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By Charles Pack

DIE castings may be defined as metal castings made by forcing molten metal, under pressure, into a metallic mold or die. It is necessary to keep this definition in mind to avoid confusing this process with other permanent-mold casting processes. The fundamental principles of the process have been known and practised many years. The simplest application is embodied in the modern linotype machine in which molten metal (usually tin-lead alloy) is forced under pressure into a metallic mold. The pressure is derived from a piston and cylinder immersed in the molten metal. Progress in the art of die casting may conveniently be divided into threee groups: Machine for imparting pressure to the metal, material for the die or mold, casting alloys. CASTING MACHINES The problem of delivering molten metal under pressure into a die is comparatively simple, when dealing with low-fusing-point alloys, as the alloys of lead and tin, but it is much more complicated when dealing with metals of higher fusing points, such as the alloys of zinc, aluminum, and copper. Although the art of die casting is comparatively new and, to a large extent, unknown, the records of the patent office are replete with patents on the subject. Fig. 1 shows the Underwood machine patented in 1902; this is probably one of the first machines designed for the production of commercial die castings. The relation of this machine to the linotype casting machine is clearly. apparent. A cylinder and piston are immersed in the molten metal, the application of power to this piston forcing the molten metal, under pressure, into the mold or die. The Doehler machine, Fig. 2, patented in 1907, is based on the same general principles. This machine is used to a large extent at the present time, throughout the United States, for the production of zinc, tin, and lead alloy die castings.

Jan 2, 1919

W. R. Ingalls, since 1905 editor of the Engineering and Mining Journal, retires from that position with the issue of Mar. 22, to open offices in New York City as a consulting engineer. The severing of this connection .will not be complete, however, as Mr. Ingalls will continue as consulting editor, and will handle the metal-market quotations in the Journal which are now the accepted authority for the government settlements of ore importations and the basis of practically all the ore settlements between miners and smelters throughout' the country. No greater compliment can be paid to Mr. Ingalls than this, unless it is the recognized fact that these quotations have been made what they are by his ability and his integrity, which secured for him channels of information vital to the accurate estimating of the market, but denied to anyone else. The Journal, under the. strong hand of Mr. Ingalls, has always been the acme of ethics in technical journalism, and the best wish that can he given to his successor, not yet announced, is that the Journal may long continue to live up to the standards not originated, but so consistently maintained and strengthened by Mr. Ingalls. His spelter statistics are accepted as authoritative wherever the English language is read and zinc ore is mined. He has found time during his very arduous years on the Journal to he the author of several works on the resources and metallurgy of zinc, lead, cadmium, etc.; for 5 years was the editor of Mineral Industry; and was consulting engineer for the Bureau of Mines and joint author of their voluminous and authoritative work on mine safety rules. His retirement from the Journal is a distinct loss to every one of the Journal's readers individually and to the profession as a whole. Universal good wishes go with Mr. Ingalls to his new field, which has for a long time been offering him professional attractions that his confining editorial work has not permitted him to accept.

Jan 4, 1919

By R. A. Blake

Measurements of the quantity of xanthate abstracted from mineral surfaces and put into solution by an increase in the hydroxyl ion concentration were made. A residual xanthate concentration of 59.6 ppm was found in one case at a pH of 11.8. The abstracted xanthate is capable of acting as a collector on fresh mineral surfaces under proper conditions. It was learned that as the hydroxyl ion increased and the xanthate abstracted, the coarse particles lose their floatability first. A volume weight relationship based on percentage coverage was established and seems to offer a reasonable explanation of the cause of observed results.

