bluuebunny/crossref_metadata_2025 huggingface dataset:
The Interpretation of Chemical Water Analysis by Means of Patterns
Authors: Stiff Henry A.
Published: April 2012

The classification and correlation of water analysis data presents manyproblems which can be solved by graphic methods. The pattern system, a new typeof graphic procedure described in this communication, is believed to haveseveral advantages over older methods. Examples of the application of thepattern system to the solution of problems encountered in petroleum productionare given.

Introduction

Several graphic methods for presenting analytical water data have beendeveloped and are now in use. It is believed, however, that a recentlydeveloped type of graph called the "pattern" offers several advantagesover other methods. This system presents a better picture of the total saltconcentration than is usual in such graphs. The effect of dilution orconcentration has been reduced to a minimum, and at the same time distinctionbetween various types of water has been improved. The system is extremelyversatile, yet so simple it can be plotted on ordinary graph paper and adaptedto almost any type of filing system.

Discussion

The essential feature of the pattern system is the graph shown in Fig. 1.Horizontal lines extending right and left from a vertical line at zero form thegraph. Positive ions are plotted to the left while negative ions are plotted tothe right. The figure immediately beneath each ion gives the scale. Most oilfield waters can be plotted on a scale where 100 milliequivalents of sodium andchloride and 10 milliequivalents of each of the other ions are represented byone scale unit.

T.N. 84
A High Temperature Gauge Glass for the Visual Observation of Critical Phenomena
Authors: Spencer John R.
Published: April 2012

A capillary tube variable volume cell is described, which has operatedsatisfactorily over a range of 100'F and 3,500 psi to 550'F and 1,500 psi. Thecell contents are entirely visible over the length of the capillary with theexception of a space at the top amounting to three per cent of the totalvolume. Observations on the critical behavior of simple systems have beengreatly facilitated by the apparatus, it being possible to establish thecritical conditions for a particular mixture in the course of a day'srun.

Introduction

Many types of apparatus have been designed for obtaining data on the phaserelationships of hydrocarbon systems. Such apparatus can in general besubdivided into two classifications;indirect measurement of phase volume, anddirect visual observation of phase volume, each of which hasoutstanding advantages and disadvantages.

Indirect measurement of phase volume requires the use of rather elaborateapparatus including internal probes in which are located the device fordetermining the locus of the interface between phases. Such equipment is by itsvery nature costly, and is complex from the standpoint of operating technique.Probing techniques can be used, however, over wide ranges of temperature andpressure with a high degree of reproducibility.

Apparatus for visual observation of phase behavior obviously has theadvantage of enabling the experimenter to see exactly what takes place, butbecause the material to be tested is contained in a cell constructed of bothmetal and glass, is limited severely as to the temperature range of operation.Furthermore, the maximum pressure usually is limited by the choice of materialused for sealing the glass to the metal, and by the strength of the glassitself. In the interest of increased efficiency of observation, as much of thecell as possible should be visible to the eye. Glass capillary tubes have beenused successfully but have always given difficulty at the metal-to-glass seal.An apparatus has been devised to overcome the problems of sealing andresistance to temperature effects that have heretofore been the limiting factorwith glass apparatus in the observation of phase volumes at elevatedtemperature and pressure.

T.N. 85
Efficiency of Gas Displacement From Porous Media by Liquid Flooding
Authors: Geffen T.M. , Parrish D.R. , Haynes G.W. , Morse R.A.
Published: April 2012

Flow tests on small core plugs have indicated that a large amount of gas istrapped and not recovered by water flooding a gas sand. Instead of 1 to 15 percent pore space, as is usually assumed, the residual gas saturation is 15 to 50per cent pore space, and is thus of the same magnitude as residual oil afterwater flooding oil sands.

A thorough investigation was made to ascertain that large amounts ofresidual gas actually remain in reservoirs after a water flood and that thiscondition is not merely a laboratory phenomenon. In field experiments, theamount of gas left in a watered-out gas sand was measured by use of a pressurecore barrel and the residual gas saturation of two watered-out gas sands wasdetermined by electric log evaluation. In the laboratory, an investigation wasmade of factors that could possibly cause the value of residual gas saturationas measured on small core plugs to differ from that in the reservoir, and theeffect of these factors on the amount of residual gas saturation was studied.The factors studied include flooding rate, static pressure; temperature, samplesize and saturation conditions before flooding. All evidence established that arelatively high gas saturation is trapped in water flooded gas sands and thatthis residual gas saturation can be measured in the laboratory by tests onsmall core plugs.

Introduction

There has been general agreement among engineers that very high recovery ofgas could be obtained from natural reservoirs by water displacement. Gasrecoveries of 80 to 95 per cent of the original gas in place have become thenormal expectation in water drive fields. The assumption of high recovery hasbeen based on:low density and viscosity of gas compared with water;the erroneous assumption that the flow relationships in a gas-liquid systemwhere gas is the displaced phase will be the same as when it is the displacingphase.

