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By A. A. Stripling

The Cretaceous limestone wells of the Mara/Maru-caibo Dist. of Venezuela are extremely prolific producers. To maintain production on cessation of natural flow, large scale gas-lift operations were commenced involving high production rates on caring Flow. For the design of these gas-lift installations it was essential to have some knowledge of the pressure gradients involved in casing flow, so that the required injection pressures, optimum gas injection raws, etc., could be forecast. This paper presents a method of calculating these annular pressure gradients. Basically the method makes use of an energy balance equation coupled with an empirical energy loss factor derived from field data. The calculations have been put in a form suitable for "punch card-type" calculating machines. A set of gradient curves for Mara/Maracaibo conditions covering flow rates up to 12,000 B/D, and GOR's of 500 to 2,000 cu fd/bbl is presented. From these curves the flowing BHP can be predicted from surface data and the vertical pow performance under varying conditions of gas injection can be estimated. The method has been applied to La Paz and Mam gas-lift operations for over three years and has given consistently accurate results. INTRODUCTION The Cretaceous limestone fields of the Mara/Maracaibo area in Venezuela are characterized by the presence of widely distributed fissure systems. Under these conditions individual wells frequently have extremely high potentials and such wells are generally flowed on the casing-tubing annulus in order to reduce the pressure loss in vertical flow. To maintain production on cessation of natural flow, an extensive gas-lift system was planned. As a first approach to this gas-lift design problem, an attempt was made to construct a set of empirical flowing gradient curves from the available subsurface pressure data. Such a method has been used successfully for tubing-flow conditions in California by Gilbert'. Unfortunately, the empirical construction of casing-flow gradient curves presents additional difficulties, as pres- sure bombs cannot bc run in the casing-tubing annulus against high rates of flow. Thus, the Full flowing gradients cannot be defined by actual measurement and the best that can be done is to obtain spot pressures at the tubing shoe. Under these conditions a vast accumulation of BHP data is required to construct a set of gradients. To the La Paz and Mara fields the majority of the available flowing pressure measurements fall into a relatively narrow GOR range, in the neighborhood of the solution ratio. While there appeared to be reasonable prospects of constructing gradient curves for this limited range, measurements at higher GOR's, which were of major interest for gas-lift operations, were relatively few and the prospects of constructing empirical curves cor~spondingly remote. As an alternative approach, the possibilities of a mathematical analysis of vertical flow conditions were investigated. May and Laird2fV n 1934 presented an excellent analysis of the vertical-flow conditions in the Anglo-Iranian Oil Co.'s fields. Their analysis was based on an energy-balance equation and calculated the losses due to kinetic energy, friction and slippage separately. By combining these losses with the total calculated available energy, the required depth-pressure traverse could be deduced. On applying the method to La Paz conditions, good results were obtained for tubing flow at high tubing-head pressures. However, for lower wellhead pressures (300 psi and under) the discrepancy between calculated and measured values increased appreciably. It was considered that this was probably due to energy losses caused by slippage or liquid hang-up in a continuous gas phase, for which it was difficult to visualize any analytical approach. In 1952 Poettmann and Carpenter4 presented a method of pressure gradient calculation which, while based on an energy-balance equation similar to that employed by May and Laird, made no attempt to evaluate the various components making up the total energy loss resulting from irreversibilities of flowing fluids. Instead, they proposed a method of analysis which assumed that all significant losses for multiphase flow could be correlated in a form similar to that of the Fanning equation for frictional losses in single-phase flow. They then derived an empirical relationship linking measurable field data with a factor which, when applied to the standard form of the Fanning equation, would enable the energy losses to be determined. The total available

By A. W. Schlechten, W. J. Kroll

As this paper is written, the only method for the commercial production of lithium metal is by the fusion electrolysis of LiC1-KC1 mixtures, as first proposed by Gunkz.2 The details of the industrial process have not been made public hut Osborg8 stated that an efficiency of more than 90 pct is obtained with a lithium metal recovery above 95 pct and that the metal is 99.5 pct pure. Pletenev9 gave a power consumption of 66 kw-hr per kilogram of lithium metal produced with a salt consumption of 9 kg of LiCl and 0.4 kg of KCI. Pletenev's figures indicate a somewhat lower recovery than that given by Osborg. In a recent report on' German lithium plants, Motock7 gives figures that are also less favorable than those reported by Osborg. At the German plants the lithium recovery in electrolysis was only 83.4 pct, with a power consumption of 140 kw-hr per kilogram of lithium. The metal averaged only 97 pct pure, with sodium and potassium as the chief impurities. The presence of SO2, SO3, SiO2, Ba, Ca, and appreciable amounts of Na and Fe2O3 were especially disturbing in the electrolysis, and it was necessary to run the cell for some time to eliminate most of these impurities and condition the bath. It may be noted here that most of these impurities do not interfere with a thermal reduction process. These facts show that the present method of producing lithium is fairly efficient and would suggest that other methods could not compete. However, fusion electrolysis has certain drawbacks, such as the necessity of supplying costly, low-voltage direct current and of collecting and processing the anodic chlorine if it is not to be wasted. An even greater disadvantage is that lithium chloride must be used for an electrolyte. It is one of the most expensive salts of lithium, since it cannot be produced in anhydrous form by precipitation from aqueous solution, as is done with LiF or Li2CO3. The reduction of lithium by a vacuum process similar to the ferrosilicon method for the production of magnesium would have certain advantages. Small units such as Pidgeon retorts, would give flexibility of production to meet demand, and a small plant would require moderate capital outlay. There is a possibility of using idle Government-owned magnesium plants for such purposes. The raw materials needed for vacuum thermal reduction would not have to be extremely pure, Director, with respect to the iron and calcium Content. This paper describes a series of experiments to determine the effectiveness of various agents for the reduction of lithium compounds. The investigation is part of a program of vacuum metallurgy con-

