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By J. D. Rice, H. H. Rachford, G. H. Bruce, D. W. Peaceman

The problem of unsteady-state gas flow through porous media leads to a second-order non-linear partial differential equation for which no analytical solution has been found. In this paper a stable numerical procedure is developed for solving the equation for production of gas at constant rate from linear and radial systems. An electronic digital computer is used to perform the numerical integration using an implicit form of an approximating difference equation. Solutions are presented in graphical form for various values of dimension-less parameters. The solutions are compared with the laboratory study of gas depletion in a linear system. INTRODUCTION Production of fluids from porous rock reservoirs is essentially a transient process. Transient gradients develop as soon as production begins, and further withdrawals continue to cause disturbances which propagate throughout the reservoir, each adding in some way to the prior ones. A correct mathematical analysis of this behavior is complicated by the fact that the transient or unsteady-state flow of compressible fluids must be described by difficult second-order partial differential equations. As a practical matter, three distinctly different cases arise: 1. Flow of single-phase liquid 2. Flow of gases 3. Multiphase flow The first of these has been found to give a linear second-order equation similar to the well-known heat flow equation. where 7 is fluid density, 8 is time, and a a constant for the system, provided d 7 = r cdp, where the compressibility, c, is constant over the range of pressure, p, considered. Solutions of Equation (1) for both linear and radial flow are available in several forms.2'3' On the other hand. the second case, which is the flow of gas, gives a non-linear second-order equation, the solution of which is not known. Although a number of approximate solutions have been proposed, each is limited in value by the associated simplifying assumptions. Inasmuch as the analysis of transient flow is limited to liquid systems, a solution of the second case is necessary if further progress is to be made in studying underground fluid movement. For this reason a solution of Equation (2) was undertaken by means of numerical integration of approximating difference equations. BASIC DIFFERENTIAL EQUATION Equation (2; is derived by combining the equation of continuity, the perfect gas law, and Darcy's law to give the basic differential equation Strictly speaking, the fluids present in a gas reservoir are not perfect gases. Furthermore, there are indications that over certain velocity ranges, Darcy's law is not applicable. It would not be practicable. however, to attempt to obtain numerical solutions which would take into account all the possible variations from these laws which could occur in actual systems. The

Jan 1, 1953

By M. G. Arthur

This paper is a theoretical analysis of fingering of water and coning of water and gas in homogeneous sand. Investigation of this idealized case illustrates the relative magnitude of the factors involved in actual conditions. The body of the report presents equations, example calculations, and charts that facilitate solution of such problems. Derivation of the equations introduced in this paper and a discussion of previously published equations are included in the appendix. Introduction Production of water from oil wells as a result of the pressure gradients established by flow of fluids through oil-~roducing sands is a common occurrence, which influences the cost of oil production, the degree of depletion and the efficiency of expulsion of oil from naturally occurring reservoirs. Control of water production and encroachment are important both in primary and secondary phases of of exploitation in order to produce oil and gas at lowest cost and in order to achieve the greatest ultimate recovery of the oil in the reservoir. Although many actual oil reservoirs present a multitude of variables that influence fingering and coning of water and gas, an inspection of the relationship and magnitude of the forces involved in the case of a homogeneous sand may indicate satisfactory methods of controlling water production. Application of equations relating the variables may indicate the geometric type of drainage that exists in a particular reservoir or in the vicinity of a particular well. A homogeneous sand body is assumed within the portion of the reservoir influenced by the well. Two geometric types of drainage are considered theoretically. The first is water fingering into an oil sand that is relatively thin compared with the lateral extent of the sand. This sand may represent the entire oil-producing reservoir or it may represent one interval in an oil reservoir, which is separated from other producing intervals by competent lithologic barriers to flow of fluids. For the condition of complete penetration of a well in such a sand body, it may be assumed that no flow occurs across bedding planes. A mathematical relation is developed between the limit of approach of a water finger to the well without being drawn into the well and the corresponding operating pressure drawdown. The second condition considered is that of water or gas entry into an oil well as the result of coning through bedding planes. The theory and graphical solution developed by Muskat' for the limit of approach of a water or gas cone to a well, without its entry into the well, related to the corresponding maximum pressure drawdown, is reviewed and amplified, Charts are presented, which facilitate graphical solution of the problem. A method is presented for the extension of this type of graphical solution to the case where gas and water coning occurs simultaneously~

Jan 1, 1944

By Thomas Fraser, H. F. Yancey

Prior to the war just ended, Germany was the greatest coal producer in continental Europe. In 1943 the production of coal, bituminous and higher in rank, together with brown coal calculated to the equivalent amount of bituminous coal, is estimated to have been about 240 million metric tons, according to the War Department. Before the war production in Germany exceeded consumption. No other country in continental Europe except Poland had a large surplus. However, England's surplus was the largest in Europe as a whole. Before World War II the Ruhr Basin normally supplied about 70 pet of the total production of high-rank coal, the Saar and Aachen about 6 pet each, Upper Silesia about 14 pet, and Silesia and Saxony the remainder. Nearly one third of the brown coal was produced in the Rhineland, a little less than one half in central Germany nest of the Elbe River, and about one fourth east of the Elbe. Bituminous coal and brown coal together constituted by far the most important energy resources of the old German Reich. Bituminous coal furnished nearly 70 pet of the total energy requirement, brown coal supplied about 25 pet, and water power, wood, petroleum and alcohol together aggregated only 7 pet. Because it was the most important single mineral resource of Germany, an excess of coal enabled the Reich to import nearly all the other mineral products that she lacked, such as iron ore from Lorraine. The area adjacent to the coal fields was supplied with gas from an interconnected grid. Similar electric grids are based on brown coal with the power stations at the mines. Coal tar provided the foundation for the development of the extensive German chemical industries as exemplified by the I. G. Farbenindustrie. For almost a century, German scientists have been adequately supported both by the State and by industry in studying improved methods of utilizing coal. In Germany the mineral rights were reserved by the State and ordered eatraction of coal was enforced. Each lease comprised a relatively extensive area. which accounts for the generally large size of the mines and mining companies In 1938 there were 160 mines in the Ruhr, with a total output of 125 million tons but 90 pet of the production was controlled by 20 companies. By far the largest single coal-mining company in Germany was the Gelsen-kirchener Bergwerke A. G., which produced nearly 27 million tons in the Ruhr in 1937. Second was Saargruben A. G. a State-owned company operating in the Saar, which produced 'lore than '3 million tons. Third was Bergwerksgesellschaft Hibernia A. G., with 10 million tons, also in the Ruhr. Briquettes are made from both bitumillous coal and brown coal, but in 1938 some 44 million toils of brown-coal bri-

