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By S. S. Lau

The authors of the previous comment stated that Dorn and Rajnak33 and others34-40 concluded that "agreement with this function [(t'/tp) -f(Un/2Un) = T/Tc} may be used as a criterion for that (the Peierls) mechanism of deformation". In contrast, however, Dorn and Rajnak33 and others34-40 never made such a statement. In order to clarify the issues involved it is appropriate to recapitulate the conditions that must be satisfied in order to suggest that some deformation process might obey the Peierls mechanism: 1) Within permissible variations due to changes in the slope of the Peierls hill the T*/Tp - T/Tc relationship must be obeyed. Although some mechanisms, e.g.. solute atom stress field, recombination of dissociated partials in bcc metals, intersection of dissociated dislocations, and so forth, give about the same t* - T relationship, other mechanisms, such as cross slip, disruption of attractive junctions, climb, motion of jogged screw dislocations, and so forth, give distinctly different t*-T relationships. On this basis some distinction can be made of the various mechanisms. 2) An important feature of the Peierls mechanism concerns its physical origin based on the nucleation of pairs of kinks. The value of T* at 0°K increases with the density of dislocation (i.e. , cold work) for the intersection mechanism and it increases with the square root of the atomic fraction of solute atoms in the solute atom interaction mechanism. In contrast the value of t* at 0°k, for the Peierls mechanism which depends only on the line energy and the shape of the Peierls hills. is independent of cold working and the square root of the solute atom concentration. These differences have been employed by various investigators for elimination of a few other possible mechanisms. On the other hand it is not possible to eliminate all mechanisms, e.g., the recombination of dissociated dislocations in bcc metals, and so forth, on this basis alone. 3) Further discrimination between possible mechanisms is based on the activation volume. For the in-

Jan 1, 1968

By F. E. Crane, J. Downie

The general application of Darcy's law to natural rocks has already been challenged in the literature.1 The evidence shows that the permeability as calculated from the Darcy equation can be a function of the pressure drop and the salt concentration of the water phase. Most explanations for aberrant behavior involve clays and their properties and have been qualitatively satisfactory.Recently, however, Odeh2 revived the theoretical views of Yuster.3 Since Yuster's concept implies a fundamental error in using Darcy's relationship for two-phase flow, and not merely that conditions may limit its use, Odeh's experimental support arouses considerable interest. However, Odeh's work as presented is thought to to be inadequate. He has omitted important information about his materials and procedures; therefore, acceptance of his conclusions should be withheld. Since a clay effect is possible, Odeh should have been allowed space to present a more detailed account of the rocks which he used and the precautions which he took to avoid confounding the effects of clay and fluid circulation. In addition, it follows from Odeh's discussion that the oil relative permeability should increase as the viscosity ratio increases. Odeh presents data corroborating this deduction. It also follows that the oil relative permeability should decrease as the viscosity ratio of oil to water decreases. However, our results show that a high relative permeability, when once attained by using a viscous oil, may be maintained when that oil is replaced by an oil of much lower viscosity. EXPERIMENTAL PROCEDURE The results are shown in Fig. 1 and were obtained as follows. Sandstone cores. 3-in. long X l-in, in diameter and which contained clays, were saturated with

In 1975, the US produced 10 900 tons (12,000 st) of U3O8 from ores whose grade ranged from a low of 0.160% to a high of 0.196% U3O8. By the early 1980's if the current mining projects described here are allowed to go on stream, Australia will be able to produce at least 10 900 tons of U3O8 annually from ores whose grade ranges from a low of 0.150%to a high of 2.300%. As pointed out in the previous article, this initial rate of production could have been reached now-giving an immense boost to the depressed Australian economy. So, let's have a close look at current mining projects.

