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By Henry S. Mackay

The interesting paper recently submitted by Messrs. Tobelmann and Potter1 shows that chemical problems have developed which are of great interest in this new and important branch of metallurgy. Those who realize what a process of this kind really involves will agree that it deserves a better name than '(leaching process." The word leaching conveys the idea that the copper is simply leached out of the ore with acid and then precipitated on iron; the chemistry of such a process would be of little interest. As, however, during the first year's operation of this plant 24,400,532 lb. (11,067,837 kg.) or about two-thirds of the produce, was electrolytic copper, while 7,992,033 lb., or about one-third, was cement copper, it would seem more appropriate to term the process electrochemical. It further appears, from the particulars given, that efforts have been made to have the entire production in the form of electrolytic copper. This could be done if the chemistry of the problem were kept in balance, so that it would not be necessary to discard any solutions that carried copper and acid of commercial value. A process, such as that under consideration, in which the copper is precipitated from solution by electrolysis, the solvent being at the same time regenerated, is one that requires special chemical and electrochemical knowledge and experience if all the copper in solution that has been extracted from the ore is to be successfully and economically produced as electrolytic copper. The object of this paper is to discuss, from the practical and theoretical standpoints, the chemical and electrochemical problems involved in the working of a process of this kind, and which must be solved to keep it in chemical and electrochemical equilibrium. In such a process, if the chemical balance is maintained, a solution can be used alternately as a solvent for the copper in the ore and as an electrolyte of high efficiency for the precipitation of the copper. To maintain the chemical equilibrium and so attain this result, the process must be so controlled that the solu-

Jan 1, 1921

By C. B. Manula, R. Venkataramani, T. V. Falkie

A linear programming model has been developed to solve a production planning problem for a multi-plant stone operation serving several customers. The factors considered are production capacities, inventory restrictions, demand requirements, and available stone reserves. The objective function to be optimized is the total annual net returns from the quarry operations. For the purposes of model testing, annual stone sales from each plant were divided monthwise, productwise, and assigned to a market. The concept of assigning demands to market sectors and not to any particular plant creates the self-correcting interplay between the plants and the markets. Along with the inventory restrictions, and ending inventory requirements, this interaction enables the model to minimize the external diseconomics. The model was tested against an operating prototype and a number of alternative problems were also considered. Finally, the basic linear programming model has been enlarged by the addition of another dimension and the problem has been derived in a decomposition format.

Jan 1, 1972

By C. H. Li, R. J. Stokes, T. L. Johnston

A portion of the Ni3Cr-Ni3Al phase dzagram has been investigated, including the precipitation of 1 (Ni3Al) as well as the existence of ordered Y (Ni matrix), Extensive metallographic studies by electron microscopy have been carried out and X-ray diffraction diagrams have been taken at both elevated and ambient temperatures, No long-range ordering of the phase was found above 893°C (1639°F) in the compositional range investigated. The high rate of formation of the ordered ?1 phase upon quenching has been confirmed, a phenomenon which up to the present Lime has retarded the understanding of this phase diagram, Specimens with controlled amounts of ?1 exhibited up to a six-fold improvement in yield and creep strength compared with single-phase Ni-Cv-A1 alloys. MOST of the important high nickel heat-resistant alloys are related to the nickel-chromium-aluminum system. One of the important functions of the aluminum, often accompanied by titanium, is to produce a precipitate of the very fine ?1 phase (Ni3A1, X) where X may be Ti, Cr, or other elements. A number of investigators1-" have demonstrate the presence of y' in these alloys but most of their materials contained large amounts of other elements resulting in appreciable amounts of con- fusing phases such as carbides. Further clouding of the precise role of y' has been the suspected existence of an ordering reaction in the y matrix itself, ro-3,12-17 It appeared from these investigations that aluminum in Ni-Cr alloys would raise the ordering temperature of the matrix from 540°C at NisCr to 1300°C at Ni,Al. In support of this possibility, the matrix phase in the parallel Ni-Fe-A1 system is ordered to very high temperatures.1 OBJECTIVES OF THIS RESEARCH From this survey of the literature it appeared desirable to conduct an investigation of the simple Ni-Cr-A1 system using the alloys of the highest available purity to avoid the complication of foreign phases and thereby isolate the structures in the Ni-Cr-A1 system. Procedures were developed to study ? - ?o and ? - ?1 equilibria. Preliminary mechanical tests at elevated temperatures were also conducted.

