whether annular velocities of about 200'Ft per minute were just abovethe minimum necessary to remove cuttings, or whether such velocities could bematerially reduced without sacrifice of the ability of the mud to removecuttings. It is apparent that if annular velocities could be reduced withoutimpairment of cutting removal, a considerable saving in power requirementswould result.

T.P. 3026
Effect of Free Gas Saturation on Oil Recovery by Water Flooding
Authors: Holmgren C.R. , Morse R.A.
Published: April 2012

The production of oil by water flooding can be substantially increased bythe maintenance of free gas saturation in the reservoir during the floodingoperation. This effect is accomplished by the alteration of oil relativepermeability characteristics and the occupation by gas of pore space that wouldotherwise be filled with residual oil. The amount of reduction in residual oilcan be calculated from appropriate water-oil relative permeabilitycharacteristics.

This paper presents experimental data in support of the foregoingconclusions and an example of the calculations. The microscopic pore saturationconcepts of the mechanism are discussed. A method of practical application tofield floods is presented together with discussion of certainlimitations.

Introduction

The presence of free gas has been reported by a number of investigators tosignificantly affect the oil recovery which can be obtained from sandstone flowsystems by water flooding. The effect of gas, noted in every instance, has beento cause lower residual oil saturations than could be obtained by waterflooding the same systems in the absence of free gas. The degree of improvementin recovery has been observed to vary widely, depending on the systems used andthe conditions of the tests. The increased oil recovery obtained because of thepresence of gas during a water flood has been variously attributed to changesin physical characteristics of the oil, selective plugging action of the gas, inclusion of oil mist in the free gas phase, and the additional sweeping ordriving action of the free gas.

All but the first of these suggestions imply changes in the displacementmechanism. The change in viscosity and interfacial tension of the oil phase, within the pressure range used for all the experimental work, is certainly notsufficient to account for the differences in residual oil saturation notedunless there is a drastic change in the displacement process.

One other effect which logically seems capable of causing differences inresidual oil saturation of the magnitude noted in the experimental work is thatof simple replacement. In a water-wet system containing oil, water, and gas, itis to be expected that the gas will exist inside the oil.

T.P. 3055