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By ROBERT R. RICHARDS

My. first paper, read at the Cobalt Meeting of the Institute,1 July, 1907, dealt with the behavior of a small Wilfley table when concentrating galena from quartz, the table being fed with natural products, with sized products; and with classified products. Since galena, having a specific gravity of 7.5, is among the heaviest minerals ordinarily concentrated by Wilfley table, it was desirable that a similar set of tests upon a mineral of, lighter weight should be made. Chalcopyrite, of a specific gravity of 4, would have been the best mineral for this purpose, on account of its great importance as an economic mineral, but in carrying out the test, however, I was obliged to content myself with a cupriferous pyrite, the specific gravity of which was 4.68 and the contents in copper 8.80 per cent. Through the kindness of Mr. H. 0. Cummins, this material was obtained from Shasta, Cal.,in very pure, clean, homogeneous condition. It was broken by rolls to 2 mm. in size, taking care to make a minimum of slimes. The quartz used to mix with it was pure, white, New England quartz, broken in the same way to the same size. In studying the accompanying tables, it should be borne in mind that the material concentrated was of low copper-content, and in many cases the quantity fed to the machine was 1 kg: or less.. As a consequence of the smallness of the 'quantity treated it was very difficult to adjust the table and get it in condition to do its best work before the feed became exhausted, and for this reason many results were obtained which appear irregular.

Sep 1, 1908

Jan 1, 1925

By T. A. Read, H. K. Birnbaum

Deformation of AuCd alloys having the 8 (orthorhombic) and (3" (tetragonal) structures occurs by the stress induced motion of twin boutdaries. A restoring force acts on displaced twin boutdaries as a result of internal energy increases in the volume through which the boundaries are displaced. The phenomonology of the twin boundary motion is described and a mechanism for twin boundary motion and the restoring force is proposed. A time-dependent stabilization behavior of the twin boundaries, which is observed after the twins are formed by the diffusionless phase transformations, is described. THE AuCd 8 phase (ordered bcc structure) exhibits a transformation to a phase having an orthorhombic structure, 8' (space group D'), for compositions in the vicinity of 47.5 at. pct Cd and to a phase having a tetragonal structure, 8" (point group 4/m, m,m), for compositions in the vicinity 50.0 at. pct Cd. Both transformations are diffusionless, occur on cooling at 60" and 30OC, respectively, and are crystallo-graphically reversible.' They are accompanied by an inhomogeneous deformation which was observed to be twinning in the low-temperature phase. 3'4 The transformations may occur by a "single interface" or by "multiple interfaces."5'6 In the "single interface" transformation, the twinned product phase consisted of two twin orientations as shown in Fig. 1. In the multiple interface transformation the product phase contained "domains" each of which contained two twin orientations, Fig. 2. Deformation of specimens containing transformation twins was achieved by motion of the twin boundaries. Releasing the applied stress resulted in the displaced twin boundaries returning towards their initial positions. This "pseudo-elastic" behavior of the boundaries varied with time after the formation of the twin boundaries by the transformation.

Jan 1, 1961

By Notman, Arthur

THIS is a day of surpluses, some good and some not so good. One can hardly pick up a newspaper, magazine, review or economic treatise without confronting the fact that we have or are threatened with more .of certain goods than we have use for, whether it be corn, wheat, cotton, coal or oil, -lumber, 'leather, newsprint, automobiles, zinc, lead, copper or what not. How did this unprecedented state of affairs arise? Who is to blame? How shall we avoid smothering ourselves in our own production? The voice of the farmer is raised in appeal to the Government to relieve him from the dilemma of his own fertility. In answer the Government employs thousands of experts and spends millions of dollars to aid the farmer. But to what end? To make him still more efficient so that he may produce even greater surpluses? Not satisfied with the result, it spends other millions to prepare vast areas of the arid land of the West for more farmers to cultivate and insure yet larger surpluses. Then what? Naturally another appeal to the Government to fix prices by financing the

Jan 1, 1928

By William B. Plank

FOR the third consecutive year, I have collected the data on enrolment and employment of graduates from the schools in. the United States and Canada that grant degrees in mineral technology. The data were collected in the same way as formerly; namely, by questionnaire, dated Jan. 5, 1935, and are therefore comparable with the figures reported for former years. This year, along with the names of the 48 schools in the United States and the six in Canada, are listed the courses offered and the degrees granted by each, school, together with the names of the professors in charge. The names and addresses of the four schools in Mexico are also given. The list is on pages 450-1, which should he valued as a directory by those interested in mineral technology education. So far as is known, this is the most complete and up-to-date list that has ever been published.

