bluuebunny/crossref_metadata_2025 huggingface dataset:
Repressuring During Early Stages of Development
Authors: Beecher C.E.
Published: June 2014

The application of gas or air under pressure to obtain more oil from a sandwhich has been practically exhausted by ordinary production methods has beenpracticed to a limited extent for many years. Until recently such methods wereconfined to the Eastern fields, principally those of Ohio and West Virginia, where in many cases the production obtained after applying pressure for a fewyears was nearly equal to the total production prior to that time which hadbeen obtained by the usual production methods. As early as 1917, J.O. Lewiscalled attention to this method of increasing the recovery of oil and cited thephenomenal results obtained by H. E. Smith, I. L. Dunn and O. C. Dunn, whopioneered the application of air or gas pressure recovery methods. With thisinformation available it would appear that other oil-producing sections of thecountry have been extremely slow to realize the advantages of repressuring.However, after a few successful projects in the Mid-Continent area, the oilproducers appreciated the value of this method for obtaining further andprofitable production from their practically exhausted leases and are nowmaking extensive use of it.

In general, it has been the practice to apply pressure to the sands whenproduction has declined to a small yield per well. The purpose of this paper isto discuss some of the advantages which may be expected from returning gasunder pressure to the oil sands during the early stages of development, beforethe rock pressure has been dissipated and the gas exhausted, and to stimulatediscussion of this subject on which comparatively little actual field data areavailable.

The Function of Gas

Gas associated with or dissolved in the oil is the source of energy causingmovement of the oil to the well. When this energy is dissipated productionceases.
Effect on Producing Wells of Shutting in the Offset Wells
Authors: Nickerson C.M.
Published: June 2014

In times of overproduction such as the operators have been strugglingagainst for the past several years it is the practice of the oil industry toshut in certain wells in order to reduce the flood of oil. The purpose of thispaper is to present certain variations in production of oil wells when theoffset wells are shut in. The scope of the study has been confined toCalifornia fields, and more especially to those of the San Joaquin Valley.

The accepted definition of a shut-in well is a well where production hasbeen suspended by closing in the casinghead and tubing or by cessation of pumping. The immediate effect of such a procedure, of course, is to reduce theoil production from the lease, which is the result desired. However, it appearsthat certain types of wells vary widely in production of oil, gas and gasolineafter adjacent wells have been shut in, which variation has a very materialeffect on the ultimate recovery of oil from the property. The increase ordecrease in the oil production itself may not be of sufficient volume to occasion comment, but wide fluctuations in the gas and gasoline recovery underthe changed conditions are of the utmost importance in the future recovery of oil.

The scope of this paper includes:the effect on producing oil wells ofshutting in offset wells, the wells being studied in three groups arrangedaccording to their relative stages of depletion;probable source of excessgas and the effect on the ultimate recovery of oil;suggested procedurewhen wells are shut in;methods that could be employed to prevent unduemigration of gas from the shut-in area; andthe need for future studies ofthe situation.

Three Classes of Producing Oil Wells

For the purposes of this paper producing wells in California have beenarranged in three groups according to the age of the well, or to the relativestage of depletion of the producing zones. The first group consists of thosewells with a high fluid level, or in other words those wells whose fluid levelsare a considerable distance above the top of the perforations.
Unit Operations in Eastern United States and in Foreign Countries
Authors: Hill H.H. , Estabrook E.L.
Published: June 2014

This report summarizes the information that was obtained by the Committee onUnit Operation in Eastern United States and in the foreign countries.

Letters and questionnaires were sent to all of the Eastern members of thePetroleum Division of the American Institute of Mining and Metallurgical Engineers and to those who are living outside of the United States, asking themto advise the Committee of any unit operations that are in effect in thevarious countries of the world and to furnish the names of men to whominquiries should be directed for detailed information on the differentprojects. The response to the Committee's request is worthy of note.Practically all of the members who had knowledge of foreign operations repliedto the questionnaire and not only furnished information that was of value tothe Committee, but they evidenced a real interest in the subject of unitoperations and assured the Committee of their willingness to assist in every---way possible in order to make the study a success. The Committee wishes, atthis time, to express its appreciation of the excellent cooperation that wasreceived from the members of the A. I. M. E. to whom questionnaires weresent.

Unfortunately, the limited time that has been given to this survey did notpermit the collection of detailed data on the different unit operations thatare now in effect. It required several weeks to get back replies from the members located in some of the foreign countries and as a result the men who were asked to furnish information on the various projectshave not had sufficient time to submit the detailed data that were requested.The Committee has been assured, however, that information relating to a numberof unit operations will be furnished in the near future.

