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By E. S. Mardock, Robert E. Bush

The object of this paper is to report recent developments in the quantitative interpretation of radioactivity logs. The use of reference lines is described in the application of the new zero radioactivity reference line for the determination of neutron derived porosities is discussed. Illustrated examples are shown of logs from the reef limestone of the North Snyder Field and from the Lansing-Kansas City limestone of central Kansas. A method of using an interrelation factor calculated from the neutron and gamma ray curves, called the neutron Productivity number, for the estimation of productivity from sandstone formations is discussed. When used in a relative manner the neutron productivity number has aided in Predicting whether a given zone will produce gas or liquid or whether it is too shaly to produce. Examples of logs from wells in the Freites District, Venezuela, and in East Texas are shown to illustrate the application of the neutron productivitv number. INTRODUCTION The petroleum industry was introduced to some of the preliminary results of investigations into the quantitative interpretation of radioactivity logs in October, 1949." It was stated at that time that the methods presented were entirely relative because they involved the use of reference points obtained from the radioactivity log, i.e., shale reference lines, dense zone reference lines, or a combination of both shale and dense zone reference lines. These relative methods offered many advantages to the industry in interpreting radioactivity logs in terms of porosity with particular application to limestone and dolomite reservoirs. However, these relative methods did not offer the wide range of applicability desired because the esta1)lishment of reliable reference points from shale in some areas were difficult. It was recognized that a more reliable mean; of establishing reference lines was vitally needed. Such a method is now available through the introduction of an instrumeutal zero device. It is the purpose of this paper to discuss the application of this new zero reference to the quantitative interpretation of radioactivity logs. Previously all applications of quantitative interpretations of radioactivity logs have been made in limestone reservoirs with little or no emphasis placed on sandstone reservoirs. A brief resumé of investigations into the quantitative interpretation of radioactivity logs in sandstone reservoirs is presented here. This discussion deals primarily with the interrelation of the gamma ray and neutron curves and the response of the latter to the density of the fluids filling the pore space in relatively homogeneous sandstones of uniform porosity. The authors believe that the methods presented herein are only applicable locally to specific fields and reservoirs, and that they probably do not offer a wide range of applicability. However, tile authors believe that the wider use of the new instrumental zero references in sand areas will reveal more information about the specific response of the gamma ray and neutron curves to changes in lithology and saturation. Two applications of quantitative interpretation using the new instrumental zero references are presented. Examples are given which show the comparison of logs and porosity in the limestones and dolomites of West Texas and Kansas. Logs of wells in 'Venezuela and East Texas are compared with the drill stem test data, production data, etc.. to illurtrate the interrelation of the gamma ray and neutron curve: and the rise of methods involving these interrelations to determine certain saturation variables. THE QUANTITATIVE APPLICATION OF RADIOACTIVITY LOGS TO LIMESTONE AND DOLOMITE RESERVOIRS Tile theoretical basis for the gamma ray and neutron curves has been discussed elsewhere.9 he method of recording the logs and apparatus involved has also been thoroughly covered and will not be discussed here.'."".'" It has been shown that the neutron curve responds exponentially to liquid filled porosity over the 1 1/2 to 35 per cent

