Search Documents

By Gregoire Gutzeit

THE development reported in this paper was begun by the author a number of years ago, while he was a lecturer on complex chemistry and metallurgy at the University of Geneva, Switzerland, and in charge of that institution's research laboratory. Completion of the development and reduction to practice did not occur until last year at the Westport mill, laboratories and testing plant of the Dorr Company, where this method is now in general use for identifying and localizing the mineral constituents of both metallic and nonmetallic ores. It has proved to be a practical tool of the metallurgical staff at the Westport mill, devising unusual milling flowsheets for complex and refractory ore bodies. In a number of instances the findings have been successfully used as fundamental factors in the design and specification of complete metallurgical plants. Seven examples of the use of this method in solving practical milling problems are included in this paper. GENERAL OUTLINE The microscopic study of an ore, at first only of scientific interest, has proved extremely useful both in practical geology and in ore dressing. The binocular magnifying lenses for rough observation of the products of an ore-dressing plant have been in use for a long time; but only within the last few years has a systematic microscopical examination of ore samples become a normal tool of any research laboratory dealing with ore-dressing problems. Such an investigation avoids considerable loss of time as well as empirical trials and useless experimentation. It will generally indicate the correct grinding and often will suggest the proper method of treatment. The petrographic determination of transparent minerals in thin sections, or even in grains, has been perfected, and very accurate methods have been devised to meet any requirement, such as Feodorof's rotating stage on the petrographic microscope. Almost all transparent minerals can be positively identified by their optical properties; i.e., isotropism, anisotropism, color, pleochroism, refractory index, cleavage, crystal form, birefringence, and others. The identification of opaque minerals is a much more difficult problem and can be done only by using polished specimens. Unfortunately, most of the valuable metallic ores, and even some of the nonmetallic ones, are not transparent; therefore it has been necessary to develop a special technique for the determination of these minerals. Some optical properties-for instance, isotropism, anisotropism, color, cleavage, reflecting power-are often adequate in roughly classifying the mineral. Only "reflecting power" is a measurable value, provided special photometric equipment (ocular photometer or Orcel's photoelectric cell) is available. The other optical properties mentioned are more or less relative,

Jan 1, 1942

(Members are urged to send in for this column any notes of interest concerning themselves or their fellow-members.) Members and guests who called at Institute headquarters during the period Mar. 10, 1916 to Apr. 10, 1916: R. C. Blanchard, London, England. George H. Packard, Boston, Mass. F. Lynwood Garrison, Philadelphia, Pa. Harvey B. Small, Mangangue, Colombia, S. A. S. A. Horton, Altoona, Pa. H. De Witt Smith, Kennecott, Alaska. J. S. Lane, New York City. Richard Tarantous, Terlingua, Tex. Harry T. Mercer, Painesdale, Mich. S. A. Taylor, Pittsburgh, Pa. A. L. Blomfield, for many years in the employ of Bewick, Moreing & Co. as metallurgist, and for the last eight years mill superintendent of the Golden Cycle mill at Colorado Springs, has become associated with The Dorr. Company as consulting metallurgical engineer, with headquarters at Denver. He retains his connection with the Golden Cycle mill as general superintendent.

Jan 5, 1916

By Ernest Kirkendall

The amount of research done in the last fen years on the subject of diffusion in solid metals is significant of the importance of this problem. To review the literature dealing with diffusion is unnecessary here. Deschl in 1912 reviewed the work that had been done on diffusion in solids and gave a bibliography of the literature published before that time. Mehl's paper in 19362 is an excellent review of diffusion in metals and contains a large bibliography. Of importance also for it? review and bibliography is an article by 14. I. Krynitsky.~ While considerable material lias appeared in the literature on diffusion in brass, the amount of information is not great compared to that pertaining to some of the other alloys. Most of the information published is of a qualitative nature; that which is quantitative varies considerably. Thus the quantitative determination of the rates of diffusion of copper and zinc in alpha brass by a new method appeared worth while. In the present investigation the rate of diffusion of zinc in approximately the same composition alpha brass has been determined :it three temperatures. Procedure The method used consisted of plating copper on a beta brass, heating it, to allow diffusion to take place, and measuring the concentration of copper by determining the lattice constant of the alloy. This method is unique in that it uses a beta brass of such a composition that at the tem perature at which diffusion takes place the beta brass is saturated wit11 copper. Thus, while the beta brass supplies thc zinc, no diffusion takes