Jan 1, 1973

By J. Elmer Thomas

The evolution of the oil business is one of the great industrial romances of modern times. First used as a medicine, then as a lubricant, then as an illuminant, and finally as a motor fuel, each change in its principal usage caused large increases in consumption. Producing Successes The producing branch of the industry responded ably to the demands made upon it. Never was there a famine, rarely any threat of scarcity, and stored inventories were gradually accumulated to form comfortable working stocks. Originally an erratic and hazardous undertaking, the discovery and development of oil fields has made such strides as to classify now as a science. When storage stocks were low, production in close balance with consumption, and demand trending sharply upward, considerable concern was expressed over future needs. Price was very responsive to fluctuations in supply under those conditions, and quotations for crude and refined oils exhibited wide swings. A very different situation exists today. Consideration of the statistics only since the war will show how recent has been this change. In the 10-year period from 1918 to 1927 inclusive, we produced in the United States 6,100,000,000 bbl. of crude and imported 900,000,000 bbl., our total supply being 7,000,000,000 bbl. The consumption was 6,600,000,000 bbl., thus adding to stocks 400,000,000 bbl., an accumulation of somewhat less than 6 per cent. of the total supply. During that period virtually every field was promptly developed as soon as discovered and nearly every well in the country was producing at full capacity. With the maximum production of the wells required to take care of the rapid increases in consumption, with storage stocks moderate and proven reserves very slight, the producing division of the industry acquired a tempo not needed now. Potential Surplus Today the situation is vastly different. The economic consumption is about 2,700,000 bbl., with current production slightly in excess of that.

Jan 1, 1930

By Donald Barton

THE elastic, earthwaves produced naturally by earthquakes -have been used for a long time as evidence from which to draw conclusions in re-gard to the constitution of the interior and crust of the earth. The elastic earthwaves produced artificially by occasional explosions and recorded by seismological observatories were used to draw conclusions regarding the-geology of the intervening area. Intentionally pro-duced elastic earthwaves in the past five years have come to be used extensively in the investigation of very local geologic structure. The seismic method of work-ing geologic structure, which makes use of artificially controlled explosions and the resulting earthwaves, has developed almost `clairvoyant power in handling certain geologic situations, and in the discovery of salt domes in the Gulf Coastal: Plain region of Texas and Louisiana has 'scored the, most brilliant success. The. first, proposal for the use of artificial earth-quakes in the study-of velocity of elastic earthwaves in the surface formations of the earth's crust was made before 1888 by the English seismologists, Mallet and Abbot. Partly on the basis of their work, A. Schmidt in 1888 proposed- the use of the time-distance graphs of artificial earthquakes to study the variation of ve-locity with depth. Belar in 1902 proposed the practical application of such investigation in connection with boring tunnels. Galitzen repeatedly (1912, 1913) pro-posed the use of explosions to study the velocity of the longitudinal and transverse waves in the uppermost formations and pointed out that the velocity depended in a high degree on the physical character of the beds and that from changes in the velocity, conclusions could be drawn in regard to the compositions of the beds. Somewhat the same thought: was proposed by von dem Borne (1908), by Benndorf, Udden, and others.

Jan 9, 1928

Jan 1, 1941

ON Coal's Horizon one development rises above all others. That is the swift expansion of output to make Soviet Russia the largest coal producer on earth next to the United States. Few Americans are aware of the speed and extent of that expansion nor of the accompanying creation of a strong, resourceful mining machinery industry, nor of the extent and character of the mechanization of Soviet coal mining. Two initial clarifications are necessary for better understanding. First, we must keep in mind the sharp distinction between the Russian people and the communist Soviet dictators who rule them. The great mass of the Russian people are not members of the Communist Party as people here are Republicans or Democrats. They are not permitted to be members. There are, by various estimates, only 2 to 4 million members of that party in all Soviet Russia. The other 196 to 198 million are the victims of their tyranny and their terror. It is the activity of the Soviet rulers that concerns us here.

