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By Lewis Smith

CHROMIUM is one of the new metals, but considerable research has been required to determine an approximate record of its production from 1827 until the present. Its use in the form of pure metal is not extensive; of the chromite mined, about one-half is required for making ferrochromium, about two-fifths goes directly into refractories and the remainder is absorbed chiefly by the chemical trades. The industries that demand chromite for such uses are mainly in countries that produce little chromite, while the important chromite-producing countries are not generally consumers. The international flow of chromite is therefore of interest, as yell as the political and commercial control of resources of the metal.

Jan 1, 1931

By Stuart E. Buckley

The application of hydrocarbon equilibrium data to various problems encountered in refining and in natural gasoline recovery is an old and well established practice. Both generalized data and data on specific hydrocarbon systems have been made available by a number of investigators. More recently such data have been applied to the relations governing the separation of oil and gas both in the reservoir and at the surface. Most of the applications to production problems, however, have been based upon examinations of surface samples of oil and gas. This paper describes a technique that has been used satisfactorily in a number of cases to calculate directly from the hydrocarbon analysis of and auxiliary laboratory data on a subsurface sample of the reservoir fluid the behavior of the oil and gas during the various stages of separation at the surface incident to production. Types of Information Calculated The system of calculations is not designed to supplant field data, but rather to correlate with them laboratory data obtained under controlled conditions in order to obtain a more complete and exact picture than usually is possible through the use of field data alone. The chief advantage of the calculations is the possibility of their use at a minimum of both time and expense to determine completely the effect of any possible operating technique upon each of the following: (1) The gas-oil ratio resulting from liberation of the dissolved gas; (2) the composition and gasoline content of the liberated gas; (3) the composition and gravity of the residual oil; (4) the amount and composition of the gas liberated upon flashing the oil from the separator to the stock tank; (5) the shrinkage of the oil in passing from the reservoir to the stock tank. This information is frequently essential to the correct determination of the advisability of installing a natural gasoline plant, to design such a plant to take care of seasonal production, and to determine the optimum separator pressures to carry in various parts of a field.

Jan 1, 1938

By A. G. Weber, H. J. Welge

A published calculation method for predicting incompressible, multidimensional fluid displacement has been adapted to the problems of water and gas coning in oil wells. Since depth and radial distance from the wellbore are the two key dimensions affecting the shape of a gas or water cone, coning calculations are well suited to the use of two-dimensional methods. The alternating direction implicit procedure (ADIP) was used for relaxation calculations of two-phase potentials in a two-dimensional grid. From the potentials and the capillary pressure relationship, saturation and pressure distributions were calculated which trace cone growth with time. Predictions have been made for well producing histories both before and after core breakthrough. To check validity of the method, two-dimensional calculations have matched the coning behavior and produced water-oil ratio history of a laboratory sand-packed model. They have also matched the coning behavior of several producing wells, for which the calculations were compared with produced water or gas cuts and logs showing water or gas cone movements. INTRODUCTION The application of two-phase, two-dimensional calculations using ADIP to various reservoir flow problems has been described in the literature.1-3 When adapted for computer solution, this method has proved to be a powerful tool for simulating well and reservoir behavior. This paper discusses the method as applied to well coning calculations. Single-well and coning calculations comprise an especially difficult class of two-dimensional problems which require special techniques for computer calculation and determination of reservoir characteristics. Refs. 4 through 8 describe previous approaches to the coning problem. Several examples of water and gas coning calculations, including studies on both laboratory models and producing wells, are presented here. The two-dimensional method accounts realistically for the most critical parameters affecting coning behavior, including production rate, formation stratification, horizontal and vertical permeabilities, depth of well penetration, gravity and capillary forces. The method considers the different densities and viscosities of the two phases and the relative permeability and capillary pressure characteristics of the rock and fluids. In addition to tracing cone growth in the vicinity of the wellbore, the method calculates the overall movement of the fluid interface throughout the well's drainage volume. Incompressible fluid flow is assumed to occur between the producing interval and the well's limit of drainage. Calculations can be made for the producing history both before and after cone breakthrough. A typical two-dimensional grid or array of blocks used to solve a coning problem contains about 400 blocks. The well's cylindrical drainage volume can be represented by about 20 radial subdivisions and the formation thickness by 20 vertical subdivisions. The grid spacing is normally smaller near the withdrawal interval to define the cone shape accurately. For this work we used an IBM 7074 digital computer having a core memory of 10,000 ten-digit words. A typical study, covering 5 to 10 years of well producing history, required from three to six hours of computing time. MATHEMATICAL SIMULATION OF CONING BEHAVIOR BASIC METHOD In coning calculations, the reservoir volume drained by the producing well is represented by a two-dimensional system of blocks as shown in Fig. 1 for water coning studies. The horizontal dimensions of the blocks increase with radial distance from the well axis in geometric progression, i.e., the block size is small near the wellbore and large near the well's drainage radius (re). Vertically, the blocks are bounded by horizontal planes located at different depths through the

