Search Documents

By C. G. Fink, G. L. Putnam

The dissolution of gold by cyanide solutions was studied by determining the time required for the solvents to dissolve gold leaf. Minute traces, even 0.5 ppm, of sulphide ion retard the dissolution of gold, and this behavior cannot be accounted for by the presently accepted hypotheses involving oxygen-depletion or thiocyanate formation. On the other hand, traces of the salts of lead, bismuth, mercury, and thallium considerably accelerate the dissolution. The beneficial effect of lead is dependent upon the pH and cyanide ion concentration of the solution. ALTHOUGH cyanide solvents are used very ex-x*. tensively for the recovery of gold from ores and concentrates, the normal rate of solution of the precious metal as determined by Barsky, Swainson, and Hedley,1 and others2 is less than about 3 mg per sq cm of exposed gold surface per hour, corresponding to a corrosion depth of approximately 1.5 microns (0.00006 in.) per hr. Although the slow rate may be increased to some extent in certain cases, as, for example, when the the gold is partially imbedded in iron pyrites,3 the leaching operation is generally the most time-consuming step of the cyanide process. Frequently it is necessary for the leaching solvents to remain in contact with the ores for 50 to 200 hr in order to dissolve all of the gold particles.' Not only does the slow solution rate cause some increase in the capital costs, but the cyanide consumption also may be increased because of vaporization of hydrocyanic acid and secondary reactions with minerals such as malachite (CuCO3 • Cu(OH)2), and pyrrhotite, which often are associated with gold. It is not surprising that numerous attempts have been made to accelerate the dissolution of gold in cyanide solutions. Experimental Gold Leaf Test: The gold leaf test was apparently originated by M. Faraday, who, by means of it, discovered that dilute cyanide solutions would dissolve gold readily in the presence of oxygen. The usefulness and reliability of the test have been discussed elsewhere.5,6 Essentially, the method consists of determining the time required for 5-ml portions of cyanide solvents to dissolve squares of 23 carat gold leaf, 0.5 cm on edge, when shaken in 10-ml test tubes with the solvents. The weight of gold leaf per test was 0.051 mg as determined by the direct weighing of a leaf 8.6x8.6 cm (weight = 15 mg) and measuring the area of the test sample (0.25 sq cm). Gold leaf is of remarkably uniform thickness.6 Since gold leaf, like native gold, contains small amounts of copper and silver, the results are comparable with those one might expect in cyaniding gold ores. As six or more tests can be made simul- taneously, the relative efficiencies of the solvents can be evaluated readily. All dilute solutions of lead, bismuth, thallium and mercury salts were prepared by the ordinary dilution method used by chemists. Our C.P. sodium cyanide and buffering reagents had no detectable amounts of either sulphide ion or heavy metals. Soluble Sulphides in the Cyanide Process: The action of soluble sulphides is of interest in the study of the dissolution of gold in cyanide solutions. That gold ores which contain compounds of arsenic and antimony often are not amenable to direct cyanide treatment is well known, and it said that arsenic and antimony are "cyanicides."7 It is commonly believed that part of the sulphur content of such ores is soluble in alkaline solutions to give sulphide ion, which reacts with the free cyanide content of the leaching solutions to form inert thio-cyanates or reacts with the dissolved oxygen to form sulphites or sulphates.8 A purpose of this paper is to demonstrate that sulphide ion may behave in a manner that cannot be explained by either the oxygen-depletion or thiocyanate formation theories and to prove directly that concentrations of sulphide ion which cannot be detected even by colorimetric methods may retard the dissolution of gold.