It has long been recognized that gas can flow at very low gas saturations(in the range of 1 to 15 per cent pore space) in systems where liquid is beingdisplaced by gas. By assuming the reversibility of this process, the conclusionwas reached that the residual gas saturation following water flooding of a gasreservoir would be the same (l to 15 per cent) as that at which gas firstflowed continuously as a displacing phase.

T.P. 3279
Improved Multiphase Flow Studies Employing Radioactive Tracers
Authors: Josendal V.A. , Sandiford B.B. , Wilson J.W.
Published: April 2012

Two radioactive tracers have been tested as a means of determining coresaturation in multiphase flow studies. Cesium 134 chloride was tried as awater-phase tracer, but complications in its use in low permeability coresresulted from sorption of cesium by the core or water-wet pads. Iodo 131 benzene proved very satisfactory as an oil-phase tracer. The synthesis ofiodobenzene from the sodium iodide as received from Oak Ridge is simple anddirect. The tracer is insoluble in water and there was no evidence of sorptionby any of the core materials used.

Use of the method to determine saturation profiles during capillary anddynamic desaturations and relative permeability measurements on oil-water andoil-gas systems is described. Comparisons of the dynamic and capillary methodsof relative permeability determination were made using the tracer to check coresaturation and saturation distribution. Other experiments are also described inwhich mobility of the oil phase at various saturations was measured bydisplacing labeled oil by flowing inactive oil. Similar experiments were madeusing water labeled with cesium 134.

Introduction

To be fundamentally sound, any laboratory method of determining relativepermeability must meet, among others, the following requirements:the coresaturation between the pressure taps must be uniform, andthere must beuniform pressure difference between the phases in the region between thepressure taps.

In practice it may eventually be shown that appreciabledeparture from either or both of these conditions may be permitted withoutintroducing sensible error, but the magnitude of such error remains to beestablished. There is need then for methods of saturation determination whichwill determine the saturation profile in a core as well as the overall averagesaturation given by the gravimetric or material balance methods usuallyemployed.

Methods which have received consideration include resistivity, X-rayabsorption, gamma ray absorption, neutron diffraction, and radioactive tracers.The resistivity method has use in the determination of profile, but needschecking by independent means. The X-ray method has been used successfully, butrequires elaborate equipment and calibration. At present gamma ray absorptionis practical only for very large cores. The neutron method does not appearadaptable to measurement of saturation variations in short cores since it is ascattering method. Russell, Morgan and Muskat employed radiovanadium in a studyof the mobility of interstitial water. Coomber and Tiratsoo used radioiodine asan oil-phase tracer and measured profiles in unconsolidated sand packs.

T.P. 3284
The Resistivity of a Fluid-Filled Porous Body
Authors: Owen J.E.
Published: April 2012

A model of a porous body is presented in which the pore space consists of asystem of voids and interconnecting tubes. Relationships between porosity andresistivity formation factor are determined partly by calculation, partly byexperiment. Constriction effects characteristic of the model are shown to besufficient to account for high formation factors. It is shown that constrictionmay be combined with moderate amounts of tortuosity to give model pore systemsexhibiting to a first approximation porosity and resistivity properties similarto those of natural porous bodies.

Introduction

The relationship between the electric resistivity of a fluid-filled porousbody and the geometry of its pore space is so complex that the calculation ofthe resistivity of a natural porous rock is a practical impossibility. Both theresistivity of a body and its porosity are measurable quantities, however, andprevious successes at relating them have been reached by an empirical approach.Efforts at obtaining theoretically derived formulae relating them havegenerally been unsatisfactory. One of the reasons for this may lie in the puregeometry that has been assumed.

The Tortuosity Concept

A parameter called the formation factor is useful in discussing theresistivity of a fluid-filled porous body. This parameter is the ratio of theresistivity of a fluid saturated porous body to the resistivity of thesaturating fluid. Formation factors are often available from measurements oncores or from electric logs, and many attempts have been made to correlateformation factors and porosities of geological formations. Whenever asuccessful correlation is found, the engineer working with electrical logs hasa useful tool for the determination of porosities of pay sections.

T.P. 3352
The Strataflow Process: A Recent Development in Locating Water Entry in Wells
Authors: Hartline Ralph E. , Tapper Wilfred
Published: April 2012

The Strataflow process for locating water entry in producing wells is nowavailable. This method as now practiced utilizes the fact that fluids ofdifferent salinities have different electrical resistivities. By introducinginto the well a fluid of a markedly different salinity than that of the fluidbeing produced, a pronounced resistivity change will occur at the point ofentry. By running a Strataflow survey the points of major and minor water entrymay be interpreted from changes in the resistivity of fluid in the hole.

Strataflow results are obtained with the well operating under almost normalproducing conditions, and are a logical primary step in any workover program, having as its purpose shutting off of the water.

Introduction

Water production is a serious problem in many producing oil wells. Itcertainly increases lifting costs and in some cases presents a disposalproblem. It often aggravates corrosion problems and can even endanger oilproduction. With accurate information to guide an effective workover program, many marginal wells could be restored to profitable production.