Jan 1, 1951

By A. D. K. Laird, John A. Putnam

This paper describes the application of x-ray theory to design procedures in connection with fluid saturation determinations during fluid flow experiments with porous media. A reliable and rapid method for calibrating the x-ray apparatuy is described. Extension of the method to fluid saturation determinations in three-fluid systems is described. INTRODUCTION In rerearch on oil production problems a method is required which will give quickly the quantity of each component of a fluid flow system present at any cross-section of a porous medium. The sample of porous medium under investigation is usually referred to as a core. The ratio of the volume of one component to the total fluid volume is defined as the saturation of the porous medium by that component. This ratio is generally given as per cent saturation. Some means of measuring saturation which have received consideration include: electrical conductivity of the fluids;1,2 emissions from radioactive tracers dissolved in the fluids; the radioactivity of silver caused by reflection of neutrons from hydrogen atoms in the fluids;' the attenuation of a microwave beam. the diminution and phase shift of ultrasonic wave trains.4,5 and the reduction in intensity of x-ray beams in passing through the fluids. X-rays have already been used with some success. Since every material has a different power to absorb x-rays, the reduction in intensity of an x-ray beam as it passes through a core depends on the fluids present. The strength of the emergent beam can be found by converting its energy into a measurable form such as heat or ionic current. or by its effect on a photographic plate or fluorescent screen. The beam strengths could be interpreted as quantities of known fluids in the core if, previously, these beam strengths had been identified with a known combination of the same fluids. With some fluid cornbinations it might be desirable to dissolve powerful x-ray absorbing materials in one or more of the fluids, to increase the differences in the beam strengths for various fluid saturations. Boyer, Morgan and Muskat6 have described a method of measuring two component fluid saturation. One component was air or water; the other. minerat seal oil in which was dissolved 25 per cent by weight of iodobenzene to increase its absorbing power. The x-ray source was a tungsten target tube operated at 43 kv potential. The beam emerging from the core was measured as ionic current flowing across an air-filled ionization chamber by means of an amplifying circuit and galvanometer. Another portion of the beam from the x-ray tube was passed through a metal plate and measured in another ionization chamber. This portion, called the monitor beam, was used as an indication of the performance of the x-ray tube. The galvanometer readings were calibrated against air-oil core saturations, gravimetrically determined. The method was apparently established by experimental means. In the present investigation the available theory of x-radia-tion was surveyed with a view to extending the usefulness of the method and to developing design procedures for its application to measurement of fluid saturation in porous media. Application of the theory permits prediction of relative meter readings to be expected for any combination of porous matrix, various saturating fluids and auxiliary filtering media. It is thus possible to calibrate the equipment in terms of fluid saturation by an indirect but rapid technique. The results of calculations based on x-ray theory indicate. and results of the saturation calibration technique confirm. that a valid measurement of the saturation of the core can be made for any two components and in some cases for three components. THEORY The strength of an x-ray beam, after it has passed through a distance. 1, of matter of density, p, and mass absorption coefficient, µ at a given wavelength, A, may be expressed by the absorption formula I = I0 e ...........(1) where I, represents the intensity of the incident x-ray beam and I is the intensity of the emergent beam. The expression e is called the transmission factor of the material. The variation of I,, with wavelength depends upon the materials through which the x-ray beam has previously passed and upon the spectral distribution of energy at the source of the x-radiation. A group of curves. called spectra. which show the variation of intensity with wavelength and x-ray tube voltage are given in Fig. 1. These curves represent the general radiation from a tungsten target tube. When the tube voltage is greater than 69.3 kv, the characteristic radiation of the tungsten is emitted and is superposed on the general radiation. At a given voltage the minimum wavelength A,,,,, at which energy can be emitted by an x-ray tube is given by the formula 12,340 xml. = ——..........(2) volts where A,.,,.. is in Angstrom units. The wavelength at which the spectra have maximum intensity a1so decreases with increasing x-ray tube voltaue. The area under each curve represents to an arbitrarv scale the total energy emerging from the x-ray tube for that voltage. The variation of µ with wavelength has been determined for many substances and may be found in such references as those by Compton and Allison7 and by Hodgman.8 The phenomenon of absorption is composed chiefly of the capture of photons by the atoms of the absorbing material with associated displacement of electrons, and of the scattering, or the deflection, of the photons by the atoms. Curves of these mass absorption coefficients show jump discontinuities. or absorption edges. at wavelengths which are short enough for the photons,

Jan 1, 1951

By William B. Stephenson

The paper describes efficient and effective methods of automatically controlling sand pump installations. Particular reference is made to liquid-level controls actuating variable speed pump-driving units. Included is a discussion of various combinations of equipment, with schematic drawings. HERETOFORE many sand pump installations in the mining and metallurgical field involved guesswork as to the size of the pump and then simply direct-connecting it to a constant speed motor which was often large enough to do twice the work required. Considerable thought was given to mill location in an effort to avoid as much pumping as possible. Hillside design of mills with gravity flow of tailing was much to be desired. Power costs were low, construction was relatively cheap, and labor in many places meant nothing in comparison to the values derived from the ores being treated. Today most of these conditions are reversed. Ores are becoming more complex with lower values per ton of ore treated. Power is more expensive, construction is higher, and labor definitely takes a very important place in the profit and loss statement. Each piece of equipment incorporated in the design of a new mill is selected to provide highest efficiency based on careful metallurgical analysis of the ore to be treated both in good and poor markets. Each is designed with its flexibility in mind and with provision for adjustments in its performance to meet actual conditions in the operation of the mill. Sand pumps have taken an important position in mill design. Operators the world over are relying more and more on the performance of a sand pump in the efficient operating of their plant. Many ordinary jobs are being done today with pumps driven through adjustable pitch diameter V belt drives in order that changes in pump speed can be made easily to meet actual operating conditions. Operating costs have long since proved the folly of operating a pump at too high a speed for the volume and head to be overcome. Metallurgical results have shown the benefits derived from a smooth flow as contrasted with a surging flow from an uncontrolled pump. Construction costs have risen to such an extent that surge bins and other means formerly employed must be omitted from today's flowsheet. Several installations of considerable size and involving the use of automatic pump speed control have proved the adaptability of such controls since they were placed in service in recent years. In the following presentation each system discussed and illustrated schematically has been installed in one or more instances and has proved itself reliable and definitely economical from the standpoint of capital investment, operation and maintenance. Variable Volume-Head Speed Control: Probably the most popular, effective and efficient automatic control setup for sand pumping installations is the one shown schematically in fig. 1. Commonly used

