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A method has been developed to remove calcite from the leaching circuit in the uranium in situ leaching system. The process involves injecting the leachate and a pH control agent tangentially into an inverted cone reactor containing calcite seed catalyst. The leachate can be treated at high throughput to obtain clear effluent containing 5 ppm or lower Ca. Both lime and ammonia are effective pH control agents and consumed according to stoichiometry.

Jan 1, 1985

By Chester Wells Purington

Situation.—The Camp Bird mine is in Imogene basin† (Fig. 1) at the head-waters of Canon creek, a branch of the Gunnison, in the southern part of Ouray county, Colorado, towards the northern edge of the region known as the San Juan mountains, and about 10 miles W. of the continental divide. It is 8 miles by wagon-road from Ouray, the terminus of a branch of the Rio Grande' Southern railway. The distance from Denver to Ouray is 387 miles by rail. In an air-line, the mine is 190 miles SW. of Denver. The altitude of the town, tunnel and buildings is 11,200 ft., and level No. 2 is 11,500 ft., and No. 1 is 11,670 ft., above sea-level. The lowest point of the lode-ontcrop, which crosses the basin E. and W., has an elevation of 11,850 ft., and that of the highest point, on the divide between Imogene and Tomboy basins, is 13,250 ft. On the eastern slope of the Imogene basin (towards Ironton) the vein is less clearly defined on the surface. Ownership and Extent.—At the time of the writing of this paper, the property is owned by Mr. Thomas I?. Walsh, and operated under the management of Mr. J. W. Benson. It

Jan 1, 1903

THE slag performs two useful functions in open-hearth steel- making. First, it is the means of disposal of all the impurities, save carbon, which are removed from the charge materials in refining the steel, so it must be suited to receiving and retaining as much as possible of undesirable elements with minimum loss of iron and useful alloying elements. Second, the slag serves as a buffer between the flame and the bath and transfers oxygen to the metal at a measured pace contrasted with the violent and difficultly controlled oxidation of the bessemer process. At the same time, the slag is a thermal insulator that limits the rate at which heat can be delivered to the metal from the flame, and a heavy slag blanket thereby serves as a brake on production rates. It has been said with justification that the secret of good steel- making is to make a good slag and the steel will take care of itself. In a broad sense, the subject of slag control includes not only the adjustment of the composition of the slag but also of its relative weight in terms of percentage of the metal-bath weight. The slag is made up essentially of: (1) oxides formed by oxidation of silicon, manganese, phosphorus, and iron in the charge, (2) Si02, MnO, MgO, and other oxides charged as such or introduced incidentally with ores or fluxes or by refractory erosion, and (3) lime charged or fed to the heat to neutralize the "acidic" oxides present (Si02 and P205). Obviously, if practically perfect control were possible over the composition of the charge as well as over the oxidation process during the melting period, both slag weight and composition would be very nearly predetermined; and the control problem would be solved. Unfortunately, only a somewhat imperfect control over these factors is possible, so the operator must begin during the lime boil and continue through the refining period to discover and correct departures from the normal pattern of slag development. To do this as the heat progresses, the first helper must be able to make quick estimates of the composition and physical state of develop-