The shortcomings of previous methods of water entry location wererecognized. The Strata flow process is the result of several years ofdevelopment and field testing directed toward overcoming these limitations. Itrepresents the continued development of a process reported by Silverman andBrown. The earlier work established the basic soundness of fresh-to-salt waterresistivity contrast in delineating zones of water entry, but its applicationwas limited by the difficulty of maintaining static balance of the well duringpreparation for the test. A more serious deterrent to its use, however, was itsunadaptability to existing well logging service equipment and field operatingmethods.

Strataflow Principle

The general principle of the new method involves, first, conditioning thewell by displacing the fluid in the bore of the well adjacent to the zone to betested by a conditioning fluid which is miscible with the formation fluid. Thisdisplacement is carried out without interruption of the well production. Theconditioning fluid must have some measurable physical, chemical, nuclear, orelectrical property which is distinctive from that of the formation fluid.

T.P. 3351
Some Properties of Mixed Paraffinic and Olefinic Hydrates
Authors: Reamer H.H. , Selleck F.T. , Sage B.H.
Published: April 2012

An experimental investigation was made of the effect of temperature upon thethree-phase pressure associated with the propane-water and propene-watersystems when hydrates were present. In addition, the characteristics of thepropane-propene-water system were established over a limited range oftemperatures under conditions such that hydrate was formed. The hydrate phasefor this system may be a solid solution and the distribution of propane andpropene in it is similar to that found in the coexisting hydrocarbon liquidphase.

Introduction

A knowledge of the characteristics of hydrates of the hydrocarbonsencountered in industrial practice is of importance in connection with thedesign of process equipment. Villard carried out early studies of hydrates, andde Forcrand considered the more probable compositions of the hydrates ofhydrocarbons. Hammerschmidt presented information about the propane-water andthe isobutane-water systems. Scheffer studied the hydrate of hydrogen sulfidein detail, and de Forcrand reported on the hydrates of krypton, argon, andxenon.

Roberts and co-workers determined the nature of the hydrates formed in themethane-water and ethane-water systems. Carson and Katz studied themethane-propane-water, methane-pentane-water, and the methane-hexane-watersystems in the four-phase region. The results of this rather extensiveinvestigation indicated that the paraffinic hydrates formed solid solutions.The experimental evidence now available does not support the existence ofhydrates of the pentanes-and heavier hydrocarbons but it cannot be stated withcertainty that such hydrates are not formed. Stackelberg made extensive studiesof the crystal structure of paraffinic hydrate, by means of x-ray techniquesand found that hydrates posses, a definite structure and composition. Theexistence of such a structure does not preclude the formation of solidsolutions of hydrates in aqueous systems containing two or morehydrocarbons.

Wilcox, Carson and Katz reviewed the information on the hydrates ofimportance in the processing of natural gas and presented data concerning theirformation from natural gas. Kobayashi and Katz made studies at high pressure ofthe hydrate of methane, and Unruh and Katz investigated hydrates in mixtures ofcarbon dioxide and methane.

Frost and Deaton contributed to the knowledge of the composition of theparaffinic hydrates. The irregularities in the experimental results wereseveral times the expected uncertainties. This experience confirms the behaviorencountered by other investigators indicating that hydrates tend to occludewater during their formation, thus rendering difficult the direct measurementof their composition.

T.P. 3376
Electrical Resistivity Measurements on Reservoir Rock Samples by the Two-Electrode and Four-Electrode Methods
Authors: Rust C.F.
Published: April 2012

Experimental evidence is presented showing that reproducible formationresistivity factor measurements and resistivity index determinations onreservoir core samples may be made utilizing either the two- or four-electrodemethods. Equipment is described which permits the application of eithertechnique to the core specimen without loss of time and with a minimum amountof effort. Since electrical resistivity measurements on reservoir rocks areimportant not only in electric log interpretations, but also in the study offundamental rock parameters, it was considered desirable to compare theapplicability of both techniques of resistivity measurement.

Introduction

The techniques employed in the measurement of electrical resistivity onreservoir rocks, as practiced in the petroleum industry, may be reduced to twofundamental methods: one utilizing two electrodes only, usually referred to asthe two-electrode method; the other using two additional electrodes andcommonly known as the four-electrode method. In the former, the core samplewhose resistivity is to be measured is mounted between two electrodes, usuallymetal discs, which serve to pass a current of known magnitude through thesample. The potential drop across the sample, measured between these same twoelectrodes, and the core dimensions furnish the necessary data to compute theresistivity of the sample. In the four-electrode technique the end plates, again usually of metal, still serve as current electrodes. Additional probes orelectrodes dispersed along the sample are utilized to measure the potentialdrop. Both methods are used in practice, and it is the purpose of this paper tocompare the two techniques as applied to the determination of formationresistivity factors and the resistivity index exponent n, in Archie's empiricalequation. To evaluate the two techniques it is desirable to point out theexperimental precautions which must be taken to insure reliable results. It isevident from the electrode arrangements of the two- and the four-electrodemethods that, for a given sample, the volume of sample included by thefour-electrode method is less than the volume included by the two-electrodemethod.