Jan 1, 1951

By P. G. Nahin, A. Grenall, R. S. Crog, W. C. Merrill

A progress report of an experimental investigation into the role of clay in reservoir performance is presented. The Paper gives some of the reasons for considering clay as a significant component and outlines the objectives of a broad field of stud) which it is intended to pursue. Descriptions of the analytical methods used are given; these include X-ray diffraction. elec tron miscroscopy, thin section petrography, infrared spec-troscopy, and cation exchange analysis. A suite of the more important clay minerals has been assembled and characterized l~y these methods for use as standards in core analysis. From the data obtained it appears that although no one method of analysis is diagnostic for all of the clay minerals the infrared technique shows considerable promise in this direction. For the present, one or more supplementary methods should be used to confirm the clay mineral identifications. The methods of analysis are applied to field cores taken from repesentative and widely differing strata especially as regards their susceptibility to damage by fresh water. well.; completed in the stevens and Gatchell zones in San Joaquin valley are I,articularly clear-cut examples of this behavior with stevens zone wells being more adversely affected by fresh water. cores from these zones have been studied and are discussed. It appears that differences in this behavior can be ascribed to differences in the nature of the contained clays. The value of the infrarecl spectra of the clay fractions in establishing the identity of the predominant clay minerals is given particular emphasis. INTRODUCTION It is a challenge to the technical resources of the petroleum industry that when the economic limit of production is reached, from 40 to 70 per cent of the oil in California reservoirs remains unproduced even by use of the best presently known methods of recovery. The magnitude of this abandoned volume of oil can be appreciated when it is considered that to 1950 in excess of 8 billion bbll has been produced from California reservoirs with estimated economically recoverable reserves in known fields and pools totaling nearly 4 billion bbl.24 If for every barrel of oil produced there is at least another barrel still in place, it is evident that the revenue obtained from the recovery of only a .few per cent of this volume would repay the cost of the required research manyfold. From well completion experience. production behavior, and a growing body of laboratory data it now appears certain that the mineral composition of a producing stratum has an important bearing on the productivity and ultimate yield. In addition to the organic component and water, the cores con,ist of gravel, sand. silt, and clay" in diverse variety of (a, composition and (b) texture. It is the composite effect of these two factors which is probably responsible in large measure for the way in which the oil flows to the well. The role of the clay and fine-size accessory minerals is not clear but there is a growing opinion, based on their physical and chemical properties, that it is a significant one. of particular importance are the prime facts: 1. The silt and clay fractions of the reservoir matrix possess the highest surface area per gram, and 2. The silt and especially the clay fractions are the most chemically reactive of the inorganic constituents present. Only within the last few years has the knowledge of clay mineralogy and the techniques of identifying the clay minerals reached such a stage as to enable reliable inquiry into the composition of argillaceous sediments.2,8,10,11,12,16,26 It is the purpox of this and succeeding papers to add to the fund of information on the role which these materials play in the production of petroleum from California formations by correlating their presence and associated properties with observed reservoir behavior. In the present paper attention is directed to their possible influence on damage by fresh water. OBJECTIVES The attack on this problem divides naturally into two broad phases: 1. Determination of the nature of the clays and their relationships to the other mineral components, and 2. Determination of the physico-chemical relationships between the clays and the interstitial fluids. In the work described in this paper the emphasis has been on phase 1, which stems logically from the necessity of identifying and understanding the materials to be dealt with in Phase 2. Based on the authors' present opinion that not all of the minerals which occur in oil-bearing formation are of equal importance in their effects on the flow and recovery of oil, it was decided to focus attention first upon the clay minerals content and then. later perhaps. work into the field of the normally larger size non-clay minerals and fractions. The

Jan 1, 1951

By M. R. J. Wyllie

Eight laboratory-prepared aqueous base drilling muds representing common mud types, and 15 aqueous base drilling muds sampled in the field, have been used in an experimental investigation of the relationship between the streaming potential developed across a mud filter cake and the differential pressure causing filtrate flow. It has been established that the relationship is of the form, ES = kPy, where Es is the streaming potential, P the differential pressure and k and y are constants for any particular mud system at constant temperature. Beyond a certain minimum thickness this relationship is independent of filter cake thickness. Experiment has shown that both k and y are temperature dependent parameters and that in certain mud systems there is a critical value of P above which the simple relationship Es = kPY ceases to hold. The constant k tends to be a function of the mud resistivity at 77ºF, but the exponent y has not been found to be related to any commonly measured mud property. Certain field experiments are described which serve to demonstrate that the total SP (self potential) developed opposite a formation may be quantitatively accounted for as the algebraic sum of an electrochemical potential and an electrokinetic potential. A chart to permit the simple use of mean solution activities in the interpretation of electrochemical SP data is given and its use described. Various field methods for computing the electrokinetic SP component of the total SP are considered and rejected as being unduly complicated and inaccurate. It is shown that the employment of low resistivity drilling muds is essential if optimum accuracy is desired in the use of the S.P. curve for the purpose of computing connate water salinities by the electrochemical SP method. The use of such low resistivity drilling muds is accordingly recommended. INTRODUCTION In a previous paper' a quantitative analysis of the electrochemical compovent of the SP (self potential) curve was made and it was shown that the electrochemical* emf, E, could be expressed as E = ZtRT/F In a,/a,, where t is the transference number of the chloride ion, R is the gas constant, T the absolute temperature of the formation water and mud, a, the mean activity of the connate water (assumed to be sodium chloride) and a, the mean activity of the mud (as sodium chloride). The essential accuracy of this expression was confirmed by an investigation 2 of the SP kicks opposite sands of known water salinity. The logs examined had been routine runs in oil wells in a number of Mid-Continent states. Further confirmation of the original analysis of the electrochemical SP is implicit in the paper by Tixier3 wherein a relationship between the SP and the ratio of connate water and mud resistivities, based only on field data, is given. Allowing for the fact that mud and connate water resistivities were used instead of activities, and that electrokinetic effects were ignored, the constant reported by Tixier is essentially 2tRT/F. The error involved in the universal substitution of resistivities for activities will receive further reference below. Possible reasons for the fact that the electrochemical properties of shales do not appear to be significantly dependent upon either the nature or the quantity of cation exchange materials, such as clays, they contain has been considered at some length by Wyllie and Patnode.4 In the same paper, the probable effects of shale thickness and compaction on electrochemical efficiency, and hence the inherent difficulty of obtaining reliable laboratory-scale data, were also pointed out. However, it is

