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By W. E. Rice

The ceramic industry has to do with forming or molding articles of clay, and imparting to them their characteristic properties of permanence, strength and color by subjecting them to heat treatment in kilns. This heat treatment is commonly known as "firing" or "burning." The art of firing clay ware antedates the industrial use of coal; hence wood was the fuel first used, and the earliest kilns were built to burn wood. The majority of the clay ware produced today is fired in periodic kilns that are essentially enlarged structures similar to the earliest enclosed kilns; a kiln consists of a large chamber 16 to 32 ft. dia. (or rectangular) in which the ware is charged and fired either in direct contact with flame or hot gases from the fuel, or in saggers which shield the ware from direct contact with the gases. The fuel is burned in a number of small furnaces built in the thick wall that encloses the chamber; these furnaces are from 16 to 36 in. wide and from 3 to 5 ft. long; some of them have horizontal or sloping grates, but many have no grates; the last are called "dead-bottom" furnaces. The temperature necessary to mature the charge in the kiln varies for different clays; for some it is as low as 1800°, and for others as high as 2700" F. Wood was an ideal fuel for the low temperatures that were used in early kilns; it burns freely and produces a long, clean flame, which promotes uniform distribution of the heat in the kiln; it does not coke and so restrict the passage of air through the fuel bed; the ash does not melt in the fuel bed to form clinker; and the ash that is carried into the chamber and deposited on the charge does not contain iron and sulfur to discolor the clay. The extent of the ceramic industry now precludes the general use of wood in kilns, so that today this industry is one of the large users of bituminous coal, burning more than eight million tons annually in kilns. Manufacturing plants usually are at or near the source of clay, with deposits of coal suitable for kilns occurring near the clay. The cost of coal is the largest single item of expense in the manufacture of clay ware, and, because all coals are not equally suitable for the process, the careful selection of coal is important. In this selection the desidera-

Jan 1, 1932

By J. E. Warren, J. H. Hartsock

Because of the extensive utilization of hydraulic fracturing for the stimulation of low-productivity wells, the two related problems of fracture design and evaluation have become economically significant and, as a consequence, helve motivated this investigation. The producing characteristics of horizontally fractured wells were studied to determine the fracture configuration that should be employed as the basis for the design of the treatment and to develop a method that can be used to establish the degree to which the design objectives have been achieved. The equations which describe the steady-state flow of a single-phase fluid into, and through. a finite-capacity fracture were solved numerically for an idealized reservoir-fracture model. The numerical results were used to obtain an apparent skin effect for each combination of the parameters considered. Based on the computed results, subject to the limitcitions implied by the assumptions that were made, the following general conclusions were drawn. 1. For a radius of drainage at least four times us large as the radius of the fracture, an apparent skin effect that is independent of the radius of drainage can be calculated. 2. The productivity of the hydraulically fractured system, relative to that of the unfructured well, can be determined from the apparent skin effect and can be used to establish design objectives. 3. In the evaluation of a fracture job, it is not Possible to determine both the radius of the fracture and its flow capacity uniquely from the apparent skin effect; an independent determination of one of the quantities is necessary. lNTRODUCTION Although hydraulic fracturing has been employed as a method for stimulating the productivity of literally hundreds of thousands of wells during the past 10 years, it is only in the last few years that improvements in fracture design1-6 and fracturing technique' have combined to increase the probability of obtaining a successful treatment to such an extent that the mechanics of the method may be considered to be standardized. From an economic point of view, however, two related questions must be satisfactorily answered before hydraulic fracturing can be used in the most profitable manner. The two questions are the following. I. For a particular well in a given formation, what are the optimum design specifications for the fracture treatment? 2. Have the design objectives been achieved by the fracture treatment? The significance of these questions has been recoguized, and some attempts to obtain answers have been made. Howard, et al,8 endeavored to determine the optimum treatment, based on maximizing profits, for any given formation; unfortunately, this work was based on a crude method for approximating the productivity of a well. Carter and Tracy9 utilized the same approximation to study the effect of fracturing on the behavior of a well producing by virtue of a solution-gas drive. Electrolytic models were used by van Poollen10 to investigate the variation in productivity due to fracturing; however, only a limited number of results were presented. Later, from the same model results, van Poollen, et al,11 attempted to justify an approximate expression for determining the productivity of a fractured well. It is quite apparent that there is a definite lack of the practical information necessary for specifying the optimum fracture configuration to be considered for design purposes. The only detailed attempt to develop a procedure for evaluating the result of a given fracture treatment appears to be that of van Dam and Horner.12 These authors described a technique for analyzing pressure build-down data, obtained immediately after fracturing, to determine the final fracture volume, the final fracture porosity, the fracture area, the fracture thickness and the in situ fluid loss of the fracturing fluid. While this approach should be useful whenever acceptable pressure measurements are available, it does not yield a value for the flow capacity of the fracture. Since the problems of fracture design and evaluation are inversely related, it should be sufficient to study the effect of the fracture configuration on the performance of a well. The primary objective of this investigation is to evolve a technique for computing the desired solutions. The secondary objective is to analyze these computed results in order to prescribe a method for evaluating fracture treatments. Because this study is exploratory in nature, its scope

