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By B. Otto Pixler

Mud-analysis logging provides identification of the fluid content of formations drilled by the rotary method and permits the accurate correlation of oil and gas shows with the depth. Mud-analysis logging eliminates much coring and has an especially important application in drilling programs when coring is particularly hazardous or the electric log is difficult to interpret correctly. An appreciation of the factors that influence the results of the mud analysis, such as rate of penetration, mud properties, coring, and characteristics of reservoir rock as related to the "flushing effect," permits a better understanding of the mud-analysis log. Recent studies of the relationship of the two gas readings obtained by the gas-detector instrument have proved significant. The difference between the total combustible gas reading and the higher molecular weight gas reading indicates the presence of methane. With few exceptions, zones not showing an increase of methane probably can be condemned. Mud-analysis logging furnishes valuable information, which generally cannot be obtained by other methods. Introduction Logging by mud analysis of wells drilled with rotary tools is a direct method of locating oil-and-gas-bearing formations. The use of this method of logging has increased each year until now more than 20 field units are being used in 13 oil-producing states and in some foreign countries. Several papers1-9 have been published in the petroleum trade journals describing in detail the equipment and the application of mud-analysis logging. This paper will discuss briefly the method and review its application and some of the late developments. Method As the drilling of a well progresses, the drilling bit dislodges and disintegrates a cylindrical section of the formation. If oil or gas is contained in the pore spaces of the cylinder, some of the contents of these porous spaces will be entrained in the drilling fluid. In wall logging by mud analysis, the mud is continuously examined for oil and gas on its return to the surface, and the results are correlated back to the actual depth of the hole at the time the mud was clearing the eyes of the bit. The test for gas is made by diverting a portion of the circulating mud from the flow line to a separator or gas trap, where the mud is thoroughly mixed with air and a portion of the gas entrained in the mud is removed. A stream of air is drawn coun-tercurrent to the flow of mud in the gas trap, thus materially assisting the separation of the gas from the mud. The air-gas mixture is then drawn into a "hot-wire" gas-detector instrument where the percentage of the combustible gas is determined. The presence of oil in the formation drilled is detected by a physical examination of the drilling mud under ultraviolet light. A sample of the mud is treated to reduce the surface tension and gel strength, after which it is placed in a viewing box. This box is so constructed that all external light is excluded and so that the sample may be subjected selectively to either ultra-

Jan 1, 1946

By B. Otto Pixler

Mud-analysis logging provides identification of the fluid content of formations drilled by the rotary method and permits the accurate correlation of oil and gas shows with the depth. Mud-analysis logging eliminates much coring and has an especially important application in drilling programs when coring is particularly hazardous or the electric log is difficult to interpret correctly. An appreciation of the factors that influence the results of the mud analysis, such as rate of penetration, mud properties, coring, and characteristics of reservoir rock as related to the "flushing effect," permits a better understanding of the mud-analysis log. Recent studies of the relationship of the two gas readings obtained by the gas-detector instrument have proved significant. The difference between the total combustible gas reading and the higher molecular weight gas reading indicates the presence of methane. With few exceptions, zones not showing an increase of methane probably can be condemned. Mud-analysis logging furnishes valuable information, which generally cannot be obtained by other methods. Introduction Logging by mud analysis of wells drilled with rotary tools is a direct method of locating oil-and-gas-bearing formations. The use of this method of logging has increased each year until now more than 20 field units are being used in 13 oil-producing states and in some foreign countries. Several papers1-9 have been published in the petroleum trade journals describing in detail the equipment and the application of mud-analysis logging. This paper will discuss briefly the method and review its application and some of the late developments. Method As the drilling of a well progresses, the drilling bit dislodges and disintegrates a cylindrical section of the formation. If oil or gas is contained in the pore spaces of the cylinder, some of the contents of these porous spaces will be entrained in the drilling fluid. In wall logging by mud analysis, the mud is continuously examined for oil and gas on its return to the surface, and the results are correlated back to the actual depth of the hole at the time the mud was clearing the eyes of the bit. The test for gas is made by diverting a portion of the circulating mud from the flow line to a separator or gas trap, where the mud is thoroughly mixed with air and a portion of the gas entrained in the mud is removed. A stream of air is drawn coun-tercurrent to the flow of mud in the gas trap, thus materially assisting the separation of the gas from the mud. The air-gas mixture is then drawn into a "hot-wire" gas-detector instrument where the percentage of the combustible gas is determined. The presence of oil in the formation drilled is detected by a physical examination of the drilling mud under ultraviolet light. A sample of the mud is treated to reduce the surface tension and gel strength, after which it is placed in a viewing box. This box is so constructed that all external light is excluded and so that the sample may be subjected selectively to either ultra-