Jan 1, 1965

By R. L. Moment

The anisotropic elastic behavior of rolled beryllium sheet has been measured, using a pulse echo technique, and compared with X-ray diffraction data. Calculated elastic stiffness constants compared favorably with published values for beryllium single crystals which were attributed to the strong (0002) rolling plane texture. Variations of Young's modulus in the yolling plane could be associated with the velative distribution of (0002) planes out of their ideal position in the rollitzg pkule. WHEN a metal is subjected to cold working such as drawing, forming, or rolling, a crystallographic texture develops which can significantly alter its physical properties. One method for detecting this texture is X-ray diffraction, but Alers and Liu' have recently pointed out how the prediction of anisotropic physical properties from pole figures alone is not always accurate due to differences in interpretation. Variations in Young's modulus with orientation or, more completely, the values of the effective elastic constants of the worked metal, also serve to indicate the presence of a texture. In fact, as Alers and Liu' pointed out, calculated variations in Young's modulus for assumed orientations, when compared with experimental data, can be used to eliminate some of the uncertainty in interpretation of X-ray pole figures. Thus, elasticity measurements can serve not only to clarify any unusual elastic behavior of worked metal, but also to detect and in part determine the nature of its texture. X-ray determination of the texture of rolled beryllium has been reported by Smigelskas and Barrett,2 who found a strong texture of (0002) in the rolling plane with (1070) planes normal to the rolling direction. In the case of metal rolled at room temperature, they reported that [1010] directions also appeared at positions 60 and 120 deg from the rolling direction in the rolling plane, while in more recent work Keeler3 found these directions were also tilted towards the rolling plane. The texture for beryllium rolled at 80O0C, however, only showed (1010) planes normal to the rolling direction and the spread of (0002) planes out of the rolling plane was less. In looking for elastic anisotropy one might consider unidirectional rolling of a metal as introducing an or-thorhombic symmetry through reorientation of the grains, since the three deformations, compression, extension in the rolling direction, and extension in the cross direction, are orthogonal to each other and unequal in magnitude. Thus the rolled sheet could be treated like an orthorhombic single crystal and the nine stiffness constants of the elasticity tensor used to calculate the anisotropy of Young's modulus, the shear modulus and Poisson's ratio. In this case we could write: which is symmetric about its diagonal. Borik and Alers4 have recently used this approach on rolled die steel with very good results. They found, however, that instead of displaying orthorhombic elastic symmetry their specimens could be considered tetragonal in which case Cr1 = c22, c13 = Ca, and c44 =cjj. This conclusion was made solely on the basis of the measured tensor elements, and serves to point out the advantage of this method for studying the anisotropy of rolled metals. Their calculated values for Young's modulus as a function of angle in the rolling plane also checked very well with direct measurements made on different specimens using the resonance technique. In the present study, cross-rolled beryllium was used which had been unidirectionally rolled about 11 pct for the final reduction. This imparted a slight anisotropy in the rolling plane which was detected both by X-ray techniques and elasticity measurements. For purposes of discussion in this paper, the rolling direction is that direction in which the most reduction passes were made and cross direction is the normal to the rolling direction in the rolling plane. It was also decided to consider the rolled sheet as displaying orthorhombic symmetry for the purpose of obtaining elasticity samples with the direction defined as in Table I. Any change in the final symmetry attributed to the sheet would then be made on the basis of the measured elastic stiffnesses. The final data would then be compared with that expected from the X-ray study and that reported for beryllium single crystals. EXPERIMENTAL PROCEDURE Rolling Schedule. The samples used in this study were taken from a large sheet which, because of its size, had to be unidirectionally rolled for the final reduction. The resulting texture was that of cross-rolled metal with a slight unidirectional texture superimposed. A cast beryllium ingot, 9.500 in. sq by 3.325 in. thick, was cross-rolled to 81 pct reduction followed by unidirectional rolling for an additional 11 pct to give a total reduction of 92 pct. The thickness of the final sheet ranged from 0.265 to 0.280 in. Reduction up to 67 pct was done at 980°C and the final 25 pct at 870°C. Analysis for metallic impurities showed aluminum 0.06 pct, iron 0.19 pct, and silicon 0.11 pct, giving a beryllium purity of 99.64 pct.