Jan 1, 1964

By N. Mungan

A study was made of the effects of wettability and interfacial tension on the immiscible displacement of a Iiquid by another Iiquid from porous media. The influence of viscosity ratio was also investigated. Porous media used were polytetrafluoroethylene (TFE) cores prepared by compressing TFE powder under different pressures. lt is shown that displacement of a wetting by a nonwetting Iiquid is always less efficient than the displacement of a nonwetting by a wetting fluid, all other things being equal. In the former case, the recovery efficiency can be increased substantially by either reducing the interfacial tension or increasing the viscosity of the displacing fluid. A qualitative discussion is given on the implications of this work to the recovery of crude oil by water flooding. INTRODUCTION The high cost of oil exploration and new recovery schemes makes it imperative that waterflooding be conducted under conditions favoring most efficient oil recovery. To improve oil recovery by waterflooding, it is essential that the role played by interfacial forces in the entrapment of residual oil be studied and understood. Interfacial phenomena in natural rock, connate water and crude oil systems are very complicated because of the complexity of the natural liquids found in petroleum reservoirs, because of our inability to adequately describe the geometrical structure of the porous media and because of a lack of understanding of physical and chemical interactions between the liquids and surface of the pores. The problem becomes further complicated when one tries to elucidate the role of interfacial phenomena in fluid flow. Numerous studies of the displacement of oil by water under different interfacial tension or wet-tability conditions have been made.lm3 These studies have been performed in silica, alundum or sandstone systems using water and paraffin oil and also some surface active material to control the interfacial tension s and the contact angle 0. Unfortunately, the high energies of various interfaces involved favor adsorption and orientation of the surface active material at the interfaces. Also the surface active material concentration at the interfaces exceeds that in the bulk of the liquid phases. Such surface excess may cause the surfactant distribution, the contact angle and the interfacial tension to differ from their measured static equilibrium values and makes interpretation of the displacement experiments difficult. Furthermore, as changes in s also lead to changes in cos 0, the role played individually by one of these parameters in the displacement becomes obscured by the effect of the other. To circumvent these difficulties, a low surface energy solid and true solutions or pure liquids should be used. Use of a low surface energy solid minimizes adsorption and orientation effects at the solid-liquid interfaces. By controlling s and cos 0 through use of selected pairs of pure liquids or true solutions rather than by surfactants, the adsorption effects at liquid-liquid interfaces are eliminated. In the present study TFE cores were used as the porous media. Liquids used were water, sucrose solutions, paraffin oils and benzyl, n-butyl and isobutyl alcohols. The interfacial tension was varied from 40 to 1.1 dynes/cm by suitably choosing the liquid pair. A surface active material was added to the water-oil system only in the case where interfacial tension of 0.5 dyne/ cm was desired. No precise changes of cos 0 were attempted. However, either the displaced or the displacing liquid could be made the one which preferentially wets the TFE surface. Using sucrose solutions and blends of paraffin oils proved to be a convenient way of changing the viscosity ratio between the displaced and displacing liquids. The present investigation examines the effect of interfacial tension, wettability and viscosity ratio on the immiscible liquid-liquid displacement from porous media. Observed data permit a

Jan 1, 1967

By Ionel Gardescu

IN connection with some of the experiments carried out by the writer on the behavior of gas and oil in a sand reservoir,1 an interesting phenomenon was observed which may throw some new light on the problem of recovery of oil from a natural reservoir. The experiments are intended to show the effect of the surface area of the occluded gas masses, originally present in a reservoir, on the further evolution of gas from the oil and its consequent effect upon the rate of production of oil. The apparatus used in the experimental work is shown in Fig. 1. It consists primarily of a sand reservoir R and a displacement chamber D, which is used to induce small variations in volume. The reservoir and displacement chamber form a unit, and a lowering of the plunger D is equivalent to increasing the volume occupied by the oil and gas in the reservoir. The reservoir was first filled with dead oil and maintained under pressure until it was ascertained that most of the free gas had gone into solution. The volume of free gas present in the reservoir was computed from the coefficient of compressibility of the fluids by means of the dis-placement chamber D, reading to 0.005 c.c. and a special gage J reading to 0.02 lb. per sq. in. The oil was saturated with gas under pressure in reservoir S by circulating the oil for a long period of time through the gear pump B. Subsequently, the saturated oil was circulated through the sand reservoir following the circuit S6, B, S5, R4, the sand reservoir R, R1, R2, F4, F1, back to reservoir S. In the following experiments the sand reservoir R was filled with gas-saturated oil at a pressure of 415 lb. per sq. in. with no free gas present. This was ascertained by. closing off all the outlet valves, and determining the coefficient of compressibility of the system by means of the dis-placement chamber D.

Jan 1, 1932

By C. A. Stetefeldt

In a former paper (Runs., xxi., 286) I described the plant of the Marsac Refinery, and the manipulations of the process, but cou1d not, at the time, give reliable statistical results. To supply the latter is the object of the present paper. I shall give actual facts as correctly as possible, without any bias one way or the other. For all statistics I am indebted to Mr. W. G. Lamb, who has charge of the Marsac lixiviation-plant and refinery; to Mr. A. Luebeck, assayer at the Ontario mill; and to the Daly Office, Salt Lake City.* Before starting on the work of the year 1892, a most careful clean-up was made, and any remnants were charged to the refinery. During 1892 the Marsac lixiviation-works produced 48.8 tons of so-called "regular" sulphides, which contained, on an average, 11,449 ounces of silver per ton; 11.77 ounces of gold per ton; and 569.8 pounds of copper per ton. To this must be added, 266 pounds of sulphides and by-products left over from the product of 1891, which contained 1380 ounces of silver, 1.41 ounces of gold, and 63 pounds of copper. Before giving the results of the clean-up, a general discussion of the items of expense, methods of assaying, etc., is desirable.