By Benjamin Smith Lyman

There seems to be dire need of repeated preachment against the too-frequent sad neglect of instrumental surveying and mapping in geological surveys. The value of the map as an illustration of the statements and opinions of a report is too apt to be overlooked; and its essential necessity in working out during its construction the proper conclusions from the observed facts is generally altogether misunderstood. Practical geology seeks, of course, to ascertain and indicate the character of workable or unworkable beds or veins, their depth, position, dip, and horizontal course, or strike, even below the surface; also their outcrops, and therefore, if workable, their extent; and so, taking account of their thickness and specific gravity, their weight in tons. It might, therefore, be called quantitative geology. For the study of more abstruse geological questions, too, it is in many cases necessary to gain some knowledge, or reasonable opinion, in regard to such hidden facts. In some cases, careful instrumental surveys are made; in others, from necessity or choice, there are few or no instrumental observations. It was said, 15 or 20 years ago, that there was an engineer in the anthracite-regions who was capable of telling, on first glancing at a new place, exactly what coal-bed was to be found there at a certain depth, and how thick—a splendid second-sight! "' 0, there be,' " you may be tempted to exclaim, " geologists ' that I have seen' geologize ' and heard others praise, and that highly, not to speak it profanely, "'—but let them pass without being fully characterized, lest the temptation towards profanity be altogether too strong. Yet such second-sight does not exceed the expectations of many men of imperfect geological knowledge, men who have heard of marvel-ously successful geological predictions, but are unaware of

Jan 1, 1910

INTRODUCTION Great emphasis has been given throughout this text to the necessity of maintaining the integrity of mineralogical populations when operating upon sample data drawn from mixed populations. Mineral deposits rarely are completely homogeneous and often consist of many subsets separated by geological and mineralogical boundaries. Sometimes different mineral populations are difficult to distinguish, and may be inadvertently lumped together-often without serious consequences, but more often with detrimental effects upon analytical results. The geologist must accept the responsibility for recognizing and recording mineral boundaries that may include: changes in mineral suites, lithological horizons, host rock types, faulted and offset segments, zones of enrichment or depletion, and several other geological and mineralogical changes that effect mineralogical structuring and distribution within a deposit. When employing conventional methods for assigning estimated values to irregularly shaped mineral inventory blocks, it was only necessary for the geologist or engineer to con- fine the block limits to the known geologic boundaries. Thus if a fault interrupted the mineral zone, the trace of the fault could be used as a block boundary. Intelligent decisions could always be made as to which blocks to include in each mineral population. However, with the advent of the computer, which per- mits the computation of mineral inventory blocks using better mathematical estimation techniques, there now enters the "boundary problem." Unless the computer can be programmed to recognize population differences and geologic boundaries, greater estimation errors will be found in computer-generated mineral reserves rather than in less sophisticated conventional inventories. Much disillusionment has been expressed over the years by experienced mineral appraisers as a result of their study of computer-generated inventories that failed to account adequately for geologic vagaries. Many, thus disillusioned, have concluded that computer techniques are not satisfactory, or have only limited applications to simple deposits. As with all problems in the mineral industry,