Jan 1, 1951

By C. G. Fink, G. L. Putnam

The dissolution of gold by cyanide solutions was studied by determining the time required for the solvents to dissolve gold leaf. Minute traces, even 0.5 ppm, of sulphide ion retard the dissolution of gold, and this behavior cannot be accounted for by the presently accepted hypotheses involving oxygen-depletion or thiocyanate formation. On the other hand, traces of the salts of lead, bismuth, mercury, and thallium considerably accelerate the dissolution. The beneficial effect of lead is dependent upon the pH and cyanide ion concentration of the solution. ALTHOUGH cyanide solvents are used very ex-x*. tensively for the recovery of gold from ores and concentrates, the normal rate of solution of the precious metal as determined by Barsky, Swainson, and Hedley,1 and others2 is less than about 3 mg per sq cm of exposed gold surface per hour, corresponding to a corrosion depth of approximately 1.5 microns (0.00006 in.) per hr. Although the slow rate may be increased to some extent in certain cases, as, for example, when the the gold is partially imbedded in iron pyrites,3 the leaching operation is generally the most time-consuming step of the cyanide process. Frequently it is necessary for the leaching solvents to remain in contact with the ores for 50 to 200 hr in order to dissolve all of the gold particles.' Not only does the slow solution rate cause some increase in the capital costs, but the cyanide consumption also may be increased because of vaporization of hydrocyanic acid and secondary reactions with minerals such as malachite (CuCO3 • Cu(OH)2), and pyrrhotite, which often are associated with gold. It is not surprising that numerous attempts have been made to accelerate the dissolution of gold in cyanide solutions. Experimental Gold Leaf Test: The gold leaf test was apparently originated by M. Faraday, who, by means of it, discovered that dilute cyanide solutions would dissolve gold readily in the presence of oxygen. The usefulness and reliability of the test have been discussed elsewhere.5,6 Essentially, the method consists of determining the time required for 5-ml portions of cyanide solvents to dissolve squares of 23 carat gold leaf, 0.5 cm on edge, when shaken in 10-ml test tubes with the solvents. The weight of gold leaf per test was 0.051 mg as determined by the direct weighing of a leaf 8.6x8.6 cm (weight = 15 mg) and measuring the area of the test sample (0.25 sq cm). Gold leaf is of remarkably uniform thickness.6 Since gold leaf, like native gold, contains small amounts of copper and silver, the results are comparable with those one might expect in cyaniding gold ores. As six or more tests can be made simul- taneously, the relative efficiencies of the solvents can be evaluated readily. All dilute solutions of lead, bismuth, thallium and mercury salts were prepared by the ordinary dilution method used by chemists. Our C.P. sodium cyanide and buffering reagents had no detectable amounts of either sulphide ion or heavy metals. Soluble Sulphides in the Cyanide Process: The action of soluble sulphides is of interest in the study of the dissolution of gold in cyanide solutions. That gold ores which contain compounds of arsenic and antimony often are not amenable to direct cyanide treatment is well known, and it said that arsenic and antimony are "cyanicides."7 It is commonly believed that part of the sulphur content of such ores is soluble in alkaline solutions to give sulphide ion, which reacts with the free cyanide content of the leaching solutions to form inert thio-cyanates or reacts with the dissolved oxygen to form sulphites or sulphates.8 A purpose of this paper is to demonstrate that sulphide ion may behave in a manner that cannot be explained by either the oxygen-depletion or thiocyanate formation theories and to prove directly that concentrations of sulphide ion which cannot be detected even by colorimetric methods may retard the dissolution of gold.

Jan 1, 1951

By A. C. Veatch

THE MIDLANDS of England contain large areas of important oil lands, which, however, will not become of commercial importance for at least 5 years, because the ownership of the oil has become a political issue. In Great Britain, except in certain special areas, all minerals, except for gold and silver, belong to the surface owner. The leasing of minerals on the large estates is a very complicated business, as the family solicitors have many forms and formalities that must be observed. In the case of one of the large estates, the principal revenues of which for several hundred years have been from coal leases, the average time between the agreement on terms for a coal lease and the signing of the same has been 8 years. In 1916, one coal lease on this estate had been pending for 15 years, and was still unsigned, although the important terms had been agreed upon 15 years previously. Under war conditions, and considering the extreme importance that the production of petroleum in England would have had, such delays could not be tolerated. Most of the British landlords, relying on the almost, universal opinion of their own countrymen that there were no commercial deposits of petroleum in Great Britain, were prepared to give all their oil rights to the government, but they feared that such action might establish a precedent with respect to coal. For years the Labor Party and extreme radicals have protested against the payment of royalties to landlords on coal. The government, therefore, introduced a bill taking over all the oil rights and providing for the payment of a small royalty to the landlords, to safeguard the principle of compensation in case the coal mines should ever be nationalized. The provision of this bill, with respect to the payment of royalty to landlords, was defeated by a vote of 44 to 35 in a night session of the House of Commons on Oct. 25, 1917, when most of the members were absent, but when a group of labor members and extreme radicals were present. The resubmission of the point to the House of Commons was prevented by the labor members of the coalition government, who reminded the cabinet that the agreement