Jan 1, 1895

By Alvin H. Lense

In the spring of 1967, after a careful study of existing geology along the Pacific Coast including Alaska, the USBM, in conjunction with the USGS, decided that the offshore area around Nome, Alaska, presented an unparalleled land-to-sea comparison site for the evaluation of marine core drilling techniques and sampling equipment. Considering the geological evidence available and the production history of the Nome Beaches (5-6 million oz. of gold recovered), it appeared likely that gold in commercial quantities could occur in the offshore area. A 180 sq mi area of Norton Sound, extending roughly 14 miles to the east and west of Nome and averaging 6 miles to the south, was tested by approximately 530 line-miles of sub-bottom profiling. A total of 4043 ft (56 holes) were drilled in unconsolidated sediments, yielding mixtures of gravel, sand, silt and clay. Of the total holes drilled, 16 went to bedrock and six were terminated short of their intended depths due to boulders which halted penetration, or rough seas which caused the ship to move as the anchors slipped over hard sea-floor surface. The rest of the holes were terminated when the penetrative capabilities of the drills were reached, or when the required amount of geological data were attained.

Jan 8, 1968

Polluted air and water, despoiled land and excessive noise are the unwelcome results of the population growth and a rising standard of living. The consumption of goods and services, including metal products and minerals, by all people is increasing so rapidly that civilization is in danger of destroying the environment in which it lives. This is true because every human activity affects the environment, whether it is air, water or land. While E. F. Osborn, director, U.S. Bureau of Mines, says . . . "some members of the mineral industry are reluctant to recognize environmental demands" . . . William T. Pecora Under Secretary of the U.S. Department of the Interior.. . says that, "to maintain levels of resource development and environmental quality needed to satisfy our affluence, we must trade off values rather than turn off troublesome operations." What it seems to boil down to is how much control of its operations is the mineral industry willing to accept-internal policing or strict government control? The answer lies in how well the mineral industry maintains a balance between mineral development and environmental quality.

Jan 1, 1971

By F. H. Deily, Jean M. Quets, Milton E. Wadsworth, John R. 222-000-000-012 Lewis, D. S. Rowley, R. J. Howe

Samples of synthetic magnetite were reduced in hydrogen-water vapor atmospheres in the temperature range 450o to 900oC. The reaction was always surface controlled, indicating the final products of reaction are nonfirotective. Three separate cases have been identified from the kinetic results: Case I, reduction of magnetite to iron below 570°C; Case II, reduction of magnetite to iron above 570°C; and Case 111, reduction of magnetite to wustite above 570 oC. In Cases I and 111 the kinetics have been explained by the formation of oxygen anion vacancies in the magnetite surface followed by associated diffusional processes. In Case 11 the observed kinetics have been related to the concentration of iron cation vacancies in the wustite layer formed, followed by associated steady-state diffusional processes. The concentration of cation vacancies in the wustite is maintained constant by the magnetite-wustite equilibrium. THE reduction of the oxides of iron has been a subject of study and interest for many years. However, few attempts have been made to interpret the results in terms of the mechanism of reduction of an iron oxide by either hydrogen or carbon monoxide. Stalhane and Malmberg' using CO, H2, and CO-Hz mixtures, developed the rate expression: where m = mass of oxide reduced, t = time, k = a constant, s = surface area, P = partial pressure of of CO or H,, and P, = partial pressure of the reducing gas at equilibrium. The rate of reaction per unit area was proportional to the difference between the partial pressure of the reducing gas and its pressure at equilibrium. Hansen, Bitsianes, and Joseph2 studied the reduction of pellets of hematite to magnetite with mixtures of CO-CO,. They concluded that below 450°C the reaction proceeded according to a model in which CO reacts with the hematite surface producing an oxygen ion vacancy. The rate controlling step was then assumed to be oxygen ion diffusion through vacancies resulting in the formation of magnetite. They derived an expression giving the rate of reduction proportional to the cO/CO, ratio. Recently McKewan3 published results for the reduction of magnetite spheres in atmospheres below 570°C. He explained his results by an equation of the form where K, is the equilibrium constant for wustite-iron equilibrium attributed to the formation of wustite as an intermediate in the reduction of magnetite. According to McKewan, Kp is an equilibrium constant for H, -HO adsorption in which oxygen is deposited on the surface from the H,Oand subsequently acts as a poison for reduction by hydrogen. Sample Preparation and Experiments. In this work the authors used the same apparatus and experimental procedure employed in the hydrogen reduction of magnetite. Sintered disk samples weighing approximately 1.5 g and measuring 1.2 cm in diameter and 0.25 cm in thickness were prepared by a method described previously.4 Partial pressures of hydrogen and water vapor were controlled by bubbling hydrogen through a series of flasks containing distilled and deionized water maintained at constant temperature in an oil bath. The total flow rate of the reacting gases—hydrogen and water vapor—was approximately 0.5 liter per min. The entire external system was maintained at a temperature above the oil bath to prevent condensation of water vapor. This was accomplished by wrapping electrical resistance elements over all surfaces. The glass column containing the weighing system-a McBain balance suspended from a gold chain-was enclosed in an aluminum tube heated by nichrome resistance wire enclosed in an insulating material. The temperature of the glass column was held constant by means of a series of thermocouples connected in parallel to a Leeds and Northrup temperature controller. This was necessary since variations in temperature resulted in expansion and contraction of the glass column and could be readily observed with the cathetometer. The spring extensions were measured through a window with a gaertner cathe-