Jan 1, 1951

By E. J. Roberts

The theory is developed that the tons ground through a given mesh per day in a wet ball mill is proportional to the percent plus that mesh in contact with the balls and the net power applied to the balls at this point. A grindability test is described. DURING the course of a study of the fundamentals of classification in 1937, the need for a more basic understanding of the action of a ball mill became acute. Unless one knows how classification affects grinding, one cannot hope to effectively improve on classification. The methods of evaluating grinding efficiency that depend on surface developed were studied but soon discarded for two reasons: 1. There was no apparent method which could be generally used to give a reliable figure for the actual new surface developed as a result of grinding. Subsequent papers have not changed this conclusion. 2. The practical evaluation of grinding in the main ore dressing applications was in terms of the percentage retained on a screen which passes 90 to 99 pct of the material and not in terms of surface area. The Probability Theory With the background of our experience in the field of closed-circuit grinding, together with the papers of Lennox,1 Gow,2 Gaudin,8 Fahrenwald,4 Coghill, and others, the approach of the theoretical physicist was then tried. The thought was somewhat as follows: When one grinds in a ball mill, a given expenditure of power leads either to a certain number of point to point blows per hp-hr or to a certain distance of line contact per hp-hr, depending on whether the action of the balls is considered to be cascading or rolling. It is also assumed that the balls actually come together on each blow or during the roll. Then a volume of slurry will be covered per minute which is some function of the size of the particle being considered (see fig. 1). All particles coarser than this size will be reduced through this size. This volume of slurry contains a certain weight of ore, depending on the percent solids and the density of the solids. If we fix the percent solids and the density of the solids and let w be this certain weight of ore in the volume covered, then, in mathematical terms, what we have just postulated is, w —— 8 hp (a) dt If W is the total weight of ore present in the mill, then we can write. W w/8 hp (b) W dt and if C is the cumulative percent plus the size chosen at the start of the time interval dt, w w c/dt W 8 hp x c (c) wc But wc/100 is the weight plus the size chosen which at 100 wc the close of time dt is finer than that size, and W is the decrease in the percent plus of the whole mass of ore or —dC. Then, —W dC/dt 8 hp x C. (d) In other words, the mesh tons ground through a given size per unit of time is proportional to the hp and the percent plus the mesh. A crude analogy would be to picture a 1-ft-wide steam roller going down the road at 1 ft per sec. If we place one egg on the road per square foot, one egg will be smashed per second. If we place a dozen eggs per square foot, a dozen eggs will be crushed per second. Similarly, if all the particles in w are plus the mesh, i.e., C=100, we should have a maximum rate of reduction. If only 10 pct of them are plus the mesh (C=10), we would have only one tenth the maximum rate; if only 1 pct are plus the mesh, the balls have a hard time finding anything to work on. This is where the term "probability theory" comes from. The chances of the balls crushing a particle through a given mesh depends directly on the concentration of particles coarser than this mesh in the general pulp in the mill. Giving W the units of tons and dividing equation (d) through by W, we obtain -dC hp ----- = k---— C [1] dt ton where k is a constant for any one size of particle, density of solid and moisture content of pulp. Eq 1 is the rate equation for a first order reaction and says that the rate of decrease of the percent plus a given mesh with time is directly proportional to the hp per ton applied to the body of ore and to the percent plus the mesh in the ore mass as a whole. Since it is a differential equation, it only

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 Orville R. Lyons, A. C. Richardson

F. X. Ferney—We are pleased that this paper was presented at this meeting and thank Mr. Richardson and Mr. Lyons for their effort and work in preparing it. We agree with the authors that it was unfortunate that more comprehensive data were not available when the paper was prepared, this being particularly true since we had no knowledge that the paper was being written and could not make available data which were in our process files. Further, it is our opinion that because the data are not sufficiently comprehensive the results which are presented are erratic and will lead to false conclusions. As we see it, there are three Specific reasons why the data which are presented cannot be considered accurate. 1. The preparation plant was not at equilibrium while the samples were being taken. This is indicated by the fact that the percent of solids in the circulating water varied from 3.9 pct to 10.7 pct during the period when the plant was sampled. 2. We do not believe that the samples of Bird feed which were taken were representative and could indicatc the true feed to the filter. Evidence of this is shown in the data where the dewatered product leaving the centrifuge contains more coarse material than the feed to it, that is, material which is +6-mesh in size. 3. We question if the data concerning screen analysis in the fine sizes is accurate and would conclude (from the data) that these tests were made by a dry-screen method. We have found that wet screening is always necessary to obtain a true picture of the quantity of —200-mesh fines which is present. The test work described in the Lyons-Richardson paper was conducted some time ago and the tests were carried on during a period when the preparation plant had not ironed out all of their start-up problems. Since that time most of these problems have been corrected and now this is a smooth running, well-operated prep-