Jan 1, 1968

By Peter Nalle

12.3-1. Reporting. NEED. It seems almost unnecessary to comment on the need for reporting research and development results and activities, and yet much of the difficulty and misunderstanding surrounding a Research and Development (R&D) group results from poor or nonexistent reporting. Certainly no evaluation can be made without reports of results or plans. It is as important to report accurately and fully for the department's own use as it is for external use. Research unreported might as well be considered research undone. This section will discuss, in part, the need for reporting, the general types of reports which may be generated to satisfy the need, and finally, the evaluation of a project as judged by various commonly used standards. PURPOSE. Some specific observations might be appropriate concerning the reporting of R&D results. The requirements and background of the group receiving the report must be considered. A particular report is usually directed towards the background of a particular group, such as ((technical," "operational," "financial," or "marketing." It is essential that the emphasis and coverage be geared to the training of people receiving the report. It should be obvious that the financial department will be less interested in the technical details of the process and more interested in the capital funds and tax implications involved in the project. Operating personnel will be greatly interested in the effects of a new method on mining plans, and so on. This does not mean that the reporting in any way should slight pertinent details, nor should a patronizing attitude be assumed by the writer. However, it is essential that the needs of the reader be recognized. For reports that might have large and varied distribution, it is often feasible to group, either as sections or appendixes, the special details and information of interest only to certain functions within the organization. A

Jan 1, 1968

By F. J. Tuck

THE Hayden mill of the Ray Mines Division, Kennecott Copper Corporation, is now equipped with two 9 by 12-ft. rod mills having a daily capacity of 6000 tons of coarse-crushing plant product from the mine. These two mills crush a 3/4-in. product to approximately 19 per cent on 14 mesh, with only one pass through the mills. Each rod mill has taken the place of four sets of 42-in. Garfield rolls with their attendant screens, and is making a product for the fine-grinding department comparable to that formerly made by rolls in closed circuit with screens. The rod mills are lined with wave-type liners of white iron, varying in thickness from 2 to 3 in. The shell and end liners last approximately 600 to 700 clays. Manganese-steel lifter bars, 3 5/8 in. thick, are used, spaced about 11 in. apart, and they give a life of 350 to 450 clays. Fig. 1 shows the general design and thickness of the wave-type liners and lifter bars; 1 1/2 -in. liner bolts are used to fasten the lifter bars to the shell. The shell liners are held in place by the tapered lifter bars. A ¾-in. wood hacking is used between the shell and the liners. The rod-mill scoop has removable manganese-steel lips, which last 250 to 300 days. The scoop proper has shown some wear in spots; and these spots have been protected by rubber bolted over them. Water and milk of lime are added to the elevator feeding the mill, but not enough water to cause a pounding of the rods against the shell. Roughly, the water added amounts to 2.5 to 33 per cent of the ore. Addi-tional water is added to the mill discharge to facilitate distribution to the classifier bowls in the fine-grinding department.

Jan 1, 1938

By C. D. Locker

COMMON salt is mentioned in the most ancient writings as an impor-tant article of diet. It is fairly certain that it was used by men and animals long before the dawn of civilization. Its presence in natural springs has often been the determining factor in colonization; wars have been fought for possession of salt deposits; trade routes have been estab-lished expressly for the purpose of traffic in salt. Naturally this led men into adventures and discoveries that altered history and advanced civilization. In the early days the uses for salt were few and the methods of manu-facture were crude and the purity low when compared to salt of the pres-ent day. Then the salt came largely from springs, shallow wells or the ocean, while today deep wells must be drilled to the natural brines or beds of rock -salt and spacious shafts sunk so that the ancient deposits may be made to yield their supply of stored mineral.