Jan 1, 1949

By AIME AIME

R. A. Hadfield, W. H. Bleckly, The Rt. Hon. Sir James Kitson, Bart., M. P.', E. Windsor Richards, E. P. Martin, Andrew Carnegie, Sir Hugh Bell, Bart., Bennett H. Brough. Patrons. Adamson, Joseph, & Co., Hyde; Aird, John, & Co., London ; .Akrill, C., & Co., Ltd., West Bromwich ; Anderson Foundry Co., Ltd.,. Port Clarence, Middlesbrough ;. Armstrong, Sir W. G., Whitworth & Co., Ltd., Newcastle-on Tyne ; As¬sociated Portland Cement Manufacturers (1900), Ltd., London; Babcock & Wilcox, Ltd., London; Baird, William, & Co., Ltd., Glasgow ; Baldwin's, Ltd., Stourport; Barclay, Andrew, Sons & Co., Ltd., Kilmarnock; Barrow Hematite Steel Co., Ltd., Barrow-in-Furness; Bayliss, Jones & Bayliss, Ltd., Wolverhampton ; Beardshaw, J., & Son, Ltd., Sheffield ; Bell Brothers, Ltd., Middlesbrough ; Bolckow, Vaughan & Co., Ltd., Middlesbrough ; Booth, Joseph, & Bros., Ltd., Leeds ; Briton Ferry Works, Ltd., Briton Ferry; Butlin, Thomas, & Co., Ltd., Wellingborough ; Butterley Co., Ltd., Alfreton ; Byrne, James, & Co., Middlesbrough; Cargo Fleet Iron Co., Ltd., Middlesbrough.;. Carnforth Hematite Iron Co., Ltd., Carnforth ; Cochrane & Co., Ltd., Middlesbrough ; Coltness Iron Co., Ltd., Glasgow ; Colville, David, & Sons, Ltd., Motherwell ; Consett Iron Co., Ltd., Consett ; Cooke, William, & Co., Ltd., Tinsley ; Craggs, R., & Sons, Ltd., Middlesbrough ; Darwen & Mostyn Iron Co., Ltd., Mostyn ; Dorman, Long & Co., Middlesbrough ; Dunlop, J., & Co., Ltd., Glasgow ; Ebbw Vale Steel, Iron & Coal Co., Ltd., Ebbw Vale ; Engineer, The, The Proprietors. of, Lon¬don ; Engineering, The Proprietors of, London ; Etna Iron & Steel Co., Mother¬well ; Farnley Iron Co., Ltd., Leeds ; Firth, Thomas, & Sons, Ltd., Sheffield ; Rather, W. T., Ltd., Sheffield ; Fraser & Chalmers, Ltd., Erith ; Frodingham Iron & Steel Co., Ltd., Doncaster; Gjers, Mills & Co., Ltd., Middlesbrough ; Glenboig Union Fire-Clay Co., Ltd., Glasgow ; Glengarnock Iron & Steel Co.; Ltd., Glengarnock ; Guest, Keen & Nettlefolds, Ltd., Birmingham ; Hadfield's Steel Foundry Co., Ltd., Sheffield ; Hall, J. & E., Ltd., Dartford ; Harkness, W.; & Sons; Ltd., Middlesbrough ; Harrison & Co., Ltd., Lincoln ; Head, Wrightson & Co., Ltd., Stockton-on-Tees ; Hill, John, & Co., Middlesbrough ; Hingley, N., & Sons, Ltd., Dudley ; Hopper, John I., Ltd., Thornaby-on-Tees; Hull Forge Iron &-Steel Co., Ltd., Hull; Iron and Coal Trades Review, The Proprietors of, London ; Ironmonger, The, The Proprietors of, London ; Jackman, Joseph, & Co., Ltd., Sheffield ; Jessop & Appleby Bros., Ltd., Leicester and London ; Jes-