Jan 1, 1920

By J. G. Bartram

Jan 1, 1934

By C. V. Corless

WE are living at a period of the world's history in which social phenomena are on so vast a scale, are of so profoundly soul-searching a nature, and are occurring in such rapid succession in the great world drama in which we are both actors and spectators, that, in our efforts to obtain a rational point of view in relation to them, our minds may fail to discern the simple in the complex and our understanding is liable to be-come confused or even overwhelmed. To the social student whose scientific training has convinced him of the truth of the evolutionary law, Natura non facit saltum, it is neither the vast scale of the events; their deeply soul-stirring nature, nor their rapid succession that matters so much, as the discovery of the underlying principle or law in accordance with which the disintegration and reintegration, which are the two aspects of social evolution, or indeed of evolution everywhere, are occurring. He is most deeply concerned in seeking an answer to the question: Have we in the present great and perplexing upheavals in human society, whether regarded in Central Europe, in Russia, in Great Britain, or in America, a really new cause at work, or, have we, though on a very- large scale, merely new manifestations of the working out of an old principle? When we think of the appalling struggle in Europe, into which the world's greatest exemplar of democracy was finally drawn, no one has any hesitation in admitting that the great conflict was fundamentally a life-and-death struggle for self-preservation and self-propagation on the part of autocracy. The variations we meet with in the statement of the cause of the war arise mainly from differing distances of perspective: but in the last analysis all agree that the autocratic system of political government, which found its very soul and center in Prussian despotism, was consciously arrayed in a final "world-power-or-downfall" struggle against a love of freedom which was steadily widening and-deepening throughout the world, and particularly throughout those parts of the world where this love of freedom and justice has found expression in democratic institutions. It is not irrelevant to our discussion to recall in passing that this most imposing structure ever conceived by the human mind as an instrument of tyranny is lying today an irretrievable mass of ruins, completely over-

Jan 4, 1919

By Daniel R. Hull

IN 1026 Genders' reviewed the existing theories of this subject and stated his views in support of the gas-pressure theory. Again, in 1937, the subject was thoroughly reviewed by N. B. Vaughan,3 and by Phillips and Brick,2 so that no resume is called for here. The purpose of this paper is to describe certain observations made in the course of mill work, and to point out that they mostly tend to confirm the gas theory of Genders. VAPOR SEGREGATION There is, however, one type of inverse segregation that can be accounted for by considering the volatility of one of the constituents of an alloy. The most familiar case is ordinary brass, which is subject to a zinc enrichment of a few tenths of a per cent at the surface of a chill casting. This has been noted in 70-30 brass by Genders, and a typical example of it is given in Table I, which represents a [ ] cylindrical billet 7 in. in diameter by 5; in. long. After lathe-turning 1/32 in. from the surface, the remaining distance to the center was sampled at six equally spaced intervals. The lead, which is essentially the same throughout, will be mentioned later. Consider a brass-mill mold, either round or rectangular in cross section, standing several feet high. It may require a minute or two for pouring. Before it is full, the metal in the lower end has partly solidified and contracted somewhat away from the mold. The initial shell of solidification follows not far behind the top of the column, even if the central portion is liquid for a long way down. There is, then, a space between metal and mold that is filled with zinc vapor. The vapor has no exit, because the liquid at the top of the rising column is not only in contact with the mold but keeps up a fresh supply of zinc vapor, which has, perhaps, already begun to condense in the lower portion. The cycle is short. Within a minute or two after the mold is full the bar has cooled enough to condense all the zinc. Some of it may condense on the mold; it might be expected that most of it would condense there, but the mold at that time is well coated with a velvety carbon residue from the oil dressing, overlain by fluffy zinc oxide that commenced covering the inside of the mold as soon as pouring began. The clean skin of the freshly cast brass offers a preferred surface for condensation. Reabsorption is quick and inevitable. A simple experiment indicates that a surprisingly large quantity of zinc vapor is trapped in the space between mold and