Part of the delay has been due to the fact that the purpose of the study wasnot understood and because the terms "unit" and "near-unit"operations were not clearly defined.
Unitized Operations in Oklahoma and Kansas
Authors: Ambrose A.W. , Beecher C.E.
Published: June 2014

It is the purpose of this paper to summarize data on unitization projects inOklahoma and Kansas as obtained from replies to questionnaires sent out by theA. I. M. E. committee for these states. The information received indicates thatunitization is growing rapidly in this area, but has not been in operation fora sufficient length of time to develop production history. It was impossible toobtain a record of all unitization projects in the time available. Themagnitude of such projects is indicated by the fact that reports were receivedcovering a total of 171,420 acres in Kansas and 49,350 acres in Oklahoma. Mostof these units have been formed during the past 2 years, the greater numberhaving been completed in 1929. It is anticipated that even more will be formedduring the present year.

The following important facts have been emphasized by answers to thequestionnaire and discussion with various operators:Unitization is growing rapidly, as evidenced by the number of units and thelarge total acreage now included in units as compared with practically noacreage 2 years ago.Operators are convinced that unitization is reducing development andoperating cost and they anticipate greater reductions as experience is gainedin unit operation.Producing units have not been in operation for a sufficient length of timeto give significant production history from which to estimate the ultimaterecovery of oil, but the general opinion seems to be that more oil will berecovered.In view of the benefits to be derived from unitization, many operators arerefusing to carry on wildcat operations unless a unit has been formed. If thisattitude continues to grow there will be no large pools developed in Oklahomaand Kansas in the future except under unit control.

The following tabulation gives a condensed summary of the information receivedon unit operations in Oklahoma and Kansas, but does not include all units, because many were not reported.
Unit Operation and Unitization in Arkansas, Louisiana, Texas and New Mexico
Authors: Lahee F.H.
Published: June 2014

Questionnaires and special letters soliciting information were sent to agreat many geologists, petroleum engineers, independent operators, andrepresentatives of large companies in Arkansas, Louisiana, Texas and NewMexico. Replies to more than 50 percent of these letters were received. Asurvey of the facts and opinions presented in this correspondence will be madea little later, but first some of the general aspects of the problem will bereviewed.

By "unit operation," we mean the development and operation of a singleentire pool, or reservoir, of petroleum by one management, on a systematic andscientific plan which is best calculated ultimately to extract from the paysand and bring to the surface of the ground the largest possible amount of oilwith the greatest possible total profit.

No one, as far as the author has been able to ascertain, denies the advantages, both scientific and practical, of unit operation. All are agreed that it issound in theory. It permits the proper distribution of wells, which shouldalways be spaced on the ground according to a regular geometric plan with theintention of maintaining the same spacing all the way down and into the paysand, or pay sands. This spacing will be different for different fields, depending on such variable factors as the lithologic character of the payformation, the nature of the controlling structure, the depth of drilling, theviscosity of the oil, and so on. From the viewpoint of engineering practice, asapplied to economical extraction of oil,! there is no more importantconsideration than well spacing-well spacing in the pay formation, and notmerely on the surface 'of the ground -for the method of well spacing has adirect bearing upon all such engineering practices as pressure control, repressuring by gas, the water drive, and so on.
Equilateral Triangular System of Well Spacing
Authors: Corbett C.S.
Published: June 2014

Early in the development of every oil field, the operators of relativelylarge tracts of land must decide upon a spacing plan for the wells to bedrilled upon their respective tracts. Usually it is desirable to have a systemof regular spacing laid out over the entire tract, making such adjustments asmay be necessary near land boundaries.

Unless the dip of the producing formation is very steep, the equilateraltriangular arrangement is the one most generally preferred, for the very goodreason that it gives the maximum amount of drainage area for the wells up tothe limit at which mutual drainage interference begins.

Assuming that the equilateral triangular pattern is to be used, there stillremains to be decided the matter of distance between wells. Many variablefactors enter into the problem of proper spacing, some of which are physicaland some economic. It is not the purpose of this paper to discuss thesefactors, as that has been done in several comprehensive articles during thepast few years. In the end the decision must be based upon an estimate of therelative importance of various factors which apply to the field in question andto economic conditions in the oil industry at the time the development isgetting under way. Even if the best possible spacing distance should be chosenwhen the problem arises, changing economic conditions and variation in physicalconditions in different parts of the field may cause the original choice tobecome more or less unsatisfactory.

Obviously, it is advantageous, once a spacing plan has been adopted, to avoidalteration of it as the field becomes better known or as conditions in theindustry change, and yet be able to vary somewhat the acreage per well inextending the area of development. Or, it may be desired to provide for anultimate spacing considerably closer than conditions seem to warrant early inthe development of the field. With these contingencies in mind, it is ofinterest to examine the possibilities which the equilateral triangular systemaffords.