Jan 1, 1954

By P. H. Bohart

THe answer to the title question will be found by considering the ultimate influence of the petroleum engineers on industry and by considering the tools with which petroleum engineers must be equipped. Some 2000 to 3000 petroleum engineers are being absorbed by the industry yearly, indicating the magnitude of influence which they may exert on the industry. The petroleum industry is a highly technical one and it is inevitable that management be entrusted more and more to executives with technical training. The industry, therefore, expects the petroleum engineering schools to provide a broad basic training and a social and economic orientation which goes beyond merely supplying the minimum technical qualifications necessary to discharge responsibilities for a particular job. Because of the many branches of industry, emphasis must be placed on the Student's being trained in fundamentals, as well as grounded in other engineering branches, such as mechanical, civil and electrical engineering. The petroleum engineering graduate must know how to outline and organize the material for an engineering report and should be thoroughly grounded in English, both written and spoken. Even to the end that a five-year course may be required, they should receive instructions in auxiliary cultural and social science courses, industrial relations, and public speaking. Training in the method of approach to an engineering problem is something in which industry is deeply interested. A standard of ethics, a desire to arrive at the truth, and leadership training should be stressed. Introduction The basis of an an to any ques- tion concerning the petroleum engineering schools' responsibility to the industry will be found by considering the ultimate influence of the petroleum engineers on the industry and by considering also the tools with which petroleum engineers must be equipped in order to achieve success and happiness in the role in which their training, individual talents and choice of a profession ultimately will cast them. The problem must always be considered as it relates to a large group and not as it relates to a particular individual possessing strong natural talents and destined, by virtue of them, to pursue a certain course. The question implies that petroleum engineering schools have a responsibility, and indeed they do, not only to the industry but also to the students and even to the public. Because the responsibility is concentrated in a relatively few schools whose graduates are absorbed largely by the one industry, the responsibility is more apparent and the effect of failure to discharge the responsibility fully is more serious than the effect of similar failure on the part of schools supplying a smaller portion of the industry's intake of engineering graduates. This fact is especially true with respect to an industry such as the petroleum industry whose ratio of technical to nontechnical employees is relatively high and is increasing.

Jan 1, 1948

By P. H. Bohart

THe answer to the title question will be found by considering the ultimate influence of the petroleum engineers on industry and by considering the tools with which petroleum engineers must be equipped. Some 2000 to 3000 petroleum engineers are being absorbed by the industry yearly, indicating the magnitude of influence which they may exert on the industry. The petroleum industry is a highly technical one and it is inevitable that management be entrusted more and more to executives with technical training. The industry, therefore, expects the petroleum engineering schools to provide a broad basic training and a social and economic orientation which goes beyond merely supplying the minimum technical qualifications necessary to discharge responsibilities for a particular job. Because of the many branches of industry, emphasis must be placed on the Student's being trained in fundamentals, as well as grounded in other engineering branches, such as mechanical, civil and electrical engineering. The petroleum engineering graduate must know how to outline and organize the material for an engineering report and should be thoroughly grounded in English, both written and spoken. Even to the end that a five-year course may be required, they should receive instructions in auxiliary cultural and social science courses, industrial relations, and public speaking. Training in the method of approach to an engineering problem is something in which industry is deeply interested. A standard of ethics, a desire to arrive at the truth, and leadership training should be stressed. Introduction The basis of an an to any ques- tion concerning the petroleum engineering schools' responsibility to the industry will be found by considering the ultimate influence of the petroleum engineers on the industry and by considering also the tools with which petroleum engineers must be equipped in order to achieve success and happiness in the role in which their training, individual talents and choice of a profession ultimately will cast them. The problem must always be considered as it relates to a large group and not as it relates to a particular individual possessing strong natural talents and destined, by virtue of them, to pursue a certain course. The question implies that petroleum engineering schools have a responsibility, and indeed they do, not only to the industry but also to the students and even to the public. Because the responsibility is concentrated in a relatively few schools whose graduates are absorbed largely by the one industry, the responsibility is more apparent and the effect of failure to discharge the responsibility fully is more serious than the effect of similar failure on the part of schools supplying a smaller portion of the industry's intake of engineering graduates. This fact is especially true with respect to an industry such as the petroleum industry whose ratio of technical to nontechnical employees is relatively high and is increasing.

Jan 1, 1948

Prior to World War I, zinc was universally made by the distillation process. Small plants were operated at Cockle Creek, N.S.W., and Port Pirie, S.A. Then the electrolytic process was developed at Great Falls, Mont., in 1915 and at Trail. B.C. encouraging the Broken Hill companies to investigate the process. England's war-time need for zinc gave impetus to the development, and the site at Risdon, Tasmania, coincided with the developing hydro-electric power there. Experimental work was begun in 1917 by a proprietary company formed and owned by Broken Hill interests. Then in 1920, the principal features of the process having been established, a public company. Electrolytic Zinc Company of Australasia Ltd. was formed, now known as E.Z. Industries Ltd.