Nov 1, 1906

By Ivan Simon, R. K. McConnell

Anticipating the availability of tiltmeters suitable for use in boreholes, this article proposes a method of using one or more of these meters to determine in situ stress distribution before and after mining operations. Several ways of using relief techniques to measure in situ stresses in rocks have been developed. These techniques, summarized by Merrill,1 involve measuring deformations which take place when a specimen of rock is wholly or partially isolated from the stress field in the surrounding rock. Measurements of rock deformation caused by stress relief from mining operations can, in principle, also be used to estimate in situ stress distributions. Müller2 has mentioned experiments being carried on in Austria with a "deformation indicator" to determine the tilting of holes drilled before a mine opening is made. Similar work using borehole extensometers has been reported by Potts? and Duvall4 has called attention to the possible use of tiltmeters in making these measurements. Considerable attention is now being paid to the use of tiltmeters in detecting rock deformation associated with fault movements, earthquakes, earth tides, etc. The instruments used for these measurements have usually been of the mercury tube, water tube, or quartz fiber type, but because of their large size, and/or fragile nature, such instruments would not be suitable for use in mining stress measurements. Recent instrumentation developments, however, give promise that rugged, sensitive tiltmeters small enough for use in boreholes may soon be available.' In anticipation of these developments, this article presents a number of calculations of the possibility of using one or more tiltmeters emplaced in a drill hole prior to mining operations to determine the in situ stress distribution both before and after a mining operation. Consider point p (x, z) near a tunnel of radius a

Jan 1, 1969

By R. R. Joseph, K. A. Gschneidner

The solid solubility of magnesium in the close-packed modifications of lanthanum, cerium, praseodymium, neodymium, gadolinium, dysprosium, and lutetium was determined from approximately 250°C to the eutectoid temperature by the X-ray parametric technique. The maximum solubility at the eutectoid temperature was found to be 9.4 at. pet in La, 8.2 in Ce, 9.2 in Pr, 8.2 in Nd, 14.1 in Gd, 13.5 in Dy, and 11.5 in Lu. The solubility when compared at a homologous temperature was found to increase in a smooth manner with decreasing size factor from lanthanum to lutetium. It was found that the apparent atomic radius of magnesium when dissolved in the lanthanide solvent was constant and could be accounted for by consideration of several models dealing with departures from Vegard's law. The eutectoid temperatures for the lanthanide-rich La-Mg, Ce-Mg, and Nd-Mg systems were found to be 544", 505°, and 551°c, respectively. A study of the solid solubility of magnesium in the lanthanide metals was initiated because the valency and electron egativity difference are essentially constant and favorable for solid-solution formation, and thus one could examine the effect of size on terminal solid solutions. The size factors based on metal radii range from 14.6 pet for lanthanum to 7.5 pet for lutetium. Since the electronegativity difference is small, 0.06 unit or less, application of the Hume-~othery' and Darken and Gurry2 criteria for solid-solution formation indicates that the solubility of magnesium would be expected to be small for lanthanum (between 5 and 10 at. pet) and to increase as we proceed along the lanthanide series. A search of the literature revealed no data on the solubility of magnesium in the lanthanide metals except for the solubility of magnesium in cerium at 450oCA typical phase diagram for the lanthanide-rich end of the lanthanide-magnesium phase diagram is shown in Fig. 1. EXPERIMENTAL PROCEDURES Preparation of Alloys. The lanthanide metals used in the preparation of alloys for this investigation were prepared from the corresponding fluoride by metallothermic reduction techniques previously described by Daane.4 The chemical analyses of the metals used are listed in Table I.