Jan 1, 1946

By W. K. Lewis, Lombard Squires, W. I. Thompson

The authors presented an article2† last year on colloidal properties of clay suspensions in which they attempted to sustain the position that the behavior of clay suspensions is due primarily to the mechanical interference of the platy particles, the nature and extent of the interference being profoundly influenced by the character of the surfaces of the particles, which in turn is determined primarily by the nature and amount of adsorbed foreign materials held on the surface of the particles by forces which are predominantly chemical in type. The following discussion is a continuation of that article to extend these same interpretative points of view to the behavior of clay gels. Insight into the mechanism of gelation is certainly of outstanding importance in the handling of drilling muds. In the former article it was suggested that the thin, flat plates that constitute the ultimate clay particles may build up aggregates by the overlapping of the ultimate plates face to face much longer and perhaps also much wider than the ultimate plates themselves, but not appreciably thicker. Exhaustive microscopic examinations of characteristic clays show no tendency for the larger particles, clearly visible under the microscope, to orient themselves in this way. It is true that the gelation of the clays is due primarily to the smallest particles, unresolvable other than by the ultramicroscope, so that the possibility of the deve1opment by them of an overlapping structure is not excluded. Furthermore, as one approaches the limit of resolving power of the microscope, the difficulty of observing accurately the shapes and relative positions of particles incresses excessively. However, in the absence of any observable tendency toward overlapping orientation of the large, visible particles, one hesitates to ascribe such a tendency to the smaller particles beyond the range of visibility. Should it develop that one must exclude the assumption of overlapping orientation, the explanations offered in the previous article are changed in only one respect; namely, one would now have to assume that the ultimate particles themselves have length, and probably also width, very large in comparison with their thickness.

Jan 1, 1936

By Lombard Squires, W. K. Lewis, W. I. Thompson

The authors presented an article2† last year on colloidal properties of clay suspensions in which they attempted to sustain the position that the behavior of clay suspensions is due primarily to the mechanical interference of the platy particles, the nature and extent of the interference being profoundly influenced by the character of the surfaces of the particles, which in turn is determined primarily by the nature and amount of adsorbed foreign materials held on the surface of the particles by forces which are predominantly chemical in type. The following discussion is a continuation of that article to extend these same interpretative points of view to the behavior of clay gels. Insight into the mechanism of gelation is certainly of outstanding importance in the handling of drilling muds. In the former article it was suggested that the thin, flat plates that constitute the ultimate clay particles may build up aggregates by the overlapping of the ultimate plates face to face much longer and perhaps also much wider than the ultimate plates themselves, but not appreciably thicker. Exhaustive microscopic examinations of characteristic clays show no tendency for the larger particles, clearly visible under the microscope, to orient themselves in this way. It is true that the gelation of the clays is due primarily to the smallest particles, unresolvable other than by the ultramicroscope, so that the possibility of the deve1opment by them of an overlapping structure is not excluded. Furthermore, as one approaches the limit of resolving power of the microscope, the difficulty of observing accurately the shapes and relative positions of particles incresses excessively. However, in the absence of any observable tendency toward overlapping orientation of the large, visible particles, one hesitates to ascribe such a tendency to the smaller particles beyond the range of visibility. Should it develop that one must exclude the assumption of overlapping orientation, the explanations offered in the previous article are changed in only one respect; namely, one would now have to assume that the ultimate particles themselves have length, and probably also width, very large in comparison with their thickness.