Jan 10, 1964

By A. M. Gaudin

THE so-called Kick law' is generally accepted to . mean that for each reduction to one-half in particle diameter, in a unit weight, the same amount of work is required. In crushing-efficiency calculations on crushing tests it is customary, when basing the calculation on Kick's law, to assign ordinal numbers to each standard sieve size. These ordinal numbers increase by a constant difference with each successive sieve aperture, because standard sieve apertures are in constant ratio. Minus 200-mesh is generally assumed as equivalent to 37 microns in size. By definition, the ordinal number multiplied by the per cent material of any size is equal to the energy units in the material of that size in a unit weight of sample. The sum of all energy units is the energy units content of a unit weight of sample, whether it be crusher feed or product. The difference between the energy units in the product and that in the feed is the tangible result of the work input per unit weight of feed. From this the amount of work necessary for one energy unit may be calculated. This has been done for a quartz crushing-test made at the Intermountain Experiment Station of the U. S. Bureau of Mines at Salt Lake City, in which the net work going to crushing was carefully measured. The results of this crushing test are given in Table 1.'

Jan 1, 1929

By M. D. Cooper

FOr the purpose of obtaining some first-hand data in regard to the shooting clown of coal in bituminous 'nines, it was the writer's good fortune to be employed as a shot-firer for almost one year. In all, 6,020 shots were fired by him during this period. All of the work was clone in what is known as the South Main section of the No. 2 Mine of the Ellsworth Collieries Co., Ellsworth, Pa., a subsidiary of the Lackawanna Steel Co. Position of Shot-firing in the Cycle of Operations The established practice of the Ellsworth Collieries Co. calls first for the undercutting of the coal by electric chain machines across the face of the entry or room. This is followed by replacing any posts removed by the machine-runners, or the setting of new posts or timber, as may be required. After this has been done the machine cuttings are loaded into cars. Then the coal is spragged, and a shot hole drilled to the depth of the undercut. Next in order, the shot-firer loads the hole and fires the charge. The working place is then cleaned up, timbered if necessary, the sides and face squared up, and loose material taken down. The face is again ready to be undercut.

Jan 1, 1917

By Benjamin N. Webber

During World War II the Pocos de Caldas bauxite deposits of Minas Gerais in Brazil yielded some 60,000 tons. Since then they have maintained a small but almost continuous production. Known for many years, the deposits have been reconnoitered by a number of geologists,1-4 but no dimensional study has been possible because there have not been enough exposures to show clearly the depth, bedrock, and habit of occurrence. The deposits are somewhat unorthodox in their occurrence mainly on steep slopes of mountainous terrain. Although the parent rocks are a sequence of alkalic intrusions that bauxitize readily under the proper conditions, bauxitization has not been the dominant weathering process in the area. It is limited to certain localities where important volumes of bauxite have formed by laterization of several rock types, each yielding a distinctive type of bauxite. Bauxitization may be observed in several stages and in both direct and indirect cycles of formation. The deposits are unique in being of demonstrably recent age, so that the conditions under which the bauxite formed are essentially those of the present time. The bauxitization sequence is postulated in Fig. 1.

Jan 8, 1959

By Robert Glass Cleland

Jan 1, 1952

By H. C. Lay

No one who knows the conditions of altitude, difficulty of access, shortness of working-season, etc., under which the work of the U. S. Geological Survey in the Rocky Mountains is carried on, can fail to be impressed with the magnitude and accuracy of the results obtained. Yet, in the necessarily brief time given to any one district, maily minor features must remain unregistered. The purpose of this paper is merely to place on record observations, made during nearly eighteen years, of local phenomena in themselves unimportant, which, however, if collated with similar memoranda from neighboring regions, may lead to something of value. The Telluride quadrangle in southwest Colorado is a tract of fifteen geographical minutes on a side, the NW. corner of which is in Long. 108º W., Lat. 38º N. Topographically it is essentially a lofty horseshoe, some of the peaks of which rise more than 14,000 ft. above tide, the interior (with an average altitude of 9000 ft.) being the eastern edge of the rolling Colorado-Utah plateau, and, in its turn, deeply cut by the canons of the San Miguel river and its tributaries. The range-summits are mainly igneous rocks, partly intrusive (such as massive " stocks" and laccolites, left bare by superior erosion), but mostly bedded volcanics of an average vertical thickness of 3500 ft., which change with changing height from andesite to rhyolite. The lowest series of these volcanic rocks, known as the San Juan formation, lies conformably upon the sedimentary San Miguel conglomerate, which dips gently east., and is attributed provisionally to the