Jan 1, 1947

By John I. Yellott

Since the days of Newcomen and Watt, when men first sought to turn the energy of fuels to useful purposes, coal-generated steam has supplied most of the power needed for both stationary and mobile applications. The low efficiency and large water requirements of the nineteenth century steam-power plant caused many engineers to turn their thoughts toward more direct means of converting heat into power. As far back as 1791, John Barber secured an English patent on a combination' which he might well have called a "gas turbine." He proposed to generate producer gas from coal or charcoal, to burn it under pressure in air obtained from a reciprocating compressor, and to drive a turbine wheel with the resultant hot combustion products. With the optimism characteristic of the inventor, he hoped that the turbine would not only operate his compressor but also perform useful work. There is no record that Barber ever built his machine, but if he had done so he would have learned that useful power can result from such a combination only when both turbine and compressor are highly efficient and when the temperature of the gas entering the turbine is not far below 1000°F. Hot-air prime movers continued to attract attention, and both Stirling in England and Ericsson in America2 built reciprocating engines that operated with some success upon coal-heated air. The internal-combustion engine, burning liquid fuels, supplanted the hot-air type, and, for the first time, challenged the supremacy of both the steam cycle and its familiar fuel, coal. Liquid Fuels Compete with Coal As the increasing use of the automobile multiplied the demand for gasoline, the supply of residual fuel increased rapidly, and heavy oil declined in price to the point where it became competitive with coal. First in the marine field and later in stationary plants in areas adjacent to refineries, oil began to be widely used. Oil's greater convenience and higher heating value per pound of weight or per cubic foot of bunker space have caused it to take over much of the marine field. The introduction of the highly efficient diesel engine, capable of burning a fuel that is cheaper than gasoline, again threatened the position of coal, for the operating costs of the diesel became directly competitive with those of coal-burning equipment. In isolated power plants and smaller marine installations, the diesel provided the medium by which oil again successfully invaded fields formerly dominated by coal. The diesel engine, provided with an electrical transmission, found an excellent application in railroad service. The high availability of diesel-electric locomotives, resulting in part from freedom from water

Jan 1, 1947

By E. C. Carris

The loading of bituminous coal mechanically was recognized about the year 1900, but during the following 28 years less than 5 per cent of the bituminous production in the United States was loaded by mechanical means. During the past 16 years, however, the usage of some form of mechanical loader has had a very rapid and accelerated growth, until at present production of bituminous coal by mechanical means has reached an all-time high of approximately 46 per cent, and is still increasing. This rapid growth in the use of the mechanical loader has been supplemented by an increase. in mechanical cleaning. The importance of mechanical cleaning of coal was recogniaed many years before the mechanical loader was introduced. because of the impossibility of cleaning manually the sizes below 2 in.. and the increasing competition from other fuels. Utilization of mechanical loaders without nleclianical cleaning 011 the surface for at least one or more sizes is the exception, rather than the rule. One exception is a mine that employs caterpillar-mounted mobile loaders exclusively, and mines the entire seam without any selectivity, and yet loads and ships six grades of coal of the very highest quality without mechanical cleaning. Such a fortunate situation can exist only where mining conditions are ideal, where top and bottom are exceptional and there are no impurity partings, and where there is loader height. The conversion from hand loading to mechanical loading has definitely introduced many problems in the preparation plant of yesterday and in the modern streamline plant as well. Many of these problenis have been solved by good, sound, conscientious initiative on the part of the plant personnel, with minor expenditures; the solution taking the pattern of rearranging 2nd improving the equipment at hand. Other problems have caused, and are causing, considerable concern and difficulty. Large Impurities The removal of large quantities of large impurities from the lump coal, and their handling and disposal, is definitely a troublesome and costly problem. The cost of manually removing the impurities from the picking table alone, based on the actual recovered lump coal, can reach a cost of 42 cents per ton or more. In the design of future plants it would be wise to give this phase of preparation considerably more time and thought, particularly if the seam of coal contains one or more heavy partings and the mining procedure is all seam. This same caution applies to seams that may not contain heavy partings but have poor and heavy draw-slate top, which falls with the coal during the mining cycle. One of the more recent of the modern preparation plants has answered this problem by installing a rock crusher under the picking table in such a manner that the impurities can be diverted by gravity directly to the crusher. This reduces the