One of the prime difficulties associated with the two-electrode method isthe possible occurrence of an abnormally high resistance between the electrodesand the brine-saturated sample, which results in erroneous resistivity valuesfor the core sample itself.

T.P. 3397
Procedure for Use of Electronic Digital Computers in Calculating Flash Vaporization Hydrocarbon Equilibrium
Authors: Rachford H.H. , Rice J.D.
Published: April 2012

The effectiveness of digital computing machines in making technicalcalculations depends on how well the work is arranged to utilize the capabilityof the machines. This note presents a particularly useful way of calculatinghydrocarbon vapor-liquid equilibrium in the flash vaporization (orcondensation) system. The method is well suited to sequence-controlledcomputing equipment. It is not limited to equilibrium calculations and may beused for solution of most implicit equations in one variable.

Introduction

There is increasing interest in the use of electronic digital computers inresearch and engineering calculations. This is a fortunate and inevitable trendin view of both the increasingly extensive numerical work which is becoming aroutine part of many daily production operations and growing demand for theoverwhelming amounts of calculations required by newly developed numericalmethods for solving heretofore unsolved problems.

Machines are in many ways ideally suited to the task but of necessitypresent certain difficulties for a particular problem to be solved must oftenbe formulated quite differently from the way it would be arranged for manualsolution. This is done in order to take advantage of the inherent speed andprecision of electronic computers and at the same time to limit the need fornumber storage to the capacity of the machine. Therefore, this note issubmitted to present a general and quite powerful method of finding solutionsof the frequently encountered implicit equation:

(Equation 1)

where the root, x0, is to be found for a given set of y1… yn. Theprocedure is well suited for use with computing machines, for it usuallyrequires but little storage or programming beyond that necessary to evaluateF.

Hydrocarbon Equilibrium

The method is described in terms of the problem it was designed to solve, i.e., the calculation of hydrocarbon vapor-liquid equilibrium in flashvaporization. Given the composition of a hydrocarbon mixture and appropriatevalues of the equilibrium ratios K, to find the phase ratio and compositions ina closed system: let zi be the mol fraction of the i-th component in themixture.

T.N. 136
Reduction in Permeability With Overburden Pressure
Authors: Fatt I. , Davis D.H.
Published: April 2012

Oil bearing rocks, usually found at depths of 2,000 to 10,000'Ft, areelastically deformed by overburden pressure. Although the change in porositywith pressure in a number of example rocks has been shown to be small, it wasthought that overburden pressure might have a significant effect onpermeability. This note presents results of an investigation to determine themagnitude of the change in permeability with pressure.

In routine core analysis, permeabilities are measured on rock samples whichare not under overburden pressure. If permeability measured in this way differsfrom permeabilities measured under overburden pressure, a systematic error isintroduced into well productivity calculations. The experiments described inthis report were made to determine the magnitude of the change and thus to givean estimate of the error introduced into the calculations. The error introducedby the neglect of the change in permeability when overburden pressure isremoved may account for part of the difference between well productivitycalculated from core analysis and the actual well productivity.

The results obtained in this investigation have only qualitativesignificance because of the difficulty in reproducing in the laboratory thestress conditions on the rock buried in the earth. The assumption which isusually made is that the rocks in the earth are under a uniform pressure equalto the weight per unit area of the vertical overburden column from the rock inquestion to the surface of the earth less the pressure of the liquid in thepores of the rock. For an overburden consisting of sandstones and shales (ofassumed average specific gravity of 2.3) and for a liquid pressure equal to thepressure in a salt water column (of specific gravity 1.0) reaching from therock to the surface, the resulting net pressure on the rock is approximately0.56 psi per ft of depth.

Experimental Method

Clean, dry sandstone core plugs one in. in diameter and about three in. longwere mounted in a copper foil jacket as shown in Fig. 3 or molded in a Lucitejacket as shown in Fig. 4. All cores except those labeled "2" in Fig. 1and "8" in Fig. 2 were measured in the copper foil jacket. Cores"2" and "8" were measured' in the Lucite jacket.

T.N. 147
Reservoir Performance and Well Spacing, Spraberry Trend Area Field of West Texas
Authors: Elkins Lincoln F.
Published: April 2012

The Spraberry Trend Field of West Texas was discovered in January, 1949.Drilling of 2,234 wells and production of some 45 million bbl of oil byJanuary, 1953, indicated this to be an important field which will ultimatelycover more than 400,000 acres. In addition to being the world's largest fieldin areal extent, the Spraberry has presented many problems in well completionand operation and has demonstrated unique reservoir performancecharacteristics.

The pay section consists primarily of a few fine grained sandstone orsiltstone members in a thousand-ft thick section of shale, limestone, andsiltstone. Since porosity averages only 10 per cent and nearly allpermeabilities are less than 1 md, conventional core analysis does notdelineate the "pay" section. Mercury injection was used as a capillarypressure test adaptable to rapid routine use to select those intervals havinglow enough connate water saturation to contain commercially significant oilsaturation. In the central area of the field this "pay" amounts to 16ft of Upper Spraberry and 15 ft of Lower Spraberry sands.

