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By Samuel H. Dolbear

THE value of a mine is basically dependent on its capacity to yield profits. Since the ore must be mined, treated, and sold, some of it in various future years. there is a risk involved as to future costs, selling price, and working conditions. It cannot be expected that the economic condition existing at the time of valuation will continue unchanged for long periods in the future. During the past 20 years, mineral production in the United States has been conducted under a changing economy in many respects more exacting than that applied to other businesses. There have been increased production incentives, technical aid, exploration of privately owned mineral deposits by government at federal expense, and liberal loans for development and equipment, with risk partially assumed by government.. Some of these benefits have been counterbalanced by price ceilings, consumption controls, and stimulation of competition from foreign producers who have been offered the same advantages extended to American operators. For the present, mines will operate under a government policy directed toward reducing federal aid and control. The tenure of this change will depend upon future elections and the status of foreign relations. War and threat of war are now of the most vital significance to the mineral industries. Other factors which influence cost of production, markets, and price of mine output might be classified as Acts of God or Acts of Government. In some countries expropriation and the difficulty of exporting earnings or investment returns are risks that must be considered by foreign capital. Recognizing that this retards American investment in foreign countries, the Mutual Security Agency offers insurance against such expropriation and guarantees the convertibility of capital and profits. Since it is impossible to predict with certainty either cost of production or selling prices of metals for long periods, some assumptions must be made as to profits in the future. The basic assumption must be that the price of the company's product will vary in proportion to changes in operating cost. There is often a lag in this reaction, however, for prices of minerals are generally more sensitive to declines and less sensitive to increases than are costs. This reflects in part the resistance of labor to downward wage revision and a corresponding alertness in realizing its share of price advances. Some labor contracts include automatic adjustments to metal prices. Notwithstanding the complexity of the, problems involved and the difficulty of weighing their effect on value, such risks may be appraised with reasonable accuracy and a rate of earnings adopted that is compatible with the risk. It is, of course, possible to revert to a yardstick of value such as the commodity dollar, which has been advocated from time to time, but while revaluation in 1933 disturbed public confidence, the theoretical gold dollar continues to be the standard of greatest stability. Its gain or loss in purchasing power is reflected ultimately in cost of production and selling price of the mine product. At present 35 dollars are allocated to one ounce of gold. Measurement of Risk In the application of the Hoskold and most other formulae, a yearly dividend rate commensurate with the risk involved is set aside out of annual earnings. If the risk is great, this rate may be 15 to 25 pct of the amount invested. The remainder is placed in a sinking fund invested in safe securities such as high grade bonds or conservative equities, and the interest or dividends from these securities are added to the sinking fund. The sum of these sinking fund payments and the compounded interest at the end of the mine life is taken as the value of the mine. Admittedly the decision as to the size of the risk rate is the most difficult element in valuation and one requiring the most exacting consideration. It is necessary to look years ahead in an effort to determine future costs, market prices, demand, competition which may develop, including that of substitutes, and other influences common to the mine and to the region in which it is situated. Another phase of risk is the enactment of unfavorable legislation, taxes, and what appears to be an alarming spread of nationalization and expropriation. Capital is sometimes borrowed from the government to finance strategic production. Such loans may be collectable only out of production and involve no liability otherwise. Valuation in these cases must recognize the effect of such a reduction in liability. Offsetting some of these risks are the possibilities of mechanization and other cost-reducing discoveries, improvements in mining and treatment methods, new uses for minerals and metals, and normal growth of markets. In this paper, the terms risk rate, dividend rate, and speculative rate are synonymous. Safe rate and redemption rate are also used interchangeably. These alternatives are used here because they are commonly found in the literature on mine valuation. In Michigan, the State Tax Commission has long employed a risk rate of 6 pct in its valuation of iron mines. There the outline of reserves is well established and operating costs and conditions are based on adequate experience. The following comment on rates appears in the report of the Minnesota Interior commission on Iron Ore Taxation submitted to the Minnesota Legislature of 1941.1 Most engineers agree that 7 percent for the specu-lative rate is "an absolute minimum". C. K. Leith in