Jan 1, 1947

By D. P. Morton

Since 1923, which closed the speculative era in the bituminous coal fields of the United States, there have been wide annual fluctuations in the national production of bituminous coal. These changes in annual output have been variously attributed to: (1) increased competition from petroleum products, natural gas and hydroelectric power; (2) lower unit consumption of coal; and (3) fluctuations in the general business level. The purpose of this paper is to measure, from a practical standpoint, the net effect upon the annual trend of bituminous coal production, and to give those who are interested a basis for estimating in advance the probable output of bituminous coal. It can readily be shown that changes in the level of general business affect the national production of bituminous coal more than does any other factor. Therefore it is necessary to use some standard measure of the relative business level for purposes of comparison. The Federal Reserve Board Index of Industrial Production offers the basis for such a measure.l This Index, a weighted composite of 81 different series, rests upon the averages of the years 1935 to 1939 as 100, and is presented graphically in Fig. I. Even a cursory examination of the chart will indicate a definite uptrend for industrial production over a period of years. This uptrend is due to at least two factors: (I) an actual increase in national population, and (2) a probable increase in the per capita consumption of goods. This means that there is no such thing as a fixed Normal, rather Normal is a variable, tending to increase from year to year. In order to measure the amount of annual increase in normal, the Index of Industrial Production must be studied in relation to its major components, Durable Goods and Nondurable Goods, Durable Goods are those made from the lasting materials such as iron, steel, other metals, lumber, stone, cement, clay, glass. Nondurable Goods are those for early consumption, such as foods, textiles, tobacco, chemicals, paper, gasoline, and goods made of leather and rubber. The purchase of Durable Goods may be postponed, but Nondurable Goods must be purchased currently unless the standard of living is lowered. The Federal Reserve Indexes of durable and nondurable goods are shown graphically, 1920 to 1939, on Fig. a (pp. 764-765 of ref. I). It is apparent that fluctuations in the production of nondurable goods are not nearly so wide as in the production of durable goods, and that the curve of Industrial Production (Fig. I) would fall between the two curves on Fig. 2. It would, however, seem logical that both curves should follow the same long-term trend, or that over a period of two to three decades the relative proportion of durable and nondurable goods, in periods of normal production, should be the same. It is neces-

Jan 1, 1942

By Donald B. Hunter

The Ti-Be system up lo 10 wt pct Be with cortlmercialll' pure titanium has been determined using metal-lographic techniques. Beryllium forms the p eutec-toid type of dinqarz with titanium; the eutectoid occurs at 0.5 xt pct Be azd 1500 F, while an eutectic is foritled at 1887°F containing between 5 and 7.5 rt pct Be. The solubility of beryllium in a titanium does not exceed 0.05 zvt pct and the maximum solubility of Beryllim in 0 titanium is 1 wt pet. PREVIOUS work on the Ti-Be phase diagram indicated that additions of beryllium to titanium resulted in a marked lowering of the melting point,''' and it was also observed that the solubility of beryllium in both a and p titanium was retricted.- With the limited data available, McQuillan and McQuillan constructed a partial hypothetical diagram of the Ti-Be system,= assuming that beryllium formed the 0 eutectoid type of system with titanium. Subsequently Bedford published a tentative diagram of the entire Ti-Be system: although he did not investigate alloys containing less than 10 wt pct Be. This diagram included several compounds described by other authorities.'-l3 The following account describes work directed toward determining the form of the titanium-rich portion of the phase diagram up to 10 wt pct Be. MATERIALS AND METHODS Titanium sponge and a master alloy containing 25 wt pct Be were used in the formulation of the alloys; the chemistry of these materials is detailed in Table I. The alloys were prepared as 250-g compacts which were melted into buttons by arc melting under purified argon on a water-cooled copper hearth. Results of analyses for beryllium are shown in Table I but no determination of other elements was made at this stage. The alloys were hot-rolled at 1650°F to produce 0.1-in.-thick sheet. Alloys containing up to 1.5 pct Be were fabricated without trouble; samples containing 2 pct cracked initially upon hot rolling, but thereafter rolled satisfactorily to sheet. The 5, 7.5, and 10 pct were hot short and could not be rolled. Surface contamination was removed from samples by sandblasting and pickling in a 5 pct HF-35 pct HNOs solution. For metal log raphic examination, heat-treated specimens were mounted transverse to the rolling direction, ground on silicon carbide papers of increasing fineness to 600 grit, and electropolished at 20 v using a solution containing 600 ml of methanol, 60 ml of perchloric acid, 360 ml of butyl cellosolve, and 2 ml of Solvent "X". Difficulty was experienced in obtaining good electropolished surfaces with samples containing more than 1 pct Be, the degree of difficulty in-

Jan 1, 1967

By H. L. Eiselstein, F. P. Huston, B. B. Betty

An extensive program for the establishment of creep data on high-nickel alloys has been in progress during the past seven years. This paper presents the accumulated data on two solid solution alloys, cold-drawn, annealed Monel and cold-drawn, annealed Inconel. Data on these two alloys in other conditions will be published at a later date. Monel, a nickel-copper alloy, is normally considered a corrosion-resistant material, but it will be shown that it also has considerable creep strength, validating its use at temperatures up to and including 900°F. Inconel, a nickel-chromium-iron alloy, is definitely a heat-resisting alloy possessing good creep strength and oxidation resistance up to iiooOF., and because of its oxidization resistance has been used successfully at much higher temperatures for lightly stressed parts. The literature contains but meager data on the creep properties of high-nickel alloys. Howevcr, Bennett and McAdam have presented a substantial quantity of creep data for cold-drawn Monel.1 The material as tested was not representative of mill production for it was cold-drawn to a reduction of area of 40 per cent as against 13 per cent, which is the mill standard for Monel. Twenty-two individual tests were run on each alloy in the investigation described in the following pages. The data and curves presented herein represent an integration of all the tests to obtain the most accurate picture of the creep properties of these alloys. Neither of the two alloys was found to be embrittled by the combination of temperature and stress, as evaluated by room-temperature tensile and impact tests that were made following creep testing. These data indicate that no tendency toward embrittlement exists. It is recommended that 6300 lb. per sq. in. be used as a working stress for cold-drawn, annealed Monel at 900°F. and 13,200 lb. per sq. in. for cold-drawn, annealed Inconel at the same temperature. Table 8 lists recommended working stresses, based on 80 per cent of the stress to produce a minimum creep rate of 0.01 per cent per 1000 hr., for Monel and some steels. Equipment The equipment used for these tests consists of Colville creep-testing machines manufactured by the Tinius Olsen Testing Machine Co. The load is adjusted, depending on the stress level, to give an error in the stress of not more than ± 0.1 per cent. This is based on considerations of lever sensitivity and the stress used for the standard (A.S.T.M. Tentative Standard E22-38T) 0.505-in. diameter creep specimen having a 2-in. gauge length. The single-specimen furnaces are provided with primary and secondary windings, from