An interconnected system of vertical fractures, observed in cores, providesthe flow channels for oil to drain into the wells but most of the oil is storedin the matrix since the void volume of fractures is estimated to be less than 1per cent of that in the sand. Initial potentials of wells range up to 1,000 BIDafter fracture treatment which should be compared with estimated capacity of 5to 10 BID if oil had to flow into the wells through the sand itself.

Without exception initial pressures of later drilled wells weresignificantly lower than initial pressures of earlier drilled nearby wells in alarge area some 6 miles long. This means the earlier drilled wells had drainedfluids from areas much greater than their 40-acre proration units.

T.P. 3622
Capillary Desaturation in Unconsolidated Beads
Authors: Bethel F.T. , Calhoun John C.
Published: April 2012

Glass beads have been surface treated with Dri-film to render them oil wetby n-octane to varying degrees, and capillary desaturation curves have beendetermined by the restored state method. The desaturation curves show aregularity of increasing displacement pressures as the oil wetness increases.This has been used to compute apparent contact angles between n-octane andwater on glass. The family of desaturation curves also shows a regularcrossover, such that the residual wetting liquid saturation values are inreverse order to the displacement pressures. A semi-logarithmic variation isshown between the apparent contact angle and the residual saturation. Thedesaturation data are interpreted to mean that the wetting liquid ceases to bea continuous phase within individual pores before the capillary pressure can beraised sufficiently to force out the wetting phase completely. The saturationof wetting liquid at which this break in liquid continuity occurs is higher asthe oil wetness decreases.

Introduction

The petroleum industry has for some time been using measurements ofcapillary pressures on porous media for research correlations and engineeringcalculations. It has been generally recognized that the capillary desaturationcurve reflects the character and arrangement of the pores within the media andthe distribution of fluids within the pores. Methods have been proposed forcomputing pore size distributions, tortuosity factors, and relativepermeabilities from capillary desaturation data.

There is little doubt that the interactions between porous rocks and theircontained fluids resulting from surface forces play a dominant role indetermining the magnitude and direction of capillary pressure measurements.There have been attempts to introduce as variables two quantities - interfacialtension and contact angle - generally used to characterize surface forces, butin spite of the wide interest in these quantities as important variables, fewdefinite conclusions have been drawn concerning their qualitative orquantitative significance.

Interfacial Tension

The interfacial tension appears in a capillary pressure function given byLeverett for correlating capillary desaturation type curves. Use of theinterfacial tension in this function seems to be justified by other experimentsreported. Apparently, interfacial tensions have little bearing on wetting phaseresidual by desaturation.

T.P. 3639
Gas Storage in the Playa Del Rey Oil Field
Authors: Riegle John
Published: April 2012

To date, utility company underground storage of gas has generally beenrestricted to depleted dry gas fields. The Playa del Rey project is probablythe first to successfully store gas in a partially depleted oil reservoir withthe recovery of large volumes of gas at high rates as the main objective. Oilrecovery has been a secondary consideration.

Problems encountered unusual to those of storage in a dry gas zone were:the removal and retardation of formation of emulsion,the up structuremovement of fluid during withdrawal periods which formed fluid blocks, andreservoir shrinkage resulting from encroachment of edgewater.

The solution of these problems as outlined in the paper has resulted inincreasing the withdrawal rate from the original design capacity of 4,000 Mcfper hour to the current 10,000 Mcf per hour. Additional increase is anticipatedas the operations continue.

Migration, reservoir performance, operational procedure and a historicalrecord are included to make this a resume of the project from its war-timeinception in 1942 to the first of 1952.

Introduction

The Playa del Rey underground gas storage project is probably the firstproject in which gas has been stored in a partially depleted oil reservoir, with the recovery of large volumes of gas at high rates as the main objectiveand the recovery of oil a secondary consideration. Problems unusual to those ofstorage in dry gas zones have made this a pioneer endeavor.

The total storage capacity of approximately 1,500,000 Mcf of this reservoiris small in comparison with other underground gas storage projects. However, bystudy and experiment the deliverability into transmission lines, operating atpressures in excess of 150 lbs., has been nearly tripled in the past threeyears to the current 10,000 Mcf per hour rate, without the life of compression.It is anticipated this rate will gradually increase as additional fluid isremoved from the formation.

Location and History

Playa del Rey is located on Santa Monica Bay about two miles south of thebeach community of Venice and 15 miles southwest of the center of the City ofLos Angeles. Fig. 1.

T.P. 3669
Effect of Quick-Freezing vs Saturation of Oil Well Cores
Authors: Kelton Frank C.
Published: April 2012

It is perhaps not widely realized that extraction and saturation processescarried out on oil well core samples alter the properties of these samples tovarying degrees. On the other hand it is felt by some that quick-freezing ofcore samples increases their permeability and porosity significantly.Accordingly, laboratory tests were carried out on 49 pairs of horizontallyadjacent samples in order to differentiate between the effect of quick-freezingper se on permeability and porosity of the samples, as distinguished from theeffect of the identical saturation treatment on permeability and porosity ofthe companion samples. Also, additional field data were obtained on comparisonof frozen vs unfrozen companion samples.