Jan 1, 1954

By N. Standish

Heat transfer coefficients have been measured in beds of various packings irrigated with mercury and molten fusible alloy countercurrent to hot gases. The measured coefficients for both systems were found to increase with gas velocities and liquid rates. Correlations were determined which show this dependence and also indicate that heat transfer in these systems is influenced by the liquid flow characteristics and the thermal conductivity of the gas and the solid packings. A heat transfer model has beer2 proposed which explains the various features of the experimental results. On the basis of this study, which gives an insight into the heat exchange in the melting zone of the blast furnace, it was concluded that by comparison with the furnace stack heat transfer coefficients are about 1.5 times higher in the melting zone. EACH year large tonnages of metal are produced in operations which, in part, involve liquid metal irrigation of "packings" countercurrent to hot gases. The melting zone in blast furnaces and in cupolas is a good example of packings irrigated with a liquid melt countercurrent to gases. In all instances of this kind large amounts of heat are exchanged and it is desirable to have some knowledge of heat transfer phenomena involved in these systems. So far the most common method of analyzing furnace efficiencies, fuel requirements, and the general thermal state of the furnace has been through the use of heat balances. As heat balances are essentially statements of the first law of thermodynamics they give no real indication of the factors which govern heat transfer between phases in the various zones of blast furnaces. Hence, rational improvement in production efficiency and the development of theoretical models is only possible if the heat transfer characteristics are known at every stage of the process and related to the important variables involved. This has been generally recognized for some time but it was only recently that Kitaev et al.' have produced a comprehensive treatment of heat transfer in solid-gas countercurrent systems such as the blast furnace stack and the packed bed regenerator. Using their treatment it is now possible to predict the effect of particle size, thermal conductivity, bed porosity, and the flow rates of both the gas and the solid material on the heat transfer in the blast furnace stack. However, the stack of a blast furnace is only one part of an integral unit for which the heat transfer analysis cannot be complete without also considering the heat exchange in the melting zone. The complexity of heat transfer processes in this region of the furnace has so far escaped quantitative description. Yet, the melting zone accounts for a greater amount of heat exchange than all the other zones of the furnace put together. Moreover, if the reduction of oxides in the melting zone proceeds in part in the liquid state the importance of heat transfer on furnace productivity and on the metal and slag temperatures is obvious. THEORY Heat transfer for two-phase flow in packed beds is a complex problem involving a number of heat exchange paths for which interphase areas are not known with any degree of certainty. Analytical solution is, therefore, difficult. This difficulty is emphasized by noting that Rabinovich~ and Luck have only recently solved the steady-state heat transfer for simplified two-phase heat exchangers of known area. However, useful progress can be made for the system considered by making a not unreasonable assumption that the usual heat transfer considerations apply and restricting treatment to the steady state. For these conditions the rate of heat transfer dq in a height dz of a packed bed of unit area is: dq = UaATdz [I.] Integration of Eq. [I] then gives the total heat transferred: assuming both U, the overall heat transfer coefficient, and a, the interphase area, to be independent of bed height. Since a, in these systems, is unknown it is convenient to combine this term with U. The group U, then represents the overall heat transfer coefficient on a volumetric basis. If AT is linear with q, then for a bed of unit volume Eq. [Z] can be integrated to give: is the log mean of terminal temperature differences. From Eq. [3] U, can be readily calculated as q and {AT)im are experimentally obtained quantities, but a difficulty arises in interpreting its meaning. Two approaches are possible depending on whether the effect of packing in the transfer of heat is neglected or not. If the packing is thermally decoupled then the resistance concept gives the relationship: which states that the overall resistance is the sum of the gas phase and the liquid phase resistances (assuming areas are equal throughout). Because the resistance to heat transfer in liquid metals is negligible by comparison with that of the gas,4 Eq. [4] can be simplified, i.e.:

Jan 1, 1969

By C. Richards Honeycutt, Frederick C. Langenberg, Guenter Pestel

Solidification in a moving electromagnetic field was successful in altering the as-cast grain structure of steel ingots. The equipment is described and exerimental results are presented for several different alloys. Conditions for optimum grain refinement are described and an empirical design constant presented. The effect of the grain refinement on hot workability is briefly discussed. T HE grain structure of a steel ingot teemed into a metal mold can be defined by macroscopic examination in semiquantitative terms. For example, the relative volume of obviously differing structures can be estimated with the classic definitions of chill, columnar, and equiaxed zones. Experimental evidence has proven that the grain structure of an ingot is affected by changes in such factors as teeming temperature, rate of teeming, degree of turbulence, size of ingot, mold characteristics (including preheat temperature, design and coating), and composition of the metal (especially as it affects the range of solidification). Significant advances have been made in fundamental solidification studies; but the principles which have been developed are difficult to apply tothe complex and changing phenomena that occur simultaneously during ingot solidification. In particular, many attempts have been made to refine the as-cast structure of ingots, with special emphasis on the columnar grains. The formation of large columnar grains is generally considered harmful to the further fabrication of an ingot. It may also result in undesired ani-sotropic properties. However, columnar grains are not undesirable in all grades, or product applications, and caution must be exercised to determine in which grades and applications columnar grains are not desired in the ingot. Although the literature on the refinement of as-cast ingot grain structures is too vast in general to review here, it is noteworthy that such methods are additions of artificial nuclei, mold vibration, mechanical stirring or ultrasonic agitation of the molten metal, and controlled cooling and reheating during solidification have been tried with varying degrees of success. However, it is doubtful that any method of refining the as-cast ingot grain structure has been completely successful on a commercial basis. The purpose of

Jan 1, 1962

By Ernest F. Burchard

The Pao deposits of iron ore are in the State of Bolivar, Venezuela, near Upata, about 30 miles south of the Orinoco River and 90 miles east of Ciudad Bolivar. They were discovered 4 or 5 years ago and have not yet been developed to the stage of mining. In March-April, 1929, the writer devoted a week to the examination of these deposits. The maps, drill records and chemical analyses presented herewith were derived from original sources, and the field photographs were made by the writer. The petrographic and metallographic data are from notes by C. S. Ross and M. N. Short, of the U. S. Geological Survey, who have kindly collaborated in these special phases of the study. The Iron Obebodies Topography and Accessibility The deposits are in a region of low mountains representing northern outliers of the Guayanan Highlands. These mountains reach altitudes of 1800 to more than 2000 ft. above sea level, as determined by aneroid barometer. The iron ore is found on mountain crests that reach altitudes of 1915 to 1930 ft., and may be followed down precipitous slopes for 200 • to 300 ft. or more. The greatest vertical range in outcrop is nearly 400 ft., and drilling has indicated that the ore extends to this depth below the surface in one place, at least. The superior hardness of the iron ore accounts for the preservation of the local mountain crests with the intermediate valleys eroded in softer granitic rock. The deposits of iron ore are reached by a private road for automobiles branching northeast from the Ciudad Bolivar-Upata road, a distance of about 12 miles. This road was used in 1928-29 by trucks for transportation of food and camp supplies, gasoline, drilling equipment, etc., but was not suitable for the transportation of iron ore. Between Ciudad Bolivar and the iron-ore area the western two-thirds of the automobile road passes through nearly level, open country known as the savanna, largely used for grazing cattle. About 96 km. (60 miles) east of Ciudad Bolivar at