Jan 1, 1936

By William E. Schoeneck

This paper presents the problem of oil-well abandonment as a group of studies involving the compilation of physical well data, the use of special curves, maps, and interpretative Procedures, in order that operations can be analyzed and means for reducing costs can be effected. Methods for the calculation of the economic limit of production and resultant oil reserves are suggested in order that profitable production may be continued and premature abandonment prevented. INTRODUCTION Purpose Extensive studies have been made and much has been written on the procedures for prospecting, drilling, completion, production and repair of oil wells, but the writer has long felt the need for a study of the procedure that should be followed when considering the abandonment of a well. The production from numerous well bores of a fluid material (a circumstance peculiar to the oil industry) that is continually decreasing in quantity leads to an increasing ratio of operating cost to production. It is for this reason that oil fields are not abandoned as a whole and detailed consideration of each well is required before it can be determined whether more is being expended than will be returned On any well or lease in question. It is the purpose of this paper, therefore, to compile, correlate, and present all matters worthy of consideration in the problem of oil-well abandonment; to suggest interpretative procedures based on such compilations, to the end that reliable estimates of reserves and life may be obtained; to show, as a result of such interpretative procedures, the possibilities for corrective measures conducive to economical production, thereby extending both profitable reserves and length of life. Scope and Approach Compiling data and outlining a study having the complexity of the problem at hand are naturally subject to the personal experiences of one who undertakes the study; however, the chosen approach and grouping of the subject material may be helpful in the consideration of abandonment problems. Consideration has been given to wells that make gas and water incident with the production of oil; but consideration has not been given to either gas wells or condensate-producing wells, for wells of the latter type have sufficient problems to warrant separate investigation. The major subdivisions of this paper-— physical considerations and economic considerations—do not imply that either of these phases can be considered independently, but rather that the two are mutually dependent and are the component parts of an engineering study.

Jan 1, 1946

By William E. Schoeneck

This paper presents the problem of oil-well abandonment as a group of studies involving the compilation of physical well data, the use of special curves, maps, and interpretative Procedures, in order that operations can be analyzed and means for reducing costs can be effected. Methods for the calculation of the economic limit of production and resultant oil reserves are suggested in order that profitable production may be continued and premature abandonment prevented. INTRODUCTION Purpose Extensive studies have been made and much has been written on the procedures for prospecting, drilling, completion, production and repair of oil wells, but the writer has long felt the need for a study of the procedure that should be followed when considering the abandonment of a well. The production from numerous well bores of a fluid material (a circumstance peculiar to the oil industry) that is continually decreasing in quantity leads to an increasing ratio of operating cost to production. It is for this reason that oil fields are not abandoned as a whole and detailed consideration of each well is required before it can be determined whether more is being expended than will be returned On any well or lease in question. It is the purpose of this paper, therefore, to compile, correlate, and present all matters worthy of consideration in the problem of oil-well abandonment; to suggest interpretative procedures based on such compilations, to the end that reliable estimates of reserves and life may be obtained; to show, as a result of such interpretative procedures, the possibilities for corrective measures conducive to economical production, thereby extending both profitable reserves and length of life. Scope and Approach Compiling data and outlining a study having the complexity of the problem at hand are naturally subject to the personal experiences of one who undertakes the study; however, the chosen approach and grouping of the subject material may be helpful in the consideration of abandonment problems. Consideration has been given to wells that make gas and water incident with the production of oil; but consideration has not been given to either gas wells or condensate-producing wells, for wells of the latter type have sufficient problems to warrant separate investigation. The major subdivisions of this paper-— physical considerations and economic considerations—do not imply that either of these phases can be considered independently, but rather that the two are mutually dependent and are the component parts of an engineering study.