Laboratory Investigation of Freezing vs Saturation Effects

Procedure

The samples used in these tests were two-cm cubes cut in horizontallyadjacent pairs from cores from eight Gulf Coast and Mid-Continent wells, whichcores had not previously been frozen. These samples were extracted with carbontetrachloride, dried, and air permeabilities run in the conventional manner.They were then evacuated and saturated with brine of 25,000 ppm sodium chloridecontent, and porosities determined by gain in weight. The samples werepartially desaturated by evaporation down to an average brine saturation of 68per cent. One sample from each pair was quick-frozen by covering with dry iceafter wrapping in a single layer of paper, and allowed to remain frozen forabout two hours; the companion sample from each pair was not frozen. Afterthawing the frozen sample, all samples were immersed in tap water overnight inorder to leach out most of the brine. Air permeabilities were re-run, and thesamples were again saturated with brine to determine a second porosityvalue.

For purposes of averaging of data, the samples were grouped according tofour permeability ranges, from 0 to 10, 10 to 100, 100 to 1,000, and 1,000 to3,840 md. Average permeability and porosity changes for the frozen vs theunfrozen adjacent samples are shown in Table 1.

Discussion

As may be seen from Table 1, the averages of the per cent permeabilityincreases for the quick-frozen samples ranged from 3.8 to 12.9 per cent amongthe four permeability groups.

T.N. 151
Comments on Capillary Equilibrium
Authors: Jones-Parra J.
Published: April 2012

In previous Technical Notes, W. R. Rose and W. Purcell have discussed thecapillary pressure data presented by Welge. Welge obtained capillary pressurecurves of the imbibition type in which it was necessary to apply to theapparent wetting phase a greater pressure than that of the non-wetting phase tocomplete the cycle and reduce the non-wetting phase saturation to low values.Rose suggests in his Note that conditions of equilibrium could not haveprevailed, since the non-wetting phase pressure must always be the greater.Purcell in his Note, proceeds to postulate a pore system consisting of a seriesof "holes in a doughnut," in which he contends that under equilibriumconditions it is necessary to resort to negative capillary pressures beforesignificant wetting phase displacement can take place. There is a remarkablesimilarity between the shape of the capillary pressure curve calculated byPurcell and those measured by Welge.

It is the purpose of this Note to show that, because Purcell neglected toaccount for the behavior of the residual wetting phase saturation, his systemwas not in equilibrium during imbibition; and, furthermore, that if his systemhad been in equilibrium, negative capillary pressures would not have beenpossible.

In Purcell's pore system, the residual wetting phase will form pendularrings at the interstitial spaces existing somewhere within the system, forexample, such as those spaces between "doughnuts" as shown in Fig. 1.The true capillary pressure is that across the pendular ring interface, and forthe system to be in equilibrium the pressure drop across all interfaces must bethe same, including that across the interface in the tight pores A of diaphragmB (Fig. 1). As the pressure across the cell is reduced, the advancing interfacewill move into the pore from the diaphragm, but at each pressure, the curvatureof the pendular rings must be the same as that of the advancing interface ifequilibrium is to prevail. Since equilibrium conditions are the basis for theentire argument, it follows that pendular rings must grow as wetting phaseenters the pore, that is, as the pressure across the cell is lowered. InPurcell's calculated curve, the residual wetting phase saturation remainsconstant as the capillary pressure decreases. Thus, his curve does notrepresent an equilibrium process.

T.N. 152
Determination of Graphite in Drilling Mud
Authors: Jones Frank O. , Lummus J.L.
Published: April 2012

A field procedure for determining graphite in drilling mud is presentedwhich is sensitive to 0.25 lbs/bbl and accurate to 20 per cent. The method, utilizing oil flotation principles, is suitable for use in all oil-free waterbase muds except those containing lignosulfonates, lignites, or surface activeagents.

Introduction

Graphite was proposed as a drilling lubricant as early as 1940, but has notbeen used extensively until recently. Graphite has been substituted for oil incertain instances to avoid oil contamination of core samples since it has beenfound that graphite does not interfere with routine core analysis.

A major difficulty in using graphite is the lack of a satisfactory field testfor determining the concentration of graphite in mud.

Discussion of Method

Several possible methods of analysis were investigated, including chemicalseparation, density fractionation, radioactive tracers, and oil flotation. Theinvestigation indicated that a satisfactory method for field use could bedevised using an oil flotation method. It was found that toluene shaken with ahighly diluted mud sample would recover sufficient graphite to be apparent inthe oil phase. Refinement and standardization of technique made it possible todetect as little as 0.25 lb/bbl graphite and to estimate graphite content towithin 20 per cent by using a visual comparison method.

The test is limited to oil-free water base muds. Quebracho, phosphates, orbarytes in the mud do not interfere with the test but surface active agents, lignosulfonates, and lignites evidently render the graphite water-wet so thatnone may be recovered by oil-flotation.