Jan 1, 1931

By H. M. Davis, T. S. Jones

A methodfor accelerating the reduction of a metal oxide by carbon monoxide is to incorporate in the reduction system a nonreducible oxide which has a strong affinity for carbon dioxide and will remove it from the product gases. The effectiveness of this method was investigated by veduction experiments on specially prepared powder mixtures of SrO-ZnO ("active'.) and SrCO3-ZnO (reference). Measurements at 750o and 677°C showed that the rate of reduction of ZnO by CO was as much as an order of magnitude greater in the presence of SrO. Under the experimental conditions at least as much CO2 as generated by veduction was absorbed when SrO was present. Enlzancernent of the veduction rate by SvO resulted from modification of' gaseous djfitsion processes. THE specific question posed in this investigation was whether the reduction reaction CO + ZnO - Zn(g) + COa [1] could be accelerated by incorporating strontium oxide into the oxide charge undergoing reduction. Provided the strontium oxide was active enough, it could remove carbon dioxide from the product gases of ( 11 and form strontium carbonate, thus modifying Reaction [ 1] to CO + ZnO + SrO = Zn(g) + SrCO3 [ 2] This study of the comparative rates of Reactions [ I] and [2] can be considered as a particular case of a general scheme for increasing the rates of reduction of metal oxides by carbon monoxide. The limits of applicability of this scheme are indicated in the simple thermodynamic analysis presented in the appendix. This analysis primarily dictated the choice of the system, CO-ZnO-SrO, employed in this investigation. In addition, it was thought that a study of this scheme by use of the CO-ZnO-SrO reaction system would be of special interest in view of indications in the literature1-3 that the gaseous reduction of zinc oxide is prone to rate control by diffusion in the gas phase. The distinction should be pointed out between this and other efforts to increase the rates of reduction reactions through the use of addition agents. Additions of a wide range of chemicals have been tried with de- grees of apparent success varying from slightly negative to highly positive. The reasons for making additions have included the use of salts to produce effects akin to catalysis,4, 5 the alteration of the microstruc-tural details of the reduction process (including solid-state diffusion),6-8 and the conversion of an en-dothermic reaction into one that is exothermic or autogenous.9-12 The means used to attempt alteration of the enthalpy change has commonly been to incorporate lime into the charge, so that heat is generated by reaction with either of the reaction products, carbon dioxide or water. The use of lime in this way makes endeavors such as that of Edstrom and Wiberg similar to the present one. Furthermore, the basic principle behind the present work has previously been set forth.13 However, a detailed investigation of the type of reaction described in this work does not appear to have been conducted. EXPERIMENTAL PROCEDURE From both conceptual and physical standpoints, Reaction [2] is to be considered as the sum of two reactions:

Jan 1, 1968

By R. P. Abendroth

This study is concerned with the kinetics of selective oxidation of chromium in a commercial Fe-Cr-Ni alloy. Selective oxidation of chromium in this alloy, by use of a low oxygen-potential atmosphere, leads to the formation of a compact, protective layer of Cr2O3. This layer serves to protect this alloy from gross scaling when it is subsequently exposed to severe oxidizing conditions at high temperature. The interaction of low oxygen-potential atmospheres close to equilibrium with Fe-Cr and Ni-Cr alloys has been studied by others."' These studies werk concerned with the surface-structure variations under slightly oxidizing conditions. NO detailed study was made of the oxide scale formation kinetics, however. The alloy samples were cut from 0.012-in.-thick sheet, with an apparent surface area of 7.1 sq cm. These sheet samples were abraded through 4/0 metallographic paper, and washed in alcohol and acetone. The analysis of the sheet alloy is (in weight percent): 42 pct Ni, 5.5 pct Cr, 0.09 pct C, 0.18 pct Al, 0.36 pct Si, 0.26 pct Mn, balance Fe. The weight gain vs time data were obtained with a 2-g capacity fused-silica spring—cathetometer system. The spring deflection was optically magnified ten times before being read by the cathetometer. A sensitivity of about 0.01 mg was attainable. The spring was enclosed in a water jacket maintained at 60°C to minimize the effect of temperature changes. The sample was suspended from the spring with a fused-silica hangdown and was positioned in the thermal center of a mullite furnace tube. Sample temperature was read with the aid of a thermocouple placed outside the mullite tube and an inside vs outside temperature calibration. Temperature change during the course of a run was ±0.25°C, with a temperature gradient of less than l.O°C over the length of the sample. Total temperature uncertainty was no more than ±3.0°C. Alignment difficulties between the hangdown and radiation shields in the furnace tube required that the sample be positioned in the furnace when cold, and heated with the furnace until the temperature stabilized at the desired point. This required 5 to 6 hr, and was carried out in Matheson ultrahigh-purity hydrogen. Oxidation was started, after evacuation, by introducing a hydrogen-water vapor mixture, obtained by saturating hydrogen with water vapor at 31.00o ± 0.02oC. Oxidation was continued for 90 min. Gas flow was 300 ml per min during heat up and oxidation. Since only several milligrams of oxide are formed on each sample, chemical analysis of the oxide is difficult. A representative analysis is: 80 pct Cr2O3, 5 pct Fe2O3, 3 pct Al2O3, 4 pct MnO, 7 pct SiO2, 1 pct or less NiO. X-ray diffraction analysis of the oxide as formed on the alloy gives rhombohedra1 Cr2O3, and barely distinguishable amounts of a cubic spinel phase, and possibly AlZOs and SO2. The identification of these latter two compounds is by no means certain. The spinel phase could be based on iron or manganese as these elements are present in significant amounts in the oxide. The results of the kinetic studies using 31°C dew-point hydrogen-water vapor mixtures were found to conform to a parabolic rate law. In many cases the parabolic plot consisted of two intersecting straight lines, defining an early and a late rate for a particular run, and in the other cases the parabolic plot consisted of one straight line for the entire run. The slopes of the various straight lines were determined by the method of least squares. Reproducibility of the data was good enough for multiple runs at the same temperature such that the value given for the rate constant is the average for two or more closely similar values, rather than widely varying values of the rate, where more than one determination is indicated in Table I. The exhibition of only one or of two rate constants during a run can happen at the same temperature. Thus, Table I shows that at 11'74°C a single rate constant was obtained from one sample, while other samples oxidized at the same temperature gave an early and a late rate constant. It should be noted that the single rate constant corresponds very closely with the early rate constant. This is also true at 1153°C. The time at which the late rate started to appear was variable, usually occurring 20 to 40 min after oxidation had started.