Jan 1, 1946

By John O. Farmer

The wire-line tubing perforator is a mechanically operated tool that is run on an ordinary steel measuring line into the tubing of a well, under pressure, to drive into the wall of the tubing, and securely lock in place, a tapered, cylindrical insert containing an orifice. Use of the perforator obviates the necessity of pulling and rerunning the tubing to install jet collars or flow valves, reduces the cost, and simplifies the task, of placing an oil well on gas-lift operation. More important, however, is the use of the tool with a removable check valve and stop, to provide a means of washing drilling mud from the annulus between the tubing and casing, and to complete the well for gas lift operation without exposing the producing formation to the mud column and without moving the tubing string. This paper discusses the origin, development, and mechanics of the wire-line perforator, the various purposes for which the tool was designed, and the method of selecting orifice sizes for any depth, and gives the results obtained thus far in practical application. Origin and Development Several years ago, a tool that could be lowered on an ordinary steel measuring line into the tubing of a well under pressure was designed and constructed for the purpose of punching a hole in the tubing walls above a shale bridge that had completely plugged the tubing of a well in the Long Lake field, East Texas. The well was in a low, swampy area, which excessive rainfall had caused to be in- accessible by car or truck for about four months. The only equipment at the well site consisted of an ordinary steel wire line that had been carried there to measure the depth of the bridge. Since a pulling unit could not be moved to the well site, and as the pressure on the casing was 2100 lb. per sq. in., it became apparent that the only way out of the predicament was to make a perforating tool that could be lowered into the tubing on a measuring line and operated under Pressure. Thus, the first wire-line tubing perforator was designed and built as an expedient, and was not used extensively until it had been redesigned to meet more frequent and increasingly urgent needs. Until recently, it was necessary to pull the tubing to install jet collars or flow the when a well was to be placed On gas lift. Because most companies either maintained or had access to pulling units and crews for this work, little or no thought had been given to eliminating or even simplifying this task. When the manpower and steel shortage became so acute, however, many operators suddenly found themselves without facilities to equip their wells for gas lifting. The wireline tubing perforator already had been tried and proved successful, therefore operators immediately requested its use to punch gas-jet holes in the tubing, to eliminate the pulling and running of tubing strings. The first deficiency revealed by more general use of the perforator lay in the inability to regulate the size of the hole punched through the tubing. The size could not be controlled to any degree of

Jan 1, 1946

By John O. Farmer

The wire-line tubing perforator is a mechanically operated tool that is run on an ordinary steel measuring line into the tubing of a well, under pressure, to drive into the wall of the tubing, and securely lock in place, a tapered, cylindrical insert containing an orifice. Use of the perforator obviates the necessity of pulling and rerunning the tubing to install jet collars or flow valves, reduces the cost, and simplifies the task, of placing an oil well on gas-lift operation. More important, however, is the use of the tool with a removable check valve and stop, to provide a means of washing drilling mud from the annulus between the tubing and casing, and to complete the well for gas lift operation without exposing the producing formation to the mud column and without moving the tubing string. This paper discusses the origin, development, and mechanics of the wire-line perforator, the various purposes for which the tool was designed, and the method of selecting orifice sizes for any depth, and gives the results obtained thus far in practical application. Origin and Development Several years ago, a tool that could be lowered on an ordinary steel measuring line into the tubing of a well under pressure was designed and constructed for the purpose of punching a hole in the tubing walls above a shale bridge that had completely plugged the tubing of a well in the Long Lake field, East Texas. The well was in a low, swampy area, which excessive rainfall had caused to be in- accessible by car or truck for about four months. The only equipment at the well site consisted of an ordinary steel wire line that had been carried there to measure the depth of the bridge. Since a pulling unit could not be moved to the well site, and as the pressure on the casing was 2100 lb. per sq. in., it became apparent that the only way out of the predicament was to make a perforating tool that could be lowered into the tubing on a measuring line and operated under Pressure. Thus, the first wire-line tubing perforator was designed and built as an expedient, and was not used extensively until it had been redesigned to meet more frequent and increasingly urgent needs. Until recently, it was necessary to pull the tubing to install jet collars or flow the when a well was to be placed On gas lift. Because most companies either maintained or had access to pulling units and crews for this work, little or no thought had been given to eliminating or even simplifying this task. When the manpower and steel shortage became so acute, however, many operators suddenly found themselves without facilities to equip their wells for gas lifting. The wireline tubing perforator already had been tried and proved successful, therefore operators immediately requested its use to punch gas-jet holes in the tubing, to eliminate the pulling and running of tubing strings. The first deficiency revealed by more general use of the perforator lay in the inability to regulate the size of the hole punched through the tubing. The size could not be controlled to any degree of