Jan 1, 1939

By Ernest Kirkendall

The amount of research done in the last fen years on the subject of diffusion in solid metals is significant of the importance of this problem. To review the literature dealing with diffusion is unnecessary here. Deschl in 1912 reviewed the work that had been done on diffusion in solids and gave a bibliography of the literature published before that time. Mehl's paper in 19362 is an excellent review of diffusion in metals and contains a large bibliography. Of importance also for it? review and bibliography is an article by 14. I. Krynitsky.~ While considerable material lias appeared in the literature on diffusion in brass, the amount of information is not great compared to that pertaining to some of the other alloys. Most of the information published is of a qualitative nature; that which is quantitative varies considerably. Thus the quantitative determination of the rates of diffusion of copper and zinc in alpha brass by a new method appeared worth while. In the present investigation the rate of diffusion of zinc in approximately the same composition alpha brass has been determined :it three temperatures. Procedure The method used consisted of plating copper on a beta brass, heating it, to allow diffusion to take place, and measuring the concentration of copper by determining the lattice constant of the alloy. This method is unique in that it uses a beta brass of such a composition that at the tem perature at which diffusion takes place the beta brass is saturated wit11 copper. Thus, while the beta brass supplies thc zinc, no diffusion takes

Jan 1, 1939

By J. A. Herbst, A. L. Mular

Digital simulation is defined and simulation techniques are re- viewed. Typical methodology involves the selection of models, the adjustment of raw data, the selection of a fitting strategy, the assessment of model accuracy in a statistical sense, and the development of an executive simulation structure. Simulations serve as aids for process engineers in evaluating the feasibility of a proposed flowsheet and the effect of a modification to an existing flowsheet. In addition, simulation plays an important role in off-line optimization and in the evaluation of alternative circuit control strategies. Several examples are presented to illustrate these uses for simulation including applications in crushing circuits, grinding circuits, and flotation circuits. It is the opinion of the authors that, within the next decade, mineral processing plants will be studied routinely via digital simulation during the preliminary design stage. Simulation will constitute an important component of the design decision making process.

Jan 1, 1978

By Ronald W. Utley

INTRODUCTION The ''Do's and Don'ts" of installing equipment in a comminution circuit begin during the study stage of a proposed project, continue through preliminary engineering, detail engineering, procurement, the actual placement of equipment at the job site, and end with turnover to the owner. Equipment supplied for a modern comminution circuit will be high quality, rugged machinery designed according to appropriate manufacturing standards for long hours of trouble-free service. However, certain precautions and procedures must be observed in plant design and layout, equipment handling, installing and servicing in order to obtain optimum performance. This chapter contains general installation "DO'S and Don'ts" for the major equipment in the circuit. •Primary Gyratory Crushers •Rock Breakers (Hammer) •Belt Conveyors •Apron Feeders •Weigh Belt Scales •Secondary Crushers •Vibrating Screens •Grinding Mills •Mill Liners •Open Gear Sets •Speed Reducers •Electric Motors •Cyclones •Slurry Pumps Some questions will not be covered in this chapter, or may not be applicable to the actual equipment purchased, as requirements do vary from manufacturer to manufacturer. Additional specific information can be obtained by contacting the manufacturer's local representative or the factory. All inquiries should be accompanied by the following information: •Unit size and type of equipment •Manufacturer's shop order number (after order placement) •Serial number (after manufacture) DO'S 8 DON'TS FOR INSTALLATION OF ALL COMMINUTION CIRCUIT EQUIPMENT Installation By Design DO obtain tables of weights and clearances from manufacturer. DO obtain WR2 forces from manufacturer to determine that the foundation is adequate. DO determine compression strength of foundation soil and/or rock. DO obtain manufacturer's recommended typical foundation drawings. If substantial alteration to manufacturer's drawings is required, check with the manufacturer before proceeding.