Jan 1, 1962

By G. H. Kessler

ALTHOUGH considerable attention has been devoted to reaction mechanisms and equilibria of a number of endothermic reactions through which metals or their refractory compounds can be formed upon heated surfaces, only a comparatively small amount of work has been done to develop rate information for these systems. The interestin and very worthwhile work of Holden and Kopelman, Runnalls and Pidgeon,Dijring and Moliere, and Herrick and ICrieble4 is to be noted; however, their work was done under very specific conditions and the rate information which they have developed is not applicable to many systems which have been studied experimentally. That a more generalized approach is needed is shown by the diversity of these systems and of the experimental conditions which they require. These include the preparation of titanium, zirconium, tungsten, molybdenum, chromium, co-lumbium, aluminum, and silicon by decomposition or disproportionation of their halides, in some instances through hydrogen reduction; the preparation of nickel and iron by decomposition of their car-bonyls; and the preparation of copper by decomposition of the acetylacetonate. They may be carried out at temperatures ranging from 100" to over 2000°C and at pressures of from less than one mm Hg to superatmospheric. The physical mechanism of the overall process can be broken down into several steps, any one of which may be rate-determining; and the rate associated with each of these basic physical processes can be predicted. Consequently, by proper application of the present technology of rate processes, it is possible to arrive at a rate of metal deposition in the system of interest and to reach an understanding of the influence of' each major variable upon the deposition rate. It is the purpose of this paper to illustrate how this can be done and to present experimental results for a specific system for comparison with theory. The overall process of deposition of metal upon a heated surface which is immersed in vapors of a compound of the metal can be broken down into the following steps: 1) Transport of the reactant vapors to the surface. 2) Decomposition of the reactant in the immediate vicinity of the surface to a) establish chemical equilibrium if reaction rates are high; or to b) establish a dynamic equilibrium in accordance with the several reaction rates. 3) Diffusion of reaction products away from the vicinity of the surface, with or without simultaneous recombinations to form still other products. The overall process is said to be diffusion controlled if Step 1, or the equivalent Step 3, is slow; it is reaction-rate controlled if Step 2b is slow. When experimental evidence shows the reaction rate to be controlling, the well-known theories of Eyring' and others can be used as a basis for correlating and extrapolating the experimental data. Although these theories give only approximate estimates of reaction rates, they are of considerably greater value in correlating experimental data. Most deposition systems operate at surface temperatures sufficiently high that reaction rates near the surface are very high. Mass-transport rates then become controlling; and it is this regime of diffusion controlled rates which is most often of concern and Which will be considered here. When the system pressure is very low, i.e., in the micron range, then the transport processes are those of molecular movement, and the results of kinetic theory can be applied to specify a rate of arrival of reactant molecules at the heated surface. If the condensation coefficient can be estimated, then the deposition rate will be given by the product (rate of arrival) x (condensation coefficient), Conversely, experimental data can be used to determine a condensation coefficient, as was done by Holden and Kopelman' for the decomposition of zirconium tetraiodide upon a heated molybdenum surface, who found the coefficient for zirconium on molybdenum to be 1.0 at temperatures of 1382°C and above. In this pressure range, the geometry of the system. and in particular the distance between the source of reactant molecules and the heated surface, can exert a considerable effect upon the deposition rate;