Jan 1, 1951

By Shiro Watanabe

To determine the potentialities of nickel as a substitute for cobalt in catalysts for the synthesis of hydrocarbons from carbon monoxide and hydrogen, RESULTS The maximum oil yields obtained in bench-scale equipment were as follows: Using 100N1:20Mn:100 kaolin:200 diatomaceous earth catalyst, a maximum yield of 133.8 cm.3/m.3 of pure CO+2H2 was obtained from one pass of the feed gas, With a nickel:cobalt mixed catalyst (Ni:Co - 3:7) having the composition 100(Ni+Co):8MgO: 5Th02:200 diatomaceous earth, a maximum of 172.2 cm.3/m.3 of pure C0+2H2 was obtained.

Jan 1, 1951

By K. E. Stanfield

This report presents the results of analytical studies made on two series of oil-shale samples from the Mahogany ledge of the Green River mine the character of the various grades of oil shale that are being mined and processed into shale oil and refined products at the Bureau of Mines Oil-Shale Demonstration Plant at Rifle, Colo. The analytical work was part of a synthetic liquid fuels program being conducted at the Petroleum and Oil-Shale Experiment Station, Laramie, Wyo. The 16 oil shales ranG6d in color from a gray brown ( or a sample that assayed 10.5 gallons of oil per ton to a very dark brown for a sample that assayed 75.0 gallons of oil per ton. In general, the samples were similar as to the types of organic and inorganic matter that they contained but varied widely in the amounts or these constituents. The principal constituents were calcite, dolomite, illite, and yellow organic material, while the minor constituents were quartz, feldspar and plagioclase feldspar, pyrite, marcasite, analcite, opal, black organic material, and small woody fragments. Some micro-fossils, spores and pollen grains were found also.

Jan 1, 1951

By C. J. Osborn

The temperature dependence of the free energies of formation of metallurgically important oxides, sulphides, chlorides, carbonates and sulphates is presented graphically, whereby the task of deriving practical metallurgical information is greatly simplified. The diagrams have been revised according to the latest available thermodynamic data. WHILE it is true that much careful investiga-tional work remains to be done, there are already available in the literature sufficient thermo-dynamic data to enable the metallurgist to predict with reasonable confidence the equilibrium conditions to be expected in most important, and potentially important, metallurgical reactions. In this connection, the careful, critical compilations of K. K. Kelley and his collaborators in numerous U. S. Bureau of Mines Bulletins are particularly valuable. However, the translation of reliable thermo-dynamic data into metallurgical language unfortunately involves lengthy manipulations of the cumbersome formulas which can be set up from heat of formation, entropy, and heat capacity data. Many years ago, Kelley20 predicted that thermo-dynamic calculations would be made in the future "with the aid of free energy, heat content, and entropy tables, rather than by means of the algebraic methods employed at present", and where such tables are available they greatly simplify the task of deriving practical metallurgical information. However, in addition to these tables, there are also available one or two reliable graphical presentations, particularly of free energy data, which may be used in the same way as the tables, but which have the added advantages that interpolation is never necessary, and that the behavior of different metals or compounds may be compared at a glance. Some years ago Professor Robert Lepsoe, Head of the Department of Metallurgy at Norways Institute of Technology (N.T.H.), began a compilation of curves showing the temperature dependence of the heat contents of the elements, and the heat contents and heats and free energies of formation of the common metallurgical compounds. With such a compilation, the thermal and free energy requirements of a reaction may be read from curves in a matter of seconds; and this statement applies not only to the formation of compounds from their elements, and to the reverse dissociation, but to any reaction involving substances whose thermodynamic properties are available. This follows from the fact that heats and free energies of formation are completely additive. For example, the free energy change associated with the chlorination of a metallic oxide at any temperature, T, is given by the free energy of formation of the chloride at temperature T minus that of the oxide also at T; both of these quantities may be read directly from curves of the type suggested above. Since this early, unpublished work of Lepsoe, both Ellingham7 and Richardson and Jeffes46 have