Jan 1, 1982

By David P. Hale

The Cartersville barite district is near Cartersville, Ga., in the southeastern part of Bartow County, about 43 miles northeast of Atlanta. The area over which active mining is being done extends about six miles in a northeasterly direction and is about three miles wide. Barite production in Georgia began about 1907,' but the existence of the mineral was known much earlier. At present four companies are operating washing plants and three other plants are operating on leases from those companies. The chief impurities in the ores are silica and iron oxide. The silica is easily washed and jigged out and gives little trouble. Any gravity separation between the iron and the barite is generally poor, owing to the slight difference in specific gravity. Two operators have turned to magnetic separation as the solution to the problem and have made remarkable improvements in the finished product. By very close sizing prior to jigging, the separation between iron and barite has been greatly improved. In some localities manganese occasionally appears as an impurity, but is fairly easy to eliminate by gravity methods. A considerable percentage of iron and silica is eliminated by being broken free in crushing. Until methods for the recovery of fine ore were introduced a minimum of crushing was done, but modern methods allow more than formerly. The depression years brought about the need for increased recovery of ore handled on the part of the producers and a demand for a higher grade of product on the part of the buyers. Improvements in milling and mining practice have had a far greater effect, however, than merely the production of a better grade of ore with greater recovery. They have opened for mining large areas that a few years ago were considered noncommercial deposits because of their inaccessibility and their high iron content. It is no exaggeration to say that the new methods have more than doubled present known reserves of barite ore of economic value.

Jan 1, 1942

By David P. Hale

The Cartersville barite district is near Cartersville, Ga., in the southeastern part of Bartow County, about 43 miles northeast of Atlanta. The area over which active mining is being done extends about six miles in a northeasterly direction and is about three miles wide. Barite production in Georgia began about 1907,' but the existence of the mineral was known much earlier. At present four companies are operating washing plants and three other plants are operating on leases from those companies. The chief impurities in the ores are silica and iron oxide. The silica is easily washed and jigged out and gives little trouble. Any gravity separation between the iron and the barite is generally poor, owing to the slight difference in specific gravity. Two operators have turned to magnetic separation as the solution to the problem and have made remarkable improvements in the finished product. By very close sizing prior to jigging, the separation between iron and barite has been greatly improved. In some localities manganese occasionally appears as an impurity, but is fairly easy to eliminate by gravity methods. A considerable percentage of iron and silica is eliminated by being broken free in crushing. Until methods for the recovery of fine ore were introduced a minimum of crushing was done, but modern methods allow more than formerly. The depression years brought about the need for increased recovery of ore handled on the part of the producers and a demand for a higher grade of product on the part of the buyers. Improvements in milling and mining practice have had a far greater effect, however, than merely the production of a better grade of ore with greater recovery. They have opened for mining large areas that a few years ago were considered noncommercial deposits because of their inaccessibility and their high iron content. It is no exaggeration to say that the new methods have more than doubled present known reserves of barite ore of economic value.

Jan 1, 1942

By B. R. Coil

One executive writing on capital equipment re- placement stated: "We keep extremely close watch over repair costs and when we reach the point of uneconomical operation, we replace the machine." This, of course, is most elementary, but a very basic premise. However, it seems advisable to set forth several equally obvious principles, so that all discussion will start from the same point. The subject is intended to deal with the point of uneconomical operation due to high operating costs in general and high repair costs in particular. This is not concerned with a similar problem of high costs because of an insufficient number of machines, be they trucks, shovels, or dozers.