Jan 1, 1945

By A. Madrazo

The Standing-Katz method for predicting liquid densities of reservoir fluids has been tested using experimental data of 154 bottom-hole or recombined reservoir fluid samples. New pressure- and temperature-correction curves for the Standing-Katz type correlation are presented which improve the accuracy of prediction. INTRODUCTION The present study was undertaken to investigate the known methods of determining liquid densities and to select one of them which might yield a better correlation if additional data were employed. An appropriate correlation would incorporate the following characteristics: (1) ease of handling in the computations, (2) results within engineering accuracy and (3) data easily accessible. After careful investigation of the different methods, the Standing-Katz correlation1 appeared to have these characteristics. The Standing-Katz correlation for liquid densities of hydrocarbon systems is based upon limited data. The original work, which employs apparent densities for methane and ethane, was based on data of 15 saturated crude oils in equilibrium with natural gas. Therefore, a test of the correlation using additional experimental data would serve either to validate the Standing-Katz correlation or to form a basis for corrections if such were necessary. PROCEDURE AND GRAPHICAL SOLUTION The data of 154 bottom-hole or recombined reservoir fluid samples were employed to calculate the densities at 14.7 psia and 60°F by the method described in Table 1. Volume contributions for methane and ethane were assigned from the pseudo liquid density plot (Fig. I), but volume contributions for N2, CO2 and HzS were not considered. The densities computed at reference conditions of 14.7 psia and 60°F were then elevated to their respective temperatures and pressures by the use of the correction curves proposed by Standing.' The percentage differences between the experimental values and the calculated values were determined; these samples were grouped into temperature, pressure and density ranges to determine a possible trend. It appeared that, at temperatures above 160°F, the calculated density values were consistently larger than the experimental density values; however, no obvious trend was found for the density and pressure ranges. There is a relationship between the pressure-correction and temperature-correction curves. This relationship, embodied in the temperature-correction curve, can be expressed as follows. The experimental densities of 125 samples above their bubble points were known. From these isothermal data, it was possible to determine an experimental-density difference between two pressures; and (from Fig. 2*), a calculated density difference between the same two pressures was determined. The relative effect of temperature must be considered in the calculated-density values. The effect of temperature can be determined by entering Fig. 3* at the two densities in consideration and obtaining the change in density at constant temperature. This change, or delta density, must be added

Discussions of the papers of DORSET A. LYON and SAMUEL S. ARENTZ, RICHARD D. DIVINE, H. A. WENTWORTH, and S. E. BRETHERTON, presented at the Salt Lake meeting August, 1914, and printed in Bulletins Nos. 91 and 92, July and August, 1914. GEORGE W. RITER, Salt Lake City, Utah.-We have every reason to believe that oil flotation Will soon come into general use as a final guard against slimes losses in concentrating mills, not only in the case of zinc ores, but also in the case of other semi-precious ores. It also promises much as a primary process for the concentration of minerals that are not adapted to gravity methods. Moreover, modifications of the process involving selective or preferential flotation are gradually becoming understood, and will make it possible to eliminate pyrite and other minerals occurring as undesirable impurities in zinc concentrates. And what perhaps is of equal importance, further modifications promise an effective method of separating zinc blende from ores that are chiefly valuable for copper, lead, anti precious metals, thereby making an asset out of zinc which has heretofore been a liability. The tendency of certain pulverized minerals to float on water, especially after having been in contact with grease, has been known to mill-men for a long time, and was formerly something to be deplored and to be striven against. All at once, this tendency has become a saving grace; and now, like tardy converts to a new faith, we are zealous advocates of something we once despised. I was once employed at a mine in the Tintic mining district of Utah¬the old Eureka Hill property-where ores that were too low in value to Warrant being sent to copper or lead smelters were treated in a combination mill. The ores contained gold, silver, lead, copper, zinc, manganese, arsenic, etc., in varying quantities and in varying mineral forms, mingled in a quartz and calcite gangue. The material was stamped fine and then concentrated on Frue vanners so as to make a smelting concentrate, after which the tailings were thickened and treated in amalgamating pans for the recovery of non-concentratable precious metals. In the amalgamating pans, under the influence of heat and agitation, a dark greasy froth or scum sometimes formed on the surface of the ore mixture. This froth or scum was composed mainly of mineral sulphides, and its occurrence might have meant only casual losses in the previous concentration, except that the phenomenon was accompanied by faulty amalgamation of the precious metals and by excessive losses in the mill tailings. Grease and oil, present by accident, were the cause of the trouble.