Jan 1, 1965

By B. A. Eaton

The subject of many discussions and technical papers in the last 20 years has been the prediction of the well-bore pressure gradients that are required to induce or extend fractures in subsurface formations. The subject merits this attention because of the frequently recurring problems that arise from an inability to predict fracture pressure gradients. Encountered in several common types of operations in the oil industry are problems associated with the prediction of formation fracture pressure gradients. When wells are being drilled in both new and old fields, lost circulation is often a very troublesome and expensive problem. Complete loss of circulation has been disastrous in some cases. Many times, such disasters could have been avoided if techniques for calculating fracture pressure gradient had been employed in the well plans, and if casing strings had been set, and mud weight plans had been followed accordingly. In areas of abnormally pressured formations, the prediction of fracture gradients during the well-planning stage is extremely important. In fact, it is as important as the prediction of formation pressure gradients, which has received a great deal of attention in recent years. There are several published methods used to determine fracture pressure gradients. However, none of these methods appears to be general enough to be used with much reliability in all areas. In 1957, Hub-bert and Willis published a classical paper that included the development of an equation used to predict the fracture extension pressure gradient in areas of incipient normal fau1ting.l Overburden stress gradient, formation pore pressure gradient and Poisson's ratio of rocks were the independent variables that were shown to control fracture pressure gradient, the dependent variable. In 1967, Matthews and Kelly published another fracture pressure gradient equation that is different from that of Hubbert and Willis in that a variable "matrix stress coefficient" concept was utilized.3 Later the same year, Costley wrote about a similar idea.5 Goldsmith and Wilson used a least-squares curve-fitting technique and field data from the Gulf Coast area to correlate fracture pressure gradient with formation pore pressure gradient and formation depth.' They noted that the fracture pressure gradient increased with increasing depth while the pore pressure gradient remained constant. In each of these cases, the problem for which a solution was sought was to determine the bottom-hole pressure gradient required to initiate or extend a fracture. Results of the previous work show that fracture pressure gradient is a function primarily of overburden stress gradient, pore pressure gradient, and the ratio of horizontal to vertical stress. There is argument for a fourth variable in that in many cases breakdown fracture pressure gradient is greater than the fracture extension pressure gradient. However, if the fracturing fluid is able to penetrate the formation through the pores or existing cracks, there is very little

Jan 1, 1970

By M. M. Singh, J. W. Brown

Three rocks of highly varied physical properties are selected for the first reported experimental study concerning microseismic activity of rock under tension to determine the effects of static fatigue, loading rate, repeated loading and rock anistropy compared to compression and bending loads. The microseismic method of detecting rock under deformation may be a great potential tool in surveillance and location in situ of dangerously stressed strata, as well as predicting rock failures. Noises emitted under load or the rate of energy (energy of noise pulses generated per unit time) are computed for varying conditions. The tests are conducted at constant load on a dead weight loading machine to eliminate all possible extraneous noises — an indispensable precaution — at various load levels. Experimental results are reported including the relation of total energy emitted to tensile strength of rock and the possibility of simulating a phenomenological model for microseismic activity. Plots of some of the experiments are included. INTRODUCTION Rock failure, whether on a large scale faulting in the earth's crust and rock bursts in mines, or on small scale ruptures of laboratory test specimens, generates transient vibrations in the rock mass. Mechanisms of intermittent deformation, such as twinning and cracking through and between mineral grains, also produce similar vibrations, but of very small amplitude. Such vibrations from both deformation and failure are referred to as microseismic activity, rock noise, or occasionally seismo-acoustical activity. An individual rock noise is sometimes

Jan 1, 1967

By H. F. Silliman, Daniel R. Hull, Earl W. Palmer

THE brass-rolling industry has not had a great deal of experience with antimony in its product. There have been some recent excursions with antimony as a corrosion inhibitor in tubes, but in sheet brass it has been regarded with apprehension and generally avoided. This is not to say that [ ] contaminations have never occurred, and probably a great many brass mill men have had their own ideas on the effect of such contamination. Our own views were based upon certain experiences some years ago with strip castings that split lengthwise in the early stages of rolling. The nature of this splitting is shown in Fig. I, from a photograph taken in 1922 as a record of 20 bars of 65-35 common brass made with an antimonial brand of copper. These bars were cast 6 ¾ in. wide by 1 in. thick by 45 in. long. In the first pass through the rolls, 19 of the 20 split lengthwise throughout their length, while each half curved outward in a wide arc as it emerged from the rolls. [ ] In those days, if splitting was not a frequent occurrence, it was not unfamiliar. One can recall periods of short duration when large amounts of common brass would behave in this way. There was nothing imaginary about these spells. The affected metal would split lengthwise in the breaking rolls, and no maneuvering of mill practice made any difference. The condition would descend like a plague, demoralize the mill for several days, and disappear. It is doubtful if anyone knew the cause-however many explanations may have been current. In 1921 a quantity of split brass was traced to the use of fired small-arms

Jan 1, 1943

By Thomas Donnelly

Introduction THE Province of San Cristobal is situated on the south side of the island of Santo Domingo about 25 miles west of Santo Domingo city, the capital of the republic. The copper mineralization is found about 1.-CAMP BUCARO. THE TOP OF THE RIDGE IN THE BACKGROUND MARKS THE CONTACT OF THE LIMESTONE AND TUFFS. S miles north of the town of San Cristobal, in the section known as Bucaro Hill; in San Francisco Hill; on the Nigua River; and on the Jaina (Liver. The district is reached by automobile from Santo Domingo city over an excellent road for 25 miles to San Cristobal, and then, by horse-back 6 or 8 miles up the Nigua River to what is locally known as "Camp