Oct 1, 1955

By Donald E. Cummings

MEASURES appropriate for the control of the silicosis hazard in mining cannot be formulated precisely, but sufficient has accumulated during the past quarter century to permit the suggestion of useful, though partly empirical, rules for its alleviation. The industrial hygienist today recognizes that the peril incurred by the inhalation of harmful dust is a function of two variable factors-the degree of harmful exposure and the specific susceptibility of the exposed individual to pulmonary injury. Control of the danger arising out of prolonged contact with pernicious air- borne particulate matter is consequently best exercised by influencing both of these recognized variables. Obviously the problem has two broad aspects-one, medical; the other within the province of the engineer. I-FACTORS COMPRISING THE DEGREE OF INDIVIDUAL SUSCEPTIBILITY Thorough investigations conducted among miners who have labored for years in the presence of recognized silicosis hazards usually reveal an impressive difference in the injury incurred by men whose exposure to dust has been nearly identical. After a quarter century underground, one individual is short of breath and incapacitated with miners' complaint, while a fellow workman suffers no pulmonary embarrassment and is in good health. Physicians ascribe this oft-observed difference in reaction to individual susceptibility and express a universal regret when they deplore the fate that chose to make the predisposed youth a miner rather than a farmer. To trust the health of miners to fate at the present time is even more unfortunate, because many of the factors that influence man's susceptibility to dust are known, and can be accurately determined by competent medical methods. Among the most important factors comprising susceptibility to injury by dust are the anatomical peculiarities of the individual's respiratory mechanism, his physiological response to the inhalation of dust, his previous dust exposure, the existence of pulmonary infections or other pathological processes in his lungs, his age,

Jan 1, 1938

By J. B. Austin, R. H. H. Pierce

IN developing a consistent picture of the thermal expansion of the commercial chromium steels, which cover a range of, carbon contents, it is desirable to know the expansion in the limiting case of the binary, carbon-free, iron-chromium alloys. We have, therefore, determined the thermal expansion of a series of five special alloys, ranging in chromium content from 3 to 10.5 per cent, with not more than 0.03 per cent carbon, over a temperature range extending beyond the transformation region; this low carbon content enables us to draw reasonably reliable conclusions as to the behavior of the carbon-free system. Moreover, the measurements serve to determine the beginning and the end of the alpha-gamma transformation; and they emphasize once more the fact that a transformation temperature determined by any method in which the specimen is .cooled at an appreciable rate is apt to be seriously in error, particularly if the metal contains a transformation-retarding element such as chromium or managanese. The lag, or undercooling, observed at the ?-a transformation is explained in terms of the influence of temperature on transformation velocity; the rather unusual shape of the ? loop is attributed to a change with temperature and with composition of the distribution of chromium between the alpha-iron and gamma-iron solid solutions. The exact composition of the alloys which were obtained through the courtesy of Dr. W. Rohn, of the Heraeus Vakuumschmelze A-G., is given in Table 1. Determinations of the linear thermal expansion and of transformation temperature were carried out in the vacuum dilatometer previously described,1 using a rate of heating and of cooling of 3.0° to 3.5° per minute unless otherwise stated. Magnetic susceptibility, which was measured in studying the rate of transformation, was determined with a magnetic balance, which also has. been described.2

Jan 1, 1935

By M. C. Cheney

The active development of the vast East Texas oil field, the attendant effects of the rapidly increasing flow from its prolific wells and the efforts to bring order out of chaos precluded or dwarfed other oil development in Texas during 1931. In a paper by Dr. F. H. Lahee1 presented at the October, 1931, meeting, the early history of the East Texas oil field is described and the sequence of events in connection with its development and efforts to control its production up to Sept. 25 is narrated. At that time the Railroad Commission of the state reduced the production of the field to a maximum of 400,000 bbl. per day by restricting the allowable daily production per well to 185 bbl. By further reduction in the daily production per well to 100 bbl., the field was held below that maximum figure during the remainder of the year. Meanwhile, as a result of an injunction against the Railroad Commission, its authority in the field was superseded on Oct. 13 by the Governor of the state, and after that date production was controlled directly by his orders issued under authority of martial law. Suits to contest this authority were brought in the Federal courts and were pending at the close of the year. On March 5, 1931, as a result of the East Texas production, posted prices for Mid-Continent 40' A.P.I. crude slumped from $1.07 to $0.67. As East Texas production continued to mount, posted prices in East Texas were reduced to $0.37 on June 3 and $0.22 on July 8, although in that field most of the oil was sold for much less, bringing the producer and royalty owner as low as $0.025 per barrel. Northeast Texas To the information contained in Dr. Lahee's paper, it can now be added that the East Texas field has produced over 105,000,000 bbl. and registered about 3700 successful completions during 1931. There may be some merit to the recent prediction that a large part of the field will have passed its flowing period by the middle of 1932 unless