Jan 1, 1941

By W. J. Slatosky

As a means of effecting better control of endpoint temperatirres at the Jones & Laughlin basic oxygen furnace plant, a set of mathematical equations has been developed. The eqlutions are the product of a themlochemical anaysis of the process and aye designed to calculate the required scrap, lime, and hot metal additions in terms of a number of independent variables. Results of test heats have warranted adoption of this technique by the Prodrrction Department. BECAUSE of the autogeneous nature of the basic oxygen steel-making process, bath temperature can be controlled without an external fuel supply by charging the furnace with additions that are thermally balanced. The thermal requirements of the charge materials are such that, during the refining process, they throttle the heat generated by the metallurgical reactions in a manner designed to result in a speci-fied temperature at the completion of the heat. In the past, operating personnel at the basic oxygen furnace plant of Jones & Laughlin's Aliquippa Works relied on their experience and technical knowledge of the process to determine the quantities of charge additions needed to result in a finishing temperature in the range 2880"to 2920" F. (The charge consists primarily of 93 tons of scrap and hot metal plus an amount of lime sufficient to maintain a basicity ratio of 2.8 to 3.2). Estimates of these materials are based on a consideration of the effects on finishing temperature of 1) iron silicon content, having a variation of 0.8 to 1.8 pct; 2) iron temperature, ranging from 2250°to 2600°F; and 3)any excessive cooling of the furnace due to a production delay. The end temperature of the preceding heat also serves as a guide in that, if a heat was within the specified temperature range, the succeeding heat could be charged with materials of nearly the same proportions, provided the hot metal used in each of the two charges was of approximately the same temperature and composition. On the other hand, if a heat was outside the specified tapping range, or if the hot metal used in that heat was of different analysis and temperature from that of the iron to be charged, an adjustment in the proportion of additions is in order for the following heat. Due to the complex thermochemical behavior of the process and to the inexact and subjective nature of the described method of determining charge additions, consistently accurate temperature control was not to be expected. Therefore, those heats out- side the specified tapping range necessitated subsequent adjustments by either reblowing the cold heats for a suitable length of time so as to elevate the bath temperature to the desired level, or cooling hot heats with a proper amount of scrap. Because extra time is required to make these adjustments, production is delayed. In an attempt to devise a method for improving temperature control, an analysis of the thermochemistry of the process was undertaken. This, in turn, led to the development of a set of mathematical equations which enable the calculation of the quantities of scrap, lime, and hot metal needed to result in any specified tapping temperature range. The analysis was not intended to be a repetition of work done by others such as McMulkinl or ~hilbrook.' It was meant to be an extension of their work so that charge additions could be calculated not in terms of silicon alone but, rather, as a function of all independent variables. This paper presents the derivation of these relationships, their effectiveness in controlling bath temperatures, and a method of utilizing them on an operational basis. The Heat Balance—The first step undertaken in the analysis of the problem was the enumeration of the pertinent variables. A list is presented in Table I where it is noticed that these quantities have been separated into the following three categories: important variables, variables considered as constants, and variables to be neglected. The breakdown was an arbitrary one designed to facilitate the analysis; otherwise, the mathematical treatment would have been exceedingly cumbersome and complex. Fortunately, experience has shown that these simplifying assumptions do not seriously impair the accuracy of the calculations. These variables along with the limiting assumptions listed in Table n were then used to write a heat balance of the process by applying the equation of continuity, Rate of Rate of Rate of Increase = Income - Outgo PI ] of Heat of Heat of Heat.

Jan 1, 1962

By AIME AIME

INSTITUTE members attending the Annual Meeting in New York who want to see one of the mining engineers' newest aids, photoelastic stress analysis, are due for an interesting afternoon on Thursday, Feb. 15, when open house: will be held at the Columbia University mining laboratory. Information as to the direction and distribution off stresses in mine structures, which has been developed by Professor Bucky, associate professor at the Columbia School of Mines, and David Sinclair, research assistant, is useful in the design of pillars and in the placing of openings relative to working places such as gangways and haulage levels.: This work has been sponsored during the last ten years by the Engineering Foundation.. It is fully reported in T. P. No. 1140.

Jan 1, 1940

By C. P. Mangelsdorf

The roof truss as a means of secondary or supplemental mine roof support has enjoyed increasing acceptance in recent years, particularly in bituminous coal mines. In those entries where long life is required or doubtful performance from other forms of support seems likely, trusses in many cases have provided the necessary protection for continuing operations. Although relatively expensive and time-consuming in their installation, trusses, particularly with the new resin point anchor system, appear to be justifying their higher premium. It seems inevitable that techniques and equipment for installing them within the cycle will soon be developed. The actual mechanism by which trusses contribute to the stability of a roof is, as yet, poorly understood, and it may be that more than a single mechanism is involved. There are, however, a number of useful observations which can be made concerning the structural behavior of the truss itself, based solely on the mechanics of rigid and deformable bodies. The purpose of this article is to present some of these observations, particularly relating to friction in the system. A few speculations concerning the roof must, of course, be made. From a knowledge of the structural behavior, some insight into the truss-roof interaction may be gained. The concept of the truss is quite simple. As shown in [Fig. 1], it consists of two inclined chords (usually at 45') anchored in holes drilled in the roof over the ribs. A horizontal chord is formed connecting the exposed ends of the inclined chords, either with a third piece or by bending extensions of the inclined chords until they meet in the middle. A distinction can be made between active and passive chords of a truss depending upon the manner of installation. If the inclined chords are fully grouted and the horizontal chord is merely attached to them, it may reasonably be assumed that no significant forces exist in the truss until the roof begins to work. Such would be a completely passive system. On the other hand, if the inclined chords are anchored only at their upper extremities and the horizontal chord is formed in such a way that all three chords can be pretensioned to a significant portion of their tensile strengths then the truss may be regarded as fully active. Combinations of active and passive chords are also possible. * The discussion here is confined to the fully active truss such as the Birmingham steel rod system or the Galis wire rope truss. In both cases, pretensioning is accomplished by tightening of the horizontal chord, some of which tension is transferred to the in-