Jan 11, 1914

By M. T. Simnad, G. Derge, Ling Yang

STUDY of diffusion in molten substances is important in at least two respects. Diffusion data, combined with thermodynamic and kinetic information, throw light on the structure of the liquid state. Moreover, a knowledge of diffusion coefficients and their temperature dependence is useful in ascertaining the controlling step in many metallurgical reactions. Although diffusion measurements have been made on a number of molten salts, slags, metals, and alloys,'-'" the results available are still limited and widely scattered, especially for the high temperature melts. It is the purpose of this investigation to establish reliable procedures for the measurement of self-diffusion coefficients in high temperature melts and to use these procedures to determine the self-diffusion coefficients of iron in molten Fe-C alloys of different carbon contents. Experimental Measurement of self-diffusion coefficients in high temperature melts is usually carried out by using one of two methods. In the first, diffusion takes place between two cylindrical samples of the same material, one of which is made radioactive. The diffusion coefficient is calculated from the radioactivity penetration curve in the solidified sample after the diffusion. In the second method, samples contained in capillaries of an inert substance are immersed in an infinite reservoir of the same material. Either the material in the capillary or that in the reservoir is made radioactive and the diffusion coefficient is calculated from the change of the radioactivity of the sample in the capillary after the diffusion. The second method is simpler because a radioactivity penetration curve is not needed for the calculation of the diffusion coefficient; however,.it is valid only when no convection has occurred in the capillary during the diffusion. A radioactivity penetration curve is therefore always useful in indicating that the required conditions for the diffusion are ful- filled. Towers and Chipman" recently studied the self-diffusion of calcium and silicon in CaO-Al,O,-SiO, melts by using the capillary method. Instead of measuring the change of the radioactivity of the sample in the capillary, they autoradiographed the sample after the diffusion and calculated the diffusion coefficient from the intensity distribution of the autoradiograph. Their method is useful when the radioactive isotopes are weak ß-emitters, but is very difficult, if not impossible, to apply to cases involving strong ß or y-emitters. For such cases, sectioning of the sample according to the method of Morgan and Kitchener' may be used for the construction of the radioactivity penetration curve. The self-diffusion of iron in molten Fe-C alloys has been studied in this manner and the experimental procedures are described as follows: The diffusion apparatus is shown schematically in Fig. 1. The bath consisted of about 200 g of an Fe-C

Jan 1, 1957

By J. C. McCarthy, J. B. Stone

AT Fresnillo a series of veins that has yielded very large quantities of silver and other metals has been developed over a length of 6500 ft. and to a depth of over 3000 ft. In the course of this work striking changes in the mineralogy and metal content of the principal veins have been disclosed and are well illustrated by assay data and ore reserve calculations. This paper describes those changes and suggests their bearing on theories of ore deposition. LOCATION The Fresnillo mines and the adjacent city of Fresnillo are in the central part of the state of Zacatecas, 35 miles northwest of the capitol city of Zacatecas, once a great silver-mining center whose total production is said to place it fourth in the world. Another famous old silver district, Sombrerete, lies northwest of Fresnillo. Fresnillo is connected by a 5-mile branch with Fresnillo station on the Mexican National Railways line from Juarez to Mexico City. Lying near the southwestern edge of the central plateau of Mexico, Fresnillo ís surrounded by a semi-arid rolling plain from which rise widely scattered low hills. One of these is Proaño hill, an inconspicuous elevation rising barely 300 ft. above the plain, but in and around Proano hill are the Fresnillo mines, and it is marked now by a great gash cut by glory-hole mining. HISTORY According to an account written in 1834 by Francisco García, then Governor of the state of Zacatecas, Fresnillo was discovered in 1554, and a presidio was established there in 1568 to protect travelers on the road between Zacatecas and Sombrerete. Little is known of the earliest mining at Fresnillo, which seemingly began soon after its discovery, but by piecing together various accounts, it appears that mines there were working in 1717 and were notably active ín 1751 under an administrator named Murguía, who left detailed notes describing them. In 1757, however, the mines became inactive because of difficulties with creditors and no doubt also because of increasing water troubles, and they remained abandoned until 1830. In 1830 the mines at Fresníllo became the property of the State of Zacatecas because the interest of Governor García had been aroused by the long disregarded notes of Murguía. Under García's energetic leadership the mines were reopened, and silver production began in 1832 ín spite of serious difficulties, including abnormal rains and an epidemic of cholera. In 1835 English capital was sought to allow installation of steam-driven Cornish pumps at the two principal shafts and to build the great hacienda de beneficio (the present Proaño hacienda). The company formed in 11835 (Cia. Zacatecano Mexicana) operated successfully until 1872, when its career was brought to an end by the political and economic disturbances