Jan 1, 1902

By H. R. Banks

PONDERING the action of a ball mill employed to carry on comminution from the product of fine crushing to the point where flotation, cyanidation or other concentrating methods are applicable, one wonders where this machine had its origin. When Henry Wadsworth Longfellow reiterated the observation of that older poet Von Logau, and wrote “Tho’ the mills of God grind slowly, yet they grind exceeding small," he probably visualized the type of mill that was employed in medieval times for the production of flour, and can therefore not be considered as having gained admittance to the fraternity of millmen, on behalf of, either poet. He does, however, make it quite clear that the efficiency of even these Mills of Destiny was low, and to that extent voices a characteristic of fine-grinding equipment that has been the bugbear of all metallurgical engineers. PRINCIPLE OF BALL MILL The principle of the ball mill probably is traceable to the action along the coast line of oceans or lakes, or in the mountain streams. Wave action on rocks and pebbles, close to the shore line, gives the potential energy to the grinding media, which, in their rolling and tossing, break down the sands, and the resultant "pulp" carried out from the shore is classified and settles out in sizes ranging downward to extremely fine mesh. Surely, these are the real mills of God. If we allow our minds to dwell on the total tonnage that has been handled in this way, adding to the sands and clays at present in existence those enormous tonnages of metamorphosed sedimentaries, we sense the vast quantity of rock that has been so reduced. Is it not likely, therefore, that the answer to the beginnings of pebble milling, and eventually ball milling, came through the perception of this natural mill by one of our engineering forebears? METHODS OF GRINDING The relatively low return of mechanical input to a ball mill, in terms of useful work accomplished, has always intrigued me immensely. The potential energy absorbed by a ball raised to a high point in its path is apparently released with a very small return in useful work. Is the ball mill the most desirable means of fine grinding, or is there some other method through which we can recover a reasonable amount of the energy input in terms of useful work? Some years ago, on his retirement, H. W. Hardinge was questioned as to his thoughts on the trend of fine-grinding equipment. As I recall, his prophecy at that time was that the most likely field for improvement in grinding media would be toward a charge of flat disks with some mechanical scheme to cause them to slide over each other. Undoubtedly, Mr. Hardinge went through the usual experience of the muller and bucking board, the customary introduction of the budding millman to his calling. I have often wondered, but have never got beyond the wondering stage, as to the

Jan 1, 1945

THE CHAIRMAN.-Thank you. Since the papers are rather closely related, I think rather than taking them one at a time we will entertain discussion on any of these problems at this time. W. A. REICH.*-We, of course, quite a while ago got the yellow light that Mr. Cole spoke of, and like everyone else immediately started to study silicon bronzes and brasses. We were interested in the silicon bronzes and brasses because we felt that in order to replace gun metal which makes up a large part of our use we needed something with an elastic limit at least equal to that of gun metal. That means at least 12,000 lb. per sq. in. This study was aimed only at tin conservation. Then we dropped the study of silicon bronzes because high purity copper which is needed in their manufacture became a scarce item. To make a long story short we have recommended to our designing engineers that they use 85-5-5-5 wherever possible because 85-5-5-5 we understand can be made entirely from scrap with little or no tin addition. 85-5-5-5 has a lower elastic limit than 88-8-4, so we felt that we would need another substitute material, a structural alloy with an elastic limit equal to that of 88-8-4, and we immediately turned to the manganese bronze type of alloy. The poor foundry properties of standard manganese bronzes were mentioned by Mr. Thieme and since we feel that high zinc content is largely responsible for this difficulty, our development is directed along the lines of uncovering a material with a lower zinc content and which gains its elastic strength from the addition of other alloying elements, such as, aluminum, manganese and iron. It must be possible to make this alloy entirely from scrap with no additions of scarce high purity material. I would appreciate an expression of opinion on how low we can go in zinc content with this type of alloy without seriously impairing the availability, and how high we can go in aluminum content without making use of aluminum restricted for that use. We assume that the maximum lead content must be placed at 1 ½ per cent to insure good availability and we feel that about I per cent of tin in the alloy would improve salt water corrosion resistance similar to the effect of tin in Admiralty Metal. Has anyone here had experience with the effect of tin and lead on the weldability of such an alloy? C. S. COLE.-What percentage of lead and tin? W. A. REICH.-About 1 per cent of lead and 1 per cent of tin. We are studying the weldability of the alloy but perhaps someone already has the answer. (Pause, no answer) The claim has been made that 1 per cent of lead can be added to certain silicon bronzes without impairing their properties. A silicon bronze with a low zinc content requires high purity copper in its manufacture but if say the 15 per cent zinc, 44 silicon balance copper alloy could be made, with a I per cent lead content, some quantity could be made from scrap. We do not know whether the aforementioned is