Jan 1, 1981

By W. O. Brown

A laboratory investigation was conducted to determine quantitatively the extent to which connate water was contacted and displaced by invading flood water. In these experiments the connate water in unconsoli-dated sand packed columns was completely displaced by injecting water. The nature of this displacement was similar to that previously described for single-phase miscible fluid displacement studies, and thus the presence of a non-wetting immiscible phase did not appreciably change the nature of the displacement. The effects of water injection rate, column length, and oil viscosity on connate water displacement were investi-gated. It is concluded that the connate water in a reservoir is the water which actually displaces oil from the pores of the rock during a water flood. During a water flood the connate water forms a zone which separates the invading flood water from the continuous oil phase. The size and shape of connate water bank is chiefly dependent oil the oil viscosity and the column length. INTRODUCTION Water flooding is one of the most widely used techniques for the secondary recovery of oil. Presently, however, it is still not possible to recover all the oil in a reservoir by water flooding. The research described in this paper was conducted as part of a study to determine the conditions under which 100 per cent oil recovery could be attained by water flooding. The particular objective of this work was to determine if any chemical agent, regardless of its nature, placed in the flood water could be effective in influencing the mechanism of displacement of the oil by water. It has been known for many years that water does not displace all the oil in a reservoir because a portion of the oil is "trapped" and held immobile by capillary forces. This oil is trapped within the pores of a water-wet rock when it becomes broken into discontinuous globules. Initially, when oil is present at high saturations within the pores of a water-wet rock, the connate water forms rings around the points of contact of the sand grains and may even completely fill small cavities between grains, whereas the oil occupies the larger void spaces between the grains.' Under these conditions, the oil in these spaces is in the form of irregular but continuous filaments, the diameters of which depend on the geometry of the sand pores. The filaments are formed by the oil contained in the small cells which are formed between the sand grains and are connected to their neighboring cells by channels or tunnels formed by pendular rings of water. At a high oil saturation, the oil filaments conform approximately to the shape and size of the cells and their connecting tunnels. Starting with this distribution, as the water saturation is increased the water layers in the small cavities and on the surface of the grains grow. As this occurs, the water rings grow and the diameters of the oil filaments decrease. When an oil filament is reduced to a critically small diameter, the filament breaks, and its tunnel fills completely with water. Any oil which remains within a cell after all its connecting tunnels have been water-filled is trapped as a discontinuous globule. Once the oil has become trapped, the capillary forces oppose distortion of the globules and may prevent their being squeezed through the water-filled tunnels. Only a very small pressure gradient is sufficient to keep oil moving as a continuous filament. On the other hand, once the filament has broken into discontinuous oil droplets a relatively large force is required to distort the surface of a drop and move it through a water-

Jan 1, 1958

By R. H. Card

The geophysicist is interested greatly in the resistivities of different formations or parts of the earth's crust; sometimes he is interested in a single figure in the nature of an average, or what may be called the effective resistivity, of all the formations or parts of the crust at a given location to a certain depth. Conversely, the engineer whose work is concerned with the coordination of power and communication lines in such a manner as to avoid electrical interference between these two types of facilities is concerned very much with this effective resistivity; to a lesser extent he is interested in the resistivities of individual formations. In connection with his work the coordination engineer often estimates the effective resistivity of the earth from measurements of the mutual impedances of lines; in other instances he derives from measurements of a different type the resistivities of different layers of the crust and synthesizes these to obtain an estimate of the effective resistivity. In connection with problems concerning the coordination of power and telephone lines, measurements from which earth resistivities can be estimated have been made at many points in the United States by the American Telephone and Telegraph Co. and its associated companies, in cooperation with various power companies and with railroad companies having electrified sections of line. Other such measurements have been made by the Joint Subcommittee on Development and Research of the Edison Electric Institute and the Bell Telephone System. A study has been made of the correlation of these data with the ages and types of materials of the strata of the earth's crust at each of the test locations. The purpose of this study has been primarily to provide information to assist in predicting the order of magnitude of effective resistivities to be used in the preliminary consideration of problems concerned with the coordination of power and communication lines. To make the results of such a study most useful, it is essential that the geological data to be secured when such a prediction is wanted be readily obtainable. Data on the ages of strata and the types of materials composing geological structures can usually be obtained, therefore particu-