Jan 1, 1942

By Jack A. Crichton, Henry J. Gruy

This paper discusses methods used in the estimation of natural gas reserves and the general conditions under which the various methods are applicable. The factors used in estimating natural gas reserves are reviewed. Errors which have been found to occur frequently are listed. Introduction The estimation of natural gas reserves has become of paramount interest because of the increasing importance of gas in the nation's economy. Gas is a most desirable fuel, a fact substantiated by the continued rise in the market demand. In addition, new uses for gas are being developed by the chemical, plastic, and associated industries, and plants are being built to make gasoline from natural gas. These are a few of the factors contributing to the importance of the nation's natural gas reserves. With the increased importance of gas there is an increase in the need for reliable estimates of the magnitude and availability of natural gas reserves. These estimates are being used currently: (I) to determine which fields contain sufficient available reserves to justify the construction of pipe-line outlets to serve particular markets; (2) to design pipe lines necessary to serve those fields adequately;] (3) to determine the location of industrial and chemical plants; (4) to finance the development of gas properties, and the construction of gas pipe lines; (5) to determine fair and adequate depletion allowances and depreciation rates; (6) to justify applications for gas pipe lines before various regulatory bodies; (7) to determine the number of wells required to exploit the reserves most economically; (8) to aid in establishing values for the purchase or sale of gas properties, and for purposes of inheritance taxes; (9) to determine equities under unitized operations; (10) to provide a basis for calculating the economics of gas-cycling operations. History or Estimation of Natural Gas Reserves The natural gas industry in the United States had its beginning during 1826 when natural gas was used for lighting the city of Fredonia, N. Y. The first natural gas pipe line was a 25-mi]le wooden line constructed from hollowed logs, connecting West Bloomfield and Rochester, N. Y. There is no record of an attempt to estimate the gas reserve at West Bloomfield but an attempt was made to determine the capacity of the well by measuring the time required to 611 a large balloon. One of the earlier publications concerning estimation of natural gas reserves is the "Manual for the Oil and Gas Industry," published by the Treasury Department, United States Internal Revenue, in i9i9. The following methods of computing "gas depletion" are listed: (I) production decline of the gas well or property; (2) decline in open-flow capacity; (3) comparison with the life history of similar wells or properties, particularly those exhausted Art

Jan 1, 1949

By H. l. Burghoff, C. H. Mathewson

The study of the creep of metals under conditions of prolonged loading has received the attention of many investigators for several years and almost innumerable papers have been published on the various aspects of the subject. As it appeared that much could still be learned from a study of single crystals, the present work was carried out to study the effects of temperature and conditions of loading upon the properties and deformation in tension of single crystals of alpha brass containing about 70 per cent copper and go per cent zinc. In particular, it was hoped to obtain information from tests below and above the recrys-tallization temperature of the material, so that properties such as elastic limit, yield point or critical stress, and manner of deformation might be compared for tensile tests at an ordinary loading rate and for prolonged loading. Accordingly, short-time tensile tests and creep tests were made at room temperature, 300°, 500° and 700°F. The two latter temperatures are above the lowest possible recrystallization temperature of polycrys-talline 70-30 brass. Previous Work Clarke and White1 have made creep tests of some copper-zinc alloys, including 70-30 brass, and copper-zinc-tin alloys at temperatures both below and above the recrystallization temperature of the materials considered. Hanson and Wheeler2 have studied the flow and fracture of single crystals of aluminum for short-time and prolonged tensile loading over a range of temperature extending from room temperature to 400°F., their experiments being made without consideration of the orientations of the test specimens. Extensive creep and fracture tests on single crystals of lead at room temperature have been made by Betty3 and by Baker, Betty and Moore." Results of the last-named investigation were published while the present work was in progress. Miller5 examined the elastic limit of zinc single crystals at and above room temperature by means of creep tests, while Miller and Milligan6 reported the results of tests designed to show the influence of temperature on elastic limit of single crystals of aluminum, silver and zinc. The behavior of iron crystals under static tensile loading at room temperature was reported by Gensamer and Meh17 while the present investigation was in progress. Their specimens exhibited a well-defined yield point, below which no appreciable creep could be detected. The manner of yielding proved interesting, as the shape of the creep-time curve for the iron crystals differed from the common type of crcep curves. Elongation did not begin immediately, or at least was initially very slow. The rate of elongation then increased continuously and finally decreased to zero. This S-shaped type of elongation-time

Jan 1, 1941

By Thomas Fraser, H. F. Yancey

Prior to the war just ended, Germany was the greatest coal producer in continental Europe. In 1943 the production of coal, bituminous and higher in rank, together with brown coal calculated to the equivalent amount of bituminous coal, is estimated to have been about 240 million metric tons, according to the War Department. Before the war production in Germany exceeded consumption. No other country in continental Europe except Poland had a large surplus. However, England's surplus was the largest in Europe as a whole. Before World War II the Ruhr Basin normally supplied about 70 pet of the total production of high-rank coal, the Saar and Aachen about 6 pet each, Upper Silesia about 14 pet, and Silesia and Saxony the remainder. Nearly one third of the brown coal was produced in the Rhineland, a little less than one half in central Germany nest of the Elbe River, and about one fourth east of the Elbe. Bituminous coal and brown coal together constituted by far the most important energy resources of the old German Reich. Bituminous coal furnished nearly 70 pet of the total energy requirement, brown coal supplied about 25 pet, and water power, wood, petroleum and alcohol together aggregated only 7 pet. Because it was the most important single mineral resource of Germany, an excess of coal enabled the Reich to import nearly all the other mineral products that she lacked, such as iron ore from Lorraine. The area adjacent to the coal fields was supplied with gas from an interconnected grid. Similar electric grids are based on brown coal with the power stations at the mines. Coal tar provided the foundation for the development of the extensive German chemical industries as exemplified by the I. G. Farbenindustrie. For almost a century, German scientists have been adequately supported both by the State and by industry in studying improved methods of utilizing coal. In Germany the mineral rights were reserved by the State and ordered eatraction of coal was enforced. Each lease comprised a relatively extensive area. which accounts for the generally large size of the mines and mining companies In 1938 there were 160 mines in the Ruhr, with a total output of 125 million tons but 90 pet of the production was controlled by 20 companies. By far the largest single coal-mining company in Germany was the Gelsen-kirchener Bergwerke A. G., which produced nearly 27 million tons in the Ruhr in 1937. Second was Saargruben A. G. a State-owned company operating in the Saar, which produced 'lore than '3 million tons. Third was Bergwerksgesellschaft Hibernia A. G., with 10 million tons, also in the Ruhr. Briquettes are made from both bitumillous coal and brown coal, but in 1938 some 44 million toils of brown-coal bri-