T.N. 185
An Explanation of the Yuster Effect
Authors: Scott P.H. , Rose Walter
Published: April 2012

Recent papers by S. T. Yuster have called attention to the largely ignoredconcept that there will be a transfer of viscous forces across fluid-fluidinterfaces during the flow of immiscible fluid phases through porous media.This leads to the implication that the relative permeability vs saturationfunction, as applied to each of the fluid phases of the system, will in someway be dependent on the viscosities of all the other fluid phases which arecontiguous to the flowing fluid of interest. In fact, Yuster has selected andanalyzed the properties of a capillary-tube model of the reservoir-prototypeflow systems and concludes from his studies that relative permeability valueswill be very markedly influenced by the viscosity ratio in two-phase systems.On the other hand, relative permeability data have been reported in theliterature for more than 20 years; and where these data are consistent at all, they consistently show no dependence on viscosity ratio (cf. chapter 7 ofMuskat for a resume of past experimental work). This paradoxical situation hasprompted us to re-evaluate Yuster's work.

The major flaw we find has to do with the properties of the model Yusteremployed to give qualitative support to his predictions. This model isdefective in that important surface area parameters characteristic of theprototype-reservoir flow system have not been pro pertly scaled. Fig. 1 showshow we believe Yuster's model should be modified to circumvent this difficulty.It depicts the capillary tube of radius R and length L, comprised of twoelements in series. The first part of length, Li has the nonwetting phaseflowing centrally out to a radius distance r, where an interfacial boundaryexists with the wetting phase which flows in the concentric annular space ofthe tube.

T.N. 192
The Effect of Overburden Pressure on Relative Permeability
Authors: Fatt I.
Published: April 2012

Laboratory relative permeability data on reservoir rock are obtained onsamples which are not subjected to overburden pressure during the permeabilitymeasurements. These data are then used for calculating the performancecharacteristics of reservoirs in which the rock is under the pressure of theoverburden. Recent observations have shown that the permeability and porosityof reservoir sandstones are decreased by application of overburden pressure.These observations led us to a study of the effect of overburden pressure onthe relative permeability characteristics of sandstones.

A previous note from this laboratory showed that overburden pressure, simulated by applying hydraulic pressure to the outside of a plastic mountedcore, caused a reduction in permeability of the core by as much as 50 per centat 10,000 psig. In a multi phase fluid flow system, the relative permeabilityat a given saturation will change if the permeability or the effectivepermeability changes but not if both permeability and effective permeabilitychange by the same ratio. The tests described in this note were made todetermine the effect of overburden pressure on permeability and effective gaspermeability in the gas-oil system. The gas-oil system was chosen because theavailable equipment was best suited for studying this system. The resultantdata can be applied to other systems of interest because the gas permeabilityin the gas-oil system is the permeability of the nonwetting phase and, as such, is equivalent to the gas permeability in the gas-oil-water system and to theoil permeability in the oil-water system.

Cylindrical test plugs, one in. in diameter and one in. long, were cut fromsandstone core samples from three different reservoirs. After extraction intoluene, the plugs were mounted in Lucite by conventional core mountingmethods. The core properties are given in the legend in Fig. 1. The mountedcores were machined to fit the apparatus shown in Fig 4. Air permeabilities asa function of overburden pressure were measured by connecting lines (1) and (2)to a conventional air permeameter.

T.N. 194
The Steady-State Flow of Gas Through Glass Capillary Tubes
Authors: Wallick George C.
Published: April 2012

This paper describes experimental procedures for the calibration ofcapillary tubes to be employed as comparison standards in gas flow-ratemeasurements and considers several types of flow which were observed in thecalibration of seven capillaries of varying diameter. It is shown that undercertain experimental conditions deviations from Poiseuille flow are observedwhich may not be attributed to turbulence, and that this flow behavior may bedescribed empirically by introducing the classical kinetic energy correctioninto the Poiseuille equation.

Introduction

Techniques have been developed for the measurement of the volume rate offlow of nitrogen through glass capillary tubes as a function both of thedifferential pressure applied and of the absolute gas pressure. Capillary tubesthus calibrated are frequently used to determine the rate of gas flow through aporous sample in the measurement of slip-corrected permeability. The purpose ofthis note is to describe the calibration procedure and to discuss some observeddeviations from the ideal flow behavior predicted by the Poiseuilleequation.

Experimental Procedure

The volume flow rate of nitrogen as a function of the differential pressurewas determined experimentally for a series of seven glass capillary tubes ofvarying diameter. As is shown in Table 1, the capillary radii in the seriesranged from 0.004 cm for Kl to 0.07 cm for K7. The capillary tubes were cutfrom capillary tubing purchased on special order from several manufacturers andthe bore radii were determined by microscopic measurement. The gas volume flowrate was measured for each capillary tube at a series of differential pressuresin the range from 0 to 3 cm of mercury and at average absolute pressures of1.0, 2.5, 4.0, and 6.0 atm.