Jan 1, 1940

By R. H. Card

The geophysicist is interested greatly in the resistivities of different formations or parts of the earth's crust; sometimes he is interested in a single figure in the nature of an average, or what may be called the effective resistivity, of all the formations or parts of the crust at a given location to a certain depth. Conversely, the engineer whose work is concerned with the coordination of power and communication lines in such a manner as to avoid electrical interference between these two types of facilities is concerned very much with this effective resistivity; to a lesser extent he is interested in the resistivities of individual formations. In connection with his work the coordination engineer often estimates the effective resistivity of the earth from measurements of the mutual impedances of lines; in other instances he derives from measurements of a different type the resistivities of different layers of the crust and synthesizes these to obtain an estimate of the effective resistivity. In connection with problems concerning the coordination of power and telephone lines, measurements from which earth resistivities can be estimated have been made at many points in the United States by the American Telephone and Telegraph Co. and its associated companies, in cooperation with various power companies and with railroad companies having electrified sections of line. Other such measurements have been made by the Joint Subcommittee on Development and Research of the Edison Electric Institute and the Bell Telephone System. A study has been made of the correlation of these data with the ages and types of materials of the strata of the earth's crust at each of the test locations. The purpose of this study has been primarily to provide information to assist in predicting the order of magnitude of effective resistivities to be used in the preliminary consideration of problems concerned with the coordination of power and communication lines. To make the results of such a study most useful, it is essential that the geological data to be secured when such a prediction is wanted be readily obtainable. Data on the ages of strata and the types of materials composing geological structures can usually be obtained, therefore particu-

Jan 1, 1940

By R. E. Cook

This work presents the development and application of equations of the form developed by Martin1 to describe gravity segregation performance during natural depletion. One-dimensional depletion analyses are applied to several hypothetical reservoirs. Considerable attention is given to the changes in saturation distribution in the dip direction resulting from depletion at various rates. Vertical gas saturation distribution within a sand having vertical permeability is studied to illustrate conditions which provide For low gus-oil ratio production from wells selectively completed away from sand tops, as observed from well performance. Results of performance calculations are shown graphically and illustrate the rate sensitivity of the gravity segregation mechanism and the influence of reservoir geometry and withdrawal distribution. It is shown that for sufficiently high depletion rates gas saturation distribution in the dip direction is characterized by the formation of two discontinuities, or saturation "fronts"; the updip front being the gas-oil contact of the secondary gas cap and the downdip front occurring at a position dependent upon the reservoir depletion rate, withdrawal distribution and reservoir geometry. The gas saturation in the region between fronts is shown to continually increase with time, while that downdip from the lower front remains very low and relatively stable. The effect of increased depletion rate is to reduce the region of stable gas saturation and thus enlarge the portion of the reservoir producing with continually increasing gas saturation. Special attention is given to the performance of reservoirs having sufficient vertical permeability to permit liberated gas to segregate vertically within the sand section before proceeding in the updip direction. It is shown that reservoirs of this type are far less sensitive to depletion rate due to the mechanical control of producing gas-oil ratios afforded by selective well completions away from sand tops. It is shown that gravity segregation performance is adversely af- fected by decreasing reservoir cross-section area in the updip direction. It is also shown that down-dip withdrawal concentrations can restrict gas segregation rates in the dip direction. INTRODUCTION The natural depletion performance of several large producing reservoirs in Western Venezuela has unmistakably shown the significant role that gravity forces play in governing the gas-oil ratio behavior of individual wells and the over - all pressure-production performance of the reservoirs. Analysis and prediction of the natural depletion performance of these reservoirs is of great importance in determining the economics of pressure maintenance operations. In 1957, a method for the analysis of pressure maintenance performance was presented by Martin1 which, in the original and more general form of the equations involved, provides a physically sound basis for the analysis of one-dimensional gravity segregation performance during natural depletion. The work reported herein is an application and extension of Martin's outstanding developments to a series of hypothetical reservoirs in an attempt to explain the general behavior of the gravity segregation mechanism and the influence of such parameters as depletion rate, reservoir geometry and withdrawal distribution. The study considers two types of flow: "distributed flow", where vertical permeability in the reservoir is zero and fluids flow only in the dip direction while uniformly distributed over the sand thickness; and "segregated flow", where vertical permeability is sufficient to permit gas to segregate against the sand top before proceeding updip. This latter type of flow has been recognized as an important mechanism active in the massive sand reservoirs of Western Venezuela. ANALYSIS OF ONE-DIMENSIONAL DISTRIBUTED FLOW SYSTEMS For an inclined reservoir having zero vertical permeability, the velocities of oil and gas flow at any point in the reservoir can be derived from Darcy's equations as