Jan 1, 1946

By R. H. Smith, A. C. Polk

The physical properties of the materials are listed, together with a short explanation of how this material binds the sand grains together without materially reducing the effective permeability of the sand. The chemical can be used in wells with bottom-hole temperatures ranging from 105°F to more than 350°F A description of the equipment required and the techniques used for applying these plastics to the wells is included. Introduction Recovering oil and gas from unconsoli-dated sand formations offers one of the most troublesome of all production problems. These sands generally present no particular trouble while drilling is in progress, but after the well has been completed and a pressure differential has been established across the face of the producing zone, the formation begins to L'slough," resulting in "sanding up" of the well. The term "sanding up" means that sufficient volumes of sand have moved into the well bore or casing to cause a serious reduction or complete halt of all flow of oil, water or gas. In rare cases a well may produce only a small amount of sand and still continue to flow or pump, the sand being carried to the surface in the fluid stream. However, in such instances, the result may be a costly repair bill due to the effect of the sand on surface and pumping equipment. The difficulty of producing petroleum from sands that are loosely cemented has long been recognized by petroleum engineers but only within the last few years has any new approach to the problem been undertaken. This involves the use of plastics that are capable of bonding the individual sand grains in place without materially reducing the effective permeability of a formation. The successful application of plastics for the consolidation of poorly cemented sands is relatively recent but now it is widely used in many of the more difficult areas on the Gulf Coast of Texas and Louisiana. This relatively new use of plastics1 in the oil fields has been preceded by much laboratory and field research on the use of various chemicals2,3 for solving numerous well-completion and work-over problems. Plastics now are being used successfully to control gas-oil and water-oil ratios,4'6 in zone isolation, the repair of casing leaks, the elimination of caving in cable-tool drilling wells6'7 and in the setting of linerss and casing.9 Sand-consolidating plastics, however, are basically different from all others in that they must not form an impervious seal. Field Practices The approach to the sanding-up problem usually has been the mechanical obstruction of the movement of the sand grains.

Jan 1, 1947

By A. C. Polk, R. H. Smith

The physical properties of the materials are listed, together with a short explanation of how this material binds the sand grains together without materially reducing the effective permeability of the sand. The chemical can be used in wells with bottom-hole temperatures ranging from 105°F to more than 350°F A description of the equipment required and the techniques used for applying these plastics to the wells is included. Introduction Recovering oil and gas from unconsoli-dated sand formations offers one of the most troublesome of all production problems. These sands generally present no particular trouble while drilling is in progress, but after the well has been completed and a pressure differential has been established across the face of the producing zone, the formation begins to L'slough," resulting in "sanding up" of the well. The term "sanding up" means that sufficient volumes of sand have moved into the well bore or casing to cause a serious reduction or complete halt of all flow of oil, water or gas. In rare cases a well may produce only a small amount of sand and still continue to flow or pump, the sand being carried to the surface in the fluid stream. However, in such instances, the result may be a costly repair bill due to the effect of the sand on surface and pumping equipment. The difficulty of producing petroleum from sands that are loosely cemented has long been recognized by petroleum engineers but only within the last few years has any new approach to the problem been undertaken. This involves the use of plastics that are capable of bonding the individual sand grains in place without materially reducing the effective permeability of a formation. The successful application of plastics for the consolidation of poorly cemented sands is relatively recent but now it is widely used in many of the more difficult areas on the Gulf Coast of Texas and Louisiana. This relatively new use of plastics1 in the oil fields has been preceded by much laboratory and field research on the use of various chemicals2,3 for solving numerous well-completion and work-over problems. Plastics now are being used successfully to control gas-oil and water-oil ratios,4'6 in zone isolation, the repair of casing leaks, the elimination of caving in cable-tool drilling wells6'7 and in the setting of linerss and casing.9 Sand-consolidating plastics, however, are basically different from all others in that they must not form an impervious seal. Field Practices The approach to the sanding-up problem usually has been the mechanical obstruction of the movement of the sand grains.

Jan 1, 1947

By Kenneth B. Barnes, George H. Fancher

With the advent of water-flooding into active commercial usage in half a dozen areas in the Mid-Continent, the process passes the experimental stage and joins other methods and processes now in use which have been found suitable in one oil field or another in securing a more profitable production than has existed heretofore. The use of the air-gas lift, acidization, pressure maintenance and repressuring have presented their problems in economics and engineering during their introduction and extended application. When a new field is discovered or attention is turned to an old producing area in which these methods have not been considered, it is to be expected that these problems again arise. While some information is available as to the results obtained by water-flooding in a few localities in the Mid-Continent, the extrapolation of the sand data on which the results are based, for even generalized use in other areas and fields in the region, is hazardous. It is precarious to assume that the same physical condition will obtain in a sand over more than small, special areas. This paper is concerned with a brief presentation of such data as are available to the authors on existing operations, a survey of the region and extent to which application of the method seems most likely to be made, an estimation of the crude reserve existing for such operations, suggestions as to the importance of core analysis in guarding against uncontrolled floods and its usefulness in predicting ultimate recoveries, and comment on some of the economic phases involved. These subjects, as concerned with water-flooding in the East (notably Bradford, Pennsylvania), have been discussed in detail in the literature and are generally well known. Especially is this true of discussions of the mechanical equipment and various lease layouts and development patterns for water-flooding.