Experimental Procedure for Small Capillaries

A schematic diagram of the apparatus used to calibrate the three smallestcapillaries, Kl, K2, and K3, is shown in Fig. 1. By means of a standard RuskaInstrument Corp. volumetric pump (equipped with a synchronous motor drive, twostages of gear reduction, and a quick-change lathe gear box), nitrogen wasdisplaced by mercury from a metal cell immersed in a constant-temperature bath.The pump, the line to the cell, and a part of the cell were filled withmercury. As mercury was forced into the cell, it displaced nitrogen whichpassed through the capillary tube being calibrated and into a large containerwith a volume of approximately 30 liters.

T.N. 206
Computation of a Linear Flood by the Stabilized Zone Method
Authors: Jones-Parra J. , Calhoun John C.
Published: April 2012

Introduction

The purpose of this paper is to present the results obtained by solving thefractional flow and frontal advance equations to obtain oil recovery at waterbreakthrough as a function of the length of the system being flooded, thelinear velocity of injection and the displacing phase viscosity. The method ofsolution makes use of the stabilized zone concept first presented byTerwilliger, et al. when calculating saturation distributions in a gravitydrainage system. In order to check the calculated results, the equations andmethod of solution were applied to the system on which Rapoport and Leasreported experimental data.

Method of Solution

The solution of the fractional flow equation

(Equation 1)

and the frontal advance equation

(Equation 2)

is obtained by assuming that a water front forms to sweep the oil out ahead ofit. There is ample evidence that under the proper conditions a water front doesform. If this water front is not to dissipate, the water saturations whichcomprise it must have equal linear velocities. These water saturations are saidto comprise the stabilized zone. Equation (2) indicates that for all thesesaturations

(Equation 3)

and hence fw must plot as a straight line against saturation for those watersaturations comprising the stabilized zone.

The water saturations lying between the highest in the stabilized zone andthe highest that can be achieved in the porous medium comprise the variablezone.

T.N. 193
Adolescents' Impulse Buying: Susceptibility to Interpersonal Influence and Fear of Negative Evaluation
Authors: Lin Yi-Hsiu , Chen Chen-Yueh
Published: April 2012

We examined the effects of susceptibility to interpersonal influence and fear of negative evaluation on adolescents' impulse buying tendency. A survey of 453 adolescents was carried out and we found the greater the susceptibility to interpersonal influence, the greater the tendency
to buy on impulse. Likewise, the greater the fear of negative evaluation, the greater the impulse buying tendency.
The Empathy-Altruism Association and Its Relevance to Health Care Professions
Authors: Burks Derek J. , Youll Lorraine K. , Durtschi Jayson P.
Published: April 2012

It is posited in the empathy-altruism hypothesis that altruistic motivation evoked by empathy is directed toward the ultimate goal of improving another person's welfare. In this study the empathy-altruism hypothesis was examined. Measures of altruism, empathy, and social desirability
were completed by 112 individuals in a university setting. A positive and significant association was found between altruism and empathy (rs = .24, p = .01, 95% CI [.06-.41]). No significant associations were found between social desirability and altruism or between
social desirability and empathy. Because the loss of capacity to feel empathy may lead to burnout, disillusionment, and reduced altruistic helping efforts, the clinical applicability and implications of these findings are particularly important to health care and other helping professions.
Causal Attributions of Workplace Gender Equality, Just World Belief, and the Self/Other Distinction
Authors: Bastounis Marina , Minibas-Poussard Jale
Published: April 2012

We conducted 2 surveys in Istanbul, Turkey, to investigate the moderating effects of belief in a just world (BJW) on the links between perceived gender equality and causal attributions in the workplace with 2 samples of bank employees from varying hierarchical positions (M age
= 30). Results from a unidimensional BJW scale (Dalbert & Yamauchi, 1994) used in Study 1 (N = 136) showed a negative relationship between perceived gender equality and internal causal attributions only for high BJW scores. Results from a bidimensional scale measuring BJW for self
and for others (Lipkus, Dalbert, & Siegler, 1996) used in Study 2 (N = 168) replicated this pattern for BJW both for self and for others. However, only BJW for others, which was found to be linked to social discrimination indices, moderated the negative relationship between perceived
gender equality and external attributions. These findings support the relevance of the bidimensional conception of BJW and the predictions related to causal attribution theory and the just world hypothesis.
Do IRS Audits Deter Corporate Tax Avoidance?
Authors: Hoopes Jeffrey L. , Mescall Devan , Pittman Jeffrey A.
Published: April 2012

We extend research on the determinants of corporate tax avoidance to include the role of Internal Revenue Service (IRS) monitoring. Our evidence from large samples implies that U.S. public firms undertake less aggressive tax positions when tax enforcement is stricter. Reflecting its first-order economic impact on firms, our coefficient estimates imply that raising the probability of an IRS audit from 19 percent (the 25th percentile in our data) to 37 percent (the 75th percentile) increases their cash effective tax rates, on average, by nearly two percentage points, which amounts to a 7 percent increase in cash effective tax rates. These results are robust to controlling for firm size and time, which determine our primary proxy for IRS enforcement, in different ways; specifying several alternative dependent and test variables; and confronting potential endogeneity with instrumental variables and panel data estimations, among other techniques.

JEL Classifications: M40; G34; G32; H25.