By Marcel Daly

IN a preceding paper 1 the writer has pointed out some apparent relationship between the distribution, on the Surface of the globe, of the known hydrocarbon deposits and the disposition of the principal zones of deformation of the earth's body (geosynclines). He wishes to present some further remarks on this subject. Petroleum deposits, or their derivatives or descendants, are found through the whole range of sedimentary strata, from the pre-Cambrian to the Quaternary. For instance, the pre-Beltian (Shuswap) series of the Canadian Cordillera are interbedded with limestones which are sometimes rich in carbonaceous matter (Sicamous limestone) ; and the Beltian system of the same region contains layers of argillites and dolomitic limestones which are equally high in carbon content.2 This carbon may be interpreted as the last remnant of hydrocarbons previously contained in the rocks. On the other hand, the actual formation of hydrocarbons wider conditions that would eventually permit their deposition in modern sediments is conceded by some geologists.3 Between these two extreme limits, bitumens are found indifferently in all sedimentaries. They constitute a continuous series, some kind of a large family, whose individual members may be entitled to a community of origin and probably represent the differentt stages of evolution of the primitive, parent matter. . The kinship between petroleum and such substances as asphalt, ozocerite, manjak, grahamite, albertite, etc., is well known; and E. H. Cunninggam-Craig has recently shown how intimately shale fields and oil fields are connected. For this reason, no distinction is made in the present

Jan 8, 1917

By S. A. Falconer

One of the outstanding achievements in connection with this country's war efforts has been the ability of our mining industry to supply from domestic sources many of the minerals of strategic importance that formerly were obtained principally from abroad. In order to meet the war-born demands for these scarce minerals, it has frequently been necessary to develop special methods for treating ores and waste products hitherto considered too lowgrade to be workable; and to improve the efficiency of older beneficiation processes. Important in this respect have been the recent technological advances in the field of froth flotation of nonsulphide minerals. Because of the refractory nature of many of these domestic ores, and, in many cases, the limited available technical data regarding their treatment, much research work has been necessary. The following examples describe the procedures and reagents used, and the results obtained, in certain laboratory flotation investigations conducted by American Cyanamid Company's engineers at the Cyanamid Ore Dressing Laboratory on ores containing such minerals as scheelite, manganese oxides and carbonate, ilmen-ite, brookite, kyanite, garnet, spodumene, mica, feldspar, celestite, fluorite, chromite, corundum, and cassiterite. In presenting these data, we wish to point out that many of the minerals listed have previously been tested, and their amenability to flotation reported, by other investigators—notably those of the United States Bureau of Mines. In some instances the procedures and reagents used in the treatment of some of the following described ores follow rather well-established lines, and with one or two exceptions, the reagents used were well known. However, many of the ores tested did not respond well to simple conventional procedures and it was necessary to adopt special methods of conditioning and desliming, reversal of the usual order of floatability of some of the minerals, multiple cleaning, etc., in order to secure separations. Except where otherwise noted, all numbered and trade-marked reagents mentioned in this paper are marketed by the American Cyanamid Co. or the American Cyanamid and Chemical Corporation. Tungsten ORes Tungsten minerals, vitally important in the war industries of the United States, rank high in the list of those we formerly had to import in order to supply our needs. Most of our domestic ores of tungsten contain scheelite as the valuable mineral. Today there are in the neighborhood of twelve tungsten operations in this country where flotation is used as the main or accessory form of benefication. It has, of Course, been known for some time that scheelite and other tungsten minerals respond to treatment by flotation.

Jan 1, 1947

By S. A. Falconer

One of the outstanding achievements in connection with this country's war efforts has been the ability of our mining industry to supply from domestic sources many of the minerals of strategic importance that formerly were obtained principally from abroad. In order to meet the war-born demands for these scarce minerals, it has frequently been necessary to develop special methods for treating ores and waste products hitherto considered too lowgrade to be workable; and to improve the efficiency of older beneficiation processes. Important in this respect have been the recent technological advances in the field of froth flotation of nonsulphide minerals. Because of the refractory nature of many of these domestic ores, and, in many cases, the limited available technical data regarding their treatment, much research work has been necessary. The following examples describe the procedures and reagents used, and the results obtained, in certain laboratory flotation investigations conducted by American Cyanamid Company's engineers at the Cyanamid Ore Dressing Laboratory on ores containing such minerals as scheelite, manganese oxides and carbonate, ilmen-ite, brookite, kyanite, garnet, spodumene, mica, feldspar, celestite, fluorite, chromite, corundum, and cassiterite. In presenting these data, we wish to point out that many of the minerals listed have previously been tested, and their amenability to flotation reported, by other investigators—notably those of the United States Bureau of Mines. In some instances the procedures and reagents used in the treatment of some of the following described ores follow rather well-established lines, and with one or two exceptions, the reagents used were well known. However, many of the ores tested did not respond well to simple conventional procedures and it was necessary to adopt special methods of conditioning and desliming, reversal of the usual order of floatability of some of the minerals, multiple cleaning, etc., in order to secure separations. Except where otherwise noted, all numbered and trade-marked reagents mentioned in this paper are marketed by the American Cyanamid Co. or the American Cyanamid and Chemical Corporation. Tungsten ORes Tungsten minerals, vitally important in the war industries of the United States, rank high in the list of those we formerly had to import in order to supply our needs. Most of our domestic ores of tungsten contain scheelite as the valuable mineral. Today there are in the neighborhood of twelve tungsten operations in this country where flotation is used as the main or accessory form of benefication. It has, of Course, been known for some time that scheelite and other tungsten minerals respond to treatment by flotation.