Jan 8, 1915

By F. D. Richardson

STAFF: Editor, Gerhard Derge Carnegie lnstitute of Technology Schenley Park Pittsburgh, Pa. 15213 Editorial Assistant, M. A. Redmerski Production Editor, Otto T. Johnson THE METALLURGICAL SOCIETY: Jack H. Scoff, President; Richard C. Cole, Past-President; Harold 0. Emerick, President-Elect; Ralph L. Hennebach, Treasurer; Robert W. Shearman, Secretary; Donald A. Parks, Assistant Secretary; Leslie S. Wilcoxson, Assistant Secretary. PUBLICATIONS COMMITTEE OF THE METALLURGICAL SOCIETY: R. E. Lund, Chairman; T. E. Dancy, H. O. Emerick, P. R. Gouwens, R. E. Grace, J. H. Jackson, H. H. Johnson, A. E. Lee, Jr., R. R. Nosh, R. D. Pehlke, and Paul Queneau. Review and selection of manuscripts is under the supervision of the following Publications Committees: Extroctive Metallurgy Division: R. E. Grace, Choirmon; G. M. Bell, D. W. Bridges, J. M. Cigon, G. W. Heoly, T. A. Henrie, R. D. (Holli-doy, C. E. O'Neill, C. S. Somis, A. W. Schlech-ten, and Charles Shull. Iron and Steel Division: R. D. Pehlke, Choirmon; T. P. Floridis, Arnulf Muon, G. R. St. Pierre, E. T. Turkdogan, L. H.Von Vlock, and J. M. Uys. lnstitute of Metals Division: H. H. Johnson, Jr., Chairman; J. B. Clark, Vice Choirmon; M. R. Achter, G. F. Bolling. J. O. Brittoin, G. P. Conard, II, R. S. Davis, L. A. Girifolco, G. T. Hohn, J. P. Hirth, L. Himmel, G.T.horn, George Krauss, J. D. Livingston, R. D. Manning, H. M. Otte, S. V. Rodcliffe, R. E. Reed-Hill, H. C. Rogers, E. ScaIa, O. Sherby, M. T. Simnad, G. R. Speich, E. A. Steigerwald, R. A. Swolin, W. A. Tiller, W. R. Upthegrove, J. B. Wagner, Jr., Derek Wolton, H. W. Weart, W. W. Webb, and D. Published seven times yearly in February, March, April, June, August, October, and December by the American lnstitute of Mining, Metallurgical, and Petroleum Engineers, Inc., 345 East 47th Street New York, N. Y. 10017. Telephone PLAZA 2 -6800. Subscription $30 per year for non-AtME members m United States and North, South, and Central America; $32, foreign; $7.50 for AlME members Single copies, $6.00, single copier foreign, $6.50. The AiME is not responsible for any statement made or opinion expressed in its publications . . . Copyright 1964 by the American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. . . . Registered cable address, AiME New York Indexed in Engineering Index, Industrial Arts Index, and Chemical Abstracts. Second dost postaas poid ot New York, N. Y.,ond Ann Arbor, Mich. Volume 230, Number 6.

Jan 1, 1964

By R. F. Rolsten

VAN Arkel 1 prepared ductile tantalum by the thermal decompoiition of tantalum pentachloride on a resistively heated wire (2000° C) in an evacuated bulb maintained at 100°C. Burgers and Basart2'3 observed the formation of a mixture of tantalum carbide and free metal when a carbon deposition base was used. campbel14 suggested the thermal decomposition of the iodide if a lower decomposition tem- perature was desired. To date, the details for preparing high-purity iodide tantalum have not been disclosed. EXPERIMENTAL The tantalum to be purified was symmetrically placed around the clear quartz deposition surface centrally located within a 64 mm cylindrical Vycor bulb. The deposition vessel usually employed5 was modified6 by incorporating a reentrant fin,mer in place of the customary metal filament in the head

Jan 1, 1960

By E. S. Wheeler

The rapid increase in the use of monel metal and malleable nickel in the form of sheet, rod and tube has resulted in a similar increase in the demand for these metals in the form of castings. These castings range in size from small valves and pipe fittings weighing a few ounces to large centrifugal pumps, gate valves and marine propellers, some of the last weighing as much as 24,000 lb. A group of such castings is shown in Fig. 1. A large nickel agitator is shown in Fig. 2. Monel metal castings are widely used in accessories for steam power plants and in a variety of chemical plant equipment where the corrosion resistance, high strength and toughness characteristic of this metal render it particularly valuable. Nickel castings find extensive use in the construction of corrosion-resistant apparatus, and are often used in conjunction with wrought nickel sheet and tube in the fabrication of equipment for handling a variety of chemical and food products, particularly dairy products. In response to this demand for castings, numerous foundries have undertaken the production of castings of these metals and have met with varying degrees of success. The successful production of castings of monel metal and nickel requires careful attention to molding practice, proper melting equipment