Jan 1, 1935

By Oscar Weiss

An aerial magnetometer survey was carried out by the author's geophysical organization over the Vredefort dome, where Witwatersrand beds are wrapped around a granite plug 25 to 30 miles in diameter. The well- known magnetic shales of the Lower Witwatersrand system (to be referred to as LWW) give strong negative anomalies over the out-cropping portion of the dome. This is unusual as these same shales -cause positive anomalies over large areas near Johannesburg and along a strike of 130 miles between the East Rand and Klerksdorp. It is suggested that the negative polarization is caused by heat and stresses connected with the doming. This negative polarization of sedimentary beds, which usually cause positive anomalies, is a good example of how "magnetic lows" can be caused by "structural highs." Significant magnetic anomalies should be tested by gravity and seismic methods irrespective of the sign of the anomalies.

Jan 1, 1949

By L. E. Shiffman

W. J. Parton—Those operators faced with the problem of treating fine coal whether in bituminous or anthracite will find this paper most timely. I would like to take this opportunity of discussing Mr. Schiffman's paper and at the same time express certain views relating to our Tamaqua plant. I would like to ask the author what type of impeller and diffuser is used in the Denver cells? Screen analysis of products from individual cells indicate that coarser material resists flotation and only floats after greater retention time in the last few cells. Also, the need for a scavenger screen to reclaim non-floated coal particles further stresses this point. I have always felt that more efficient means of cleaning coal between 10-mesh and 28-mesh existed than flotation. Reagent and power costs are high for the flotation process. When floating +28-mesh particles, cell capacity is lowered and some of the particles are lost with the refuse. The Tamaqua plant of the Lehigh Navigation Coal Co. floats —28-mesh coal and capacity of recoverable coal is 40 tph for 1800 cu ft of Denver cells; or 0.05 tons per cu ft of cell. At Kimberly 7.75 tph for 600 cu ft of cell gives 0.013 ton per cu ft of cell. At Bessie 14 tph for 800 cu ft of cell gives 0.017 tons per cu ft of cell. It would be appreciated if the author would comment on what he feels is the upper size limit of particle to attain most efficient utilization of the flotation process. The dewatering screw is a very interesting development since it offers a simple way to prepare coal sludge for more complete clewatering by drainage or mechanical dewatering on screen or filters. In other words it could be used to accomplish the same thing as a thickener tank. I would appreciate having the author's comment on how he thinks such a screw dewaterer would work on a froth.* The process as used in floating coal at the Bessie and Kimberly plants may be referred to as more of a bulk oil float in contrast to a froth flotation process. Experiments on increasing capacity of cells is most interesting since we are going through such an experi- mental period at the present time. Recently a double overflow was installed on our No. 30 Denver cells. So far results are not conclusive. In reviewing this paper the following comments are made pertaining to investigation of methods for increasing capacity: Supercharging: Supercharged air in matte flotation or for that matter the use of the normal amount of air drawn in by the impeller would in all probability cause such an aeration in the cell as to destroy the buoyant effect given to the coal particles by the excessive amount of kerosine used. In other words, air creates an agitation zone throughout the cell, creating a boiling and thereby giving a lower recovery in the cell. It would be interesting to know whether the 7 pct increase in recovery was with no air being admitted to the stand pipe. Changing Impeller Speed: The speed of a receded disc impeller for a No. 30 cell as recommended by the Denver Equipment Co. is, I believe, approximately 250 rpm. At this speed and using supercharged air in excess of 8-oz pressure, we have observed a boiling action in the cells. In our flotation we endeavor to obtain some degree of froth flotation using pine oil as a frother. The boiling action as caused by increasing the amount of air added to the cells is detrimental to recovery in froth flotation. It is our belief that to obtain increased recovery from a cell in froth flotation, additional air must be introduced but at the same time this air must be dispersed throughout the pulp in the form of small bubbles and this can only be done by increasing the speed of the impeller. Therefore, if Mr. Schiffman decreased the speed of the No. 30 impellers and at the same time continued to use supercharged air, the boiling action may have been increased because larger bubbles developed. The lower recovery as reported could be due to this factor. Decreasing the impeller speed will definitely decrease the power consumed but may have other disadvantages. First, we believe it will permit "sanding" in the cell and this in our opinion will increase the wear on the impeller and diffuser, especially so, if there is pyrite and/or sand present in the feed. "Sanding" in the cell when air is used, as in froth flotation, will effect the dispersion of this air and cause boiling.