Orientation Of Coordinate System

In this system the well locations may be considered as the inersectionst ofthree sets of coordinate lines, the lines of each set intersecting those of theother two sets at 60?.
Flow Resistance of Gas-oil Mixtures through Vertical Pipes
Authors: Uren L.C. , Gregory P.P. , Hancock R.A. , Feskov G.V.
Published: June 2014

The resistance to flow of mixtures of gas and oil in passing up through theflow tubing of oil wells operated by gas-lift or by natural flow is a factor inoil-recovery technic that has received but little attention. Yet accuratedesign of a tubing installation for a particular set of conditions, whereoperation is by either of these methods, is impossible without quantitativedata on the pressure loss suffered by the oil-gas mixture in its passagethrough the well tubing to the surface. Because of lack of such information, petroleum production technologists have been compelled to approach this problemby "cut-and-try" methods, which, doubtless in many cases, has resultedin the installation and use of tubing too large or too small for most efficientutilization of the expansive force of the gas used in lifting the oil.Impressed with the necessity for information of this character, the authorshave conducted a series of tests with large-scale apparatus in the petroleumengineering laboratories of the University of California, designed to beproductive of data that would.afford a means of attacking the problem offlow-tubing design on a more scientific basis.

Mechanics of Expulsion of Gas-Oil Mixtures in Naturally Flowing and Gas-LiftWells

When oil is lifted from a well by the expansive force of compressed natural gasor air, the fluids enter the lower end of the eduction tube under elevatedpressure, with the gas partly in solution, but largely distributed in the formof occluded bubbles within the oil mass. As discharged from deep wells, afterreaching the surface, there will normally be at least 60 times as much gas, byvolume, as of oil; and in many cases the ratio of gas volume to that of the oilwill have a value as great as 1000 or more. On entering the lower end of theeduction tube, however, a relatively smaller volume of gas will be found in theoil-gas mixture, on account of compression of the gas in accordance with theelevated pressure necessary.
Some Observations on Principles Involved in Flowing Oil Wells
Authors: Shaw S.F.
Published: June 2014

Published in Petroleum Transactions, AIME, Volume 86, 1930, pages 220–225.

The principles involved in lifting oil in wells flowing naturally are identicalwith those underlying the flowing of wells by means of the air-gas lift, andinformation of a dependable nature obtained in the study of the air-lift can beapplied to wells with natural flow. A well flowing naturally is one in whichthe lifting is done by means of the gas-lift, for which the gas is suppliedentirely by the formation from which the oil is derived. In air-gas liftoperations, there is insufficient gas supplied by the formation to lift the oilto the surface in an efficient manner, therefore additional gas for thispurpose must be furnished from an outside source.

There may, at times, be conditions obtaining in natural flowing wells differentfrom those in wells flowed by gas-lift, but these differences do not at allconflict with the main principles of gas-lift work. One such condition is metwith in wells in which the gas supplied by the formation i8 in considerableexcess of that required to lift the oil to surface; this excess may be so greatas to reduce the quantity of oil that can be lifted through the particulardiameter of casing or tubing that has been lowered into the well. This samecondition can be brought about, however, by supplying a large excess of gasfrom an outside source to an artificial gas-lift well, and a study of theeffects obtained from injecting a large excess into the well can be applieddirectly to handling wells flowing naturally which have a large excess of gassupplied by the underground reservoir.

Conditions for Lifting Oil

The main factors to be considered in flowing wells are as follows:Submergence, or pressure at the bottom of the tubing or casing.Lift; the height to which the liquid must be raised.Diameter of the flow tubing or casing.Quantity of liquid to be lifted.Pressure at the discharge end of the flow tubing, or back-pressure, as it issometimes called.
Classification of Flowing Wells with Respect to Velocity
Authors: Donohue F.P.
Published: June 2014

The observations and data presented in this paper are the result ofextensive study of flowing wells, most of which were in the Maracaibo LakeBasin of Venezuela. The Lago Petroleum Corpn. had extensive production in thisarea, gas-oil ratios were low, and the problem was to determine whether bycareful handling of the wells with respect to flowing conditions and byconserving the gas, the oil production of the wells could be maintained bynatural flow until it had declined to a rate which could be handled with anordinary working barrel, thereby avoiding the high cost of gas-lift equipmentinstallation in the lake bed. The problem was complicated by the nature of thewells themselves. Production is from soft, comparatively unconsolidated sands, necessitating screen pipe in all wells. It was not only necessary to keep thewells flowing but to keep them flowing without heading, as the release ofpressure upon making a head brought large quantities of sand into the wells, sanding them up or possibly cutting out the screen pipe. In furtherance of theplan of keeping wells flowing as long as possible, each well was equipped witha casinghead and tubinghead recording pressure gage, and an oil and gasseparator set. About one-half of the wells were equipped with gas meters. Allwells were tubed before bringing into production. Frequently individual gageswere taken on each well. A large scale chart was plotted for each well, showingdaily oil production, gas production, gas-oil ratio, tubinghead pressure andcasinghead pressure. Any deviation from the normal was immediately checked andthe condition remedied if possible.