Jan 1, 1951

By R. L. Slobod, W. L. Prehn, Adele Chambers

The centrifuge has been found to be an extremely useful tool for determining capillary pressure curves and for establishing connate water and residual oil in small core plugs. The use of the centrifuge for determining the properties of small core plugs has been discussed in the literature,',' but practically no experimental evidence has been presented justifying the use of this method in preference to other methods (mainly disc method) now in use. Data have been accumulated and are now presented demonstrating the advantages of the centrifugal method, some of which are: (1) rapid establishment of equilibrium, (2) excellent precision yielding very reproducible results, (3) availability of high pressure differences between phases, (4) simple operational procedure, and (5) ability to establish connate water, residual oil, or to obtain complete capillary pressure curve in one day or less. A commercially available centrifuge capable of speeds up to 3,800 rpm, and a high speed attachment providing a maximum rate of rotation of 18,000 rpm were used in this work in conjunction with core holding tubes designed specifically for this application. In view of the outstanding advantages associated with the use of the centrifuge the conclusion has been drawn that this method should be used in place of the more tedious, slower, and less reliable disc method for determining capillary pressure curves and for establishing connate water and residual oil in small core plugs. INTRODUCTION The need for accurate values of connate water, residual oil, and capillary pressure curves in reservoir engineering has been recognized for many years, and the extent of the effort devoted toward solving these problems is reflected in the large number of papers3-" which have appeared in the literature during the past decade. Most of the methods discussed in the recent literature employ a porous disc as a semi-permeable membrane to separate two immiscible phases and make pos-ible the application of an explicit difference in pressure between two phases in the core. Thus, in the determination of the capillary pressure curve the wetting phase (water) is displaced by the non-wetting phase (air or oil). Several investigators1,2 have used centrifugal forces to develop pressure differences between phases. As a result of the first work' in this field the conclusion was reached that "the more rapid centrifugal method for measuring irreducible saturation may have equal value, (compared to use of discs) but more work is required to establish this point." This work was followed in 1945 by a more detailed study2 in which the concepts of this experimental work were more clearly enunciated. A method for calculating saturation for any given speed of rotation based on the observed volume of water displaced was developed and a wider application of the method was suggested. The absence of any subsequent pertinent literature on this subject is interpreted as indicating that no additional work has been completed to substantiate or deny the earlier claims and suggestions of promise contained in the original papers on this subject. One purpose of this report is to provide evidence designed to establish the practical value of centrifugal methods in determining core properties such as connate water and capillary pressure curves. It is also our purpose to suggest a broadening of the scope of this tool to include determinations of residual oil by gas or water drives. THEORY AND PRACTICE IN USE OF CENTRIFUGE Hassler and Brunner2 have clearly presented the basic concepts involved in the use of the centrifuge by relating the performance of a small core in a field of high acceleration to the

Jan 1, 1951

G. A. Moore—The tin-fusion method has been a very favorable possibility for many years. The authors apparently have settled the question that delayed the method for a long time by showing that no hydrogen is absorbed in the tin. This, of course, is very important. I want to make a few remarks concerning the absolute accuracy of analysis, which must be the final basis for deciding among the various methods. From the figures in the paper, there seems to be some re-maining slight discrepancy on the actual amount of hydrogen present in various samples which may be presumed essentially identical. (This is of the order of the precision of individual analyses but appears in averaged results.) From the analyst's viewpoint, the tally of hydrogen content can be regarded as occurring in three portions. First is a large portion which comes off easily and automatically during sample storage and later on heating in the apparatus. This is fairly easily analyzed. Second is an item which may be either positive or negative in the tally sheet. In warm or hot evolution, this is a portion which, in practice, can never be re-

Jan 1, 1951

The United States has not begun commercial operations to tap its largest poten-tial sources of oil supply - oil shale and coal. The reason is that domestic petrol-eum has been plentiful in the past and liquid products probably could be produced from it at the lowest cost. In view of the ever-increasing need for petroleum in the United States, the critical international situation threatening foreign supplies, the growing demands for steel, and the heavy costs to industry of constantly discovering and developing new oil fields, it is believed that the prompt development of a synthetic fuel industry based on oil shale and coal is not only requisite to safeguard our oil supply but is an economically sound course for the foreseeable future, To neglect its development is to close our eyes and minds to our own resources at a time when they are needed critically. It also is apparent now that neither the Government nor industry would be taking any considerable economic risk in starting the initial plants, especially as measured against their potential value in meeting critical oil and chemical demands and in building a new industry in the West.

Jan 1, 1951

By Jack White

MUFULIRA Copper Mines, Limited, conducted tests on the concentrator in 1942 to determine which type of ball mill, that is, Conical Trunnion overflow or Cylindrical Grate discharge, produced the greater quantity of finished product at the lowest cost. All the data which follows applies to Mufulira ore and to the particular degree of grinding produced with the classifiers installed at Mufulira concentrator. JACK WHITE, Member AIME, is Concentrator Superzntendent, Mufulira Copper Mines, Ltd., Mufulira, Nortltern Rhodesia. Sun Francisco Meeting, February 1949. TP 2729 B. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Feb. 28, 1949. Test Procedure: The test was carried out using ball mills No. 1 to 9 (conical trunnion overflow) as the standard with which to compare No. 10 (cylindrical grate discharge mill). The conical trunnion overflow ball mills are 10 ft diam by 72 in., and the cylindrical grate discharge mill is a No. 99. Each mill runs in closed circuit with a Dorr type DSFX classifier 8 ft wide by 30 ft long. The feed is considered as being identical to all ten units. The figures for the test were derived as follows. Dry Tons Milled: For No. 10 unit (cylindrical grate discharge mill) this figure was taken from the ball mill weightometer, which was corrected for error, and then for moisture content. The weightorneter was checked twice a week during the test, and the error did not exceed 3 pct at any time. The moisture was obtained from a 24 hr moisture sample taken by the ball mill operator hourly, and placed in a closed bucket. The sample was cut where the conveyor drops the feed into the ball mill chute. The Mill Sampling Department made a daily moisture determination on this sample. To obtain the dry tons on units No. 1 to 9 the No. 10 figure was deducted from the month's dry tons milled figure, which, in turn, was taken from the crusher weightometer tons corrected for weightometer error and moisture. All tons reported in this test are short tons of 2000 lb. Ball Mill Hours: This was taken daily from the Shift Boss reports giving actual running hours for each unit. Screen Analyses: Coarse Heads (Ball Mill Feed): The monthly composite coarse heads screen analysis, done by the Mill Sampling Department, was used for the minus 200 mesh in the feed to the mills. F. X. Classifier Overflow: The ball mill operators took an hourly 24 hr sample of the overflows of units No. 1 to 9. This was a hand sample, but cut with a special cutter, and is believed to be very reliable. On No. 10 unit, an hourly 24 hr sample, and an hourly shift sample were cut in the same way. These five samples were split, filtered, and dried by the Research Department and were then wet screened on a 200 mesh screen. The average of the three shifts samples on No. 10 unit had to check the 24 hr sample within 1.5 pct to be acceptable. A weighted composite was cut each day from both 24 hr samples, and at the end of each month it was screened as follows: Wet screened through 325 mesh, the plus 325 then screened on a rotap for 15 min through 65, 100, 150, 200, and 325. This was done in duplicate. All splitting, drying, and screening of samples was done by one of the Mill Research staff, to insure accuracy. F. X. Classifier Overflow Densities: These were taken from the Shift Boss reports. Densities were taken by the ball mill operator every hour. Circulating Loads: These were taken a number of times during the test both by direct method (weighing a measured portion of classifier rake sand, and deducting moisture) and by calculation using the formula:

Jan 1, 1951

By W. R. Evans, H. H. Kaveler, Jack Tarner

The geological features, development history and engineering detail of the Shuler Field and the results of approximately two years of unitized operation of the Shuler Jones Sand Pool, were discussed in a prior publication.' The purpose of this paper is to present the results of pressure maintenance in the Shuler Jones Sand Pool after nine years of unit operation. GENERAL INFORMATION The Shuler Jones Sand Pool is located in and about Section 18, Township 18 South, Range 17 West, Union County, Ark. The pool was discovered .in September, 1937, unitized in February, 1941, and subjected to gas injection operations in July, 1941. Water was first returned to the reservoir in July, 1944. The reservoir is an anticlinal trap covering about 4,000 acres. The 154,000 acre-ft of sandstone initially consisted of approximately 150,000 acre-ft of productive oil zone and 4,000 acre-ft of gas-cap. The average depth of production is 7,400 ft. Maximum closure of the reservoir is 135 ft and the oil column lies between a gas-oil contact at -7,270 ft and a water-oil contact at -7,370 to -7,380 ft. The field is approximately four miles long. east and .west, and one and one-half miles wide. The sand grains are angular and vary from fine to medium size. The porosity of the sandstone averages 20.2 per cent. The specific permeability averages 400 md. Some zones have as high as 30 per cent porosity and specific permeability of 4,000 md. The reservoir rock is not uniform in character but consists of sandstone zones interspersed with shale. The variation in rock characteristics is evident in the electric log and core analyses presented in the original publication. Asphalt present in the pore space of the sandstone limited the reservoir to the southeast and apparently blocked any encroachment of water from that direction. The initial reservoir pressure at a subsea depth of 7,300 ft was 3,520 psi. The reservoir temperature was 198ºF. Initially, the solution gas volume was 765 cu ft per bbl and the reservoir volume factor was 1.45. The gas solubility and formation-volume-factors of the reservoir liquid are related with reservoir pressures above 300 psi as follows: Solution gas, cu ft per cu ft, S = 0.0334 P + 18.65 Formation volume factor of reservoir oil, FVF = 8.0 x 10 -5 P + 1.168 Gas volume factor, standard cu ft of gas equivalent to one cu ft of gas at reservoir conditions of temperature and pressure, F = .062 P - 4 Pressure (P) measured in psia. The equation for the gas volume factor presented above is based on a direct measurement of a sample of the gas and is a correction of that used in the original paper. The gravity of the oil produced is from 32 to 34" API. CALCULATION OF INITIAL OIL IN PLACE The Jones Sand production history is interesting because it lends itself to analysis by material balance. Production statistics from discovery of the Jones Sand through 1949 and material balance calculations of the initial stock tank oil in place are shown in Table I. The usual procedure in testing the application of material balance calculations is to compute the apparent initial volume of oil in place, using production and pressure information obtained at different time periods. If the apparent oil in place volumes computed increase with successive time periods, water encroachment is indicated and approximations must be mads to correct for its influence. The first requirement in utilizing such calculations is reliable reservoir pressure, accumulated gas, oil and water production, and PVT data. Calculations of apparent oil in place in the Jones Pool, based on field data

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 Norman A. Parlee

Introduction The principal primary iron and steel producing capacity of the Dominion Steel and Coal Corporation is at the Dominion Iron and Steel, Limited, plant at Sydney, Cape Breton Island, Nova Scotia. The main raw materials are Cape Breton coal, Wabana (Newfoundland) iron ore, and Port-au-Port (Newfoundland) limestone. This plant, which was established at the turn of the century has gradually expanded its production facilities so that today its ingot producing capacity is over 720,000 tons annually. Principal operating units of the plant at present are three batteries of 173 Koppers by-product coke ovens with conventional by-product recovery equipment, three blast furnaces .of 15 ft. 6 in., 18 ft. 3 in., and 19 ft. 3 in. hearth diameter (inside the brick), one 700-ton hot metal mixer, ten open hearth furnaces (two of 175-ton capacity, three 12 5-ton, five 60-ton), one 10-ton electric furnace, a 40-inch blooming mill, a billet mill, a rail mill, a tie plate mill, rod and bar mills, and a wire and nail mill. Extensive machine shops and an iron and brass foundry are also available for plant maintenance and repairs. This paper will describe developments during the past five years and those now in process. It will also briefly discuss research being done and indicate the direction of future development.