Jan 1, 1980

By Newell G. Alford

With the workable area of coal prospected and known as to workability and quantity and sampled and tested for desired quality comes the determination of the projection and method of working. The best method will be the one supplying the greatest degree of safety, the most merchantable product, the minimum average cost per ton with the largest yield of recoverable coal. Based on coal elevations, taken at the bottom of the seam on all known outcrop exposures, prospect openings or drill holes, coal contours are made on the map to be used in developing the mining plan. The contour interval should be as close as available information will permit. For general utility in layout of mining, haulage, drainage and ventilation, a map scale of 400 ft. per in. is preferable. In mountainous sections, location of the main out- crop opening or hoisting shaft is often limited by the available railroad route and amount of land level enough for a plant site. In level country, where a tipple and hoisting shaft may be placed at will, choice of the plant site should depend on the minimum average underground haul for the total coal to be worked to the new

Jan 1, 1932

By V. S. Swaminathan

This year, Great Britain is looking back over a century to August 14, 1850, the day when the first "Act for the Inspection of Coal Mines" was passed in that country, an act which signaled the end of over two hundred years of hitherto uncontrolled and dangerous mining practices.

Jan 11, 1950

History of Production, of Salt Creek Oil Field, Wyoming Discussion of the paper of EDWARD L. ESTASROOK and CLARENCE M. RADER, presented at the Casper Meeting of the Petroleum Division and issued, as Paper No. 1503-G, with MINING AND METALLURGY, September, 1925. C. E. REISTLE, Laramie, Wyo.-The application of water analysis to petroleum engineering problems is successful in many cases, particularly if the water in the sands is of uniform chemical constituency and if each sand water varies definitely from the others in its chemical properties. At Salt Creek, the sand waters are not of uniform chemical character, and the waters in the various sands do not differ greatly; so a water from one sand might easily be classified as a water from some other sand. The water from the Shannon sand contains sulfates; this alone makes it possible to differentiate between the Shannon and the First and Second Wall Creek and Lakota sands. However, it is not so easy to differentiate between water of the First and Second Wall Creek sands. As a rule, the Second Wall Creek sand contains a higher concentration of mineral matter, but in Table 19, sample 2; of the First Wall Creek sand and sample 7 of the Second Wall Creek sand have approximately the same amount of total solids. As a rule, the chlorides are higher in the Second sand waters than in the First sand; but, the chlorides in sample 6 of the Second sand show practically the same amount as sample 3 of the First sand. The use of reaction properties does not. solve this trouble, as they generalize the conditions even more. For instance, the reaction properties of sample 3 of the First sand are almost identical with the reaction properties of sample 6, of the Second sand. The authors suggest that the chemical characteristics of the water in a sand are not uniform because of the concentration of the water by underground evaporation. In that case should not the ratio of the various chemical constituents remain the same? Gas does remove some mineral matter, as evidenced by deposits in the gas lines and packing in the absorbers of the natural gasoline plants, but why does the gas act selectively, removing one salt and not all of the salts in the ratio that they occur?

Jan 12, 1925

By K. S. Benson

DEPLETION is a subject of vital importance to the mining industry. Yet, in spite of its importance, its significance is not generally understood. The purpose of this discussion is to clarify the main aspects of the subject from the viewpoint of a metal mine taxpayer.