Jan 1, 1964

By E. P. Klier

THE work of Klier and Lyman1 on the bainite reaction has led to the full description of this reaction for medium-carbon low-alloy steels. Certain experimental data reported by Klier and Lyman appear, however, to be improbable of obtaining in very high-carbon steels. The study herein reported consists of an analysis of the transformation characteristics of a 3 per cent chromium, 1 per cent carbon steel by means of X-ray and metallographic methods. From the results obtained it is concluded that the bainite reaction in this steel is more complicated than that reported by Klier and Lyman for the low-carbon low-alloy steels. However, the mechanism of bainite formation in this steel appears to be essentially the same as proposed for the low-carbon low-alloy steels with the modification that the first volumes to transform are carbon-rich rather than carbon-poor. EXPERIMENTAL PROCEDURE The analysis of the steel studied was: Cr, 2.89; C, 1.02; Mn, 0.33; Si, 0.35; S, 0.012; P, 0.020. The stock was received from the Carpenter Steel Co. in rolled bars. Specimen Preparation Specimens were austenitized at 1200°C. (2192°F.) for 25 min. in purified nitrogen. The resultant A.S.T.M. austenite grain size was 0-1. Isothermal transformation was allowed by quenching the specimens into liquid metal baths controlled to ±5°C. at 540°C. (1004°°F.) and above, and to ±2°C. at 490°C. (914°°F.) and below. Following the desired degree of transformation all specimens were water quenched. Metallographic Examination Specimens 1/4 in. round by 1/4 in. were used for metallographic examination. Etchants used were Vilella's reagent (1 gram picric acid, 10 ml. hydrochloric acid to make l00 ml. ethyl alcohol solution) and alkaline sodium picrate (electrolytic). Vilella's reagent was effective in revealing all microconstituents, while the alkaline sodium picrate developed the carbon-rich structures or carbides only. X-ray Examination Two X-ray techniques were used-the Debye-Scherrer method and a back-reflection method. The small specimens necessary for the Debye-Scherrer method were austenitized and then allowed to transform, or were cut from the larger metallographic specimens. The metallographic specimens were used for the back-reflection X-ray analysis. When it was desirable to determine the structure of the carbide present, sliver specimens were electrolytically etched to develop a carbide coating, then were exposed in the cameras. This technique was frequently necessary to allow positive identification of the carbide.

Jan 1, 1945

By Sheldon P. Wimpfen

EVERYWHERE in mining circles the talk is of this new development of hard faced or insert bits which hints of many changes to come in mining practice and rock drill equipment. In the past fifteen years new equipment has appeared in rapid succession which brought one change after another in rock breaking practice. Detachable bits were an innovation which met with wide success. Blasthole diamond drilling has proven itself. Only recently, fusion piercing was announced as a possible solution to the problem of breaking taconite ores. For several years this interest in new methods has been growing and various experimental usages of tungsten carbides in rotary type rock drilling bits have been partially successful. American experts in rock drilling have been concerned with the subject for ten years but actual commercial practice was begun by European manufacturers and mining companies. At this time nearly every manufacturer of rock drilling bits is working on some type of an insert bit. On the Rand, European manufacturers are testing out various types of insert bits. The problems relating to rock drilling in South Africa vary greatly from ours. The bulk of the drilling there is limited to the 31/2-ft holes that are drilled for breaking the gold bearing reef ore. Rock drilling in most mines is far more diversified. Both drifting and ore breaking call for holes varying in length from 4 ft up to as much as 50 ft and more.