Jan 1, 1962

By W. F. Holbrock

IN a previous paper1 a method for the measurement of the compara-tive desulphurizing power of slags was described and data, were presented covering the range of likely slags containing up to 10 per cent MgO. In the present work the range is extended to include Tags containing up to 20 per cent MgO, and the effect of temperature on 5 per cent and 15 per cent MgO sings over the range 147.5° to 1525° C. is included. The method used was that described in the previous paper except that some of the temperature measurements were made with a noble-metal thermocouple instead of a tungsten-graphite thermocouple. Twelve-gram charges of 0.S per cent sulphur-metal and 5-gram charges of slag were subjected to heating for 30 min. at a prescribed temperature. The charges were analyzed for sulphur content. For purposes of comparison, desulphuriz-ing power is defined as the ratio of the percentage of sulphur found in the slag to that found in the metal. Six slag and metal charges were made coincidentally in holes in a section of all electrode graphite rod. One slag and metal charge was used as a control by means of which adjustment in the desulphurization value could be made for small varia-tions in temperature and other factors. For convenient presentation of the data, the slags are arranged in groups -in each of which one of the four main slag components is constant. Thus, the 15 per cent MgO slags are presented separately from those containing 20 per cent MgO.

Jan 1, 1938

By R. L. Rickett, W. C. Leslie, W. D. Lafferty

Notch toughness of 0.10'pct C steels, rimmed or killed, is improved by holding the steel at a temperature just above the Ae,, followed by air cooling. The improvement can be gained without apparent change in gross microstructure or hardness. The limits of the process have been determined and some possible reasons for the observed effects are discussed. The results appear to indicate that the current theories of transition temperature are inadequate. THE effects of gross microstructural variables (ferrite grain size, austenite grain size, type and distribution of carbides) on the notch toughness of mild steels have been the subject of many investigations.'-' The results indicate that increasing ferrite grain size raises the notch-impact transition temperature. The transition temperature also rises with increasing size of pearlite colonies and with increasing prior austenite grain size, but these factors are not independent of ferrite grain size. The effects of gross composition of steels have also received considerable attention. As a result, manganese, nickel, aluminum, and silicon are known to improve the notch toughness of mild steels. The other elements that have been investigated—carbon, nitrogen, boron, copper, chromium, molybdenum, phosphorus, sulfur, titanium, and vanadium—reportedly are either deleterious or have little effect on notch toughness. Despite this large volume of work, it is still not possible to predict the notch toughness of a mild steel from its microstructure and composition, even when these are supplemented by hardness and tensile tests. Steels with equivalent microstructures, but different thermal and/or mechanical histories, can differ in notch toughness. Such factors as type and distribution of precipitates, substructure, local variations in composition, or unrecognized variables, may be important in determining the notch toughness of mild steels. However, quantitative knowledge of the effects produced by these factors is almost completely lacking. In an effort to improve this situation, an investigation was begun to determine the effect of a very fine precipitate on the notch toughness of low-carbon steels. Aluminum nitride was chosen as the precipitate because of its presence in aluminum-killed steels, the ease of control of precipitation, and past