Jan 1, 1977

By H. Groeneveld, C. A. Connally, P. J. Hoenmans, J. J. Justen, W. L. Mason

A miscible displacement pilot using a slug of LPG driven by separator gas was conducted in the Cardiurn reservoir of the Pembina field. The injection pattern was a 10-acre, inverted, isolated five-spot. Upon completion of the LPG-gar phase, an experiment was conducted using a slug of water followed by gas. Calculated performance of the pilot is compared with actual performance. Equations are developed to calculate the distribution of LPG into zones of varying permeability, to estimate the progress of the flood at different times in the various zones and to estimate gas rates after breakthrough. The analysis indicates that permeability stratification was a dominant factor in controlling oil recovery and that oil was completely displaced from the swept pore volume. The results of the pilot indicated that miscible flooding is a practical means of pressure maintenance in this reservoir. The total recovery from the pilot area was good in spite of the early breakthrough of LPG. The effects of stratification were reduced by injecting a slug of water into the partially swept reservoir. INTRODUCTION The Pembina field,' located in Alberta, is the largest oil field in Canada and one of the largest in the North American continent. The reservoir is a stratigraphic trap producing from the Cardium sand. Neither bottom water nor free gas has been found. The recovery of oil by the natural depletion mechanism has been estimated at 12.5 per cent. Pressure maintenance studies of various areas have indicated that the recovery can be increased 21/2 times by water flooding, and a large area of the field is presently under water flood. However, reservoir studies of the North Pembina area indicated that miscible flooding might be competitive with water flooding. A pilot test was conducted to evaluate the performance of a miscible flood. A 10-acre, inverted, isolated, five-spot pattern was selected for the pilot. The pattern area was large enough to minimize wellbore fracturing effects and contained sufficient oil to provide significant working numbers. The performance of each of the four producers could be evaluated individually and compared. In the event of breakthrough in one direction, the effect would be isolated from the other producers. The use of a single injector minimized the volume of LPG required, and, because of the high mobility of gas, one well was sufficient to inject the necessary daily volume to replace the high rate of production. With four producers, the test could be completed in time for results to be evaluated, additional engineering studies to be made and a unit to be formed before the reservoir pressure in the North Pembina area declined below the bubble point. The pilot was located in an area developed on staggered, 80-acre spacing. The injection well was drilled at a regular location, while the four producers were drilled 467-ft north, east, south and west of the injector. Each quadrant and its associated producer were identified according to their direction from the injector— that is, north, east, south or west. The eight surrounding producers on 80-acre spacing were shut in to isolate the pilot area and provide for reservoir pressure observation. The pilot wells were completed using permanent-type completion techniques. After coring, casing was run through the pay section and cemented. Inside 51/2-in. casing, 2 1/2-in. tubing was hung. The wells were perforated opposite the Upper Cardium sand and lightly fractured. Fracturing volumes, rates and pressures were low to minimize the extent of the fractures. The fracturing treatments average 1,000 lb of 20-40 mesh sand in 700 gal of a low fluid-loss sand-carrying agent. Feed rates and wellhead fracturing pressures averaged 5.5 bbl/min at 2,535 psig, respectively. After fracturing, the productivity index was measured in each of the five pilot wells. The average PI of the four producers was 0.41 BOPD/psig drawdown. The measured PI'S were approximately the same as PI'S calculated from core analysis data, indicating that the fracturing treatments were just sufficient to overcome

R. V. Norris, Wilkes-Barre, Pa. (communication to the Secretary*):—Mr. Stow's paper presents a series of arguments, numbered from 1 to 18, concerning the relative merits of four systems of colliery-ventilation, designated by the author as " plain pressure-ventilation," " plain exhaust-ventilation," " obstructed pressure-ventilation," and " obstructed exhaust-ventilation." These arguments are subsequently compared by means of tables, in which an arbitrary numerical value is assigned to each, and which consequently serve no other purpose than that of showing his opinions and predilections, as indicated by his assignment of the said numerical values. In addition to this general summary, Mr. Stow intimates his preference for a fifth method of colliery-ventilation—namely, what he calls " alternating pressure-ventilation," which consists in the running of the fan at "pressure " during working-hours, and as an " exhaust" between shifts—a system which he proposes as, perhaps, new, yet which he thinks deserves recognition " as a standard form." This proposed " standard form " is not to be found in practice ; and I think it would be impracticable in gaseous mines of large extent, for the following reasons: 1. It takes considerable time to reverse the air-current in a large mine; and the reversal would involve a period of complete stoppage of ventilation, long enough to permit serious accumulations of gas. 2. In shaft- and slope-mines, at least, it is hardly practicable to have " every man out of the mine" during the night, and certainly impracticable to avoid keeping mules and horses inside. 3. The doors necessary to divide and direct the air-current are properly hung to open against the air-pressure; and, unless