Theory of Flowing Wells

Based upon considerable study of these records, it is believed that the flow ofa well actuated by gas is mainly a problem in velocity, a certain minimumvelocity in the flow string being necessary for the gas to carry the oil. Ifthis minimum velocity is not obtained the oil drops back and the well heads orgoes dead. The point of minimum velocity is of course at the bottom of thetubing, where the gas is under the highest pressure and therefore occupies theleast volume.
Repressuring in the Selover Zone at Seal Beach and the Effect of Proration
Authors: Bell A.H. , Webb E.W.
Published: June 2014

Repressuring, or gas drive, was first tried in the Seal Beach oil fieldduring the fall of 1927, and was carried on until the spring of 1928. Thisexperiment in the Upper or Bixby zone was highly successful in proving thefeasibility of compressing gas to high pressures and also showed greatincreases in production. The project was discontinued because there were notenough wells to protect the property lines. In the development of the second orSelover zone, many more wells were drilled and after 2~ years of production thegas was depleted so that all producing wells in the zone were either pumping oron gas-lift. Edgewater encroachment and the deepening of wells on neighboringproperties to a third zone practically isolated the lease, so that during thespring of 1929 it was considered feasible to repressure the Selover zone on theBixby lease of the Continental Oil Co. (Marland).

As shown on Fig. 1, the main Seal Beach structure is an elongated dome with anorthwest-southeast trend, and the north flank is cut by a fault nearlyparallel to the axis of the structure. Bixby well No. 24 was chosen for theinjection well on account of its location, as it is backed up by the fault andis surrounded by wells that protect the property lines. The results of the testmade in the Bixby zone indicated that an injection well on the flanks of thestructure would drive oil quickly to up-structure wells but would have atendency to cause by-passing, while the drive to down-structure wells would beslower but more evenly distributed. Preferably the injection well would havebeen located on top of the dome but property divisions made this inadvisable.Well 24 had been completed in November, 1928, but on account of gas depletionthe well failed to flow naturally. On gas-lift the well had an initialproduction of 1000 bbl. of oil with 30 per cent. emulsion. This well is 4825ft. deep, penetrating 200 ft. of oil-bearing formation.
Repressuring in Depleted Oil Zones
Authors: Nickerson C.M.
Published: June 2014

It is apparent that repressuring of the oil measures is becomingincreasingly important to the oil industry, and is a matter that warrants thebest efforts of the petroleum engineer charged with applying this method ofoperation to a producing property. Considerable attention has been directed torepressuring in various California oil fields, such as Dominguez and SealBeach, which have served to sell the more progressive operator on this idea andalso to keep him sold. The projects that have received most attention are incomparatively young fields where the fluid levels are high, the wells, perhaps, still flowing, where the wet gas production is of considerable volume, andwhere there is vital need of immediate conservation of gas, which otherwisewould be blown to the air.

The new State of California Gas Law, which prohibits the waste of gas, hasserved to interest the oil industry in means of conserving the gas that is nowbeing blown to the air because of lack of markets. This vitally affects theoperator in the older, well-depleted oil fields of the state, because in manycases he has a limited market for gas, on account of the flush production fromthe more active oil fields. While the waste of gas is relatively small in theseolder fields, such as the Midway-Sunset area, it now attains considerableimportance, since under the new State Gas Law it must be put to some beneficialuse.

Repressuring in the older fields of California has not received the attentionof the petroleum engineers that is warranted by the present situation. Thispaper was prepared with the view of presenting the salient features connectedwith repressuring in the well-depleted oil measures of the older fields, and toshow what results have already been obtained in these fields by injecting theunmarketable gas into the sands, particularly in the Midway-Sunset field in theSan Joaquin Valley of California. Other projects in the older fields of thestate offer some supporting data in this connection, such as the Shields Canyonand the Brea Canyon fields.
Methods of Tubing High-pressure Wells
Authors: Otis H.C.
Published: June 2014

During the past year or two considerable time and money have been spent indeveloping equipment for tubing large-volume high-pressure oil and gas wellswithout loss of production. That the efforts have met with success is proved bythe fact that any properly cased well, regardless of its production orregardless of its rock pressure or working pressure, can now be safely tubedwith no appreciable loss of production, provided experienced crews handle thenew equipment.

It is conceded that a far better gas-oil ratio can be secured by flowing a wellthrough tubing of a proper diameter-the diameter of the tubing depending, ofcourse, upon the volume of fluid and gas and the depth of the well-than by themore usual method of installing a choke at the mouth of the well. Wherepossible it is becoming the practice to bring wells in through tubing, thoughin the majority of instances this is not feasible. In many instances it hasdeveloped, after a well has been brought in through tubing that the tubinginstalled is either too large or too small for the most efficient operation orthat the well had not been drilled deep enough.