Jan 1, 1947

By D. Walton, B. Chalmers

A preferred orientation is known to occur frequently in the columnar zone of castings. This has been attributed to a preferred direction of growth. However, no satisfactory mechanism was proposed by which the preferred direction of growth led to the preferred orientation. The purpose of this work has been to establish this mechanism. It has been found that in general the observed preferred orientations only develop when the preferred directions of growth reveal themselves by dendritic growth. A mechanism based on this premise is found to be in agreement with the experimental data obtained in the course of this work. WHEN a liquid metal is allowed to solidify in a mold, it usually freezes in three stages, distinguished from each other by the size and shape of the grains. The first zone to freeze (the chill zone near the mold wall) consists of relatively fine grains that are equiaxed in shape and random in orientation. The next zone consists of crystals that are elongated in the direction of heat flow, i.e., normal to mold wall. These crystals are much larger in cross section than the crystals of the chill zone and have a very strongly preferred orientation. This is the columnar zone. The final zone, which is absent in very pure metals, is again equiaxed and randomly oriented, but usually has a much coarser grain size than the chill zone. The purpose of this study is to describe and account for the crystal size and orientation in the columnar zone. The occurrence of a preferred orientation in the columnar zone is well known, and in 1940, Greninger' suggested that it is apparently related to dendritic growth although at that time the only data were for metals with the face-centered-cubic structure. Table I shows that the direction of dendritic growth and the crystal axis that follows the heat flow direction coincide in all cases so far studied. The term "dendritic growth" is used here to represent the branched type of morphology that is characteristic of growth into supercooled melts.' In addition to the supercooling which is necessary before nucleation will occur at the mold wall, the necessary supercooling for continued dendritic growth can be provided in a mold by heat flow into the already formed solid at an interface whose Liquidus temperature is depressed by an accumula-

Jan 1, 1960

By N. Mungan, J. L. Thompson

Laboratory displacement tests were performed to study oil recovery elficiency by gravity drainage in fractured systems under miscible conditions. The porous media used were cylindrical Berea and Blue Jacket sandstone cores containing a number of well-defined, artificially formed, vertical and subvertical fractures. Butane and Soltrol 130 were the two miscible fluids used. The purpose of the study was to examine the influences of the displacement rate, fracture density, fracture orientation, fracture permeability, matrix permeability, crossflow, core length and connate water on the oil recovery. It was found that displacement rate, matrix permeability and the subvertical fractures affected oil recovery most. The critical flow rate, based on the matrix permeability, was found to be a significant factor in the process. For displacement rates below the critical flow rate, the oil recovery efficiency appeared to be unaffected by the density of the subvertical fractures. At the high displacement rates, the fracture density becomes important, with the recovery being the most efficient in the core having the greatest number of the subvertical fractures. The magnitude of the fracture permeability, the fracture orientation, the core length and the connate water have little effect on the oil recovery efficiency. INTRODUCTION Gravity drainage under miscible conditions from relatively thick reservoirs can be a very efficient recovery process, especially at low flow rates where the gravity forces are dominant and, consequently, the adverse viscous fingers associated with the unfavorable viscosity ratio are minimized or eliminated. Such a process might involve injection of an LPG or some solvent bank at the crest and then driving the bank with dry gas. For some favorable combination of reservoir temperature, pressure and oil composition, there may be no need to inject any solvent bank, since enrichment of the dry gas by the light ends of the crude creates an in-situ solvent bank. Slobod and Howlett2 have studied the effects of gravity segregation in vertical unconsolidated porous media under miscible conditions in the laboratory. The main variables in their study were the viscosity ratio, the density differences and the rate of flow. In this study, the objective was to find the influence of fractures on gravity drainage under miscible conditions. A greater number of related variables were also studied. LABORATORY STUDY CORE DESCRIPTION Displacement tests were performed mostly in cylindrical Berea sandstone cores. In a few cases in which a much lower matrix permeability was desired, Blue Jacket sandstone cores were used. The vertical fractures were formed by cutting the cores with a thin circular blade or by parting them along a bedding plane. The vertical fracture plane always contained the axis of the cylindrical core. The subvertical fractures, cut with a saw, were inclined 45' from the horizontal. The line of intersection between the planes of the vertical and subvertical fractures was parallel to the circular faces of the cores in all cases except one, as depicted by VF3HF-2 in Fig. 1. Fracture geometry of the other cores is also given in Fig. 1. Tables 1 and 2 give the physical properties of the solid and fractured cores, respectively. The suffixes and prefixes shown for each core have been used throughout the paper so that the reader may discern the fracture geometry from the core numbers.

Jan 1, 1970

By Olin M. Hart

Uranium ores occur in the Lower Cretaceous Inyan Kara group of heterogeneously stratified fluvial and fluvial-marine sandstones in the Black Hills of western South Dakota and northeastern Wyoming. There are three principal mining districts, each in the ancestral and present drainage area of a major river partially responsible for stripping the region to its present topographic form. Primary minerals in the deposits are coffinite and uraninite with minor amounts of paramontroseite and haggite. The ore minerals coat sand grains and fill interstices of complexly cross-stratified sandstone along solution fronts similar to "roll" type deposits of the other districts. Minerals of oxidized deposits are typically carnotite and tyuyamunite with different proportions of secondary vanadium accessory minerals. Ground water was the transporting medium and deposition of primary uranium and vanadium minerals occurred in reducing environments produced and controlled by physio-chemical characteristics of the sedimentary rocks.