Jan 1, 1961

By William B. Phillips

The concentration of natural magnetites has been carried on in this country for several years, and more or less information has been collected on the subject. Various inventors, availing themselves of the magnetism which is inherent in such ores, have devised machines for separating the impurities from the ore by means of the electric current; and a greater or less degree of success has rewarded their painstaking and persevering efforts. We are now fairly in position to judge of the value of the process as applied to such material. It is not my purpose to speak of this matter further than may be required by the emergencies of the case. I shall assume that most engineers and metallurgical chemists are already acquainted with what has been done at the Chateaugay mines, at Mineville, at the Benson mines, at the Weldon and Ogdensburgh mines, and at Cranberry; although, at this latter place, there has not been so much done as we could wish. I shall not now speak of the various types of separators. From the time of William Fullarton, to whom was granted an English patent, in 1792, for separating iron-ore by the application of magnetic attraction, down to the present time, a great. many devices have been suggested, and a great many patents taken out for this purpose; but it is not necessary now to enter upon a discussion of their merits. Perhaps, at some future meeting of the Institute, after we shall have experimented further with some of the machines on the market, there may be an opportunity to contribute something to the current knowledge of the efficiency and economy of separating-machines. In this paper I propose to give, as briefly as possible, the results already reached in converting a non-magnetic ore into magnetic ore, and then concentrating it over a magnetic separator of the alternate-polarity type. I am aware of the work

Jan 1, 1896

By W. E. D. Jr. Stokes

THE application of aviation to mining and petroleum operations, on the basis of economy and attainment, has become a demonstrated fact. According to Dominion Government records, 30 Canadian companies engaged in air transportation with northland mining camps, carried 13,000 tons of freight in 1935, and in 1936 carried 16,000 tons. In addition, many mining companies used planes to transport prospectors with canoes, outboard motors, gasoline drums and supplies to remote locations, and one company maintained a plane to take radium-bearing ore from its mine on Great Bear Lake nearly 1000 miles south to the rail-way at Waterways, Alberta. Heavy pieces of mining machinery weighing 2 tons are being carried by Ford trimotor planes over the Andes, at an altitude of not less than 15,000 feet. At Bulolo, New Guinea, 17,500 tons of disassembled gold-dredging equipment has been flown over inaccessible terrain, while supplies and building materials for a community of 1000 whites have been transported by airplane. A 31 z-ton shaft was carried on one notable trip, while at another time an automobile, 2 tons of rice and a large safe went over the mountains in one plane. Fig. 1 shows an electric generator that was carried by plane to Bulolo. Many large American oil companies operated fleets of planes during 1936, ranging from fast, luxurious air liners for executives to elaborate geological prospecting units, ambulance planes, freight carriers and pipe-line repair crews.

Jan 1, 1937

By J. T. Eash, N. B. Pilling

As a group, the alloys of iron, nickel and carbon are, in application, one of the most versatile of the ferrous alloy family, and while many investigations have been made of their properties and structure only a few attempts have been made to show the microstructural relation over a wide range of composition. It is neccssary at once to be clear about the kind of structural relation with which we are concerned. The equilibrium diagram provides quantitative data regarding structural make-up and its variation with temperature, but equilibrium structures often are far different from the technologically significant ones. This is particularly true of steels and cast irons, and some of the most important cornponents of their structure may have no place in the diagram of equilibrium. The fugitive phases that result from transFormation are dealt with in a highly detailed and descriptive manner in. the S-curves originated by Bain. The present effort lies in a still different field, which is to portray the relation between sweeping changes in composition and in resultant structure, under controlled but nonequilib-rium conditions of thermal treatment. The Guilletl diagram presented in 1903 was the initial attempt at such a correlation and frequent references to this diagram can be found in the literature even though later work has shown it to require considerable modification. Kase2 published in 1925 a diagram that was based upon observations of furnace-cooled melts: At low carbon contents this diagram agreed fairly well with experience in showing pearlite to exist in alloys containing up to 6 per cent nickel, and completely austenitic steels at 24 to 28 per cent nickel. At high carbon contents, however, irons were indicated as being martensitic at around 2 per cent nickel and austenitic at 12 per cent nickel; these interpretations are open to serious question. Based upon experience with steels and cast iron, Wickenden3 suggested a diagram that agreed fairly well with Kase's in the steel range but which presented a wide departure from it in the higher-carbon, high-nickel regions. In its broad picture, the Wickenden diagram is an approach to "practical" structures. Reference may be made at this point to the efforts of Marsh5 to construct an iron-nickel-carbon equilibrium diagram by the coordination of scattered data, which are described at length in the monograph cited. None of these preceding attempts has appeared to meet the need for an exposition of the structural sequence that is encountered in traversing the nickel-steel nickel-cast-iron range under what might be called ordinary departures from equilibrium. ExperimentaT. Conditions Since the intent has been to establish structures developed under arbitrary conditions, experimental details have perhaps more than usual importance. Three of these conditions should particularly be noticed: (I) the material was cast and not subjected