Jan 1, 1936

By F. C. Pittman, D. W. Harriman, J. C. St. John

This paper mentions briefly the history of hydraulic jetting as applied to perforating and fracture initiation. It points out the advantages of hydraulic perforation and undercutting as an aid for creating a fracture at the point desired rather than depending upon the weakest point in the formation for breakdown. It describes early experimental work with jet nozzles in search of better nozzle materials. The effect of splash-back damage and its subsequent influence on jet body and tool design during this work is discussed. A series of cutting-rate curves for jets cutting steel and steel-cement-formation combinations is presented to show the effect of hydrostatic head and the point of diminishing returns with respect to cutting time. There is a series of photographs showing various types of rock formation in which perforation and undercutting tests were made. These stones were drilled and the casing cemented in place as in an actual well. The casing was perforated and circularly cut as if preparing for a fracturing job. The conclusion reached in the paper is that hydraulic jetting with sand-laden fluid can be used for perforating and undercutting casing, cement and formation rock for the intended purpose of inducing the formation to fracture at a desired point. INTRODUCTION Hydraulic jetting as a means of cleaning a formation during acidizing has been used for many years. The acid-jet gun was used to clean formation and for drilling cement from casing with acid. This tool was dropped to a seating ring installed on the tubing and could be retrieved by reverse circulation or wire line. In this process, the fluids were directed against the formation to clean and penetrate beyond the mud-damaged area. After the development of the hydraulic fracturing process, interest in jetting the formation with abrasive-laden fluid was renewed. The cutting action of abrasive fluid on pumping equipment, which is a well known problem, has been utilized to perforate and undercut casing, tubing and formation. In this process, surface areas are provided in the formation on which the frac- turing pressures may work to produce a fracture at the location desired. EQUIPMENT The tools used consist of bodies containing two, three or four jets in a single horizontal plane equally spaced around the circumference. The body is threaded to the end of a string of tubing and run into the well. In addition, an expendable tool is available that may be left in the hole after perforating and produced through until necessary to remove the tubing. The bottom of each tool is equipped with a ball-type back-pressure valve. The ball can be reversed to the surface and recovered. This allows reverse circulation so that loose sand which accumulated below the tool while jetting may be removed before the fracturing job. The present jetting tools are of such length that, when screwed together, the jets fall on 12-in. spacing. ANALYSIS OF THE PROBLEM Early work with nozzles indicated that hardened steel was not a suitable material for jets and that more durable material would be required. Ceramics were tried and found to be superior to steel but still too shortlived for most applications. Tungsten carbide, which was tried and found to be the best material available, is now being used for jet nozzles. Analysis of the problems presented by this process indicated that the following information was needed. 1. The effect of submergence on a jet stream and the effect of submergence on the cutting rate of a jet stream. 2. The cutting rate and depth of a jet stream in steel. 3. The cutting rate in various formations and point of diminishing returns. 4. Size of hole or slot cut in a pipe by a given jet. 5. Fluids and sands used. 6. The flow of various weight fluids through the jet nozzle and the discharge coefficients. 7. The type cut formed in the formation by the jet stream. 8. The stretch and contraction of tubing due to temperature and pressure. The cutting effect of a jet stream on a target in the atmosphere is rapid and spectacular as most of the

By George W. Lower, Robert B. Booth

The use of cyanides in the extraction of gold and silver is well known1 Such extractions employ concentrations of cyanide in the range of 0.02-0.25% sodium cyanide equivalent in leaching cycles of 24-48 hr and frequently longer. Copper minerals, even though minor components of precious metal ores, dissolve in these cyanide leaching solutions, consume cyanide, cause fouling of mill solutions, and thus interfere with the precipitation and recovery of gold.2,3,4 This paper presents a summary of laboratory investigations on the use of cyanide solutions as extractants for copper from various copper-bearing ore fractions. In view of the metal contents involved, it will be apparent that larger quantities of cyanide are required to extract copper than for the extraction of precious metals. In cyanide solutions of concentrations generally favorable to copper extraction, sulfide and oxide copper minerals were found to dissolve rapidly at room temperature and atmospheric pressure.

Jan 11, 1965

US 4,152,143-Continuous precipitation of cement copper from an aqueous ore leach solution mixed with pieces of iron as the precipitant Copper depositing on the pieces of iron is loosened and removed therefrom by means of constant but regulated oscillating movement of the pieces of iron in a horizontal elongated chamber, and the loosened copper is separated and collected from the mixture E Kausel and R Nissen, assigned to Klockner-Humboldt-Deutz A G May 1, 1979 8 pp (75-100) Filed 1-12-78 (868,981) (Drawings below) [ ] US 4,156,711-Removal of metal impurities from an acidic zinc or cadmium solution prior to electrolysis. Impurities such as manganese, cobalt, nickel, and thallium are selectively precipitated by contacting the solution with persulfuric acid or an ammonium or alkali metal salt thereof while maintaining a pH value of from 1 5 to 4 5 This patent is a continuation-in-