Jan 1, 1910

By H. J. Struth

A glance into the immediate future of the refining industry, and a retrospective view of 1929, cannot fail to emphasize the need for effective measures of control of refinery still runs. With oil producers alert to the need for control of the crude supply, it has become more than ever necessary for refiners to complete the movement toward stabilization by concerted determination to maintain still run schedules within the limitations prescribed by the demand for gasoline. The outlook for continued growth in the demand for gasoline appears to be well sustained by a preliminary survey of requirements for 1930. In fact, it is apparent that the industry will be assured of a market for gasoline that will aggregate in volume at least 472,000,000 bbl. this year. This indicates a gain in total demand over 1929 of about 9 per cent. or about 4.6 per cent, less than the gain recorded during 1929 over 1928, which amounted to 13.6 per cent. Despite the indicated increase in gasoline demand this year, it is apparent that little, if any, more crude will be required than last year. This is shown in Table 1, presenting estimates of gasoline demand and probable crude requirements for 1930. Table 1.—Preliminary Survey of 1930 Gasoline and Crude Run Requirements Millions of Barrels Doniestic gasoline demand................................... 397 Foreign gasoline demand..................................... 75 Total indicated demand...................................... 472 Natural gasoline content..................................... 53 Net gasoline from crude...................................... 419 Imported gasoline........................................... 13 Net gasoline required from refineries.......................... 406 Indicated excess stock Dec. 31, 1929........................... 10 Maximum protluction required................................ 396" At 40 per cent. gasolitlc recovery, this represents a maximum crude converson of 990,000,000 bbl., or a daily average for the ycar 2,712,000 barrels. Year after year, the refining branch of the petroleum industry has been found guilty of running crude to stills greatly in excess of normal requirements, causing frequent periods of market depression. A review

Jan 1, 1930

By L. H. Morris, M. Mordecai

The emission of firedamp from the strata surrounding active workings of longwall coal faces normally follows a cyclic pattern associated with the mining operations being carried out on the face. Mining a coal seam disturbs the uniform distribution of overburden weight such that the working is enveloped by a region of high stress, both above and below the seam, advancing with the coal face. There is a decrease in stress as the strata is relaxed following the passage of the face (1). The paper describes experimental results obtained during the initial investigations of a study intended to examine the permeability of samples of coal measure strata under various triaxial stress conditions. Several investigators have studied the effect of stress on the permeability of rock, usually in the field of oil reservoir engineering. Two general lines of approach are evident. One used by among others Fatt and Davies (2), McLatchie et a1 (31, Brace et al (4) and Gunther (5) was to subject a rock sample to hydrostatic pressure. Gas or water would be passed through a sealed core mounted inside a high pressure hydraulic bomb. The second approach, favoured by Wilhelmi and Somerton (6) and also by Gray et a1 (7) was to employ a so-called 'triaxial' state of stress. Here radial confining pressure and axial stress are applied independently. The permeability is measured in the direction of the axial load. With the exception of Gunther who tested coals and Brace et a1 who tested a granite, the rocks used have been sandstones with permeabilities generally appreciably higher than British coal measure rocks.

Jan 1, 1971

By Serge L. Delinois

President Kennedy said that before 1970 this country will send a man to the Moon and get him back on Earth safely. Today, no one doubts that his promise will become reality. He who asks "What, then, is next for us in space?" is no longer considered a dreamer. And one of the very first things he discovers in trying to answer this question is that in whatever does come next, geologists and mining engineers will play a prominent role. This will be true not only in the conquest of the Moon, but also in that of the whole solar system. After 1970, it is very likely that a permanent lunar camp will be established. This beachhead, supplied entirely from Earth, in the beginning, will gradually develop into a research complex where virtually all scientific disciplines are investigated.

Jan 1, 1966

By Arthur Notman

(San Francisco Meeting, September, 1915) SACRAMENTO HILL is a mass of granite porphyry intruded along a fault between Paleozoic sediments and pre-Cambrian schists in the Bisbee district, Cochise County, Arizona. The intrusion invaded both walls of the fault to a large extent, and the accompanying extensive mineralization of the Paleozoic limestones is the locus of the great high-grade copper orebodies of the Bisbee mines. Prior to 1909, although the presence of ore in the mass of the hill itself had long been suspected, systematic exploration had not been attempted. A few shallow pits on the surface here and there had disclosed some chalcocite with associated carbonates as stringers in a mass of strongly brecciated, silicified, and iron-stained porphyry. The workings in the surrounding limestones had penetrated the porphyry in a dozen or so places for some distance from the contact but had disclosed no ore. However, the rock had been largely altered to quartz and sericite and very thoroughly impregnated with pyrite and traces of the copper sulphides. A close geological study of the conditions, both surface and underground, strengthened these suspicions, and plans for prospecting the hill were made in 1909. Reference to the accompanying illustrations, Figs. 1 and 2, will give an idea of the general appearance of the surface. The mineralization is more intense in two main zones, one at the west end and the other at the east end of the hill. The outcrop of the hill is elliptical and approximately 3,000 ft. long by 1,400 ft. wide. The Sacramento shaft, which is the main hoisting shaft of the mine and situated at the east end of the hill, as shown by the accompanying map (Fig. 3), offered a convenient base for prospecting that end of the hill, while the workings from the Holbrook shaft offered a similar opportunity at the west end. The choice of level for the first work was determined by analogy with the most favorable depth for enrichment below surface observed in the other disseminated deposits of the Southwest.