Jan 1, 1951

By E. J. Roberts

The theory is developed that the tons ground through a given mesh per day in a wet ball mill is proportional to the percent plus that mesh in contact with the balls and the net power applied to the balls at this point. A grindability test is described. DURING the course of a study of the fundamentals of classification in 1937, the need for a more basic understanding of the action of a ball mill became acute. Unless one knows how classification affects grinding, one cannot hope to effectively improve on classification. The methods of evaluating grinding efficiency that depend on surface developed were studied but soon discarded for two reasons: 1. There was no apparent method which could be generally used to give a reliable figure for the actual new surface developed as a result of grinding. Subsequent papers have not changed this conclusion. 2. The practical evaluation of grinding in the main ore dressing applications was in terms of the percentage retained on a screen which passes 90 to 99 pct of the material and not in terms of surface area. The Probability Theory With the background of our experience in the field of closed-circuit grinding, together with the papers of Lennox,1 Gow,2 Gaudin,8 Fahrenwald,4 Coghill, and others, the approach of the theoretical physicist was then tried. The thought was somewhat as follows: When one grinds in a ball mill, a given expenditure of power leads either to a certain number of point to point blows per hp-hr or to a certain distance of line contact per hp-hr, depending on whether the action of the balls is considered to be cascading or rolling. It is also assumed that the balls actually come together on each blow or during the roll. Then a volume of slurry will be covered per minute which is some function of the size of the particle being considered (see fig. 1). All particles coarser than this size will be reduced through this size. This volume of slurry contains a certain weight of ore, depending on the percent solids and the density of the solids. If we fix the percent solids and the density of the solids and let w be this certain weight of ore in the volume covered, then, in mathematical terms, what we have just postulated is, w —— 8 hp (a) dt If W is the total weight of ore present in the mill, then we can write. W w/8 hp (b) W dt and if C is the cumulative percent plus the size chosen at the start of the time interval dt, w w c/dt W 8 hp x c (c) wc But wc/100 is the weight plus the size chosen which at 100 wc the close of time dt is finer than that size, and W is the decrease in the percent plus of the whole mass of ore or —dC. Then, —W dC/dt 8 hp x C. (d) In other words, the mesh tons ground through a given size per unit of time is proportional to the hp and the percent plus the mesh. A crude analogy would be to picture a 1-ft-wide steam roller going down the road at 1 ft per sec. If we place one egg on the road per square foot, one egg will be smashed per second. If we place a dozen eggs per square foot, a dozen eggs will be crushed per second. Similarly, if all the particles in w are plus the mesh, i.e., C=100, we should have a maximum rate of reduction. If only 10 pct of them are plus the mesh (C=10), we would have only one tenth the maximum rate; if only 1 pct are plus the mesh, the balls have a hard time finding anything to work on. This is where the term "probability theory" comes from. The chances of the balls crushing a particle through a given mesh depends directly on the concentration of particles coarser than this mesh in the general pulp in the mill. Giving W the units of tons and dividing equation (d) through by W, we obtain -dC hp ----- = k---— C [1] dt ton where k is a constant for any one size of particle, density of solid and moisture content of pulp. Eq 1 is the rate equation for a first order reaction and says that the rate of decrease of the percent plus a given mesh with time is directly proportional to the hp per ton applied to the body of ore and to the percent plus the mesh in the ore mass as a whole. Since it is a differential equation, it only

Jan 1, 1951

By J. Cooperman

THE INVESTIGATION was carried out in three stages, depending on the objectives of the work and the kind of equipment used. The first stage involved testing of 11 representative Alabama coals, the source of which is given in table 1. The objective was to find whether these coals could be gasified raw by the Lurgi method, and the equipment used was a 4-inch batch generator (to be described later). This generator proved too small and difficult to control to provide adequate amounts of products under continuous operating conditions for testing. For the second stage, a 6-inch batch generator was used, which was provided with facilities for superheating the steam-oxygen mixture and for synthesizing additional methane from the residual carbon monoxide and hydrogen in the primary Lurgi gas. Selected Alabama coals, Pittsburgh-bed coal from West Virginia, "Disco," and anthracite were used. For the third stage of the work, a continuous generator of 1 square foot grate area, following closely the design of the industrial generators operated in Germany, was provided. This generator was designed by 0. Hubmann, engineer for the Lurgi company, and was expected to give results closely simulating industrial-scale apparatus. The purpose of this equipment was to test prepared materials shown to operate smoothly in the 6-inch generator under conditions approximating as nearly as possible those prevailing in industrial practice. Work of the first stage showed that Alabama coals could not be used in the Lurgi process without first destroying the coking power.

Jan 1, 1951