Jan 1, 1961

By P. Farrar, H. Margolin

The Ti-Pb diagram was investigated in the region 0 to 58 pct Pb and from 500°C to liquidus temperatures. Three reactions were encountered: I—ß?a+Ti Pb at 725 10°C; 2—ß+L?Ti4Pb at 1305+ 10°C; and 3—the possible eutectic L-+Ti,Pb and y between 1200" and 1300°C. LEAD-RICH alloys have been investigated by Nowotny and Pesl,' who used sintered compacts and studied the region from 37.5 to 100 pct Pb by X-ray diffraction analysis. The only phase found in addition to titanium and lead was the hexagonal compound Ti Pb. Alloy systems of lead with metals of the transition group, such as iron, chromium, tungsten, cobalt, nickel, or manganese, generally show little liquid or solid solubility.' Craighead et al.,3 however, indicated that lead is soluble in a and ß titanium to at least 2.1 pct. They also found that approximately 50 pct of the lead added was lost during the arc-melting of Ti-Pb alloys. In the present investigation, are-melting also was used to prepare Ti-Pb alloys and similarly large lead losses were encountered. Experimental Procedure Alloy Preparation: Considerable difficulty was encountered in the melting of the Ti-Pb alloys and a number of experiments were performed before the method described was developed. Alternate layers of lead and titanium were wrapped with titanium sheet and compacted. This "sandwich" was annealed at 300" to 350 °C and was melted according to the procedure described by Cadoff and Nielsen.' Using a low current, 150 amp, and an argon atmosphere, four to eight 10 to 20 sec melts were made on each alloy, with the button being turned over between each melt to insure homogeneity. In the high lead range, the preliminary sintering was found to be of doubtful value and was eliminated. In the region above the nominal composition of 70 wt pct Pb, the alloys prepared in this manner always consolidated into two phases. The outside appeared to be composed entirely of lead and the inside was a Ti-Pb alloy. In order to determine whether this phenomenon was caused by a miscibility gap, master alloys with a nominal composition of 40 wt pct Pb were machined and mixed with various percentages of lead sheet. This mixture was compacted and melted in the same manner as the other alloys. Although these alloys were not homogeneous, they did not show the layering that was observed

Jan 1, 1956

By G. H. Tausch, J. R. Dublin, T. A. Huber

Simplified equipment and techniques have been developed to permit cementing a completion interval in a well and recompleting higher, lower, or at the same depth in such a manner as to: 1. Eliminate the need for a conventional drilling or workover rig. 2. Eliminate mud and other cement contaminants which have long interferred with ideal cementing. 3. Eliminate need for drilling out cement. 4. Provide a more satisfactory recompletion. 5. Provide a more economical recompletion. This technique involves the use of a small-diameter, lightweight, tubing extension which is run on a wireline and set in a landing nipple previously installed in the tubing string. Low squeeze pressure and small cement volumes, with their attendant cost reduction, are successfully used when wells are completed and reworked with salt water or other penetrating fluids. Relatively low-water-loss cement is an integral component of the technique which provides that excess cement be reverse-circulated from the well to leave the casing void of cement when recompleting lower or in the same interval. Substantial cost reductions are realized by using the simplified or low-pressure cementing technique, and the ratio of successful squeeze-cement operations has been increased. Squeeze-cementing or recementing is the act of filling a channel behind casing or filling holes purposely placed in the casing. To obtain a satisfactory squeeze-cement job, it is necessary only to fill the channel or the perforation holes with a cement filter cake and to allow it to harden in that position. In the past, the presence of mud in a well has been considered the chief deterrent to obtaining a good cement bond and satisfactory cement job; however, late developments in squeeze-cementing have made it possible to eliminate cement contamination or interference. Since it is possible to form a cement filter cake with a small pressure differential, squeeze-cementing with high pressures may not be necessary in most cases. The amount of cement needed to fill the annulus about the casing and even to fill part of the casing, if necessary, is generally small in quantity. Use of low squeeze-cementing pressures and small quantities of cement provides the following advantages: 1. Longer effective life of well tubing, casing, and other equipment; and less chance of costly equipment failure due to excessive pressure. 2. Monetary savings effected by elimination of retainers and specal squeeze-cementing tools. 3. Monetary savings effected by use of small quantities of cement and fewer squeeze-cementing operations. 4. Future surface squeeze-cementing equipment may be smaller and more economical to operate and maintain.

Jan 1, 1955

By C. H. Bowen

Industry needs a generally applicable means of defining average grain sire and grain size distribution. Students of sediments have explored this field, employing methods that might also prove useful in engineering problems. Before attempting to solve specific problems it is well to review the derivation of commonly used grade scales and the reasons for their selection. This aspect of the problem seems largely to have been lost, and a review of basic factors may suggest causes for failures in using size analysis data.