Jan 8, 1915

By N. Jaffe, J. E. Dorn

The effect of stress on the creep rate of high-purity poly crystalline aluminum in the intermediate temperature range was investigated by conducting creep tests at a series of different stresses and by decreasing the stress abruptly during the course of primary and secondary creep. Three series of decreases in stress tests were conducted: the stress was decreased in primary and secondary regions of creep at 347.5°K and the stress was decrensed in primary creep at 327°K. The results demonstrate the effects of structure and temperature on the stress dependence of the creep rate. The trends in the creep rate after a drop in stress are complicated and show that recovery takes place. The experimental results were compared with Friedel's theory for cross-slip, the experimentally determined energy for a constriction being in good agreement with the theoretical estimate proposed by Stroh. PREVIOUS investigations have shown that the ap-- parent activation energy for creep of polycrystalline aluminum, over the range from about 250° to 380°K, is approximately 27,400 cal per mole,' a value that is to a first approximation insensitive to the applied stress, the creep rate, and the creep strain. Several facts strongly support the thesis that creep, in this temperature range, is controlled by the rate-determining mechanism of cross-slip: 1) Recovery of the cold-worked state can take place by a number of mechanisms prominent among which is climb and cross-slip. Astrom2 reported rapid recovery of cold-worked polycrystalline aluminum at 340° to 370°K giving an activation energy of 28,000 cal per mole and additional recovery at the higher temperatures of 455° to 478°K giving an activation energy of 36,000 cal per mole. Whereas the latter process was clearly identified with the climb mechanism, the former process. which has an activation energy in good agreement for that of creep in the same temperature range, is most likely due to recovery by thermally-activated cross-slip. 2) Single crystals of aluminum exhibit sharp slip-

Jan 1, 1962

By Reynold Q. Shotts

The small domestic underfeed stoker as now designed is unusually sensitive to the coking and plastic properties of coals, and when the attempt is made to burn the high rank coking and caking coals of the Appalachian fields, serious trouble may occur. Part of the trouble may be caused by the ash content and clinkering characteristics of the particular coal in use, but more often it is the result of an excessive ac-in of coke in the form of ''trees,, or masses in the fuel bed. Often the zone of burning becomes so restricted that the fire goes out, and in extreme cases the fire may be lifted completely out of the fuel bed and away from the air ports. Even if the fire is preserved, excessive coking may cause response to subsequent heat demand to be slow and irregular. Coke trees seem to grow most readily during periods of hold-fire operation, so that in order to preserve the fire in mild weather it is often necessary to set the timer for such a long operating period each hour that much unneeded and unwanted heat is developed, causing discomfort. During demand periods the fire may pick up so slowly that the intense burning which develops just before stoker cut-off causes a serious overshooting of the thermostat. Stoker coal performance tests which have been made in a number of labora- tories1,2,3,4,5 are one method of approach to the problem Of selecting stoker coals- As yet these tests have not been standardized and they are expensive and time-consuming. The value of the results probably increases with the length of the test. Sherman and co-workers at Battelle Memorial Institute believe that even a one-week test is not too reliable a trial2 and it is quite likely that Others will agree. A great advantage of such tests is that characteristics of coals, other than the tendency to form coke masses, may be evaluated from them. The selection of stoker coals would be greatly facilitated if there existed some simp1e measure Of the tendency Of a a to form coke in a fuel bed. Although possessing all Of the disadvantages Of any small-scale laboratory test, the test for the free-swelling index of coal has been found useful for evaluating the probable effects Of swelling properties upon combustion.7 Ostborg, Limbacherand Sherman, have shown that the test can Predict, roughly, the tendency Of coke to accumulate in the fuel bed Of a domestic stoker. They also gave instances of its value in predicting combustion behavior in some large installations. The use of the test for free-swelling index has become well established and has been adopted as a standard by the American Society for Testing Materials.8 When domestic stoker coal investigations began at the State Mine Experiment Station in the summer of 1944, it was decided