Jan 1, 1932

By Ligon Johnson

. Only the acute phase of the smelter fume problem is new. The problem itself is older than the Christian era. While both lead and copper were mined and crudely smelted some 3000 years ago, it was not until the Roman occupation of the Iberian . Peninsula and the British Isles, which occurred but shortly before the beginning of the Christian era, that there was any evidence of smelting operations on a scale sufficiently large to permit a fume problem. Around Huelva, Spain, are found more than 30 million tons of slag from lead smelting conducted there by the Romans. Pliny tells US that more than 20,000 slaves were employed in the Iberian mines. Extensive mining and smelting by the Romans in England and Wales were coincident with the Iberian proceedings. These metallurgical operations were upon a sufficiently large scale to produce marked results both upon the surrounding country and the smelter workers, but, as they were those of a conqueror upon conquered soil, conducted by slaves, imperial Rome failed to recognize that such a thing as a smoke problem did or could arise, and whatever fume question there may have been at that time remained a question only to those who had no chance to answer any phase of it. The smelting operations of the Romans extended over about 400 years, and little is recorded of lead and copper smelting from that time until the 16th century. From the revival beginning at this period up to the present century, the growth of smelting has been comparatively gradual. In Great Britain, smelting was conducted almost wholly in localities where metallurgical operations were of paramount importance, and the communities .that grew up in smelter localities were due to and dependent upon the mines and smelters. This fact had much to do with the comparative freedom of British smelting from burdensome fume litigation and legislation. To a lesser degree these conditions applied to the German operations which, when coupled with the further fact that most of the early German operations were to a greater or less degree fiscal workings of Prussia, Saxony and Brunswick-Hanover, accounts for

Jan 1, 1918

By J. R. Elenbaas, J. A. Vary, D. L. Katz

The development of gas fields, oil fields and aquifers for storing natural gas is treated from two main vieu.-points: (I) the volumetric storage capacity for gas in a given situation and (2) the prediction of the number of wells required for the delivery of gas. Other experiences in the design and operation of storagc fields are incluclerl INTRODUC TION Storage of natural gas in underground reservoirs near the terminus of long distance pipelines has been the prime factor in opening the space heating market to the natural gas industry. Storagc has permitted a major. increase in both the load and the load factor of pipe-lines; some are now operating at steady load throughout the year. Thus, underground storage has been responsible for the rapid increase in demand for natural gas in recent years. Three types of reservoirs have been used for gas storage: natural gas reservoirs, oil reservoirs, and waterbearing sands or aquifers. This paper presents the factors to be considered when developing gas storage reservoirs of these three categories. There are two prime considerations tor any storage reservoir: (1) the volume of gas which a given reservoir will store advantageously and (2) the number 01 wells needed to provide the required peak deliverability. These two problems will be considered for the three types of reservoirs just noted STORAGE IN PARTIALLY DEPLETED GAS FIELDS Early storage operations consisted of replenishing the natural gas in a depleted gas field situated adjacent to the market. Today, newly discovered fields near the market may be considered for storage, and this discussion applies equally to both types of reservoirs. For reservoirs originally containing gas or oil, the question of the impermeability of the cap rock nor-mally does not arise. However, such fields are likely to have many wells drilled either to or through the reservoir under consideration. Positive assurance must be obtained that such wells are or can be made mechanically tight. Corroded casings may need to be lined or permanently plugged. Abandoned wells should bc reopened and properly cemented. The volumetric capacity for gas storage depends upon space available in the porous rock as well as pressure and temperature of the gas in the reservoir. The production-pressure decline data on partially depleted gas reservoirs without water drive permit calculation of the reservoir space for gas. Isopachous maps of sand volume and porosity data for the reservoir rock provide an alternate method of calculating the pore volume for water-drive reservoirs. The pressure range selected for the storage cycle depends upon ()) the safe upper limit of pressure. 2) the flow capacity of wells and (3) compression requirements when injecting gas into the reservoir or delivering to market. Normally, gas and oil fields have pressures at discovery in the range of 0.43 to 0.52 psi/ft of depth. Pressures of around 1.0 to 1.2 psi/ft of depth appear to lift the overburden1-3 and invite uncontrolled movement of fluids in the porous rock. Some top pressure is normally selected for a storage reservoir ranging from below discovery pressure for deeper reservoirs to 0.65 psi/ft of depth for shallower reservoirs. Pressures to 0.66 psi/ft have been experienced without difficulty. The lower pressure limit is set by water intrusion accompanying low pressures, reduced flow capacity for wells at lower pressures and compression requirements. Depletion-type gas reservoirs often encounter water problems in the later stages of gas production. Such water intrusion may be due to movement from the surrounding aquifer. Accordingly, displacement of this water back into the aquifer by gas pressure and subsequent surges of water corresponding to the gas storage pressure cycle must be considered. Storage fields often produce in four months a volume of gas equal to its initial content. Rapid decreases in reservoir pressure occur, such as 20 psi/day. Accordingly, closed-in pressure observation wells which reflect the pressure in the bulk of the reservoir are required for following the operation of the reservoir. It has been found that a plot of observation wellhead pressures against gas content, Fig. 1, is very useful in observing operation of the field, checking the inventory and predicting future behavior. The plot is based on a given quantity of base or cushion gas in place. The injection and withdrawal curves may spread depending upon the homogeneity of the reservoir rock. permeability of the rock, well spacing and flow rates.