Jan 1, 1942

By J. T. Eash, N. B. Pilling

As a group, the alloys of iron, nickel and carbon are, in application, one of the most versatile of the ferrous alloy family, and while many investigations have been made of their properties and structure only a few attempts have been made to show the microstructural relation over a wide range of composition. It is neccssary at once to be clear about the kind of structural relation with which we are concerned. The equilibrium diagram provides quantitative data regarding structural make-up and its variation with temperature, but equilibrium structures often are far different from the technologically significant ones. This is particularly true of steels and cast irons, and some of the most important cornponents of their structure may have no place in the diagram of equilibrium. The fugitive phases that result from transFormation are dealt with in a highly detailed and descriptive manner in. the S-curves originated by Bain. The present effort lies in a still different field, which is to portray the relation between sweeping changes in composition and in resultant structure, under controlled but nonequilib-rium conditions of thermal treatment. The Guilletl diagram presented in 1903 was the initial attempt at such a correlation and frequent references to this diagram can be found in the literature even though later work has shown it to require considerable modification. Kase2 published in 1925 a diagram that was based upon observations of furnace-cooled melts: At low carbon contents this diagram agreed fairly well with experience in showing pearlite to exist in alloys containing up to 6 per cent nickel, and completely austenitic steels at 24 to 28 per cent nickel. At high carbon contents, however, irons were indicated as being martensitic at around 2 per cent nickel and austenitic at 12 per cent nickel; these interpretations are open to serious question. Based upon experience with steels and cast iron, Wickenden3 suggested a diagram that agreed fairly well with Kase's in the steel range but which presented a wide departure from it in the higher-carbon, high-nickel regions. In its broad picture, the Wickenden diagram is an approach to "practical" structures. Reference may be made at this point to the efforts of Marsh5 to construct an iron-nickel-carbon equilibrium diagram by the coordination of scattered data, which are described at length in the monograph cited. None of these preceding attempts has appeared to meet the need for an exposition of the structural sequence that is encountered in traversing the nickel-steel nickel-cast-iron range under what might be called ordinary departures from equilibrium. ExperimentaT. Conditions Since the intent has been to establish structures developed under arbitrary conditions, experimental details have perhaps more than usual importance. Three of these conditions should particularly be noticed: (I) the material was cast and not subjected

Jan 1, 1942

By Frances Jane Cromwell, D. J. McAdam, G. W. Geil

In a series of papers, the authors and their associates have shown that the technical cohesion limit is affected by the same four factors that affect the flow stress, namely, the stress system, plastic deformation, temperature, and the strain rate.16-28 Moreover, each of these factors affects the technical cohesion limit in the same way that it affects the flow stress,t The influence of any one of these factors may be represented by a curve of cohesion limits, although only one point on the curve may represent actual fracture. As the term ilfracture stress' has come into use with the same significance as 'ctechnical cohesion limit," the authors are here using the shorter term with the understanding that it does not always refer to actual fracture. This paper presents the results of an investigation of the flow of notched and unnotched specimens betqrcen yield and fracture, A study has thus been made of the flow and fracture of metals as affected by the stress system, and of the ductility of metals as affected by the stress system throughout plastic deformation. Since two of the principal stresses were equal (S2 = S3), the stress systems can be represented in terms of the radial stress ratio, the ratio of the transverse radial stress s3 to the longitudinal stress S1.* The results of the experiments are represented by a series of their flow-stress curves for each Of the metals investigated, and these diagrams have been used for the development Of Other diagrams Of various types. Ludwik was the first to suggest that fracture occurs when the flow stress becomes equal to a technical cohesion limit. Although Ludwik was incorrect in his view that the technical cohesion limit depends only on the amount of plastic deformation and not On the stress system, he was 'Orrect in his view that the flow-stress curve for any stress system terminates at a point representing a technical cohesion limit. The authors have seen some recent references to assertions by other investigators that a point representing the fracture stress need not be on the flow-stress curve. The Ludwik principle, however, "auld Seem to be axiomatic, provided that the flow Stress and fracture stress are properly defined and that the fracture stress is properly determined. Disregard Of this principle has led to some untenable theories Of criteria for fracture. When a metal is very ductile, the conventional method of determining the ductility and fracture stress by dividing the breaking load by the sectional area after fracture, generally gives values that are much too high. With some metals and in some conditions, the fracture stress thus determined may be two or more times the