Jan 1, 1949

By N. F. Schulz

The purpose of this investigation was to evaluate the effects of variables in equipment and procedure on tube test results. This information was then to be used to formulate specifications, preferably within the practical ranges of existing machines, for test procedures capable of yielding precise and meaningful data concerning the magnetic separation of any magnetite ore, regardless of its origin. A survey of current practice was conducted among laboratories using the Davis tube test. Many tube tests were performed to experimentally evaluate the variables most likely to affect test results. A simple method was then sought for adequately interpreting tube test results. The Davis magnetic tube concentrator is a laboratory machine designed to separate a small sample of pulverized magnetic iron ore into magnetic and non-magnetic fractions. It was developed in 1921 by mechanization of a test previously performed manually No significant changes have been made in the design of the apparatus since that time. The Davis magnetic tube test continues to serve as a practical basis for judging the amenability of an ore to magnetic separation and for controlling magnetic separation plant operations. The apparatus consists of an inclined cylindrical glass tube supported adjacent to closely spaced pointed poles of a powerful C-magnet. (Fig. 1). To conduct a tube test, a sample of suitably prepared ore is poured into the water-filled tube. With wash water flowing through, the tube is oscillated to gradually reject the non-magnetic and weakly magnetic ore particles until the desired degree of separation is attained. Both the magnetic concentrate and the tailings may be recovered for examination. MAGNETIC SEPARATION BY THE DAVIS TUBE Mechanical separation of a specified mineral component from an ore usually requires comminution to fine sizes for sufficient liberation. Some distinguish- ing property of the mineral is then exploited to sort the desired mineral particles from the gangue particles. The magnetic separation of iron ores is based on the fact that magnetite, Fe3O4, is strongly attracted by a magnetic field while the gangue minerals are not. Maghemite, ?-Fe2O3, which may occur in certain chemically processed ores, responds similarly to magnetite. The magnetic process is practical only when the loss of iron in the form of relatively nonmagnetic hematite, Fe2O3, goethite, Fe2O3.nH2O, or other iron mineral can be tolerated. In the Davis magnetic tube concentrator, magnetic attraction holds magnetically susceptible particles in a magnetic field. Forces due to gravity, inertia, and fluid-solid friction tend to remove the less susceptible particles from the field. The probability that a given middling particle will be rejected from the tube in a given period of time is an inverse function of its magnetite content, with some modification due to particle size and mineral specific gravities. The net result is that ore particles tend to be rejected in their order of increasing magnetite content, while the retained portion or magnetic concentrate increases in grade continuously during the process. MAGNETIC SEPARATION CHARACTERISTIC The magnetic separation characteristic or MSC of a magnetite ore is the correlation between concentrate

Jan 1, 1964

President Howe : It is not so clear to me that the facts which Dr. Waldo brings forward really argue that the nature of the combination between copper and aluminum differs from that of the combination between copper and zinc or copper and tin. As regards electric conductivity, I suppose that the fact, which he thinks points to a special intimate kind of union between aluminum and copper, is that the line in his Fig. 1 is neither straight nor uniformly curved, but that its curvature varies rapidly, not to say abruptly. But we find just such variation in like curves for the copper-zinc and copper-tin alloys. Thus, a slight addition of zinc or tin to copper causes a change in color wholly out of proportion to the quantity added; and, as we add zinc or tin to copper, the tenacity rises very greatly, only to fall off abruptly with further additions of either of these metals. Dr. Waldo : My curve related only to electrical conductivity. The President : If irregularity in one physical property argues