Jan 1, 1968

T. W. ROBINSON, Pueblo, Colo.: Mr. Potter's review is a striking testimony to the important part played by science in this branch of practice. But, the question arises, In which department has science effected most ? The available raw material, the size of furnaces, the general design and equipment of the plant, and the daily management, are particulars, each of which contributes to the general result, while the effect of each merges into that of the others. The following notes concerning the operations of the furnace-plant of the Colorado Fuel and Iron Company (formerly the Colorado Coal and Iron Company), at Pueblo, may throw some light upon the question of their relative importance. This company operates three stacks, and when the plant first came under my observation, about nine months ago, the furnaces were constructed, equipped,and run as stated below: Raw Materials.—The main sources of ore-supply were, as they still are, the Orient and Calumet mines of the company. The Brecce and Morning Glory ores, mentioned below, were formerly brought from Leadville, but are practically now no longer used. The Orient ore is a porous brown hematite, easily reducible in the furnace. The Calumet is a magnetite, very refractory in character, requiring preliminary roasting. Both are fairly uniform in composition. The Breece and Morning Glory are red hematites, resembling in appearance the soft ores of the Vermilion range, Lake Superior. The coke here used is made of coal from the company's mines in southern Colorado, and is distinct from that produced by the company in the western part of the State. The structure is similar to that of Alabama coke. The limestone employed is a calcite. The analyses are given in Table I. I would note, parenthetically, that I know of no section of the country presenting harder conditions for furnace-practice than these materials impose. Results cannot be measured by the more

Jan 1, 1894

By L. A. Schrider, J. A. Wasson

A method of predicting waterflood performance has been developed that combines certain facets of several previously published prediction techniques. The manner of combination has required the development and use of some new and some little-known relationships and has eliminated several of the weaker assumptions inherent in the original individual prediction methods. This approach, which was designed for computer solution, has removed the necessity of referring to plotted curves and permits the analytical prediction of water flood performance for a five-spot well pattern in either homogeneous or stratified reservoirs. The Predicted values are expressed in common oilfield units rather than in abstract or dimensionless terms. The calculation procedure has been programmed in FORTRAN IV and the entire program listing is available to potential users.* Introduction Prior to initiation of secondary recovery of oil by waterflooding, the possibilities of economic success or failure must be evaluated with the greatest practical accuracy. Although many prediction techniques are available, most, if not all, have serious limitations. In recent years, the Bureau of Mines has attempted to stimulate interest in the secondary recovery of oil from Appalachian pressure-depleted reservoirs. Waterflooding, because of its widespread acceptance and success, is the principal secondary-recovery method considered. During the life of the project, several performance prediction methods have been studied and applied. Because these methods, individually, have inherent assumptions and limi-tations, portions of some of them have been selected and combined in an effort to eliminate such shortcomings wherever possible. We believe that the resulting technique is as accurate as the necessary available data will permit and that it has several distinct advantages over previously published methods. Development of the Method The fractional flow equation developed by Buckley and Leverett' from Darcy's law is the fundamental mathematical statement describing immiscible fluid-fluid displacement in porous media. A generalized form of this relationship, whose derivation is readily available in the literature, is The formation dip, a, is usually very small in those petroleum reservoirs being considered for pattern waterflooding in the Appalachian area. Therefore. in many cases. a has an almist negligible value. In addition, Ap, the difference between the density of water and the density of oil, is relatively small. For these reasons the gravitational term may often be neglected. Capillary pressure is a function of saturation, which is in turn a function of distance from the upstream boundary of the system or the injection well. In this study it is assumed that the frontal zone of the waterflooding (or zone of capillarity) has negligible length and that only those saturations in the water-swept zone at breakthrough and later are of interest. As the distance in a waterflood pattern is comparatively large and the change in water saturation with distance is usually small, the change in capillary pressure with distance is negligible. The simplified form of the fractional flow equation is appropriate, therefore, in this application. Three variables must be considered in determining that fraction of the total fluid flow that consists of water: the viscosity ratio, saturation, and relative permeability ratio.

Jan 1, 1969

By D. E. Hartman, J. M. Roberts

A detailed study of the temperature dependence of the critical stress, TB . necessary to cause a damping loss of 1.41 x 10-6 g mm per mm3 in pre-strained magnesium single crystals has been carried out in the temperature range 82" to 320°K. Tb is found to be linearly related to the reciprocal of the ahsol~cte temperature in this temperature range. The temperature dependence of the anelastic limit, TA, defined as the stress necessary to form open unidirectional stress-cycle damping loops has been measured between 82" to 320°K. ta is found to be independent of temperature in this range. It is suggested that TA is determined by the stress necessary to activate Frank-Read dislocation NUMEROUS studies1-9 have been reported concerning the details of yielding and microstrain near and below the generally discussed macroscopic flow stress. The work of Kramer and coworkers10-13 is helpful in determining certain qualitative facts. concerning preyield phenomena. The absence of a stress-dependent delay time in annealed copper and aluminum single crystals between 83" and 298 suggests that the preyield mechanism is temperature-independent in this range. This is not sources. The temperature and stress dependence of the effective activation volume (Veff) has been measured in the damping-loop region in prestrained magnesium single crystals. The data suggests that Veff/kT is approximately constant, equal to 2 4.5 sq mm per g in the temperature range 130°to 298°K, and that Veff is almost independent of stress at stress levels greater than 10 g per sq mm. A restricted model is developed to predict the stress (rb) necessary to cause a small fixed damping loss as a function of temperature, effective activation volume, and dislocation density. Various possible dislocation mechanisms controlling TB are discussed. true for zinc, p brass, and iron crystals in the same temperature range, however, since the existence of a stress-dependent delay time suggests a thermally activated preyield mechanism in these materials.10-13 The work by Vreeland et a1.14 confirms the work by Liu et al.ll on delayed yielding in zinc single crystals. A stress-dependent delay time between 82" and 298°K was found12 in prestrained aluminum and copper crystals. These results suggest that the preyield phenomena may be different between prestrained and unstrained or annealed crystals. The temperature dependence of the yield point at 2 x 10-8 plastic strain found by Rosenfield and Averbach3 in annealed copper and aluminum is not in agreement with the delay-time data, unless possibly the delayed yielding experiment only de-