By Donivan L. Gordon, Fred H. Dorheim

Often, as viewed by the public and many in the mining industry, abandoned limestone and gypsum quarries offer a simple, economic solution to the twofold problem of solid-waste disposal and land reclamation. In a state where about 75% of the existing quarries are in hydrologic connection with carbonate aquifiers the rationale for considering the storage of solid waste in them must be critically examined. Consistent with the requirements of water resources protection, criteria are suggested to evaluate the potentiality of using abandoned limestone and gypsum quarries as sanitary landfill sites.

Jan 1, 1975

By M. Streat, R. Y. Qassim

Summary This paper reviews the developments in uranium process technology as a result of modern trends in the design of ion exchange equipment. The operation of the Cloete-Streat fluidised bed contactor is described and pilot-plant development of this contactor for uranium slurry work at Imperial College is outlined. The properties of a suitable ion exchange resin for slurry treatment are discussed, together with a description of relevant rheological properties of ore suspensions. A prediction of ion exchange resin- slurry behaviour is presented in order to establish the feasible operating limits for this type of R-I-P contactor.

Jan 1, 1973

By Nathan C. Rockwood

WHILE mining engineers have been searching in far corners of the country and of the world for hidden wealth there has grown up around us in nearly every city great wealth-producing mines calling for the investment of hundreds of millions of dollars and yielding products now sold for over half a billion dollars yearly-largely unknown and almost wholly neglected by mining engineers. But this neglect is explainable and excusable. They are industries of very recent origin-practically the growth of the last 25 years. They are in a very large measure the result of tremendous developments in engineering construction and the rapidly expanding use of portland cement concrete for structures of every description. Concrete as a material of construction is going through an evolution very much as did cast iron and other metals used in engineering; and this phase of the industry should appeal to the imagination of metallurgical engineers. At first iron was iron-a material of uncertain properties, owing both to small differences in chemical composition and in methods of manufacture. By successive steps iron was studied and knowledge of its properties developed-the striking effects of very small percentages of other minerals and of various heat-treatments.