The equipment described in this paper, in the hands of experienced men, permitsthe tubing of these wells after they have been brought in, with the size oftubing then determined by actual observation to be best suited for eachparticular well, and with no danger of the well getting out of control, ofcatching fire, of drilling itself deeper, or of any loss of production. Thedeeper the flowing production with the consequent future higher lifting costs, the more essential it is that the size of tubing used be such as to give thebest possible gas-oil ratio. The ability to bring in these deep wells throughthe casing and then, immediately after their completion, regardless of volumeor pressure, to tube them with the size of tubing that permits the mostefficient use of the gas present will doubtless save many dollars.
Deep Sand Development at Santa Fe Springs
Authors: Jensen Joseph , Graves McDowell , Goold W.D. , Gwin M.L.
Published: June 2014

During the present year the Santa Fe Springs field has proved to be the mostimportant oil field under development in the United States. Its production willexceed that of any other field. Without it, production within the United Stateswould have been almost in even balance with consumption. The field has forcedto the fore and compelled, more than any other single factor, seriousconsideration of the need of conserving the gas resources of the State ofCalifornia. It has also contributed much to the development of new drillingequipment and important features in petroleum engineering, and has required thedevelopment of a new cement for use in deep wells because of high temperatures.It is the only oil field in the country where wells 8000 ft. deep have becomeso common that they are no longer given special attention.

The field covers a little less than 1400 acres of land. In it 196 producingdeep-zone wells have already been drilled since August, 1928, and 224 wells arestill drilling. More wells may be drilled. This indicates that probably morethan 450 wells will be drilled in the present campaign. In hardly a year's timeit has caused the outlay of nearly $50,000,000 for drilling, and within theyear 1929 it will have returned practically an equal amount of revenue.

In contrast to conditions during 1923, when this field was once before animportant and disturbing factor, the California oil industry has not beenforced to refinance to meet the situation presented by such a large productionof oil. There has been practically no unit selling and no stock selling, norany unnecessary development far beyond the limits of the field.

Production is now about 275,000 bbl. per day and gives every promise ofremaining at this figure or increasing to nearly 300,000 bbl. Six months fromnow the field should still be capable of producing more than 200,000 bbl. perday. Obviously, the need for conserving gas that would be blown to the air, incident to the production of so large a volume of oil, represents a problem inconservation deserving of the most serious attention of the oil industry and ofthe State of California.
Economic Aspects of Unit Operation of Oil Pools
Authors: Pogue Joseph E.
Published: June 2014

There are two methods employed in the development of oil pools.

The older and dominant method is one in which the primary object is theprotection of the underground deposit from drainage through competing wells, and considerations of efficiency of extraction and cost of production aresubordinated thereto. The newer and less prevalent method is one" in whichmaximum efficiency and minimum cost are the first objectives and developmentsto these ends may proceed undisturbed by the exigencies of competitivedrainage.

The second method has developed mainly in pools under single owner? ship andthe term "unit operation" has come to be applied to this procedure. Asingle ownership, however, is not essential to the method, for unity ofoperation may be achieved by agreement under split ownership, or even by aconcert of enlightened purpose. There are examples of unit operation whereneither the ownership nor the management is a unit, but merely where unity ofprocedure has been attained, as in the Yates pool. Throughout this paper"unit operation" is used in its broad sense without implying soleownership or single management, although unit operation is more convenientlyattained where these conditions are present.

It is evident, upon reflection, hat the second method should yield results farsuperior to the first, for the work of exploitation can be conducted withoutextraneous considerations and the natural forces present in the oil reservoircan be utilized to maximum advantage. Experience has amply confirmed thisconclusion and were the facts widely known and appreciated, the efforts toextend the applications of the principle of unitization would be greatlyintensified.

Competitive Development Of Oil Pools

It has come about that the vast majority of oil pools, or reservoirs, in theUnited States are subdivided by numerous surface tracts under separateownerships. This condition arises from the prevalent practice in the oilbusiness of acquiring prospective acreage in checkerboard spreads. Thus thediscovery of oil usually reveals a mosaic of overlying ownership.
Encroachment of Edge Water at Santa Fe Springs
Authors: Weaver Donald K.
Published: June 2014

Eight different oil zones have been identified andproduced at Santa Fe Springs, of which three or four are in turn divided intotwo or three parts. These zones, from top to bottom, are the Foix, Bell, Meyer, Nordstrom, Buckbee, O'Connell, Clark and Hathaway, or third Clark. While there has been some difference of opinionover this nomenclature with reference to the different zones referred to asClark, it has no particular bearing on the water problems.