Jan 1, 1936

By Kenneth B. Barnes, George H. Fancher

With the advent of water-flooding into active commercial usage in half a dozen areas in the Mid-Continent, the process passes the experimental stage and joins other methods and processes now in use which have been found suitable in one oil field or another in securing a more profitable production than has existed heretofore. The use of the air-gas lift, acidization, pressure maintenance and repressuring have presented their problems in economics and engineering during their introduction and extended application. When a new field is discovered or attention is turned to an old producing area in which these methods have not been considered, it is to be expected that these problems again arise. While some information is available as to the results obtained by water-flooding in a few localities in the Mid-Continent, the extrapolation of the sand data on which the results are based, for even generalized use in other areas and fields in the region, is hazardous. It is precarious to assume that the same physical condition will obtain in a sand over more than small, special areas. This paper is concerned with a brief presentation of such data as are available to the authors on existing operations, a survey of the region and extent to which application of the method seems most likely to be made, an estimation of the crude reserve existing for such operations, suggestions as to the importance of core analysis in guarding against uncontrolled floods and its usefulness in predicting ultimate recoveries, and comment on some of the economic phases involved. These subjects, as concerned with water-flooding in the East (notably Bradford, Pennsylvania), have been discussed in detail in the literature and are generally well known. Especially is this true of discussions of the mechanical equipment and various lease layouts and development patterns for water-flooding.

Jan 1, 1936

By R. A. Feemster, C. M. Rader

Because of the necessity for taking regularly occurring open-flow tests in prorated high-pressure oil fields, much gas is turned to atmosphere by way of vertical vent lines leading away from the oil and gas separator. In the past, measurement of such gas has been accomplished by several methods, usually by use of the open-flow Pitot tube. The use of the closed-flow Pitot tube has been avoided apparently chiefly because the ordinary vent-line hook-up makes it necessary to apply the instrument closer to a bend, valve, or obstruction in the pipe than is recommended by rules of good practice. The many advantages that would result from the application of the closed-flow Pitot tube prompted investigation of the actual effect upon quantity rate of flow measurements computed from data obtained with the tube in a normal working position, which is closer to the tee at the base of the vent riser than is usually considered as giving highly accurate results. An effort Was first made to compare the results thus obtained to those under ideal conditions and at high velocities To make this comparison, knowledge of the characteristics of gas flowing at very high velocities is essential. Research for such information indicated that little or no work had been done that would give data necessary for such a comparison, therefore the problem was changed to a test designed to determine the relationship between quantity rates of flow as measured by an orifice meter and a Pitot tube placed at the center of a pipe eight diameters from a tee or ell at the base of a vent riser, through which gas is flowing under low pressures at very high velocities. To determine this relationship, a series of tests was run on a number of 8-in. iron-pipe vent riser., in which the Pitot tube data were taken at the position as stated above. Gas from a wet-gas gathering system was passed through an orifice meter setting and thence to atmosphere by way of the vents. Data were taken simultaneously from the orifice meter and Pitot tube from which computations for comparisons were made. The actual method of comparison is discussed later in this paper. Since Pitot-tube information is usually given in general terms, and not readily usable, it will be the purpose of this paper to discuss the applica-

Jan 1, 1934

By M. Muskat, R. D. Wyckoff

The general problem of the simultaneous movement of water and oil in a connected sand is of considerable practical interest from two points of view. First, there is the situation usually described as "edge-water encroachment." Here the water in the sands contiguous to and flanking the oil sand begins to enter the latter as the oil is removed and the reservoir pressure declines. The physical questions involved concern an understanding of the mechanism of the advance of the water and its control, so as to aid the oil recovery rather than to hinder it. In so far as the entry of the water into the oil sand means at least the partial replacement of the oil from the region of the encroachment by the advancing water, it is quite appropriate to consider this type of situation as one of natural water-flooding. For the present discussion, however, we are primarily interested in the problem of artificial flooding. Here the water is deliberately injected into the oil sand with the intention of displacing the oil and removing it through prearranged output wells. For the practical development of such a procedure rather large areas are included in the flooding program and the injection and output wells are arranged in regular patterns or networks, which are felt to be most favorable for a high oil recovery. Although remarkable success has already been obtained in such flooding programs, especially in the Bradford field of Pennsylvania, essentially by the application of the lessons of practical engineering experience, a more thorough physical analysis of the problem appeared to offer promise of leading to results of some interest and value. Another phase of the problem, which stimulated both the experimental and mathematical analysis, is that it is susceptible in large measure to empirical field tests. It, is in itself but an example and illustration of the general theory of the flow of dead (gas-free) liquids through porous media, in which the authors have been interested for the last several years. From the point of view of its applicability to actual petroleum technology problems, however, water-flooding is a particularly favorable