Jan 1, 1949

By H. Scott

Since Bohler discovered, in 1903, on cooling certain alloy steels, the phenomenon of a new and lower temperature transformation than the usual Ar 3-2-1 obtained by increasing the maximum temperature to which the material was heated, much has been published1 connecting this phenomenon with a large number of dissimilar steels of high alloy content. From the fact that the transformation divides itself, taking place at two widely separated temperatures, it has been called a "split transformation." The significant facts established by recent investigators2 are: that when the transformation occurs at the higher temperature Ar1, troostite or a decomposition product is formed, and that when the transformation occurs at the lower temperature Ar", the resulting structure is martensite. The terminology Ar' and Ar" adopted here is that of Portevin. Previous Investigations Reviewing the work on this subject published in a recent issue of Revue de Metallurgie and referring in particular to his statement that martensite is a solution of carbide in alpha iron, Le Chatelier says :4 "How then can a theory already 20 years old demand new investigations? The reason for it is that we have not succeeded in proving directly the real presence of the transformation of iron during the very short duration of the quenching. The fall of temperature takes place at the rate of several hundred degrees per second and the observation of

Jan 1, 1920

By C. G. Black

THE purpose of this paper is to present data obtained from an investi-gation conducted on the grindability of coal by the American Society for Testing Materials Tentative Standard ball-mill method. This investiga-tion has been conducted over a period of a year, during which time several hundred tests were run on a wide selection of different coals coming from Pennsylvania, Ohio, West Virginia and Kentucky. The data herewith presented tend to show that the tentative standard ball-mill method might give results that are misleading and that a volume measure might be more indicative of the true grindability 'of materials of varying specific gravity. A means whereby the time element might be reduced has been studied and other phases of this work such as preparation of samples, mechanical screening, reporting results and duplicating tests have been investigated. It is hoped that all criticism offered in this paper will be taken as constructive, with the purpose in mind of perfecting the method now tentative to show the true conditions and of making optional the manner in which certain parts of the test might be conducted to meet diversified laboratory conditions.

Jan 1, 1936

By Major N. R. Junner

Although manganese-garnets are rarely seen in hand specimens of the manganese ores and associated rocks, they have been detected by the writer in thin sections of all the ores and wall rocks that have been sliced, with the single exception of the Insuta deposit. Rhodonite, and an almost colorless amphibole, which appears to be manganiferous, are less common. Types of Occurrence (a) Rocks Composed of Manganese-garnet and Quartz The best known examples of this type are from near Bole and Wa in the Northern Territories of the Gold Coast, and from near Chama in the Gold Coast Colony. Normally these are fine and even-grained rocks, in which the garnets cannot be recognized in hand specimens. They are often stained with secondary manganese oxide. Thin sections examined microscopically are seen to be composed of aggregates of minute crystals of garnet in a matrix of mosaic quartz. Some manganese oxide and braumite (?) is often present, but other minerals are exceptional. The relative proportions of garnet and quartz in these rocks vary greatly and there is a complete gradation from quartz-rock to garnet-rock. (6) Rocks Composed Mainly of Manganese-garnet and Manganese Oxides Rocks of this type are known from Kalimbi Hill near Siripe, Pabini Hill near Bangwon, near Odumase and Konongo, and in the Ya Ya creek, about 5 miles east of Dunkwa. These are usually fine-grained banded dark-colored rocks, composed of abundant minute garnets in a matrix of black manganese oxide and braunite (?). A little microcrystalline is often present, and occasionally a little colorless amphibole. quartz (c) Rocks Composed of Rhodonite and Manganese-garnet Rocks of this type are not common. They are known from near Chama, and from the road between Senyong and Mangkuma. Some quartz is usually present. All these rocks resemble closely in texture and composition certain rocks from India, described by Fermorl as "gondite;" and they also resemble certain rocks described by Derby2 from the Queluz district,