Jan 7, 1951

By Bernard Greifer, Walter Rose

The purpose of this note is to call attention to a source of difficulty which can be responsible for inaccurate estimates of wetting liquid pressure gradients in mixture flow experiments of the Hassler1 type. It has been our experience occasionally to observe what were indicated to be negative pressure gradients, and these were regarded as anomalous in the sense that physically they seemed to contradict the requirement that the flux be in the direction of the potential field. At first it was thought that our scheme of assembling barriers and core sample led to such asymmetry in the distribution of isobars that the manometric leads at each end of the core were responding to internal pressures (within the core sample) which could be either positive or negative with respect to each other, and which in fact might tend to reflect on different effective core lengths in an unpredictable fashion as the wetting liquid saturation was changed. However, no compelling evidence of this possibility has been established. In addition, we were cognizant of the requirements to be satisfied in selecting manometric instrumentation to minimize the delay in response of the manometer to the differential pressures being measured, and were thus assured that our observations of anomalous pressure gradients could not be explained by faulty instrumentation. What we suggest is that if a leak sink occurs in the fluid lines connecting the core to either side of the differential manometer, errors exceeding 100 per cent may result in the estimation of wetting liquid pressure gradient, even though the leak is of such small magnitude that its existence would tend to be obscured by evaporation effects. This is because in a system with leaks at the specified places, the manometer rec- ords at steady state the pressure drop across the manometer barrier elements in addition to the pressure drop across the core sample. This possibility will be illustrated below analytically and by numerical example for the special case where the leak occurs on the high presure side of the core, since we are especially desirous to explain the significance of our observations of the so-called negative pressure gradients. It will be indicated, however, that leak sinks on the low pressure side of the core can account for observations of anomalously high values of pressure gradient, and that multiple leaks on both sides of the core can provide for some compensation so that the errors in pressure estimation are reduced. However, the major point to be emphasized is the fact that the impractical-ity of detecting the small leak sinks which give rise to the difficulties makes it a complicated task for the experimenter in a particular case to know with certainty that his estimation of pressure gradient lies within the limits of error which can be tolerated. Fig. 1 shows the electrical analog of the flow system we have employed in our studies. The inflow and outflow barriers. Rbl and Rb2, the manometer barriers, Rm1, and Rm2, and the core sample, Rc— for a particular fluid saturation and distribution— are all designated as resistance elements; the flowmeter is designated by an ammeter, A; the pressure source is designated by E; and the manometric device is designated by the voltmeter, V. Included in the circuit are the variable resistances, Rx and Ry, which may be regarded as the leak sinks, and which, in general, can vary in magnitude from zero (i.e., a large hole or shunt in the system) to infinity (i.e., no

Jan 1, 1950

Jan 1, 1906

By M. H. Harrington

The Transaclions of the Institute afford abundant evidence of the general recognition by mining engineers of the importance of a safety-lamp which will not only give warning of the presence of fire-damp, but will also indicate the proportion in which it is present.' Mining-men are only too familiar with the frequent and sudden changes that habitually occur at the working-face of a gaseous mine. Nothing illustrates more forcibly the pregnant condition of the strata enfolding the seam and the seam itself, than the fact that a circulation of perhaps 150,000 cu. ft. of air

Jan 1, 1907

By H. W. McCue

In 1944, in the Texas Panhandle, 245 oil wells were drilled with a total daily initial production of 32,886 bbl., representing an average initial production of 134 bbl, per well. This was an increase over 1943 of 121 wells drilled, and an increased initial production of 13,861 barrels. On Dec. 31, 1944, the field was operating on an allowable of 113,567 bbl. per day, but actually was producing 85,539 bbl. per day from the 5901 oil wells. The tota1 production for the year was 33,439,436 bbl., bringing the cumulative total to 5.04,537,048 barrels. Gas Sixty-three gas wells with a combined open flow of 992 million cu. ft., were drilled during 1944. This was an increase of seven wells over 1943, but a drop of 216 million cu. ft. in initial open flow. The