Jan 1, 1980

By H. M. Merry

THE graphic methods and records described in this article have been developed, with satisfactory results, for the use of executives of the Chino Copper Co., in Hurley, N. Mex. Particular attention is directed to the use of large wall-charts, the quick reference display of large charts, the scale notation of metallurgical charts, the inclusion of mesh extraction on screen analysis diagrams. To properly comprehend the operation and metallurgical results from a concentrating plant, a daily record of essential data is kept, usually involving the dry weight of ore milled or treated, dry weight of concentrate or metal produced, assay values of heading, assay values of tailing, assay values of concentrate, and percentage of extraction or recovery. In addition it is often necessary to record moisture, pulp density, or dilution; percentage of weight of oils and reagents employed; screen analyses of grinding conditions, oversize, etc.; assay values of non-valuable or interfering substances; cost data; and such special information as may be required.

Jan 9, 1919

By George J. Simchuk

Selection of an applicable stripping method and the subsequent determination of appropriate sizes of selected equipment are discussed. The case in point is Utah International, Inc.'s Goonyella mine located in central Queensland, Australia. A detailed study of the various types of stripping methods now practiced throughout the world led to the conclusion that large draglines would be the logical choice for Goonyella. The optimal size of dragline was then determined by first designing a series of cut diagrams using an array of machine and pit geometries followed by a cost comparison of the various sizes of machines, in terms of their effective spoil radius. A dragline with a 51-cu-yd bucket was determined to be of optimum size. Further calculations, incorporating total overburden moved from both the highwall and spoil sides, required that four drag lines, two equipped with 40-cy-yd buckets and two with 54-cu-yd buckets, be used to satisfy the stripping requirements at Goonyella.

Jan 1, 1973

By David Burgess, Hershiel H. Hayden

Experiments at the Somerset mine, Colo., under an agreement between US. Steel Corp. and the US. Bureau of Mines are described. A test was made of the tube bundle method of mine air sampling which was developed for European longwall mines; some 300,000 running feet of tubing provided continuous monitoring at 38 locations. Carbon monoxide concentrations were obtained with standard deviations of less than 1 ppm and oxygen concentrations with standard deviations of less than 0.2%. A base level of CO index (ppm CO evolved per percent 0, removed) was determined to be zero to 20 through most of the passageways of the mine. However, in one working section where the coal was initially hot (about 180°F within a pillar) the CO index was demonstrably higher, 120 trending upward to about 60 when smoke appeared and the section was sealed. The data are discussed in terms of laboratory experiments on CO evolution from coals.

Jan 1, 1977

By W. A. Wissler, B. E. Field

COBALT is a silvery white metal with a slight bluish cast. It strongly resembles nickel in its appearance and properties, notably its resistance to corrosion, although its alloys with other metals differ decidedly in their properties from those of nickel. The name "cobalt" was derived from the German Kobold, meaning goblin, and this came to be applied to the cobalt minerals which, although they resembled ores, did not readily yield metal when smelted by the primitive processes available in the Middle Ages. Cobalt minerals were used as pigments by potters and glass- workers before the Christian era. Cobalt blue glass was found in the tombs of the Egyptians and in the ruins of Troy, and many colors used by the ancient Greeks and Romans contained cobalt. The ancients were entirely unaware that the colors they used were caused by cobalt and the metal itself was not isolated until about the middle of the eighteenth century, by Brandt, although the preparation of cobalt compounds had been carried on in a small way ever since the opening of the silver-cobalt deposits at Schneeberg, Germany, in 1470. By the middle of the nineteenth century, several firms in England were engaged in the refining of cobalt products and the consumption of cobalt oxide in the British ceramic industry in the year 1866 had reached 67,000 lb. COBALT METAL AS A NEW RAW MATERIAL IN ALLOY TECHNOLOGY Nickel and cobalt are usually found together and, although the relative amounts of the two have varied greatly in different ores, those