Jan 1, 1927

By Cadwallader Evans

MY endeavor in this paper will be to tell something of the accomplishments and current problems of the anthracite producer and to suggest some of the avenues for technical development that seem to me to be the most necessary and likely to bear fruitful results. The several subjects, that I find of most interest will be taken up individually with brief reference to the future trend. Underground Mining and Loading ?In this field great progress has been made in the last twenty years, beginning with the introduction of the scraper system. The electrical hoists for the operation of scrapers have been improved, and give little trouble, but there is an open field for the improvement of the auxiliary apparatus, particularly in the application of roller-hearing sheaves to the guiding of scraper ropes. Also notable in the last six or seven years is the introduction of shaker chutes, so that far more anthracite is now loaded over them than by scrapers. This trend should continue to be manifest, particularly if those who are looking ahead and who are charged with the development of this specialty continue constantly to study and improve the mechanical design of their shakers.

Jan 1, 1938

New Jersey Zinc Co. - The Mines Franklin-Sterling Friedensville Development Austinville Ivanhoe Development Eagle Mine Hanover

Jan 12, 1953

By Vernon Read, John K. Hayes

Generally speaking, drilling equipment and techniques presently in use are not capable of meeting the complex technical-and economic-requirements of deep core drilling. Drilling to great depths involves increasing risk, time, and money. And it is especially true that costs increase with depth when conventional core drilling methods are used. Introduction of wire-line drilling techniques has been a great boon to deep core drilling, and is rapidly gaining general acceptance. But, in spite of recent progress, there remains a great need to improve productive drilling time and penetration rates, and still maintain high core recoveries.

Jan 1, 1959

Jan 1, 1923

By J. Burns Read, Charles H. Fulton

A previous article1 by the authors contained a general description of the new roasting furnace herein described but it did not go into detail as to the metallurgical behavior or the results obtained. Believing that such information would be of great value, they have elaborated on the subject and have given many unpublished details. The furnace described applies the principle of roasting finely divided zinc-sulfide ores, now produced in large quantity by the flotation process, in gaseous suspension; that is, the ore particles are carried, in suspension, in a current of air and gaseous products of the roast. The relatively great fineness of flotation concentrate presents difficulties and problems of roasting in furnaces of the ordinary type; the fine ore is forwarded through the furnace in the form of a shallow bed and its very fineness leads to dense impervious bedding which prevents oxygen from reaching the interior of the bed, thus unduly lengthening the time of roasting and preventing the elimination of the last of the sulfur. The fineness of the concentrate, normally, should lead to a rapid and complete roast, for the speed of roasting is a function of the surface exposed to oxygen, which surface is greatest, per unit of weight, in very fine material. The difficulty in bed roasting is to get the oxygen to the particle. If the fine ore, during the roasting, could be freely suspended in oxidizing gases, full advantage could be taken of the great surface conferred by its fineness. This fundamental idea, of course, is not new, for the Stedtefelt furnace, familiar to the older metallurgists, is an example of it; but the manner in which this is accomplished may be new. The numerous efforts to roast in gaseous suspension show that the idea is attractive; in fact, an analysis would indicate that it is the most reason-