Jan 1, 1945

By W. A. Hoyer

A pulsed high-energy neturon-induced spectral logging tool has been built and field-tested. The reaction of deuterium on tritium is used to generate pulses of 14-Mev neutrons. By detecting only the prompt gamma rays produced by neutron inelastic reactions in the formation, the presence and relative abundance of carbon, oxygen, calcium, silicon and other important elements may be ascertained from a gamma-ray spectrum. Gamma-ray spectra obtained in a shallow test well and in experimental field use show that it is possible to identify formations and their contained fluids. INTRODUCTION The penetrating gamma rays from naturally occurring radioactive elements in subsurface formations have been used for a number of years in well logging as a means of characterizing and distinguishing strata. Still another nuclear logging method which has been employed for some years consists of the bombardment of strata with neutrons and the measurement of the number of gamma rays produced by neutron capture reactions involving elements in subsurface strata.' Since one of the principal elements entering into capture reactions is hydrogen, the latter procedure essentially results in a hydrogen log, whether the hydrogen be in combined form in either oil or water; thus, the log gives an indirect measure of porosity. These methods, with various refinements, have been developed to such an extent that they have become routine procedures in formation evaluation. Neither gamma-ray logging nor conventional neutron logging, however, yields sufficient information to permit unequivocal identification of the mineralogic composition of formations, and neither method gives information which may be used for the positive identification of hydrocarbons in strata. Accordingly, a number of efforts have been made in recent years to gain additional information from nuclear logs. Brannon and Osoba have shown that it is possible to identify naturally occurring radioactive elements in subsurface formations by spectral analysis of gamma rays emanating from these elements. Such an identification is of value in the characterization of strata. A simplified form of spectral analysis of gamma radiation resulting from neutron capture reactions between elements in earth materials and bombarding neutrons has been used with some suc- cess under favorable conditions to differentiate between petroleum and water. This method relies upon the relatively high energy of gamma radiation from neutron capture by chlorine and, in effect, furnishes a chlorine log. In areas in which interstitial water is of sufficiently high salinity, this log can give valuable information on water saturation and, thus, indirectly on hydrocarbon saturation. Still another approach to obtaining more information by nuclear techniques is "activation logging", in which certain elements yield short-lived radioactive isotopes on neutron activation and, thus, can be detected by gamma-ray spectral analysis. From the standpoint of determining by nuclear logging methods the mineralogic composition of strata and the presence or absence of hydrocarbons, it is essential that information be obtained on the presence and relative amounts of several elements such as carbon, oxygen, hydrogen, calcium, silica and others. Some elements, such as hydrogen, chlorine and sulfur, can be determined by spectral analysis of gamma radiation resulting from neutron capture reactions."" Others — carbon and oxygen, for example — do not enter readily into capture reactions but do yield gamma rays of characteristic energies from inelastic scattering reactions with high-energy neutrons. Accordingly, the latter reactions are of particular interest as a means of identifying hydrocarbons in subsurface strata. Several years ago it was recognized that information requisite to the identification of subsurface strata and of contained fluids could be obtained by pulsed operation of a subsurface neutron generator and associated gamma-ray detector. It was contemplated that pulsed operation would be effective in discriminating in time that gamma radiation which results predominantly from inelastic scattering reactions from that gamma radiation arising from neutron capture reactions. Accordingly, research was continued and construction of such a device was initiated. Although many problems were encountered, they were solved successfully. The following sections describe the tool which has evolved, its performance and the results which have been obtained with it to date. THEORY OF OPERATION OF NEUTRON-INDUCED GAMMA-RAY SPECTRAL LOGGING TOOL THEORY OF INDUCED NUCLEAR REACTIONS Of fundamental importance is the fact that an element, when bombarded with neutrons, emits gamma radiation of energy characteristic of that element. In theory, therefore, an element may be identified by