Each of these oil zones has had waters of varyingsalinity associated with it, either within or at the bottom of the zone. Table1 is a tabulation of the zones, their maximum thicknesses, salinity and headsof various waters. Surface waters are fresh, and of high head, giving artesianflow in some instances.
Some Principles Governing the Choice of Length and Diameter of Tubing in Oil Wells
Authors: Versluys J.
Published: June 2014

A well can flow exclusively through the casing or exclusively through atubing but can also flow partly through a casing and at the top part through atubing. The main principles of the flowing of wells under these conditions wereexplained in the author's former paper. 1 Practically all factors thatinfluence the regular flow are dealt with therein. The question of irregularflow, however, will be discussed briefly here. As a rule, an irregular flowmust be avoided, as it may be assumed that the efficiency is thereby verysmall, while on many fields it is injurious to the sand of the oil-bearinglayer.

Periodical flowing often occurs with rising mixtures of gas and liquid.

The phenomenon can be explained if it is accepted that two conditions arepossible in the mixture; namely, the foam condition and the mistcondition.

If there is no stabilizer in the liquid, the foam condition can exist only whenthe liquid forms a greater portion of the volume than the gas. The mistcondition, on the other hand, can exist only when the liquid occupies a smallerpart of the volume than the gas. The foam condition occurs when there are gasbubbles in the liquid mass, while in the mist condition drops of liquid aredisseminated in a gas-filled space.

For sake of simplicity, it has been assumed that the mist condition prevailswhen 50 per cent. or more of the volume is occupied by gas, while with lessthan 50 per cent. gas the foam condition will arise. For distilled water andfor oils which do not tend to form stable foams this is probably approximatelytrue. If this does not hold good, however, two cases are possible:Thefields of the two conditions overlap orthey do not meet.

If the fields of the conditions overlap there is an intermediate field whereeither of the two conditions can exist, depending on the history of themixture.
Reservoir Pressures in the Hobbs Field, New Mexico
Authors: Christie R.S.
Published: June 2014

Reservoir pressure is the pressure at which a fluid is held in a state ofequilibrium in a porous stratum. This pressure may be a result of the genesisof oil or gas and its subsequent migration into and through an adjacent porousstratum, or of hydraulic head. Reservoir pressure is an indication of thepotential energy contained in the reservoir, and when it is known the engineeris in a position to use it to advantage in recovering and lifting the oil. Itis important to know the pressures in any type of reservoir, but this knowledgeis probably of greater value in a limestone reservoir, as at Hobbs, whereproducing rates or conditions may be more sensitive to changes inpressures.

The Hobbs field is in east central Lea County, New Mexico. The discovery wellwas completed by the Midwest Refining Co. in 1928, but intensive developmentdid not begin until after the completion by the Humble Oil and Refining Co. of No. 1-A Bowers in February, 1930. There are 143 producing wells onapproximately 5500 acres. The field has not been defined to the northwest, buta projection of structural contours indicates that the productive areaultimately may cover 7500 acres. The producing horizon is the White orCrystalline lime of Permian age. The top of the lime is found at an averagedepth of 4000 ft. and the wells penetrate it an average distance of 200 ft. Themain pay zone is an oolitic stratum about 25 ft. below the top, and varies from 2 to 15 ft. in thickness. Other porous or cavernous strata are found lower inthe lime but have little saturation. The initial production varied from 100 to25,000 bbl. per day, depending perhaps to some extent on the structurallocation but chiefly on the porosity of the pay. The initial gas-oil ratiovaried from 325 to 16,000 cu. ft. per barrel. In wells where the top of theWhite lime was found below 350 ft. below sea level (Fig. 1), the gas-oil ratiowas usually less than 1500 cu. ft. per barrel, while in wells higher than 350ft. below sea level, the ratio was usually above 2000 cu. ft. per barrel.
Determination and Application of Depth Pressures in the Yates Field
Authors: Nix Dale
Published: June 2014

During the past year approximately 400 depth pressures have been recorded inthe Yates field. Of these, 315 were "shut-in depth pressures," observedfor the purpose of adjusting well potentials without making open-flow tests. The "shut-in depth pressures" were distributed one to each well anddetermined under as nearly uniform conditions as possible. Therefore, there isa scarcity of data applicable to production problems, other than the adjustingof well potentials. A few of the data obtained have been used in an attempt tosolve some of the producing problems. These applications, however, merelyindicate partial solutions and their review herein is to emphasize the varietyof problems to which depth-pressure data can be applied, rather than to presentconclusive solutions.

Very little had been accomplished in the development of instruments todetermine pressures within the well bore, when it was decided to obtain suchinformation in the Yates field. Through the combined efforts of the YatesEngineering Committee and several producing companies, three methods ofdetermining pressures in the well bore were soon developed:the "compressor" method,the "volume chamber" method,the "depth-pressure recorder" method.