Jan 1, 1930

By J. C. Martin

Equations for three-phase, three-dimensional, compressible flow (including capillarity) are reduced to two-dimensional relations by a partial integration. This reduction allows three-dimensional flow problems to be treated with mathematics for only two spatial dimensions. The results can be used to formulate flow equations for two-dimensional reservoir simulators in which the effects of capillarity and fluid segregation in the third dimension are represented. Such reservoir simulators would retain many of the aduantages of two-dimensional simulators while simulating three-dimensional effects. The principal restriction of the method is that the thickness of the reservoir should be small, compared to the distance across the reservoir. INTRODUCTION In recent years, computers have been used to calculate the performances of many reservoirs. Most of the detailed calculations, however, are based on finite difference solutions of the flow equations, and present day computers are seldom able to handle a sufficient number of cells to produce entirely satisfactory solutions, even for reservoirs represented by two-dimensional arrays of cells. The situation becomes much worse when one wishes to approximate the reservoir by a three-dimensional array. A great saving in computation or a more detailed solution can be obtained for many reservoirs by using the partial integration of the equations of flow presented in this paper. The integration reduces the three-dimensional equations to two-dimensional relations; and, for studies of two-dimensional flows in vertical cross-sections, the equations are reduced to one-dimensional relations. Most reservoir performance calculations currently are based on one- or two-dimensional flow re1ations.l-3 In some cases flow in the third dimension is approximated by assuming a particular type of vertical saturation distribution, such as gravity segregation.l.2. The relations developed in this paper approach those for segregated flow as the capillary pressures approach zero, and they approach those for uniformly distributed saturations as the capillary pressures are increased. For this analysis, the ratio of the reservoir's thickness to the maximum distance across it must be small. The capillary pressures between the oil and water should also be small compared to the maximum pressure difference in the reservoir. This requirement is met by most reservoirs. It is assumed that the capillary-pressure curves are well defined, whether or not hysteresis effects are included. Also, the reservoir must have sufficient vertical permeability to allow the fluids to segregate. The results presented here provide a firm theoretical foundation to Coats' et aL5 assumption of vertical equilibrium and extend the relations to three-phase flow. Coats' assumption of vertical equilibrium, which he verified by calculations and experiment, is developed here mathematically from basic flow equations. DISCUSSION SATURATION AND PRESSURE DISTRIBUTIONS Appendix A presents a mathematical analysis of fluid flow in reservoirs where the ratio of thickness to maximum distance across the reservoir is small. The results indicate: (1) that the fluids along any line perpendicular to such a reservoir's upper surface are in static capillary equilibrium (vertical equilibrium); (2) that, to a first approximation, the fluid pressures and properties are functions of only areal position in the reservoir and time; and (3) that hydrostatic pressure gradients exist along any line perpendicular to the reservoir's upper surface. The results might be expected after studying several physical considerations. First, no flow is allowed normal to the upper and lower reservoir boundaries, which are relatively close together.

Jan 1, 1969

By Daniel T. Brian, O&apos

Exploration targets and results in the mining industry are commonly summarized in terms of tonnage and grade. Business appraisals require, as additional information, the expected profit or loss implied by the physical summay. The early incorporation of knowledge gained through financial analysis computations can provide a means for economically resolving many common exploration and development problems. Examples of such applications from the activities of exploration planning, reconnaissance, land acquisition, and development planning are presented. While prospecting for mineral deposits, geologists are frequently asked what they hope to find or have found. The response is usually descriptive, such as "50 million tons of 1% copper," and the economic implications are deferred until a capital investment decision is required. At that time, a financial analysis integrating the four analysis components is completed. These components are: 1) Tonnage and Average grade above cutoff grade 2) Capital and operating costs 3) Product value 4) Appropriate profit or loss accounting Close examination of these components reveals that there is no intrinsic reason for avoiding financial analyses at earlier stages in exploration, as long as the uncertainty of the estimate is realized. Tonnage and average grades are commonly estimated at early stages in exploration. For this component, the appropriate cutoff is the major uncertainty. Capital and operating costs are difficult to estimate before detailed quantitative information is available, but estimates useful for the types of applications pertinent to earlier exploration stages are possible. Product value estimates may or may not be difficult, depending on the pricing structure of the particular commodity. A simplified accounting procedure usually may be adopted without introducing any significant loss of validity. This paper describe some of the financial analysis applications which are pertinent during mineral exploration and deposit development. These applications lend additional insight during exploration planning, land acquisition, physical exploration, and development. The examples are oriented toward a hypothetical management investment policy which is based on a single criterion, a minimum 15% discounted cash flow rate of return. In reality, managements use multiple criteria. This simplification is convenient for purposes of presentation and does not invalidate the examples. Computers are useful, but not a requirement, for the applications described. The use of computers provides the results on a more timely basis at costs lower than equivalent manual computations. UNDERLYING PRINCIPLES AND ANALYSIS METHODS Data estimates are subject to uncertainty. The analyst may choose to assess this uncertainty by using one of two principles. Each principle has some advantages. The principle most commonly employed is "assumed certainty." Each financial analysis is based on one set of selected data, which may represent the average estimates, minimum expected conditions, etc. The critical data is identified by making successive calculations, varying the values used. Such studies, called sensitivity analyses, isolate the economic effect of various uncertainties, and guide the allocation of future efforts toward improving the overall accuracy of the analysis. A second principle, "assumed risk," examines the interactive effect of the current uncertainties by qualitatively assigning probability distributions to each data element. These probability distributions indicate the currently appraised chance that a given numerical value will prove to be true. The corresponding procedure, risk analysis, consists of processing many individual financial analyses, each analysis being based on randomly selected numerical values from the probabilistic distributions. The result is a numerical presentation of the uncertainty, but care must be exercised in the interpretation of results. The advantage of this procedure is the direct measurement of economic uncertainty caused by the interaction of uncertain estimates. Kennecott Copper Corp. has developed computer systems for accomplishing sensitivity and risk analyses.