Apr 1, 1956

By Harry A. Perry

The Highlad underground uranium mine is located in the southern Powder River Basin, Converse County, Wyoming. Development by Exxon Minerals Company began in 1973 and average production from the complex roll- front deposit ranges from 500 to 600 stpd. A staff of six eight grade control technicians work within the Geology Department to guide and monitor production, to minimize waste and to account production to reserve estimates. A thorough knowledge of the complex roll- front deposit aids in accounting production to reserve estimates. Grade control technicians assist the mine geologist in making geologic cross sections, in estimating reserves, and in predicting monthly and quarterly production grades.

Jan 1, 1980

By Peter J. Huck, Madan M. Singh

IIT Research Institute has investigated the potential of high pressure water jets for rapid rock excavation. During this study, an attempt was made to correlate the extent of breakage effected to the mechanical properties of rocks. Six rock types were used in these experiments and nine properties were determined for each rock variety. A regression equation using the two most significant rock properties and one jet parameter (pressure) was established. Although tests were conducted to specific pressures of 35, no minimum in the specific energy consumption was noted.

Jan 1, 1971

By D. J. Salley, M. Burke, G. L. Simard

The depression of dithiophosphate by phosphate was investigated by correlating radiotagging measurements of competition in sorption with measurements of flotation. Competition in sorption was as complex as the sorption of the individual ions, thus strengthening the conclusion that more than one process was involved in the interaction of the ions with galena. The depression of flotation was chiefly a result of reducing the amount of dithiophosphate sorbed.

Jan 1, 1951

By B. C. Wonsiewicz, W. W. Wilkening

Following a procedure proposed by Wheeler and Ireland, Plane stress yield loci were constructed from Knoob hardness numbers. Basically, six differently oriented hardness measurements were made on three orthogml surfaces through pure poly crystalline magnesium sheet, a magnesium single crystal, and sheet of the magnesium alloys: Mg + 0.5 pct Th, Mg + 4 pct Li, AZ31B, and EKOO. Hardness loci were found to be in poor agreement at small strains (E < 0.05) with loci established by a more rigorous technique. At larger strains (E - 0.10) the agreement is fair, but at this stage in deformation the conventional locus has lost much of the asymmetry that characterizes these anisotropic materials. Two effects which will lead to distortions in the Khn locus are discussed with reference to the geometry of plastic flow during a hardness test. DETERMINING a material&apos;s resistance to multiaxial loading is of interest not only from a structural design viewpoint but also from that of deformation processing. Unfortunately, the determination of the yield locus, although simple in principle, involves tedious procedures if the results are to be at all rigorous.&apos; The idea, first proposed by Wheeler and 1reland2 of determining the yield locus by means of six Knoop hardness impressions along the principal directions in a material has obvious appeal. It is simple, quick, and should be applicable to very thin sheets. If such a technique could be demonstrated to produce consistently reliable results, it would be of interest to both researcher and designer. Lee, Jabara, and ackofen have compared the yield locus determined by Knoop hardness measurements (the Khn locus) to a locus determined by more rigorous techniques. They found good agreement for two titanium alloys at a plastic strain of about 1 pct. The purpose of this paper is to investigate if the Khn locus construction is a reasonable approximation to the locus of a highly anisotropic material. Examples of such materials are magnesium and magnesium alloys which have severely distorted yield loci which in turn reflect markedly dfferent yield strength in different directions.&apos; In pure magnesium, for example, the yield stress in tension along the transverse direction may be four times the yield stress in compression in the same direction and twice the tensile yield stress in the rolling direction. Predicting such large differences ought to serve as a severe test of the Khn locus construction. EXPERIMENTAL PROCEDURES Samples of rolled sheet, 0.250 in. (6.35 mm) thick, of pure magnesium and four magnesium alloys (Mg experimental materials. The pure magnesium together with the lithium and thorium alloys were those used in the study of Kelley and Hosford. The grain size was ASTM number 4 for the pure magnesium and number 6 for the alloys. HARDNESS TESTING The materials were sectioned along the rolling and transverse planes, mounted in a quick setting resin, and mechanically polished. Most of the hardness tests were performed on a surface prepared by electro-polishing (30 pct nitric acid in methanol at 0°C and 20 v) with the exception of the AZ31B and EK00 alloys which were made directly on a metallographically polished surface. However, subsequent hardness tests on the same sample after heavily electropolishing, revealed essentially the same hardness as before. At least twenty Knoop hardness impressions under a 100-g load were made in each of the six orientations shown in Fig. 1. The average hardness number and standard deviation were then calculated for each orientation. CONVENTIONAL LOCUS CONSTRUCTION Yield loci were constructed using a technique described in detail by Lee and ackofen,&apos; in which the flow stress (stress at a given plastic strain) fixes the coordinates of a point on the locus and measurements of the strain ratio serve to establish the slope of the locus at that point. The loading paths which correspond to uniaxial tension or compression tests establish the four intercepts of the locus with the coordinate axes plus one point on the balanced biaxial tension line Tensile testing was performed along the rolling and transverse (r, t) directions. Samples had a uniform rectangular gage length 1 by 4 by 4 in. (25.4 by 6.35 by 6.35 mm) and were deformed at a strain rate of 3.33 x 104 sec-&apos;. The tests were interrupted periodically to unload the sample and measure the plastic strains by means of X-Y post yield strain gages. Compression tests in the rolling, transverse, and through-thickness (r, f, z) directions were performed on 1/4 in. (6.35 mm) cubes at an initial strain rate of 8.33 x sec-&apos;. Lubrication was provided by 0.002 in. (51 pm) Teflon sheet which was renewed after unloading for micrometer measurements used to calculate the strains.