"Compressor" Method.-A small volume compressor is used to inject gasinto the tubing. The rate of injection is low so that the frictional losseswill be reduced to a minimum. During the test, the pressures at the top of thetubing and casing are observed on recording pressure gages. As the compressedgas depresses the fluid in the tubing, the pressure on the casing decreaseswhile the tubing pressure increases. The tubing pressure becomes a maximum whenthe fluid level reaches the bottom of the tubing; and the casing pressureusually rises quickly as the gas breaks around the bottom of the tubing. Thesum of the maximum pressure recorded at the top of the tubing and the pressureexerted by the weight of the compressed gas column is equal to the depthpressure at the bottom of the tubing.
Flow of Air and Gas through Porous Media
Authors: Chalmers Joseph , Taliaferro D.B. , Rawlins E.L.
Published: June 2014

Problems dealing with the movement or migration of fluids through porousbeds have been the subject of much research. The subject is not peculiar to theproduction of oil and gas, as many investigators have studied the nature of this movement and its relationship to the problems of other industries. Darcyconducted a series of experiments relating to the percolation of water throughfilter beds. King carried on an extensive series of laboratory experiments withthe object? of formulating some conception of the rate of movement of water through soils and sand strata in the drainage of surface water into undergroundchannels and subsequent recovery of this water through wells drilled into thesource beds for irrigation purposes. Slichter undertook a study of the sameproblem from a mathematical standpoint, and more recently Furnas hasinvestigated the flow of gases through beds of broken solids with particularreference to blast-furnace operation. With specific reference to gasproduction, Muskat and Botset of the Gulf Research Laboratory undertook anexperimental study to establish quantitatively the characteristics of and lawsgoverning the flow of gases through consolidated and unconsolidated porousmaterials of fine texture with a view of predicting the performance of gas inan underground reservoir.

There seems to be a general agreement that many of the relationships betweenthe numerous factors influencing the flow of fluids through porous materialsare far too complicated to be attacked by analytical methods based upon aknowledge of hydrodynamics.
Flow of Drilling Mud
Authors: Herrick H.N.
Published: June 2014

The flow characteristics of drilling muds, as described in this paper, andthe method given for solving problems relating to the flow of these mudsthrough pipe and accessory equipment, are based on a conception that drillingmuds are plastic solids like paints or greases; not liquids. The data presentedin this report have been obtained from studies of California muds, chieflythose used in the Kettleman Hills field, by the Producing Department of theStandard Oil Company of California.

Although' no claim of scientific exactness is made for the formulas anddiagrams, since the data upon which they are based are not complete even forCalifornia muds, the method has proved to be a convenient means for estimating, closely enough for practical purposes, the pressures required to force muds atvarious rates through pipe systems in which they are handled. Certainapproximations have been made to simplify the procedures so that they can beused easily in the field.

Viscosity and Shearing Strength of Mud

For the purpose of this discussion a plastic solid is defined as a material inwhich no deformation or flow takes place when the material is subjected toshearing forces, until the shearing force reaches a value called the "yieldpoint." 'With liquids, the smallest force will produce continuousdeformation; that is, the yield point of liquids is zero. The differencebetween true liquids and muds is illustrated in Fig. 1, which shows rates offlow through a small tube under different pressures. The flow rate of theliquids is directly proportional to the pressure and that of the muds is not. The behavior of drilling mud does not conform in every detail with thedefinition of a plastic solid as given, because mud actually flows slightly atpressures below its yield point. However, for practical purposes the definitiondescribes the condition adequately and has the advantage of simplicity.
Subsurface Pressures in Oil Wells and Their Field of Application
Authors: Hawthorn D.G.
Published: June 2014

The widespread interest shown during the past year in the study ofsubsurface pressures warrants brief reference to its early development. Thoughit is impossible to set an exact date when constructive thinking on the subjectfirst began, nevertheless, evidence is available that thought was given to theproblem as far back as 16 or 17 years ago. There is record in one of theforeign journals of actual subsurface tests made by crude methods in one of theRumanian fields in 1918 and 1919. These tests were performed in conjunctionwith studies made on wells produced by bailing and, incidentally, the finaloutcome of the work led to the development of the so-called "duplexbailer" which is reputed to have trebled volumetric bailing efficiency.From this time on to 1927 a few scattered bottom-hole pressure determinationswere made with makeshift instruments of one form or another, but probably notuntil 1927 was any great amount of concerted effort directed to thesubject.

At this fall meeting of the Petroleum Division four years ago was presented oneof the first papers to appear in this country written for the express intent ofadvocating the value and importance of subsurface pressure determinations. Itis thought to have been the first to present direct data on subsurfacepressures obtained through the use of a specially designed recordinginstrument. As might be expected, the instrument had its limitations, butreasonably accurate results were obtained and, to say the least, it constituteda progressive step in the right direction. During the period from 1927 to 1931, many noteworthy improvements were made in the design and perfection ofsubsurface pressure instruments suitable to meet all conditions. Because of themagnitude of this task much credit is due the men who pioneered this work. Theyshould feel a keen sense of satisfaction in the thought that their efforts havepaved the way for the continuation of this most valuable study.