Jan 1, 1924

By Arthur F. Taggart

A general awakening of interest among mill men concerning the mechanical efficiencies of their crushing machines is evident from a perusal of the recent files of mining publications. Considering the large part of the power bill which must be debited to the crushing department, such interest is natural. When, however, the articles on the subject are read, the only statement upon which the writers agree is that fine grinding consumes a large amount of power, and that the machine which, from a concentration standpoint, offends as a slime producer is, for that reason, a serious offender in wasting power. When the mill man attempts to find a method for measuring the power wasted, or to compare the efficiency of one machine with that of another for the same work, he is confronted with a choice of methods which lead to conflicting results. There are two reasons why the work of crushing is not more generally understood. In the first place, experimental data are difficult to obtain; and in the second place, before these data can be put in general form certain assumptions must be made. A difference in these assumptions by different investigators has led to conflicting conclusions. This conflict has resulted in the proposal of two laws. The first of these is the so-called Rittinger's law, which is variously stated as follows: "The work of crushing is proportional to the reduction in diameter."—R. H. Richards: Ore Dressing, p. 304 (1903). "The work required to crush rock is very nearly proportional to the reciprocals of the diameters crushed to."—A. Del Mar: Engineering and Mining Journal, vol. xciv, No. 24, p. 1129 (Dec. 14, 1912). "The work done in crushing is proportional to the surface exposed by the operation, or better expressed for this purpose, the work done on a given mass of rock is proportional to the reciprocal of the diameter of the final product, assuming that all the mass has been reduced to one exact size, which is only theoretically possible."— A. 0. Gates: Engineering and Mining Journal, vol. xcv, No. 21, p. 1039 (May 24, 1913). ' ' " Of this law as variously stated above H. Stadler says (Grading Analyses and Their Application, Author's Reply to Discussion, Transactions of the Institution of Mining and Metallurgy, vol. xx, p. 426 [1910-111):

Jan 1, 1915

By Charles Reed

WITH the increasing importance of clay in drilling operations which demand more precise and exacting control over its behavior, there has come the realization that most of our present methods of control over many of its important properties still represent more of an art than a science. Such a situation with respect to a material of such industrial significance is unfortunate, and naturally many investigations have been conducted to improve our knowledge. In general, these investigations have revealed the complex nature of clay behavior and while sometimes they may not have seemed to contribute directly to a solution of the field operator's problems they have been of inestimable importance in bringing to light the broad fundamental scientific principles upon which must be based any effective working theory correlating the known facts of clay behavior and predicting profitable new lines of attack for its improvement.

Jan 1, 1938

By George R. Elliott

Methods are presented for measuring and comparing "degree" of water drive, and for observing the control that rate of withdrawal exerts over decline of reservoir pressure. Degree of water drive is studied from pressure-production curves of 10 reservoirs; the method used to present these comparatively is to convert cumulative oil production from barrels to percentage of ultimate. Degree of water drive is also represented by a "water-encroachment factor," representing barrels of water influx per pound-month per acre-foot of oil reservoir. Pressure-production curves for the water-drive reservoirs after a period of declining pressure show a diminishing angle of slope, in some cases to the point where pressure ceases to decline or where it even increases; the shapes of these curves are in marked contrast to the dissolved-gas type of curve, which shows a general trend toward zero pressure at ultimate oil recovery. Yearly rate of oil production in percentage of ultimate oil recovery is correlated with pressure decline. The correct rate of production of oil with its associated gas and water sustains pressure in reservoirs having a high water-encroachment factor. For reservoirs having a low water-encroachment factor, it is necessary to inject the produced water and even inject large volumes of water from an outside source. The discussion of the actual reservoirs is preceded by a general review and is followed by a substantial bibliography. It is now generally accepted that water drive is capable of yielding 60 to 80 per cent of the original oil in place in most reservoirs, as compared with 20 to 40 per cent for dissolved-gas drive. There is no need to question the importance of controlling a reservoir in order to take advantage of such an efficient mechanism. What is a water-drive reservoir? Oil reservoirs usually combine two or more of the four basic mechanisms: dissolved-gas drive, gas-cap drive, water drive, gravity drainage. A water-drive reservoir is one in which water advances to take the place of the oil and gas produced. When the oil withdrawal rate is sufficiently low, the water will tend to maintain pressure. The maximum effectiveness is attained when the water follows the oil withdrawal so closely that little or no decline in pressure occurs. Oil in its underground reservoir is associated with water. This water is significant in the production of the oil according to the source of supply and the permeability of the surrounding formation. As oil is produced and the pressure is lowered, water can move in to replace the oil. With adequate supply and sufficient permeability, actual movement takes place on an extensive scale. The first movement of water takes place by expansion of the water and its associated fluids. While this expansion is of little importance in some fields, in others it is sufficient to supply all of the energy required for the production of oil. When a pressure differential has been established

Jan 1, 1946