Jan 1, 1947

By Butler, P. B.

TRIPOLI is a rather unusual form of silica, which thus far has been found in commercially valuable quantities only in the neighborhood of Seneca, Mo., although there are numerous deposits of somewhat similar materials in several southern states. The latter have not, however, attained any position of real importance, due undoubtedly to definite structural limitations which have rendered them less suitable for the particular uses that have given tripoli its principal outlets. Raymond B. Ladoo, mineral technologist, says': "Since that time (1880-90) the term tripoli has with increasing definiteness been reserved for the Seneca material, and other siliceous materials of similar origin and physical properties."

Jan 1, 1928

It has been suggested that it would be a desirable feature in connection with the Chicago meeting of the, Institute in September to arrange for a return trip for the fuel men through the coal fields of Illinois, Ohio and Pennsylvania, stopping at various points and possibly touching also Kentucky. Perhaps the petroleum men would be interested in a similar trip and might join them stopping off at different points to visit these oil fields. If the members who would-be interested in such a trip will advise the Secretary before the first of June, indicating their desired stopping points, steps will be taken to perfect arrangements accordingly.

Jan 5, 1919

By C. D. Gilpin, Franklin Moeller

The application of electric power for driving mine hoists handling heavy loads at high speeds has recently been extended by the installation of what is probably the largest electrically driven hoist in this country at the Granite Mountain shaft of the North Butte Mining Co., Butte, Mont. While the weight of rock which is hoisted by this machine is not the largest now being handled by electric mine hoists, the speed of hoisting is so, and the combination of the high speed with the heavy load has resulted in a machine of considerable interest to all those actively engaged in mining. Aside from mere considcration of size, this installation deserves attention because of the careful attention given, not only to the question of economy of operation, but to the details of construction and installation of the entire equipment. The conditions to be met in this installation were as follows: Weight of rock to be raised per trip, 7 gross tons........... 15,680 1b. Weight of skip.......................................... 8,000 1b. Weight of cage.......................................... 1,800 1b. Maximum depth of hoisting.............................. 4,000 ft. Diameter of rope.......................................... 15/8 Total weight suspended on one rope from drum............. 42,000 1b. Normal hoisting speed.................................... 2,700 ft. per minute. Maximum hoisting speed.................................. 3,000 ft. per minute. Desired capacity-200 tons per hour from 4,000 ft. depth. The ore is mined in several levels and hoisting is carried on from the 800-ft. level down to the 2,700-ft., which is at present the maximum depth from which the ore is raised regularly. Development is proceeding and a depth of 2,900 ft. has already been reached. The rock is handled underground in cars holding % ton, and about 10 cars are the usual load for a skip. All of the ore is dumped into underground bins, which are of diffcrent capacities varying up to 250 tons. From the bins the ore is fed into the skips without passing into measuring pockets. At the surface the

Jan 1, 1916

By Franklin Moeller

THE application of electric power for driving, mine hoists handling heavy loads at high speeds has recently been extended by the installation of what is probably the largest electrically driven hoist in this country at the Granite Mountain shaft of the North Butte Mining Co., Butte, Mont. While the weight of rock which is hoisted by this machine is not the largest now being handled by electric mine hoists, the speed of hoisting is so, and the combination of the high speed with the heavy load has resulted in a machine of considerable interest to all those actively engaged in mining. Aside from mere consideration of size, this installation deserves attention because of the careful attention given, not only to the question of economy of operation, but to the details of construction and installation of the entire equipment. The conditions to be met in this installation were as follows: Weight of rock to be raised per trip, 7 gross tons 15,680 1b. Weight of skip 8,0001b. Weight of cage 1,8001b. Maximum depth of hoisting 4,000 ft. Diameter of rope 153 in. Total weight suspended on one rope from drum 42,000 1b. Normal hoisting speed 2,700 ft. per minute. Maximum hoisting speed : 3,000 ft. per minute. Desired capacity-200 tons per hour from 4,000 ft: depth. The ore is mined in several levels and hoisting is carried on from the 800-ft. level down to the 2,700-ft., which is at present the maximum depth from which the ore is raised regularly. Development is proceeding and a depth of 2,900 ft. has already been reached. The rock is handled underground in cars holding ¾ ton, and about 10 cars are the usual load for a skip. All of the ore is clumped into underground bins, which are of different capacities varying up to 250 tons. From the bins the ore is fed into the skips without passing into measuring pockets. At the surface the

Jan 2, 1916