Jan 1, 1934

By M. Muskat R. D. Wyckoff

The phenomenon called "water-coning" is that, observed in many oil wells, in which bottom water gradually and frequently sudderlly displaces a part or all of the oil production when a certain rather critical production rate from the well is exceeded. To follow in detail the process of the formation of a water cone as it breaks through the oil zone and enters the well bore is a problem so complex as to make a theoretical analysis practically impossible. However, an analytical treatment of the flow system before the water has broken through and during the time that it lies statically beneath the oil zone with an elevated or "coned" surface can be carried through under certain approximations. To present an analysis which shows the essential characteristics of the coning mechanism is the purpose of the present discussion. Physical Basis of Theory and Meaning of Approximations As will always be true for flow systems where true water-coning is at all possible, the water will be supposed to lie beneath the oil zone because of its density contrast with respect to the oil. In fact, tinder the usual field conditions, when the pay horizon is reasonably homogeneous, the water most frequently enters the well through the lower zones, but even when it enters from intermediate zones it may, in the later life of the well, displace the bottom layers of oil, thus resulting in a system wherein the oil is effectively floating on the water.

Jan 1, 1935

By Eugene A. Stephenson, Leon J. Pepperberg

The natural gas industry is essentially a byproduct of the oil industry. When first discovered the gas was usually regarded as a nuisance, and even when found immediately associated with oil, or suspected to be so, it was customary to blow it freely into the air, in the hope that gas would shortly be replaced by a flow of oil. The early methods of production,' transportation, and utilization were neither economical nor efficient; the chief value of gas was based on its use as a fuel, with no regard to (1) its effect. upon the oil with which it was associated, (2) its importance as a lifting agent, or (3) to its possibilities for the manufacture of byproducts. The spread of scientific research among major gas and oil companies, manufacturers, and academic groups, has gradually brought recognition of the fact that many of the technical problems bearing on production, transportation and utilization are common to both the gas and the oil industry. A few of the problems that have received serious study, and from which highly gratifying results have been obtained, are: (1) gas measurement, (2) oil well and gas well capacity tests, (3) elimination of field waste, (4) design of pipe lines and compressor stations, (5) extraction of constituents which might interfere with the normal flow of gas through the line, (6) control of reservoir pressure, (7) estimation of reserves of both oil and gas, (8) control of water encroachment, (9) measurement of factors which influence fluid movement through sands, (10) solubility of gases in oils, (11) effect of dissolved gases upon the properties of the solution. These investigations have demonstrated that almost every problem relating to oil production also involves some phase of natural gas engineering. During the past 15 years the use of experimental methods for the discovery and measurement of obscure, influencing factors, which cannot be determined purely by hydrodynamic or thermodynamic analyses, have contributed much towards the progress made in solving the problems of the oil and gas industries. Most of the experimental work on

Jan 1, 1934

By Lombard Squires, W. K. Lewis, W. I. Thompson

Clays consist predominantly of hydrated silicates of alumina. The formula is frequently assumed to be A1203 . 2Si02 . 2H20,'and certain of I. North Carolina. Low plasticity. 11. Same as I, after washing. Low plasticity. III. Tennessee. Good plasticity. IV. Pennsylvania flint fireclay. Low plasticity. V. Laredo, Texas. Very plastic. CaO/Na2O corrected for GO2. VI. San Antonio, Texas. Fine grained, highly plastic. Moisture and CO2 were determined together at 18.8 per cent. VII. Selected crude bentonite, California. " Data from R. Ries: Clays. John Wiley & Sons, New York, 1927. them undoubtedly have substantially this composition, but in general the ratio of silica to alumina is considerably higher. However, they always contain water of chemical constitution, as shown by Table 1.