Jan 1, 1947

By J. J. Arps

This paper reviews the methods currently in use for estimating primary oil reserves and discusses the principles on which these methods are based. Particular emphasis is placed on how these methods change with the type of information available during the life cycle of an oil property. This paper contains various novel estimating methods and shortcuts heretofore unpublished. INTRODUCTION Estimating oil reserves is one of the most important phases of the work of a petroleum engineer since the solutions to the problems he deals with usually depend on a comparison of the estimated cost in terms of dollars, with the anticipated result in terms of barrels of oil. His recommendations to management regarding the best course of action are therefore normally based on the most favorable balance between these two. Specific engineering problems which require such a knowledge of recoverable oil reserves and a projection of future rates are: [a.] the exploitation and development of an oil reservoir; [b.] the construction of gasoline plants, pipelines and refineries; [c.] the division of ownership in unitized projects; [d.] the price to be paid in case of a sale or purchase of an oil property, and the magnitude of the loan which it will support; [e.] the proper depreciation rate for the investment in oil properties; and [f.] evaluation of the results of an exploration program. This discussion will be confined to the various methods and tools which are currently in use for estimating oil reserves to be obtained during the primary phase of an oil-producing reservoir and for a projection of the future production rates. Reserves which may be obtained by secondary recovery methods or fluid injection programs and gas and gas condensate reserves will not be discussed in this paper. Unfortunately, reliable oil reserve figures are most urgently needed during the early stages when only a minimum amount of information is available. Management's interest in the oil recovery from a property—aside from its use for accounting purposes—usually declines when the property approaches its economic limit, just at the time when the reliability of the estimates is at its best. To illustrate this general idea a chart is presented (Fig. 1) showing the three periods in the life of an imaginary oil property. Time is shown on the horizontal axis, while the cumulative production and estimated ultimate recovery are plotted vertically. No particular units are used and this schematical chart is not to scale. During the first period, before any wells are drilled on a property, any estimates will of necessity be of a very general nature, based on experience from similar pools or wells in the same area, and usually expressed in barrels per acre. This will

Jan 1, 1957

By John I. Yellott

Since the days of Newcomen and Watt, when men first sought to turn the energy of fuels to useful purposes, coal-generated steam has supplied most of the power needed for both stationary and mobile applications. The low efficiency and large water requirements of the nineteenth century steam-power plant caused many engineers to turn their thoughts toward more direct means of converting heat into power. As far back as 1791, John Barber secured an English patent on a combination' which he might well have called a "gas turbine." He proposed to generate producer gas from coal or charcoal, to burn it under pressure in air obtained from a reciprocating compressor, and to drive a turbine wheel with the resultant hot combustion products. With the optimism characteristic of the inventor, he hoped that the turbine would not only operate his compressor but also perform useful work. There is no record that Barber ever built his machine, but if he had done so he would have learned that useful power can result from such a combination only when both turbine and compressor are highly efficient and when the temperature of the gas entering the turbine is not far below 1000°F. Hot-air prime movers continued to attract attention, and both Stirling in England and Ericsson in America2 built reciprocating engines that operated with some success upon coal-heated air. The internal-combustion engine, burning liquid fuels, supplanted the hot-air type, and, for the first time, challenged the supremacy of both the steam cycle and its familiar fuel, coal. Liquid Fuels Compete with Coal As the increasing use of the automobile multiplied the demand for gasoline, the supply of residual fuel increased rapidly, and heavy oil declined in price to the point where it became competitive with coal. First in the marine field and later in stationary plants in areas adjacent to refineries, oil began to be widely used. Oil's greater convenience and higher heating value per pound of weight or per cubic foot of bunker space have caused it to take over much of the marine field. The introduction of the highly efficient diesel engine, capable of burning a fuel that is cheaper than gasoline, again threatened the position of coal, for the operating costs of the diesel became directly competitive with those of coal-burning equipment. In isolated power plants and smaller marine installations, the diesel provided the medium by which oil again successfully invaded fields formerly dominated by coal. The diesel engine, provided with an electrical transmission, found an excellent application in railroad service. The high availability of diesel-electric locomotives, resulting in part from freedom from water

Jan 1, 1947

By C. Burton Clark, J. Spotts McDowell

Refractories are defined as "materials having the ability to retain their physical shapes and chemical identities when subjected to high temperatures," or as "nonmetallic materials suitable for the construction or lining of furnaces operated at high temperatures." While resistance to "high" temperatures is thus the primary requirement for refractory materials, it is by no means the sole requirement. They must be able to withstand thermal shock resulting from rapid heating or cooling; other stresses induced by temperature change; pressures from the weights of furnace parts or contents; mechanical wear (abrasion) resulting from movement of furnace contents; and chemical attack by heated solids, liquids, or gases. Refractories of many kinds are needed for the many and widely diversified industrial applications. Those in greatest demand are classified on the basis of composition or properties into a few main groups, known as alumina-silica, silica, basic and insulating refractories. In each of these groups there are several classes. In addition to those included in the main groups, there are various special refractories, including silicon carbide, carbon, zircon, zirconia, alumina, and several others. Alumina-silica refractories comprise two main divisions: fire clay and high-alumina. The alumina content of fire-clay refractories covers the range from about 45 pct to 18 pct, and the silica content from 50 pct to 80 pct. The alumina content of fired high-alumina refractories ranges from about 99 pct to 45 pct, and the silica content from about 0.5 pct to 50 pct. Silica refractories of the different classes contain 94 pct to 97 pct silica. Basic refractories include periclase (magnesite), chrome spinel, forsterite, and dolomite. Refractory materials, including insulating firebrick, are supplied mainly as preformed shapes. Other products include bonding mortars and high temperature cements, ramming mixtures, plastic firebrick, hydraulic setting castables, dead-burned grain magnesite, and dead-burned dolomite. Refractory brick are classified on the basis of their physical form as Standard Sizes and Special Shapes. The Standard Sizes are brick of certain definite sizes and relatively simple design which are used in sufficient amounts to permit quantity production. The brick most widely used are the standard 9 in. X 4 ½ in. X 2 ½in. and 9 in. X 4½in. X 3 in. straights and corresponding series of sizes. All brick of nonstandard dimensions are regarded as "special shapes." They include a wide variety of brick regularly used for specific services, such as baffle tile for boilers, checker brick for regenerators, and others; together with shapes of special design manufactured on particular orders from designs submitted by the user. Not included in the broad classifications of Standard Sizes and Special Shapes are several specific-service refractory products, usually made by companies which specialize in their manufacture, or in some cases by the consumers themselves. These products include