Jan 1, 1970

By R. G. Vardiman, M. R. Achter

Observations of dislocation structure in niobium are presented using two techniques. Triangular pits developed by electroetching are confined to orientations in the stereographic triangle between the (111) pole and planes of the (1ll) zone and require the presence of carbon. Some unusual electroetching phenomena at other orientations are noted. A chemical etch of dislocations decorated by the addition of carbon to 50 ppm reveals the complete dislocation line structure in a surface layer up to 30 p deep, with a resolution of less than 1 p. This effect is independent of surface orientation. The structure of subboundary nets may be resolved for misorientations up to about 1'. Dislocation structures found in strain anneal grown crystals, such as helices, prismatic loops, and high-density areas, are observed. The measurement of dislocation density is discussed and values obtained in different ways are compared. IN the course of some work on the response of refractory metals to thermal-mechanical treatments, it was desired to examine the defect structure of relatively low dislocation density crystals of niobium in bulk form. Surface and bulk methods for the observation of dislocations have been reviewed by ~melinckx,' and include etch pitting, decoration, and various X-ray techniques. The dislocation line structure has been developed by decoration in a few metals, although observations were limited to certain orientations, or by the coarseness and nonselectivity of the precipitate. The most commonly used technique is etch pitting. In niobium, etch pits have been developed chemically'0," in material of high impurity content and electrolyti-cally'' in relatively pure material. In this paper, etch pits developed electrolytically, and the dislocation line structure of a surface layer developed by decoration and chemical etching, are examined, and observations are presented from both techniques. EXPERIMENTAL METHODS Our starting material was electron-beam-melted niobium, swaged to 4 or -in.-diam rod. Chemical analysis is given in Table I. Single crystals were grown by a strain anneal technique using 1 to 2.5 pct of strain and growth temperatures of 1700" to 2300"~.'~ Some crystals grown by zone melting were also examined. The desired surface orientation was exposed either by spark machining or by sectioning with a cut-off wheel and prepared for etching by electro-polishing.

Jan 1, 1969

Jan 1, 1963

By D. P. Harris

This paper examines recent developments and work in progress on the application of quantitative methods and computers to the appraisal of the mineral resource potential of discrete areas by employing reconnaissance geological information and general economic relationships. The perspective of this paper might be that of a firm planning a regional exploration program or of a legislative body seeking to choose between several alternative actions on the basis of their impact upon the regional resources. In addition to this general survey and commentary, an example is presented of the use of geostatistical analysis and computer simulation to evaluate the economic mineral resources of the Seward Peninsula of Alaska.

Jan 1, 1969

By Albert Sauveur

It is delightful to read a technical paper like that of J. E. Johnson, The Effect of High Carbon on the Quality of Charcoal-Iron, presented in October, 1912, at the Cleveland meeting of the American Institute of Mining Engineers.' The clear, simple, and straightforward manner in which he describes his experiments and results makes you feel as if you had been, so to speak, at his elbow during the course of his investigations, while his method of procedure is so rational that you can fairly anticipate each step in the logical sequence of the tests performed. The following notes suggested by Mr. Johnson's paper are presented here in the hope that they may help, if only a mite, towards the final solution of a problem of considerable scientific and industrial importance. Physical Properties of Cast-Iron us. Its Ultimate Composition. Mr. Johnson writes that " an investigation along the lines of consumption showed that different irons have different characters totally independent of their analyses," and he declares that " the presence or absence of these elements [meaning carbon, phosphorus, silicon, and manganese] alone will not account for all, scarcely for a half, of the facts which have long been known." He further tells us that some foundries have " proved, by the most irrefutable tests, that they could take a certain iron of a given analysis and produce certain results," while with " another iron of the same analysis they could not produce these results at all." I feel confident that every experienced and thinking metallurgist will readily believe Mr. Johnson's statements and will share his views in regard to the hopelessness of inferring the