Jan 1, 1964

By L. H. Levenson, Charles S. Barrett

Plastic flow in metal crystals and the changes in orientation resulting from it are generally understood to take place by the following fundamental mechanisms: (1) slip on crystallographic planes, (2) homogeneous crystal rotation resulting from the slip, (3) bending of the 1attice between the planes of slip, and, under certain circumstances, (4) twinning. This paper and a preceding one on iron subjected to uniaxial compression1 concern two additional processes that must now be added to this list: (5) the formation of deformation bands, and (6) the bending and rotation of these bands. The present investigation yields a new understanding and definiteness to the common terms so loosely used when speaking of cold-worked metals —('grain fragmentation," "elongated grains," and "deformation twins," "deformation bands," "etch bands," or "X-bands." Bands have been noted on the polished and etched surfaces of cold-worked metals by various investigators for more than 25 years, ‡ yet their nature and their significance have been so little understood that they are not treated in the most comprehensive modern texts on the deformation of crystals. The experiments in this series show that they are one of the fundamental processes in the deformation of metals, of importance in the development of preferred orientations, in work-hardening (since they have the effect of reducing the effective grain size and interfering with slip), and in the recrystallization process. The present experiments were performed on the same stock of material that was used in the earlier compression experiments1—hydrogen-purified mild steel in which the carbon content had been reduced to the limit detectable under the microscope and in which single crystals could be grown by a strain-anneal treatment.2

Jan 1, 1939

By Charles S. Barrett, L. H. Levenson

Plastic flow in metal crystals and the changes in orientation resulting from it are generally understood to take place by the following fundamental mechanisms: (1) slip on crystallographic planes, (2) homogeneous crystal rotation resulting from the slip, (3) bending of the 1attice between the planes of slip, and, under certain circumstances, (4) twinning. This paper and a preceding one on iron subjected to uniaxial compression1 concern two additional processes that must now be added to this list: (5) the formation of deformation bands, and (6) the bending and rotation of these bands. The present investigation yields a new understanding and definiteness to the common terms so loosely used when speaking of cold-worked metals —('grain fragmentation," "elongated grains," and "deformation twins," "deformation bands," "etch bands," or "X-bands." Bands have been noted on the polished and etched surfaces of cold-worked metals by various investigators for more than 25 years, ‡ yet their nature and their significance have been so little understood that they are not treated in the most comprehensive modern texts on the deformation of crystals. The experiments in this series show that they are one of the fundamental processes in the deformation of metals, of importance in the development of preferred orientations, in work-hardening (since they have the effect of reducing the effective grain size and interfering with slip), and in the recrystallization process. The present experiments were performed on the same stock of material that was used in the earlier compression experiments1—hydrogen-purified mild steel in which the carbon content had been reduced to the limit detectable under the microscope and in which single crystals could be grown by a strain-anneal treatment.2