Jan 1, 1935

By C. J. Wilhem, J. M. Devine

A corrosion-testing apparatus which operates in the field and which will determine the comparative resistance of various ferrous materials to corrosion by gaseous hydrogen sulfide at ordinary temperatures is described. The principle of the uniform method of testing is to allow natural gas containing hydrogen sulfide, direct from its source in the field, to flow over the group of specimens for a given period of time, and subsequently to estimate the corrosion sustained by each specimen by determining its loss in weight. The comparative results obtained when specimens of 47 representative ferrous materials of described typical composition \\ere tested at ordinary temperatures with natural gas containing hydrogen sulfide are given in tables showing average penetration of metal, Inches per year. The primary purpose of the work Mas to determine the possible utllity to the petroleum and natural gas industries of ferrous materials that are commercially available, and no attempt is made to discuss the results of the tests from the metallurgical standpoint. The following is a summary of the results obtained: 1. Steels containing 12 to 27 per cent of chromium showed the highest resistance to corrosion. The presence of nickel In these high-chromium steels did not affect their resistance. 2. Steels containing approximately 5 per cent of chromium showed comparatively high resistance, but somewhat less than that of the high-chromium steels.

Jan 1, 1934

By B. E. Lindsly

The withdrawal of gas and/or oil in appreciable quantity from a natural oil reservoir causes the pressure within the reservoir to diminish, and if the oil is completely saturated with gas, this dissolved gas begins to evolve from solution. The liberation of gas from solution in oil causes the oil to change in several ways, the principal changes being: (1) reduction in volume or "shrinkage"; (2) increase in specific gravity (decrease in degrees A.P.I.); (3) decrease of energy in the oil; (4) increased viscosity; (5) increased surface tension. As the writer's investigations have been concerned more with the first three items than with changes in viscosity and surface tension the following discussion relates particularly to the volumetric shrinkage of the oil, to the increased specific gravity, and to the decreased energy in the oil, each caused by the liberalion of dissolved gas. One of the most surprising facts that have developed in the study of high-pressure well-head and "bottom-hole" samples is the great reduction in volume that occurs in some oils when the naturally dissolved gas is liberated. High-pressure samples taken from well heads in the Oklahoma City, Kettleman Hills and Ventura, Calif., fields decreased in volume from 11.2 to 40.5 per cent when the dissolved gas was liberated in reducing the pressure on the sample to atmospheric. The amount of shrinkage an oil undergoes when gas is liberated depends upon the quantity of gas liberated and also upon its composition. A given volume of the heavier gases, propane and butane for example, will occupy more space in the oil than an equal volume of methane. The reason for this probably is that the molecules of the heavier gases are larger than those of the lighter gases. When gases are not in solution, and particularly when they are at low pressures, the distance between the gas molecules is so much greater than the dimensions of the molecules themselves that the mere size of the molecules has little effect upon the space occupied by the gas, Avogadro's hypothesis, which in effect states that all gases under the same conditions have the same number of molecules per unit volume, relates to this phenomenon. The fact that the heavier gases occupy more space than the lighter gases in the oil, and

Jan 1, 1934

By B. C. Craft, T. J. Johnson, H. L. Kirkpatrick

Petroleum engineers are displaying considerable interest in the problems of cementing oil wells, especially in the Gulf Coast and California areas, where steep temperature gradients are encountered and where wells are being drilled to greater depths. Deep drilling, that is, at depths in excess of 7000 ft., has been undertaken in these areas only in the last few years and with this trend oil-well cementing requires more technical treatment. It is not the purpose of this paper to describe the scope and application of cement operations in the oil industry or to give the standard specifications, methods of sampling and testing of portland cement. The various testing methods have been described by the American Society for Testing Materials1, Uren2, Tickell and Wankowski3 and Rakestraw and Parsons4. The latter authors (pp. 50-58) have also described in detail the methods of cementing. The authors realize that it is impossible to reproduce in the laboratory the scale of forces and dimensions that exist at great depths, but an attempt has been made to scale down these dimensions proportionally. The selection of problems to be studied was based largely upon the practical questions asked by several of the largest operators in these fields. All cements used in these experiments met the specifications of the American Society for Testing Materials.

Jan 1, 1935