Jan 1, 1953

By C. E. Tsoutrelis

A new method for determining rock drillability in diamond drilling is discussed; the method takes into consideration both penetration rate and bit wear. The method is based on drilling a rock specimen under controlled laboratory conditions using a model bit. The technique used for determining the experimental variables is extremely simple, quick, and reliable. Drillability is then determined by the mathematics of drilling. In considering the different factors that affect diamond drilling performance, the nature of the rock to be drilled is of outmost importance since it affects significantly the drilling costs and such other variables as bit type and design, drilling thrust, and bit rotary speed. Many attempts have been made to study this effect by correlating actual drilling performances either to certain physical properties of the rock being drilled1-? or to test drilling data obtained under laboratory conditions.7-13 These attempts were aimed at providing a reliable method of predicting by simple means the expected rock behavior in actual drilling, thus giving the engineer a tool to use in estimating drilling performances and costs in different types of rock. The purpose of this paper is to describe such a method by which rock drillability (a term used in the technical literature to describe rock behavior in drilling) could be determined in diamond drilling. It is believed that the proposed simple and reliable method will cover the need of the mining industry for a workable method of measuring the drillability of rocks. It should be emphasized, however, that since drill-ability depends on the physical properties of rock and each drilling process (diamond, percussive, rotary) is affected by different or partly different rock properties,14-l6 the proposed method of determining rock drillability cannot be extended to the other drilling processes. The results presented in this paper form part of an extensive three-year research program carried out by the author in the laboratories of the Greek Institute of Geology and Subsurface Research. During this period the effects of the physical properties of rocks and of such operational variables as drilling thrust and bit rotary speed in diamond drilling were investigated in detail. DRILLABILITY CONCEPT The literature is not devoid of drillability studies. While there are a number of investigators1,3,5-7,9-0,12-13,17 who have attempted to establish by direct methods (i.e., drilling tests under laboratory conditions) or indirect (i.e., through a physical property of rock) an index from which the drilling performance in a given rock may be estimated, very few6-7,9,12, of the proposed methods seem to be of much practical value to the diamond drilling engineer and none to date has been universally accepted. Commenting on the proposed methods for assessing rock drillability, Fish14 remarks that "for a measure of drillability to be accepted it is essential that penetration rate at a given thrust and bit life are elucidated as otherwise the method is of little value." This statement should be examined in more detail by making use of the penetration rate-drilling time diagram obtained in drilling a rock under constant operational conditions. Furthermore, the merits of using this diagram to describe rock drillability will be pointed out. At the same time reference will be made to this diagram when discussing some previously proposed methods. Fig. 1 illustrates such a diagram for three rocks,A, B, and C, which have been diamond drilled under identical conditions. It is assumed here that rocks A and B have the same initial penetration rate, i.e., VOA = Vog, but since rock B is more abrasive than A, rapid bit wear occurs and as a result the fall of its penetration rate with respect to time is more vigorous than in rock A. This is shown graphically by a steeper V = f(t) (0 curve in this rock than in rock A. Rock C has a lower initial penetration rate, due to higher strength properties16 but since it is not very abrasive, only a slight fall of its penetration rate occurs during drilling (in this category are some limestone and marbles with compressive strength above 1000 kg per sq cm). It follows from the foregoing considerations that the characteristic for each rock curve (I) is a function of (i), the penetration rate of the rock Vo recorded at the instant of commencing drilling, which determines the starting point of the curve (1) on the y-axis and (ii), the abrasive rock properties which determine the rate of fall of Vo with respect to time. Thus, curve (I) provides an actual picture of the rock behavior in drilling for given operational conditions, and it can be used with complete satisfaction to assess rock drillability. It can be seen clearly from Fig. I that proposed methods for assessing rock drillability by measuring the