Jan 1, 1939

By C. B. Alcock, L. I. Cheng

By the use of radiochemical methods for the study of the gas-liquid equilibria at low temperature, and for the determination of the sulfur contents of metal beads which had been equilibrated with H2S/H2 mixtures of known sulfur potential, it has been possible to obtain the liquid solubility and the free energy of solution of sulfur in liquid tin and lead at temperatures between 500°and 680°C. THE gas-liquid equilibrium method has proved in the past to be most successful in the determination of the thermodynamic behavior of dilute solutions of sulfur in liquid metals.1,2 One of the basic requirements for success with this method is that the volatility of both the metal and its lowest sulfide should be small, otherwise sulfide will be deposited at the cool end of the furnace, where it may react with the outgoing gases to form either sulfur-rich lowest sulfide or higher sulfides. The resultant value of the apparent equilibrium constant will then be lower than the correct one. This argument applies even at sulfur potentials below that in equilibrium with a separate condensed phase of the lowest sulfide at the reaction temperature, T. The mass of sulfide which is deposited at the cold end of the furnace, and hence the extent to which further reaction occurs with the outgoing gases, depends on the time taken for equilibrium to be reached between metal and gas. Since this will depend principally on the bulk of the metal phase which is used, one should clearly attempt to uie as small metal samples as possible. These considerations are important in the study of dilute solutions of sulfur dissolved in liquid tin and lead which both have moderately high vapor pressures as metals and form volatile sulfides. The limit on the size of the metal samples which may be used is set chiefly by the difficulties of analysis for very small amounts of sulfur. The oxygen or carbon dioxide combustion method, followed by iodimetric determination of the sulfur dioxide which is formed,has been found to be successful for the determination of small amounts of sulfur in copper, iron, cobalt and nickel.4 This method was unsatisfactory for sulfur dissolved in tin and lead, mainly because the sulfur dioxide was to some extent absorbed by the copious tin or lead oxide deposits which were formed on the walls of the combustion tube. Furthermore some of the sulfur was found to segregate on the surface of the beads as flaky sulfide crystals which would easily be lost in the transfer of a bead from a boat in the gas equilibration apparatus to one in the combustion apparatus. Oxidation in aqueous media to sulfate ion followed by precipitation as barium sulfate was, therefore, adopted as the analytical procedure. The gas-metal equilibrium experiments were all carried out with radioactive sulfur and thus the analysis involved the counting of barium radiosulfate. Furthermore the use of the radioisotope meant that the approach to the gas-metal equilibrium could be followed continuously by gas counting.' The metal beads were held separately in glass crucibles during equilibration and were transferred from the furnace to the beaker for dissolution in nitric acid still in the crucibles, and thus the possibility of sulfur loss by detachment of the sulfide segregates was eliminated. The temperature range of this investigation was 500° to 680°C. EXPERIMENTAL APPARATUS AND METHOD The apparatus consisted of two furnaces placed in series in a gas recirculation system, Fig. 1. One furnace F1, which was vertical was used to heat the alumina crucible, A, holding six metal beads in separate glass crucibles. The beads weighed between 300 and 700 mg each. The crucible assembly was introduced and removed from the furnace mechanically under a stream of oxygen-free argon. The other furnace, F2, was horizontal and was used to heat a cobalt Co9S8 mixture, held in an alumina boat, and made with radiosulfur containing about 1/2 millicurie per g of sulphur. This mixture, which was finely powdered, was used as a source of known H2S/H2 mixtures6 for a given furnace temperature. The recirculation system also contained a gas re-circulation pump (P), an end window Geiger-Miiller counter (N)—placed downstream of F1 so as to monitor the H2S pressure in the gas leaving this furnace— a sample volume for chemical analysis of the gas phase (G), gas drying tubes (D), filling taps and other standard ancillary equipment. The gas sampling volume was principally used in the cali-

Jan 1, 1962

By Edward Estabrook

THIS paper gives a brief account of the geologic and production problems encountered in the Grass Creek oil field, the methods used in their solution, and the beneficial results obtained from the work. The author wishes to acknowledge the assistance received from J. H. Pearson and Miss Ninettta A. Davis in the collection of the data and the preparation of the cross-sections. Permission for its publication was given by the officials of the Midwest Refining Co. and the Ohio Oil Co. The Grass Creek oil field is located in Ts. 98-99 W., R. 46 N., Hot Springs County, Wyo. The productive area includes about 2 1/2 mi. (4 km.) on the apex of a great anticlinal fold occupying more than 150 sq. mi. Fig. 1 shows the structural contours of the field. Oil was dicovered in the field in June, 1914; development proceeded rapidly and production rose to a maximum in 1918. The marketed production has been approximately as follows: BARRELS BARRELS 1915 94,073.5 1918 2,946,774.27 1916 1,404,183.97 1919 2,000,584.84 1917 2,780,697.51 1920 1,485,080.94 About 350 wells, 800 to 1500 ft. (243 to 457 m.) deep have been drilled to reach the upper oil sands; two companies, the Ohio Oil Co. and the Midwest Refining Co., operate the entire field.

Jan 2, 1922

By W. G. Sinclair

THE North Texas district presented in this paper includes the counties of Archer, Baylor, Clay, Cooke, Foard, Hardeman, Jack, Knox, Montague, Wichita, Wilbarger and Young. It corresponds with the Texas Railroad Commission's district No. 9. Table I conforms with the nomenclature of pools as designated by the Commission. Most of the oil and gas produced in this region, generally referred to as the Red River uplift, comes from the Pennsylvanian strata. In recent years, however, increasing amounts are being developed in both the Mississippian and Ordovician.

Jan 1, 1946

By Gerhard Derge

A SERIES of studies of the corrosion of tin is under way in the Metals Research Laboratory at the Carnegie Institute of Technology. The complete program includes examination of the corrosion properties of high-purity tin and the changes produced in these properties by the addition of varying amounts of alloying elements. Other studies of this subject have been made recently under the sponsorship of the International Tin Research and Development Council, but these researches have been confined largely to the weakly acid environments commonly encountered in the canning industry.1 There is little information available regarding the corrosion of tin under alkaline conditions, but such data would be of value, for a large amount of the metal is used under such conditions. The potential measurements to be described were made because they seemed to offer the most rapid method for obtaining a general view of the conditions to be encountered in such service. These experiments will also serve to establish a technique that will be of value in further studies. It must be emphasized that the results reported are those of controlled laboratory experiments and that the conclusions drawn cannot yet be applied to service conditions; rather, they point to the directions in which more exhaustive experimental work may be done to best advantage. EXPERIMENTAL PROCEDURE The first work was devoted entirely to the problem of obtaining reproducible results from a series of potential measurements. Only the methods finally adopted as standard will be described here, except when the variations from these have furnished results of interest. The cell used is shown schematically in Fig. 1. The electrolyte is contained in the vessel A (an inverted bell jar), whose ground top is fitted to the transite-board lid B. The controlled atmosphere can be admitted

Jan 1, 1938