Jan 1, 1970

MINING, to be precise, ends when the ore is delivered to a bin outside the mine. Usually the next step is concentrating; or, as it is more often called, milling. A few elementary definitions will help make clear the discussion that is to follow. A rock is an aggregate of minerals; copper ore is rock that contains copper-bearing minerals in quantity sufficient to make it profitable to mine and recover the copper in the form of marketable metal. Manifestly, under a literal interpretation, a mass of material might be copper ore one day and merely copper-bearing waste rock a week later, if the price of copper happened to drop in the interim. Emphasis already has been placed on the expansion that took place in the ore reserves of the Porphyry companies as a consequence of the great strides made in the technique of mining and ore treatment. So, even if one inserted a qualifying phrase, "at an average price for the metal," after the word "profitable," the definition would still be open to criticism. Place is another factor. It is evident that a body of excellent ore in Arizona might cease to be ore in the economic sense if it were moved intact to the interior of China. However, it is with ore in its technical and scientific aspect that this chapter is concerned. Speaking in general terms, the ton of Porphyry ore as it arrives at the surface contains 25 to 70 lb. of copper minerals in the form of disseminated particles or thin coats along fracture planes. When subjected to appropriate treatment this ton yields 12 to 40 lb. of metallic copper. These ranges take into account conditions of today and of 25 years ago. Two procedures are available: (1) concentration, followed by smelting of the concentrate, or (2) leaching and precipitation, usually by electrolytic deposition. Smelting and leaching are metallurgic processes in that they involve chemical change; concentration

Jan 1, 1933

By R. G. Agarwal, Ramey Jr. H. J., Al-Hussainy R.