Jan 1, 1914

By J. P. Neumann, L. Raymond

At temperatures near 1000°C, only the (112) (111) slip systems are operatire in tungsten. Therefore, the substructure introduced into the billet upon rleforming a single crystal by rolling at 1000 "C can be controlled by proper selection 01. processing ral'iubles. Using a reduction of 10 pct pel- pass, the (001)[110] and the (110)[001] crystals will deform by duplex slip rip to a 50 pet reduction in thickuess. These rolled single-crystal sheels are characlerized by anisotropic hardening, retention of ductility with warm working, lattice bending which is related to the conlacl (angle, and macroscopic dimensional changecs in the length bid not the width of the billet. When several slip systems become operative, a greater degree of work hardening is itztvoducetl into the crystal. This rolling- condition is characlerized by isotropic hardening, loss of ductilily with warm working, complex lattice distortions, and macro-scopic dimensional changes in both the length rind Width of the billel. IN tungsten, the {1 10}(111) slip systems are operative below room temperature,' while above 700°C only the {112{ (111) slip systems are observed.2,3 In the transition region, i.e., room temperature. both systems appear. It is the purpose of this investigation to show that tungsten single crystals deformed by rolling at a temperature where only one slip system is operative generate dislocation substructure which depends on the crystal orientation. For a specific crystal orientation. the resulting dislocation substructure can be further influenced by modifying the rolling procedure. Crystals oriented for multiple slip display less substructural sensi- tivity to modifications in processing techniques than do single crystals oriented for duplex slip. Under simple slip modes of deformation, very little work hardening is introduced into a rolled single-crystal sheet. Mechanical properties such as room-temperature strength. ductility, and hardness are used to confirm the existence of the different work-hardened conditions generated within the crystal by modified warm-rolling techniques. EXPERIMENTAL PROCEDURE Material. Single-crystal billets of four different crystal orientations. grown by the Arc-Verneuil technique. were ground to a size of 0.25 by 0.375 by 3 in. In terms of their rolling plane and rolling direction, the billets had the following orientations: (1101 [001 ] (110) [110] (001) [110] (001) [100] The actual orientation of all crystals was within 5 deg of the ideal orientations. The typical impurity content of the crystals is given in Table I. Polishing and Etching. Polishing was done elec-trolytically in a 20 g per liter aqueous solution of NaOH at approximately 10 v. It was established by the Laue back-reflection X-ray technique that the surface damage due to grinding and cutting operations with a diamond wheel did not exceed 0.001 in. Therefore after each cutting or grinding operation at least 0.002 in. was removed electrolytically from the surface in order to eliminate surface effects. By lowering the voltage to 3 v, subgrain boundaries and individual dislocations are identified in agreement with Berlec 4 where the etch-pit traces on a cubic plane form a square. The etching time was about 5 sec at room temperature. Rolling. Rolling was carried out on a Loma 2-high mill (Model 600). The peripheral velocity of the 6-in.-diameter rolls was 500 in. per min, with the surface temperature of the rolls about 400° to 450° C The billets were heated before each pass for 30 min in argon to 1000 C. Oxidation of the crystals during rolling in air resulted in a thin layer of greenish-yellow WO 3 This oxide was removed after each pass by immersing the crystals for a few minutes in a boiling NaOH solution. Prior to the initial rolling pass, a surface layer of 0.001 in. was removed by polishing. The crystals were then annealed in vacuum (10-4 torr) at 2400 C for 30 min. All crystals were rolled in the same direction; i.e., the same end was always introduced into the rolls. The rolling program was conducted in

Jan 1, 1965

By A. H. Larson, L. G. Twidwell

DURING the roasting of zinc sulfide concentrates and by-product recovery from flue dusts, the zinc sul-fate phase may occur in various stages of the processes. In addition to zinc sulfide, other sulfide phases are usually present such as CdS, PbS, CuzS, and FeS. Consequently, the effect of these sulfides on the thermal decomposition of ZnS04 was investigated. Merck high-purity, anhydrous zinc sulfate was used as the starting material. The sulfate was heated under an argon atmosphere, at a rate of 10°C per min. With the first slight indication of decomposition as determined by gas analysis, the sample was removed from the furnace and allowed to cool. X-ray patterns showed no other phase present. It is estimated that less than 0.05 pct of the ZnS04 decomposed. The metal sulfides were also heated under an argon atmosphere to drive off any adsorbed water. The materials were then sized (-200 to +270 mesh), mixed in predetermined mole ratios, and pressed into pellets. The experimental measurement of the reaction rate consisted of purifying the argon carrier gas, continuous flushing of the heated reacting mixture with argon, and collection and analysis of the SOn product gas. The reaction system was heated to 600°C and al-

Jan 1, 1967