Jan 1, 1970

By R. V. Smith

The theoretical background for calculating friction factors for flow in gas wells by two methods is presented. The first method, requiring pressures, temperatures and specific volumes of the flowing fluids at various depths in the well bore, shows how the mechanical-energy-balance equation for vertical flow may be graphically integrated over the actual path of the expansion of the fluid in the well. Thus, assumptions regarding the effective temperature and effective compressibility of the fluid in the well are avoided. The second method presents an equation derived on a basis of the assumptions that both the temperature and the compressibility are fixed at constant effective values throughout the flowing column of gas. The second method provides a convenient and practical means of calculating friction factors for gas wells and lends itself readily to the problem of calculating subsurface pressures in a flowing gas well. The application of both methods to actual test data taken on a flowing gas well is illustrated in the paper. INTRODUCTION As friction factors for the producing strings of flowing gas wells cannot be measured directly and must be calculated from flow-test data, study of the methods of arriving at friction factors is a necessary adjunct to understanding the characteristics of flow in gas wells. There are two methods of calculating friction factors for gas wells; they differ from one another mainly in the treatment of the path of expansion of the fluid in the well. In the flowing well, the energy consumed in lifting the fluid from the bottom to the top of the well, overcoming the friction between the moving fluid and the pipe walls, and increasing the velocity of the fluid as it flows up the producing string is supplied by expansion of the flowing fluid. The available energy is determined by the expansion of the fluid that follows a path determined by conditions of temperature, compressibility and phase changes of the fluid during the expansion. A means of evaluating the available energy in a flowing gas well and determining the proportion of the available energy used in lifting the gas, overcoming friction, and increasing the velocity of flow is developed in this report. Knowing how much energy is consumed in overcoming friction makes it possible to calculate friction factors for given flow rates in given sizes of pipes in wells. Friction coefficients, as used in this report, are dimension- less proportionality multipliers used in the flow equations to satisfy the equality between the terms of the equation. The square root of the reciprocal of the friction coefficient is termed the friction factor. It has been known for many years that friction factors may be computed directly from mathematical formulas based on certain assumptions regarding the temperature and compressibility of the moving fluid in a well. A general equation is presented in this report without assumptions for vertical flow of fluids and a conventional-type equation is derived on the basis of assumptions that fix the temperature and compressibility at constant values. Accurate pressures at the sand faces in wells are required in the method of determining the productivity of gas wells, as outlined by Rawlins and Schellhardt1 in Bureau of Mines Monograph 7. Where measurements are not made with subsurface-pressure gauge; or static gas columns are unavailable, flowing pressures customarily are calculated at the sand face in the well by the use of the well-known Weymouth formula1. Natural gas engineers have realized that errors introduced by the use of friction factors as given by the Weymouth formula are relatively unimportant in testing low-capacity gas wells; they also know that such factors are important considerations in testing large-capacity gas wells. Accordingly. present research on the productivity of gas wells at the Petroleum Experiment Station of the Bureau of Mines, Bartlesville, Okla., is being directed toward measurement of the pressure loss due to friction in flowing gas wells. It is beyond the scope of this report to show how friction factors vary with rate of flow and in pipes of different diameters, as it is intended only to develop and illustrate the use of mathematical expressions for calculating friction factors from flow-test data. The equations presented apply only to turbulent flow in circular pipes. ENERGY RELATIONS FOR FLOW OF FLUIDS2 The concept of conservation of energy is usually the basis of any study of fluid flow through vertical pipes as in gas wells, horizontal pipe lines, or orifices. In deriving equations, the following symbols are used:

Jan 1, 1950

By G. S. Cole, G. F. Bolling

Fluid flow strongly influences ingl structure and the columnar -to-equaaxed transition. Artificial flow patterns siwzilar to the nuturul ones act to induce this transition, while dampening forces act to suppress this transition. It is shown here how simple mechanical forces can be applied to a systerrz in order to induce or slipPvess relative fluid flow and the change both the structure transition and the exact structures obtained. The example used is the effect of slow rotations and oscillations 012 a cooling- ingot (of laboratory scale). The details of rotution and oscillation for various cooling rates, lenlperal~ire gradients, and sizes of ingot are related to other solidzfication variables. THE grain structure of a casting can be changed by altering the fluid motion during solidification. Just how important these changes are depends directly upon the degree to which the fluid motion can be controlled. An early step in understanding the nature and influences of fluid motion was taken by studying natural thermal convection; when a static mechanical device was used to suppress natural flow the result was opposite to that obtained when an electromagnetic device was used to augnlent flow in a pattern similar to the natural one. ''2 Suppression allowed more columnar growth to occur, but "augmented natural convection" brought about an earlier columnar-to-equiaxed transition (CET). Since the solidification of a free ingot must have characteristics somewhere between those displayed during suppression and augmentation, we know that natural convection must influence the CET. Further, since heat transfer in the liquid is always some time-dependent combination of convection and conduction, it can easily be guessed that the temperature gradient in the liquid is the vital factor affecting the CET.1,2 It is obvious that the structure arising from the unadulterated solidification of an ingot, without external influence, is rarely if ever the best possible one. Although the pattern of the natural fluid flow may be considered efficient, the magnitude of the flow and the heat transfer decrease freely from the outset. For a