Jan 1, 1913

By A. U. Seybolt, F. J. Norton

A standard technique for heat treating small metallurgical samples where no appreciable contamination from the atmosphere can be tolerated is that of sealing small samples in evacuated fused-silica tubes. Since vitreous silica is relatively impervious to diffusion of gases, even at temperatures approaching the devitrification range, around 1100°C, this simple procedure has been very widely adopted as a standard technique in metallurgical research. Many workers have recognized that, with metals of fairly high reactivity, insulation from direct contact with the SiOz envelope is desirable in order to avoid displacement reactions of the type M + SOz-- MOz + Si(in M). It is not so generally known, however, that the 'rate of permeation of oxygen from the air through the SiOz enclosure at tem-

Jan 1, 1964

Jan 1, 1902

By William C. Cooley

INTRODUCTION Considerable research has been conducted on the use of steady and pulsed jets of water at high pressures to produce slots or holes in rock, and to fracture rock. The primary objectives of prior research have generally been to determine the feasibility of excavating or drilling rock or minerals and to determine the optimum jet parameters for this purpose. The present study was undertaken in order to identify the pertinent dimensionless parameters involving jet and rock properties which characterize the liquid jet penetration process and to develop empirical correlations of the existing test data which would permit engineering prediction by means of scaling relationships. The present paper is in the nature of a progress report, because not all the existing test data have been processed. Also effort has been concentrated on correlation of data on the specific energy (jet kinetic energy per unit volume of rock removed or broken), rather than correlation of jet penetration depth, hole diameter, kerf depth or kerf width. However, it is clear that this method of correlating data on specific energy in terms of dimensionless parameters shows great promise and provides insight into the nature of the physical processes of jet erosion and fracture. It therefore can help to avoid drawing incorrect conclusions from limited experimental data. DIMENSIONAL ANALYSIS The method of dimensional analysis is particularly valuable where the mathematical relationships controlling a physical process are unknown or complex. The grouping

Jan 1, 1971

By Dan McLachlan

EXPERIMENTS on ionic solids,1 Cu-A1 alloys,2 and Fe-Si alloys3 have suggested that the ability of dislocations to cross-slip is one of the most important factors governing the nucleation and growth of fatigue cracks. These experiments necessarily had to be made on materials of different composition in order to vary the propensity for cross slip. However, re-

Jan 1, 1967

By John Hillman

Reconstruction of the British mining industry began shortly after nationalization in 1947 and continued until well into the 1950s with the support of the government. This support diminished as plentiful supplies of cheap oil from the Middle East made many coal mines uneconomic. The planned rundown which followed was foreshadowed in the 1965 White Paper which outlined financial measures to speed the closure of uneconomic collieries. The decline appeared likely to continue into the 21st century as the role of coal in UK energy requirements became less and less significant. This policy was well on course in 1973 when the oil crisis led to a complete reappraisal of the position. A government examination in 1974 of the coal industry then supported the National Coal Board's general strategy of major capital investment as set out in its 'Plan for Coal'. The plan was aimed at halting the intended decline in the industry's capacity and restoring it to 120 million tons of deep mined output in 1985. The plan proposed action along the following lines: Increase output by major investment in construction at existing collieries with sufficient reserves to give 13 million tons per annum extra output.

Jan 1, 1980

By W. L. Staker

The Bureau of Mines investigated selective extraction of Au and Ag from a low-grade Au ore containing Hg. Gold and silver were extracted from the ore in cyanide slurries, and Hg extraction was suppressed with sodium or calcium sulfide. Maximum Au extraction and minimum Hg extraction were obtained using solutions containing 0.34 lb NaCN/ton of solution. Increasing the cyanide concentration increased Hg extraction without increasing Au extraction. Mercury extraction from the ore was suppressed with 0.5 to 2.9 lb CaS/lb Hg in the ore. Gold-to-mercury ratios of 100:l to 400:l were obtained in the leach solution, and on the activated carbon in a CIP circuit.

Jan 1, 1984