Jan 1, 1960

By Donald W. Scott, Adam Wesner

This paper describes the study of 23 nonmagnetic iron-formation samples from the Mesabi Range and shows the significance of their chemical, mineral, and physical properties in terms of their concentration. Data presented here resulted from a research project carried out from 1942 to 1952 by 10 major producers of iron ore, working in conjunction with Battelle Memorial Institute. THE inevitable depletion of Mesabi direct-shipping iron ores, hastened by recent wars, has increased the importance of developing methods to concentrate iron-formation materials. Many mining companies, independent research organizations, chemical companies, and equipment manufacturers are devoting attention to this important work. It is only natural that magnetic iron-formation materials have received major emphasis, since magnetic recovery methods apply and reserves of Mesabi magnetic taconites are large. However, the nonmagnetic* iron-formation materials are likewise believed to represent a large reserve and their study has not been neglected. tions over the years have shown that in addition to the unenriched taconite, which is dense and hard, and the direct-shipping ore, there are transition taconites grading into the friable wash, or intermediate ores. The transition taconites are less massive than the unaltered taconites and usually coarser-grained. This variation, coupled with the fact that there were no extensive drillings in the unaltered taconite, posed a most difficult problem of obtaining samples that would be representative of large tonnages of the fresh rock. The problem was increased by the tremendous extension of the nonmagnetic formation materials on the Mesabi and by the question of their accessibility to mining. A drilling program was evolved that would surmount these difficulties. Selection of samples was made by a committee representing producers in the area. The samples were procured from 1—taconite walls near bodies of stripping burden or wash ore and 2—from shafts in the process of being sunk through taconite for drainage or mining operations. Most of the samples were obtained from the cherty horizons because it became obvious early in the program that the slaty horizons represented an exceedingly difficult concentration problem, owing to the character of the gangue minerals and the fine grind required for liberation of the valuable minerals. More samples were procured from the lower cherty horizon than from the upper cherty because it was more accessible to mining. It is not known how well the samples selected represent the nonmagnetic iron-formation material. However, they were chosen by people Well acquainted with the geology of the Mesabi range and the mining problems involved. It is believed that they represent a fair cross-section of the types of materials that will be encountered. Table I gives data on the origin of the 23 samples and the horizon footages from which they were obtained. Samples 1 through 10, and 15 and 16

Jan 1, 1955

By J. C. McCarthy, J. B. Stone

AT Fresnillo a series of veins that has yielded very large quantities of silver and other metals has been developed over a length of 6500 ft. and to a depth of over 3000 ft. In the course of this work striking changes in the mineralogy and metal content of the principal veins have been disclosed and are well illustrated by assay data and ore reserve calculations. This paper describes those changes and suggests their bearing on theories of ore deposition. LOCATION The Fresnillo mines and the adjacent city of Fresnillo are in the central part of the state of Zacatecas, 35 miles northwest of the capitol city of Zacatecas, once a great silver-mining center whose total production is said to place it fourth in the world. Another famous old silver district, Sombrerete, lies northwest of Fresnillo. Fresnillo is connected by a 5-mile branch with Fresnillo station on the Mexican National Railways line from Juarez to Mexico City. Lying near the southwestern edge of the central plateau of Mexico, Fresnillo is surrounded by a semi-arid rolling plain from which rise widely scattered low hills. One of these is Proano hill, an inconspicuous elevation rising barely 300 ft. above the plain, but in and around Proa[n]o hill are the Fresnillo mines, and it is marked now by a great gash cut by gloryhole mining. HISTORY According to an account written in 1834 by Francisco García, then Governor of the state of Zacatecas, Fresnillo was discovered in 1554, and a presidio was established there in 1568 to protect travelers on the road between Zacatecas and Sombrerete. Little is known of the earliest mining at Fresnillo. which seemingly began soon after its discovery, but by piecing together various accounts, it appears that mines there were working in 1717 and were notable active in 1751 under an administrator named Murguía, who left detailed notes describing them. In 1757, however, the mines became inactive because of difficulties with creditors and no doubt also because of increasing water troubles, and they remained abandoned until 1830. In 1830 the mines at Fresnillo became the property of the State of Zacatecas because the interest of Governor García had been aroused by the long disregarded notes of Murguía. Under Garcia's energetic leadership the mines were reopened, and silver production began in 1832 in spite of serious difficulties, including abnormal rains and an epidemic of cholera. In 1833 English capital was sought to allow installation of steam-driven Cornish pumps at the two principal shafts and to build the great hacienda de benefacio (the present Proano hacienda). The company formed in 1835 (Cia. Zacatecano-Mexicana) operated successfully until 1872, when its career was brought to an end by the political and economic disturbances

Jan 1, 1942