Jan 1, 1968

By Elizabeth L. Robinson

INTRODUCTION The financial structure of the mining industry has changed strikingly over the last thirty years. The changes that have taken place in the last ten years include both the acceleration of adverse trends in familiar balance sheet numbers and ratios, and the subtle but extensive increase in the complexity and diversity of funding sources, both on and off the balance sheet. The objectives of this paper are: 1. to briefly trace the evolution of trends in the mining industry's financial structure; 2. to focus in more detail on changes in the last decade; and 3. to analyze those trends both within the framework of capital structure theory, and in the context of changes in business and economic conditions. This survey focuses primarily on the mining companies listed on the major U.S. stock exchanges, since financial data for these firms are readily available. The producers of minerals are a diverse lot, however, and the quantitative data on "the mineral industry" as characterized in this survey fails to encompass the financial arrangements for the bulk of production worldwide, whether owned by governments or private-sector enterprises. Even large portions of the U.S. minerals industry - subsidiaries of still larger firms, medium-sized privately-held companies, and the small miners - were not included in the quantitative part of the analysis. THE EVOLUTION OF THE INDUSTRY'S FINANCIAL STRUCTURE In the aftermath of the business failures of the Great Depression, most borrowers and lenders considered minimal debt on the balance sheet the soundest policy. By the 1950's, however, a body of literature was developing which demonstrated that the use of leverage could improve the value of the firm, given a corporate tax structure which allows interest, but not dividends, to be deducted from income. Optimal Capital Structure The objective of undertaking a new project is to improve the wealth of the current owners of the firm. If internally-generated funds are insufficient to allow growth at the desired rate, the company can raise funds either by issuing new equity, or by incurring debt. The most attractive source is the one which will provide the funds for the lowest cost. Both stockholders and lenders expect to receive compensation for use of their funds at a rate which reflects two things: (1) the return they could earn in alternative investments, and (2) the riskiness of the projected return. Factors which increase business risk include the variability of demand, sales prices and input prices, and "operating leverage", or the proportion of fixed to variable costs. In addition, from the investors' point of view, the use of financial leverage concentrates risk onto the shareholders, because lenders enjoy a prior claim in the event of bankruptcy. So although financial leverage can increase a project's expected rate of return, and therefore, presumably, earnings per share, too much debt will be perceived as uncomfortably risky by equity investors, and have a negative effect on stock prices. In theory, then, there should be an optimal level of debt which the firm's managers should seek to obtain in its financial structure. The desirable proportion of debt should in general be lower for a firm with a higher inherent business risk. In addition to their own judgement, financial managers are sensitive to the attitudes of lenders, rating agencies, and investment bankers in setting financial targets (Scott and Johnson). In practice, financial structure will also depend upon the company's growth rate and level of profitability, and conditions in the capital markets at a given time.

Jan 1, 1985

W. M. CURSE, Mansfield, Ohio.-Outside of the commercial valu-ation of the material, for what purpose does this alloy-90 per cent. of copper, 6 ½ per cent. tin, 2 per cent. zinc, and 1 ½ per cent. Lead-seem to be eminently fitted? C. P. KARR.-So far as our tests go, it would be eminently fitted for steam valves and pistons, and for the work for which 88-10-2 bronze is generally used, although for very large castings it would not be superior to 88-8-4 bronze. P. E. MCKINNEY, * Washington, D. C.-Some time hack, clue to a desire to avoid some of the objectionable features of 88-10-2 bronze, particu-larly on heavy castings, also to save tin where possible, we took up the question of a substitute for 88-10-2 bronze, where red bronze was ordinarily specified. After trying most of the mixtures, we found that when using as low a tin content as is given in this proposed composi-

Jan 12, 1919

By Robert W. Bergmann

Twenty years ago, the standard voltage for stripping machines was 4160 v and few people even thought of using a higher voltage. It was adequate for the machines of the day, which seldom exceeded 2500 hp, and higher voltages were considered to be too expensive and even dangerous. Then, in 1956, a 4500-hp machine was placed in operation and it was determined, with some reluctance, that it should operate on 7200 v. The next step, to 14,400 v, was taken in 1964 and the latest, but perhaps not final, step was made in 1967, when voltage was increased to 25,000 v. Today, 4160 v is considered almost obsolete and 7200 v is generally considered standard. However, a few mines are using 14,400 v and some eight machines soon will be operating on 25 KV, indicating that the technical and safety problems have been solved and that there must be some merit to the higher voltages. Thus, it is logical to question, "How do I determine the best voltage for my operation?"

Jan 12, 1972