Jan 1, 1943

By A. W. Edelen

THE Teziutlan copper-zinc deposit is supposed to be of late Cambrian or early Paleozoic age. The country rocks are a series of schists or phyllites, flat lying and in the form of a plunging anticline. The ore deposit occupies a single horizon in the schist for a known horizontal extent of 1200 meters. Along its strike occur four large lenses or ore bodies. These ore bodies occupy positions along the flank and extend to the crest of the anticline. The primary mineralization is in the form of quartz, pyrite, sphalerite, chalcopyrite and galena, with a few scattered silver anti-monides. Quartz and pyrite form the mineralization between the ore lenses. In the ore lenses the sulphides appear as a massive, very fine-grained intergrowth of minerals. The intergrowth suggests a contemporaneous deposition of the heavy sulphides. The grain size, usually under 0.09 mm., makes the separation difficult and fine grinding important. The ore bodies were formed at great depth by solutions probably originating in the same basic magma that gave rise to the dolerite sills that are so common in their vicinity.

Jan 1, 1937

By Walter Rose

Experimentation which measures differences in pressure across the interfaces of immiscible fluids in the interstitial spaces of porous media may be termed "capillary pressure experimentation". In the literature of petroleum technology since 1941 there have appeared twelve papers popularizing capillary pressure concepts and developing applications of these concepts for the solution of problems of practical reservoir engineering importance, such as the determination of connate water, fluid distribution. in transition zones, reservoir rock textural properties, and oil recovery from petroleum reservoirs. Although a review of the literature would be justified at this time in order to reconcile the conflicting viewpoints which are contained in the cited papers, the object of this note will be of more limited scope. It is believed that the recent paper of Muskat alls sufficient attention to many of the uncertainties which arise upon examination of the published literature. such that until satisfactory counter-proposals can be made it will serve our purpose only to mention some other like uncertainties. This will emphasize further the need confronting petroleum technologists to re. consider and reformulate the application possibilities of capillary pressure experimentation. In particular, I sug- gest that we examine the thesis that capillary pressure experimentation as above defined can lead to measurements reflecting the recovery of oil from petroleum reservoirs, as was proposed first" by Amyx and Yuster and was first reduced to practice by the experimentation of Welge . In fact. I shall deal exclusively with the Welge papers since it is the principle one on this subject which has appeared to date. I shall attempt to show that the possibility of describing oil recovery features in terms of capillary pressure phenomena has not been established entirely. The Welge paper was a pioneering effort to evaluate this recovery application possibility. P. P. Reichertz' comments on the Welge paper state that non-wetting phase discontinuities are developed occasionally in the Welge experiment, and restate Muskat's argument that discontinuous fluid elements (partially saturating the interstices of porous media which are elsewhere saturated with some other immiscible phase or phases) are not subject to the requirements of hydrostatic equilibrium. It is the purpose of my comment to show that it is unnecessary to make Reichertz' postulation regarding non-wetting phase discontinuities (however valid) when it is desired to criticize Welge's theoretical treatment of his problem. It can be shown that Welge's method of measuring values for ''capillary pressure" is invalid in many instances of application, such that his reported curves of capillary pressure Versus fluid saturation often have no physical meaning, even throughout the interval of fluid saturation where it might be otherwise suspected that no phase discontinuities occur. By considering established principles of capillary pressure experimentation it can be shown that the pressure difference experimentally observed between wetting and non-wetting fluid phases which are contained in external reservoirs will reflect on the capillary pressure difference at the interfaces of contact between these phases only when the following conditions are satisfied: (a) There shall be a balance between the opposing forces of gravity and capillarity, as obtains under conditions of hydrostatic equilibrium when the positions of the interfaces of contact become fixed in pore spaces of certain geometry (b) The wetting and non-wetting fluids within the interstitial spaces shall everywhere be continuous with the external wetting phase reservoir and the external non-wetting phase reservoir, respectively. It will become apparent immediately that in any instance when a greater pressure is recorded in the external wetting phase reservoir than in the external non-wetting phase reservoir, one may establish either that static equilibrium has not been attained or that discontinuities in one or more of the fluids have been developed. This is because the pressure otherwiee is always gereatest in the non-wetting phase at each static interstitial interface of contact with the wetting phase. such that the externally measured pressure in the non-wetting phase likewise must be greatest if the above conditions are to be satisfied.