Jan 1, 1895

By Hsun Hu, R. S. Cline

The annealing behavior and the mechanism of re-orientation during recrystallization of iodide titanium cold-rolled 94 pct have been studied in detail. Results indicate that recrystallization occurs by the nucleation and growth of new grains, as in other common metals. Recrystallization nuclei form by the coalescence of subgraim, and the change in texture as a result of recrystallization is largely due to selective growth among the nuclei formed. The annealing of titanium is characterized by a wide range of overlap of the various stages of the annealing process, which may be responsible for a range of activation energies observed, and for the apparently gradual change in the annealing texture as a function of time or temperature. The deformation and recrystallization characteristics of titanium and zirconium are very similar. In cold-rolled strip, the deformation texture consists of two symmetrically oriented components, each having the basal plane laterally tilted at about 30 deg from the rolling plane and the [1010] direction parallel to the rolling direction. Upon annealing for recrystallization, the change in texture can be described, for simplicity,* as rotations around [0001].2'6'8 According to McGeary and Lustman,' recrystallization occurs in zirconium through normal growth of the subgrains, which they called "domains", without the nucleation of new grains; and the magnitude of rotation around the [0001] axis increases gradually during the progress of recrystallization. If these conclusions were true, the mechanism of recrystallization in zirconium would be basically different from that in most metals, since it is commonly known that recrystallization with reori-entation always involves the migration of high-angle boundaries. In an attempt to clarify the situation, the mechanism of reorientation during recrystallization in iodide titanium cold-rolled 94 pct was studied in detail. The structural and textural changes upon annealing at various temperatures were examined by optical and transmission-electron microscopy, X-ray pole figures, pole density distribution measurements, and micro-beam techniques. EXPERIMENTAL PROCEDURE Material and Specimen Preparation. An iodide titanium crystal bar was are-melted and solidified in a cold-hearth crucible under a purified argon atmosphere. The solidified ingot had dimensions of approximately 3 by 1/2 by 3 in. One face of the ingot was somewhat uneven, but was as clean and shiny as the remaining parts of the ingot. Large grains with a Widmanstatten internal structure were clearly shown on the shiny surfaces, indicating the occurrence of P — a transformation upon rapid cooling from the melt. Analysis of the are-melted ingot indicated C 0.033, N 0.010, H 0.013, 0 0.002 in weight percent, and traces of iron, copper, and silicon as detectable impurities. The ingot was cold-rolled -40 pct to 0.300 in. thick with a reduction of 0.005 in. per pass. The defects on the uneven side of the ingot were then removed by machining. This reduced the thickness to 0.285 in. The piece was then recrystallized by annealing at 800°C for 1 hr in a fused silica boat charged into a fused silica tube furnace under a vacuum of 10~5 mm Hg. To refine the grain size, the recrystallized metal was again cold-rolled 40 pct to 0.170 in., then annealed at 700°C for 1 hr. These treatments yielded a strip with a uniform equiaxed grain structure, having a penultimate average grain diameter of 0.04 mm and a hardness of approximately 90 Dph. Final rolling reduced the thickness from 0.170 to 0.010 in., corresponding to a reduction of 94 pct. The strip was rolled in both directions by reversing end for end between passes. Surface lubrication was provided by oil-soaked pads attached to both rolls. Specimens of 1 in. length (for X-ray examinations) and +in. length (for hardness and microstructure examinations) were cut from the rolled strip, and a width of & in. was cut from the edges of each specimen by a jeweler's saw. These specimens were then etched in a solution of 10 cu cm HN03, 5 cu cm HF, and 50 cu cm H,O to 0.008 in. thick to remove the surface metal, as well as the distorted metal at the saw cuts, prior to annealing or measurements. To minimize any surface reaction with the atmosphere, all specimens were kept in an evacuated desiccator. Isothermal Anneals. All annealing treatments were conducted in vacuum in a fused silica tube furnace as described earlier. The temperature of the furnace was controlled to within *2"C. The specimen was placed in a fused silica boat, then pushed into the hot zone of the furnace. It took about 5 to 6 min for the specimen to reach the furnace temperature. After the specimen was held at temperature for a desired length of time the boat was pulled to the cold zone of the furnace; the heating-up period was excluded from the isothermal annealing time. Thus, the uncertainty in annealing time is higher for very short anneals, but negligible for long anneals.

Jan 1, 1969

By G. W. Lester, T. J. Nowak

The paper presents a practical method of utilizing pressure fall-off data obtained when a water injection well is shut in for determination of: (I) the static reservoir pressure, (2) the potential water injective capacity (md-ft) of the formation, and (3) the formation damage (skin effect) surrounding the wellbore. In the development of the method, equations are presented which give The theoretical background for predicting the behavior of water injection wells. Certain physical factors which limit the application of the method are discussed. The procedure and the relevant precautions in obtaining the data are discussed. A sample analysis and computation from an actual pressure fall-off curve is illustrated. Fintrlly, general characteristics of pressure fall-off curve! obtained in several reservoirs are presented. INTRODUCTIO N Theoretically, in an injection well the flow of water into the formation will continue as long as the sand-face pressure is greater than the reservoir pressure. However, in practice, engineers have observed that upon stopping injection and opening the wellhead to atmospheric pressure, some wells backflow water for time intervals ranging from several seconds to several hours although the sand-face pressure, as calculated from the hydrostatic head, is considerably greater than the static reservoir pressure. Further, field observations indicated that upon shutting in a water input well, the wellhead pressure does not drop off immediately, but a pressure decline occurs lasting from several seconds to several days. These observations make it evident that when an input well is shut in, a residual pressure lingers in the vicinity of the wellbore which is greater than the average reservoir pressure. This residual pressure declines first rapidly, then more slowly, to the static reservoir pressure: therefore, it is called transient back-pressure or pressure fall-off. The first step in investigating the mechanism of pressure fall-off is to establish what general conditions are necessary for its occurrence, and to this end, Dickey and Andresen1 have presented a qualitative explanation describing the mechanism. They point out that the formation pressure gradient in the vicinity of the well does not disappear immediately when the input well is shut in, as if the system were filled with a totally incompressible fluid, but it is maintained by the expansion of the compressible fluids and by the elasticity of the formation. In such a compressible system the decrease in pressure is possible only to the extent that the water front continues to advance until the pressure is equalized. The principal aim of this paper is three-fold; namely. (1) to present a theoretical quantitative analysis of pressure fall-off data, (2) to present an application of the developed theory to field data, and (3) to discuss the general characteristics of actual pressure fall-off curves. Under (I), theoretical equations dealing with such factors as compressibility of the fluid-reservoir system, mobility of the fluids and certain physical restrictions that