Although it has long been realized that gas recovery from a water-drive gas reservoir may be poor because of high residual saturations under water drive, it appears that only limited infomlation on the subject has been available until recently. This study was performed to show the qiiantitative potential importance of water influx. Results indicate that gas recovery may be very low in some cases: perhaps as low as 45 per cent of the initial gas in place. Gas recovery under water drive appear to depend in an important was on: (I) the prodirction rate and manner of production; (2) the residual gas saturation; (3) aquifer propertie.); and (4) the volumetric displacement effciency of water invading the gas reservoir. The manner of estimating water-drive gas reservoir recovery can vary considerably. Examples are: the steady-state tnethorl. the Hurst modified steady-state method, and various unsteady-state methods such ac. those of van Ever-dingen-Hurst, Hurst, and Carter-Tracy. The Carter-Tracy water influx expression was used in this study. In certain cases, it appears that gas recovery can be increased significantly by controlling the production rate and manner of production. For this reason, the potential importance of water influx in particular gas reservoirs should he investigated early to permit adequtrtr planning lo optirtize the pay reserves. INTRODUCTION In recent years, the economic importance of natural gas production has become increasingly apparent. This has been evidenced by more intensive exploration efforts aimed at gas production, and exploitation of both deep, as well as low-permeability gas reservoirs. Technical developments such as deep-penetration fracturing have made development of such formations economically feasible. Unfortunately, water influx has forced abandonment of a number of gas reservoirs at extraordinarily high pressures. Although reservoir engineering methods for estimating water influx have long been available, it appears that application of these methods to the water-drive gas reservoir has been sporadic.&apos;a Available methods for estimating water influx which can be applied to the water-drive gas reservoir problem include the steady-state method,1 the Hurst modified steady-state method and various unsteady-state methods such as those of van Everdingen-Hurst. Hurst, and Carter-Tracy. Interesting applications of these solu- tions to gas reservoir and the aquifer gas-storage problems have appeared recently.3,12,14 The experimental study of residual gas saturations under water drive by Geffen et al. in 1952 indicated that residual gas saturations could be extremely high. A value of 35 per cent of pore volume is often used in field practice when specific information is not available. The study of Geffen et al. showed that residual gas saturation might be much higher in some cases. Naar and Henderson concluded that the residual non-wetting phase saturation under imbibition should be about half of the initial non-wetting phase saturation. The Naar and Henderson result that residual gas saturation under water influx should be about half the original gas saturation is recommended as an estimate if laboratory measurements are not available. Thus, it is clear that a considerable portion of the initial gas in place might be trapped in a water-drive gas reservoir as residual gas at high pressure. A full water-drive would result in loss of residual gas trapped at initial reser.voir pressure. Consideration of transient aquifer behavior leads to the conclusion that high-rate production of water-drive gas reservoirs could result in improved gas recovery by reduction of the abandonment pressure. However, there appears to be little quantitative information on this possibility. One of the few advantages of water-drive gas production appears to be improved deliverability through water-drive support of the reservoir pressure. There may also be an advantage in higher condensate recovery caused by pressure maintenance for gas-condensate water-drive reservoirs. In view of the preceding, this study was made to assess the potential importance of water-drive in gas reservoir engineering. The Carter-Tracy approximate water-influx expression was used because this equation offers some advantages in hand-calculation which do not appear to have been generally recognized.&apos; However, calculations were performed in the main with a high-speed digital computer to permit evaluation of the effect of water-drive under a large variety of conditions. CALCULATION METHOD Water-drive gas reservoir performance can be estimated in a manner completely analogous to oil reservoir calculations: a materials balance is written for the reservoir, and a water influx equation is written for the aquifer. Siniltaneous solution provides the cun~ulative water influx and the reservoir pressure. When reservoir performance data (gas produced and reservoir pressures) are available, it is usually possible to match performance data to determine the initial gas in place and the water influx parameters —

Jan 1, 1966

By R. S. Hooper

IN attempting to describe recent mining developments at the Bunker Hill mine, it may be well to recall first the old days of hand mining when holes were laboriously drilled by hand to a maximum depth of three feet, and were shot one or two at a time, in order that the miner could take advantage of every slip, crack or bedding plane, and so save as much drilling as possible. Broken muck, of course, was loaded by hand shoveling into wheelbarrows or small cars, and heading advances or stope ton¬nages were governed by the number of men that could find room to work in any given place. The first big improvement over these old methods was the introduction of the reciprocating type of air-powered rock drill. This innovation, crude as it was, enabled the miners to set up a machine and drill a complete round of holes in one shift; but broken muck was still loaded by hand, and the size and rate of advance in headings were limited by time required to remove the broken rock. The next improvement of consequence was the appearance of the hammer-type rock drill, which greatly increased drilling speed over the reciprocating type, and made possible the completion of a full cycle in one shift, by the use of crossbars in headings, and permitted drilling and mucking to be carried on at the same time. Rock drills continued to improve as time passed, and finally the smaller and more efficient mucking machines appeared on the scene, and it became possible to muck out a round of broken rock and have a clean setup for one or more drill columns and machines. A complete cycle of mucking, drilling, and blasting was completed in one shift with an average advance of five feet. These conditions prevailed for several years, but as the mine grew deeper, the distances to transport the workers grew longer, and this fact together with the shortening of the working day, soon presented the problem of attempting to complete a cycle of operations in a shift of only six hours at the working faces. Anticipating this condition, the operating heads at the Bunker Hill had started an intensive study of more and better mechanization, and over a period of comparatively few years have adopted and placed in service methods and machines that make it possible for a three-man crew to consistently advance headings seven by nine feet in cross section, at the rate of eight feet, and more, per shift, doing all the mucking, switching, drilling and loading. These improvements consist of the following major items: I. The development of a light, flexible, easily transported jumbo equipped with pneumatic columns (Fig I), that has decreased the "setting up" and "tearing down" time an average of 1 1/2 hr per shift, or 25 pct of the available working time. These jumbos were developed at the Bunker Hill mine by members of the staff and consist of two pneumatic columns attached to a suitable carriage. They fold

Jan 1, 1947