At the present time more than a dozen companies are operating sub- surfacepressure instruments in the Mid-Continent field.
The Mechanics of Porous Flow Applied to Water-flooding Problems
Authors: Wyckoff R.D. , Botset H.G. , Muskat M.
Published: June 2014

The flow of liquids through porous media is known to follow Darcy's lawwhich states that the velocity of flow is proportional to the pressuregradient. This law is but a statement of the facts obtained from experimentalstudies and is, therefore, un controversial. It should be mentioned, however, that it applies only when the flow is viscous in nature and that at excessivevelocities which tend to produce turbulence, the velocity is proportional tosome power of the pressure gradient, the exponent ranging from 1 to 0.5 as thedegree of turbulence increases. However, experiments with media havingpermeabilities corresponding to those of actual producing horizons showconclusively that the actual flow of liquids in a producing horizon must beviscous except perhaps in the immediate vicinity of a well producing at a highrate. Therefore, one is justified in assuming Darcy's law to hold for cases ofpractical inrest, as will be implicitly assumed in this discussion.

Given this basic law of flow it is possible, theoretically to obtain solutionsto any problem of viscous flow of dead liquids 1 by the usual methods ofpotential theory. However, problems of practical interest often present suchcomplex geometrical configurations of sources and sinks (driving sources andoutput wells) as to make the analytical solutions extremely difficult or evenimpossible. It is useful, therefore, to note that Darcy's law is preciselyequivalent to the law of electrical conduction, so that the pressuredistribution in steady state porous flow of liquids is exactly the same as thepotential distribution in an electrical conducting medium. This analogy permitsthe use of electrical models wherein the potential distributions may bemeasured with far greater facility and accuracy than is possible in actualfluid-sand models. Such electrical models were used in determining the pressuredistribution about complex arrays of wells, an example of which will be shownlater in the discussion of the 5-spot flood.

One phase of the porous flow problems which is of considerable practicalinterest involves the tracing of an advancing fluid front.
Theory and Practice of Directed Drilling
Authors: Allen R.E.
Published: June 2014

One of the most unusual oil-field engineering accomplishments of the pasttwo years is the development and rapid advance in the directed drilling ofwells. Directed drilling as referred to herein is the controlled steering ofthe drill stem in the required direction to a given location in the oilsand.

The deliberate drifting of holes is an act so far removed from what has beenconsidered good drilling practice that all of the old questions of correlation, drillability and production difficulties are revived. Only a few years ago, during the boom days of Seminole and Santa Fe Springs, the crooked-holeproblem, as it was then called, occupied a primary position among the topics ofthe day in the fields of California and the Mid-Continent. The net result ofall the discussion and study at that time was the conclusion that oil wellsshould be drilled with as little deviation from the vertical as possible andthat crooked holes with elbows and dog legs were to be avoided because of thedrilling and producing difficulties encountered therein, but that manynonvertical holes were slanting or angling rather than crooked and were not aserious problem.
A Theoretical Analysis of Water-flooding Networks
Authors: Muskat M. , Wyckoff R.D.
Published: June 2014

The general problem of the simultaneous movement of water and oil in aconnected sand is of considerable practical interest from two points of view.First, there is the situation usually described as "edgewaterencroachment." Here the water in the sands contiguous to and flanking theoil sand begins to enter the latter as the oil is removed and the reservoirpressure declines. The physical questions involved concern an understanding ofthe mechanism of the advance of the water and its control, so as to aid the oilrecovery rather than to hinder it. In so far as the entry of the water into theoil sand means at least the partial replacement of the oil from the region ofthe encroachment by the advancing water, it is quite appropriate to considerthis type of situation as one of natural water-flooding.

For the present discussion, however, we are primarily interested in the problemof artificial flooding. Here the water is deliberately injected into the oilsand with the intention of displacing the oil and removing it throughprearranged output wells. For the practical development of such a procedurerather large areas are included in the flooding program and the injection andoutput wells are arranged in regular patterns or networks, which are felt to bemost favorable for a high oil recovery. Although remarkable success has alreadybeen obtained in such flooding programs, especially in the Bradford field ofPennsylvania, essentially by the application of the lessons of practicalengineering experience, a more thorough physical analysis of the problemappeared to offer promise of leading to results of some interest andvalue.

Another phase of the problem, which stimulated both the experimental andmathematical analysis, is that it is susceptible in large measure to empiricalfield tests. It is in itself but an example and illustration of the generaltheory of the flow of dead (gas-free) liquids through porous media, in whichthe authors have been interested for the last several years.