Jan 1, 1956

By Ihor A. Kunasz

Introduction Lithium minerals occur predominantly in pegmatites which contain mineral assemblages derived from the crystallization of postmagmatic fluids or from the metasomatic action by residual pegmatitic fluids. They have been the traditional sources of raw materials for ceramic and chemical industries. With the discovery of Searles Lake, brines became new sources of lithium. Indeed, the 1960s may well be referred to as the "brine decade" because several brine bodies of significant economic importance were discovered. In the United States, the brines of Clayton Valley, Nevada, are presently exploited by Foote Mineral Co. The brines of the Great Salt Lake of Utah, the Smackover formation, and the Imperial Valley geothermal field, have been defined as important resources of lithium. In South America, new occurrences have been identified in Bolivia and Argentina. At the Salar de Atacama, Chile, new production capacity is scheduled for 1984. Following the termination of the AEC purchase program in 1959, several companies such as Maywood Chemical Co., American Lithium Chemicals, and Quebec Lithium Corp. were forced to close their operations. Nevertheless, with the development of new applications in glass ceramics, air conditioning systems, synthetic rubber, and metallurgy (aluminum potlines), the lithium industry grew steadily, and with the potential application of lithium metal in batteries and nuclear reactors, a healthy growth can be foreseen. New products and new applications are likely to stimulate exploration for expanded, reserves as well as the search for new sources from which lithium could be extracted economically. Geochemistry of Lithium Lithium is the third element in the periodic table. It is the lightest of all the metals, having an atomic weight of 6.938, an ionic radius of 0.68Å and a charge of +1. The geochemistry of lithium has been extensively studied and has been summarized by Rankama and Sahama (1950), Goldschmidt (1937), and Hortsman (1957). The distribution of lithium in igneous rocks is controlled by its size and its charge, and by the (MgO+FeO) / Li2O ratio. In the early stages of crystallization of a magma, that ratio is very large. Consequently, both magnesium and iron are removed by ferromagnesian minerals in preference to lithium which is then concentrated in the residual magma. This results in an enrichment of lithium in silicic rocks and pegmatites (Strock, 1936). Pegmatites are coarse-grained igneous rocks formed by the crystallization of postmagmatic fluids. Minerals within pegmatites may also form by metasomatism (Jahns, 1955). Genetically, the pegmatites are associated with neighboring intrusives. Mineralogically, granitic pegmatites contain feldspar, quartz, and mica as the main constituents and a variety of exotic elements such as lithium, beryllium, tantalum, tin, and cesium, which may or may not occur in economically significant concentrations. Detailed studies by numerous investigators (Cameron et al., 1949, 1954; Hanley et al., 1950; Jahns, 1953, 1955; Page et al., 1953) indicate that pegmatites often exhibit an internal zonal arrangement, with each zone containing a specific suite of minerals. The lithium minerals are usually found in the intermediate zones, and although as many as 13 zones have been recognized by Cameron, et al. (1949), a complete zonal arrangement is rarely found. Zoning of pegmatite bodies has also been observed on a regional basis. The regionally zoned pegmatite sequences exhibit mineral assemblages and complexity according to their re-

Jan 1, 1983

By Thomas Watson

Introduction THE occurrence of zircon in pegmatites of acidic composition is recorded by many observers both in this country and abroad, and they form one of the most important geologic modes of occurrence of the mineral.' As is well known, commercially the most important American locality for zircon is near Zirconia in Henderson County, North Carolina, where many tons of the mineral have been obtained from a kaolinized pegmatite dike 100 ft. wide and traced for 1 ½ miles along the direction of strike N. 50° E. Zircon may be developed in pegmatites as inclusions in the principal rock-forming minerals, chiefly quartz and feldspar, and as a separate megascopic constituent in the form of grains and crystals not exceeding, as a rule, 2 in. in size, and usually smaller. In the Henderson County, North Carolina, pegmatite, zircon occurs in prismatic crystals with pyramidal terminations measuring up to 30 mm. in diameter, associated chiefly with the feldspar. In some of the apatite veins of Canada, which are closely allied to pegmatite dikes, zircon is reported in crystals upward of 6 in. in length and 2 in. 'and more in thickness. Zircon in large masses occurs in Virginia in the well-known pegmatites near Amelia in Amelia County, and near Gouldin in Hanover County. Both localities are in the middle eastern portion of the Piedmont Plateau province, and are separated by a distance of about 40 miles in a northeast-southwest direction. The rocks of both areas, including the pegmatite bodies, are in an advanced stage of decay, and, the hard and moderately fresh rocks are concealed beneath a cover of variable thickness of rock decay derived by the normal processes of weathering. Exposures, there-