Jan 1, 1949

By Walter Rose

Experimentation which measures differences in pressure across the interfaces of immiscible fluids in the interstitial spaces of porous media may be termed "capillary pressure experimentation". In the literature of petroleum technology since 1941 there have appeared twelve papers popularizing capillary pressure concepts and developing applications of these concepts for the solution of problems of practical reservoir engineering importance, such as the determination of connate water, fluid distribution. in transition zones, reservoir rock textural properties, and oil recovery from petroleum reservoirs. Although a review of the literature would be justified at this time in order to reconcile the conflicting viewpoints which are contained in the cited papers, the object of this note will be of more limited scope. It is believed that the recent paper of Muskat alls sufficient attention to many of the uncertainties which arise upon examination of the published literature. such that until satisfactory counter-proposals can be made it will serve our purpose only to mention some other like uncertainties. This will emphasize further the need confronting petroleum technologists to re. consider and reformulate the application possibilities of capillary pressure experimentation. In particular, I sug- gest that we examine the thesis that capillary pressure experimentation as above defined can lead to measurements reflecting the recovery of oil from petroleum reservoirs, as was proposed first" by Amyx and Yuster and was first reduced to practice by the experimentation of Welge . In fact. I shall deal exclusively with the Welge papers since it is the principle one on this subject which has appeared to date. I shall attempt to show that the possibility of describing oil recovery features in terms of capillary pressure phenomena has not been established entirely. The Welge paper was a pioneering effort to evaluate this recovery application possibility. P. P. Reichertz' comments on the Welge paper state that non-wetting phase discontinuities are developed occasionally in the Welge experiment, and restate Muskat's argument that discontinuous fluid elements (partially saturating the interstices of porous media which are elsewhere saturated with some other immiscible phase or phases) are not subject to the requirements of hydrostatic equilibrium. It is the purpose of my comment to show that it is unnecessary to make Reichertz' postulation regarding non-wetting phase discontinuities (however valid) when it is desired to criticize Welge's theoretical treatment of his problem. It can be shown that Welge's method of measuring values for ''capillary pressure" is invalid in many instances of application, such that his reported curves of capillary pressure Versus fluid saturation often have no physical meaning, even throughout the interval of fluid saturation where it might be otherwise suspected that no phase discontinuities occur. By considering established principles of capillary pressure experimentation it can be shown that the pressure difference experimentally observed between wetting and non-wetting fluid phases which are contained in external reservoirs will reflect on the capillary pressure difference at the interfaces of contact between these phases only when the following conditions are satisfied: (a) There shall be a balance between the opposing forces of gravity and capillarity, as obtains under conditions of hydrostatic equilibrium when the positions of the interfaces of contact become fixed in pore spaces of certain geometry (b) The wetting and non-wetting fluids within the interstitial spaces shall everywhere be continuous with the external wetting phase reservoir and the external non-wetting phase reservoir, respectively. It will become apparent immediately that in any instance when a greater pressure is recorded in the external wetting phase reservoir than in the external non-wetting phase reservoir, one may establish either that static equilibrium has not been attained or that discontinuities in one or more of the fluids have been developed. This is because the pressure otherwiee is always gereatest in the non-wetting phase at each static interstitial interface of contact with the wetting phase. such that the externally measured pressure in the non-wetting phase likewise must be greatest if the above conditions are to be satisfied.

Jan 1, 1949