Jan 1, 1925

By J. G. Richardson, J. W. Graham

The purpose of this paper is to present the results of theoretical and experimental studies of water imbibition. The imbibition processes are involved in recovery of oil from stratified and fractured-matrix formations in natural water drives and water flooding. An understanding of the role of inhibition in implementing the recovery of oil from such formations is deemed essential to proper control of these reservoirs to achieve maximum recovery. The theoretical studies involved development of the differential equations which describe the spontaneous imbibition of water by an oil-saturated rock. The dependence of the rate of water intake by the rock on the permeability, interfacial tension, contact angles, fluid viscosities and fluid saturatiorls is discussed. A few experiments were performed using core samples to determine the effects of core length and presence of a free gas suturation. The role of water imbibition in recovery of oil from a fractured-matrix reservoir by water flooding was investigated by use of a laboratory model. This model was scaled to represent one element of a frac-tured-matrix formation. Water floods were made at various rates with several fracture widths. Interpretations were made of the behavior expected in a system containing many matrix blocks. The presence of a free gas sntu.ration was found to reduce the rate of water imbibition. In the reservoir prototype of the fractured-matrix model, water imbibition rather than direct displacement by water was the dominant mechanism in the recovery of oil at low rates. INTRODUCTION Imbibition may be defined as the spontaneous taking up of a liquid by a porous solid. The spontaneous process of imbibition occurs when the fuid-filled solid is immersed or brought in contact with another fluid which preferentially wets the solid. In the process of wetting and flowing into the solid, the imbibing fluid displaces the non-wetting resident fluid. Common examples of this phenomenon are dry bricks soaking up water and expelling air, a blotter soaking up ink and expelling air and reservoir rock soaking up water and expelling oil. As increasingly better lithological descriptions have been made of the characteristics of petroleum-bearing formations, it has become obvious that imbibition phenomena which were once considered laboratory curiosities are of practical importance. For instance, in reservoirs composed of water-wet sand strata of different permeability in intimate contact, the tendency of water to channel through the more permeable stratum is offset by the tendency for water to imbibe into the tight sand and expel oil into the coarse sand. Also, in fractured-matrix formations the tendency of water to channel through the fractures is offset by water-wet matrix blocks. As some imbibition of the water into the of the largest fields in the world are fractured-matrix reservoirs, it has become increasingly important to understand all the factors involved in the imbibition process. Examples of fractured-matrix reservoirs are the Spraberry field in West Texas which produces from a fractured sandstone', the giant Kirkuk field in Iran', the Dukhan field in Qatar, Persian Gulf2, and the Masjid-I-Sula-main and the Haft-Kel fields in Southwestern Iran, which produce from fissured limestone3. Research into recovery of oil from fractured-matrix formations was stimulated by the rapid decline of oil productivity of wells in the Spraberry formation. One result of this research was the water imbibition process developed by the Atlantic Refining Co.4 Another idea was that much of the Spraberry oil could be recovered by conventional water-flooding procedures5. Subsequently, pilot floods were conducted in this field to test the feasibility of these ideas. It was felt that an understanding of the role played by imbibition processes in displacement of oil from a fractured-matrix reservoir could not be obtained from field data alone because of the many complicating factors and uncertainties involved. Therefore, theoretical and laboratory studies were undertaken to provide this understanding. Study of the equations which describe the linear, countercurrent imbibition process provided an insight into the role of various factors in the process, such as the permeability of rock and inter-facial tension. In addition to the theoretical studies, imbibition experiments were conducted with core samples to determine the effect on the rate of imbibition of such variables as core length and free gas saturation. The principal experimental studies were conducted by water flooding a scaled model of an clement of a frac-tu red-matrix reservoir to evaluate

By Arthur W. Ruff

One of the major challenges to management in the mining industry today is the establishment and maintenance of positive and dynamic programs for cost control and cost reduction. To meet the challenge, management must have a good cost system. There are various types of cost accounting systems in use today: some companies check their, performance by comparing the costs incurred during one period with the costs incurred during previous periods, while others compare the current costs with estimated costs which the company considers desirable. A third type of system is a standard cost system which provides predetermined allowances for the various cost elements and operating activities. Such a system, based on sound standards, can be established to fix responsibility for cost performance in each segment of the operation; recognize the impact of volume or rate of activity by establishing a standard volume and evaluating departures: take into consideration fixed and variable costs and their dissimilar behaviour at varying levels of operations: and provide consistent and equitable yardsticks for measuring performance.

Jan 11, 1962