Jan 7, 1916

By William R. Rumbold

THE Kinta valley in the State of Perak, one of the largest of the Federated Malay States, is probably at the present time the richest alluvial tin-district in the world, Perak producing from 20,000 to 25,000 tons of tin annually, and the Kiuta valley being the chief producer. The valley runs approximately north and south, and is 30 miles long by 12 wide. It is very flat, the mountain-ranges on either side rising abruptly from the plain, that on the east being the great Central range of the peninsula, and that on the west a subsidiary range marked " Kledang " on the map, Fig. 1. The valley is drained by the Kinta river, which rises in the eastern mountain range and flows south to join the Perak river, being joined by numerous streams from both mountain-ranges. The rain-fall is heavy, averaging annually about 90 in. The whole country is covered with dense jungle, except where it has been cleared for mining-operations and a small amount of cultivation. Mining villages are scattered throughout the valley, the chief towns being Kampar, Batu Gajah, Lahat and Ipoh, the latter being the center of the mining-operations. An ideal section of the main geological features of the Kinta valley is given in Fig. 2. The valley is composed of a highly crystalline limestone, usually white in color, sometimes gray; in fact, it may be called marble. It is always highly inclined and often contorted, and in some places is interbedded with shale. On the east side of the valley, near its contact with the granite, it forms a remarkable series of limestone cliffs, which rise in some cases as high as 2,000 ft. above the level of the limestone in the valley. It is non-fossiliferous, and its geo-

Sep 1, 1906

By R. G. Green, R. L. Dowdell

LEAD POISONING as a result of eating lead pellets deposited in marsh areas is a cause of high mortality among ducks, geese, and other waterfowl ingested lead shot become trapped in the gizzard with gravel and are slowly ground away by the grit. Absorption of lead as it passes through the intestine in a finely divided state produces severe lead poisoning which is usually fatal. Ducks and geese with lead poisoning develop first a typical green diarrhea. Later, paralysis of the wing muscles prevents flight. As the poisoning continues with further grinding of the shot trapped in the gizzard, increasing paralysis reduces the bird to helpless-

Jan 1, 1937

By W. F. Flanagan, D. H. Polonis, S. D. Dahlgren

Rotation diffraction patterns of Cu-4.84 wt pct Si polymystalline samples were taken during the course of isothel-ma1 affing of the suPersaturated a phase, a diffraction spots were obserzled to streak during the initial stages of aging, and this streaking was similar to the streaking of a spots observed earlier by Barvett with deformed super saturated samples of the same composition. Although it was suggested that stacking faults were the sole cause of styeaking in the deformed samples, the present study has shown that plates with one small crystallite dimension can also contribute to the streaking when there is lattice coherency across close-packed planes. THE decomposition of the supersaturated a phase in Cu-Si alloys has been reported to occur by means of both thermal and stress activation.1-4 According to the Cu-Si phase diagram,3 Fig. 1, the supersaturated a phase (fcc) is expected to transform during aging by the precipitation of the y phase. The results of earlier studies2,4 have indicated that metastable k phase (hcp with nearly ideal close packing) forms initially at temperatures below the eutectoid temperature, after which the k transforms to the a and y phases. Hof-mann et al.4 have proposed a metastable version of the phase diagram, showing the approximate boundaries for k formation below the eutectoid temperature. In view of the close-packed nature of both the a and k phases, it is essential to consider the role assumed by stacking faults in the transformation. Streaking effects have been reported by Barrett 1 in the rotating crystal X-ray patterns of strained Cu-Si alloys and were attributed to stacking faults rather than particle size effects. This deduction was based on the observation that streaks in the diffraction patterns did not occur tangent to the 220fee Debye ring. It is known that the atom movements involved in faulting leave some X-ray reflections unaffected while others are broadened,' and, in particular, it has been shown that faulting will not cause streaking of 220fee reflections tangent to the 220fee Debye ring as would be expected if all the reflections were broadened.' The formation

Jan 1, 1967