Jan 1, 1951

By L. E. Shiffman

W. J. Parton—Those operators faced with the problem of treating fine coal whether in bituminous or anthracite will find this paper most timely. I would like to take this opportunity of discussing Mr. Schiffman's paper and at the same time express certain views relating to our Tamaqua plant. I would like to ask the author what type of impeller and diffuser is used in the Denver cells? Screen analysis of products from individual cells indicate that coarser material resists flotation and only floats after greater retention time in the last few cells. Also, the need for a scavenger screen to reclaim non-floated coal particles further stresses this point. I have always felt that more efficient means of cleaning coal between 10-mesh and 28-mesh existed than flotation. Reagent and power costs are high for the flotation process. When floating +28-mesh particles, cell capacity is lowered and some of the particles are lost with the refuse. The Tamaqua plant of the Lehigh Navigation Coal Co. floats —28-mesh coal and capacity of recoverable coal is 40 tph for 1800 cu ft of Denver cells; or 0.05 tons per cu ft of cell. At Kimberly 7.75 tph for 600 cu ft of cell gives 0.013 ton per cu ft of cell. At Bessie 14 tph for 800 cu ft of cell gives 0.017 tons per cu ft of cell. It would be appreciated if the author would comment on what he feels is the upper size limit of particle to attain most efficient utilization of the flotation process. The dewatering screw is a very interesting development since it offers a simple way to prepare coal sludge for more complete clewatering by drainage or mechanical dewatering on screen or filters. In other words it could be used to accomplish the same thing as a thickener tank. I would appreciate having the author's comment on how he thinks such a screw dewaterer would work on a froth.* The process as used in floating coal at the Bessie and Kimberly plants may be referred to as more of a bulk oil float in contrast to a froth flotation process. Experiments on increasing capacity of cells is most interesting since we are going through such an experi- mental period at the present time. Recently a double overflow was installed on our No. 30 Denver cells. So far results are not conclusive. In reviewing this paper the following comments are made pertaining to investigation of methods for increasing capacity: Supercharging: Supercharged air in matte flotation or for that matter the use of the normal amount of air drawn in by the impeller would in all probability cause such an aeration in the cell as to destroy the buoyant effect given to the coal particles by the excessive amount of kerosine used. In other words, air creates an agitation zone throughout the cell, creating a boiling and thereby giving a lower recovery in the cell. It would be interesting to know whether the 7 pct increase in recovery was with no air being admitted to the stand pipe. Changing Impeller Speed: The speed of a receded disc impeller for a No. 30 cell as recommended by the Denver Equipment Co. is, I believe, approximately 250 rpm. At this speed and using supercharged air in excess of 8-oz pressure, we have observed a boiling action in the cells. In our flotation we endeavor to obtain some degree of froth flotation using pine oil as a frother. The boiling action as caused by increasing the amount of air added to the cells is detrimental to recovery in froth flotation. It is our belief that to obtain increased recovery from a cell in froth flotation, additional air must be introduced but at the same time this air must be dispersed throughout the pulp in the form of small bubbles and this can only be done by increasing the speed of the impeller. Therefore, if Mr. Schiffman decreased the speed of the No. 30 impellers and at the same time continued to use supercharged air, the boiling action may have been increased because larger bubbles developed. The lower recovery as reported could be due to this factor. Decreasing the impeller speed will definitely decrease the power consumed but may have other disadvantages. First, we believe it will permit "sanding" in the cell and this in our opinion will increase the wear on the impeller and diffuser, especially so, if there is pyrite and/or sand present in the feed. "Sanding" in the cell when air is used, as in froth flotation, will effect the dispersion of this air and cause boiling.

Jan 1, 1951

By Leslie C. Richards

The competitive position of producers of industrial minerals depends upon the delivered price of their product. Freight charges are a major factor in the sales to consumers. A comparison of freight rates on movements of limestone and silica rock in the Pacific Northwest shows a wide variance in mills per ton mile for like hauls, thereby favoring some localities over others.

Jan 1, 1950

By R. W. Nash, A. E. Schwaneke, V. R. Miller

The Bureau of Mines developed a detector for controlling sorting devices to separate the copper-bearing fragments from the barren portion of Michigan native copper and western prophyry copper ores. A successful sorter could be used to preconcentrate the ore and eliminate costly hoisting or hauling of waste. An induction balance unit was developed and used in sorting tests on crushed sized - 2.5 + 1. 3-cm (- 1 + 1/2- in.) ores from the Kingston (0.9% Cu) and Centennial (1.6% Cu) mines of Upper Michigan. Concentrates of 4.0% and 7.5% Cu, respectively, were obtained at recoveries of 85 and 80% of

Jan 8, 1978

By H. E. Ellis, O. L. Patterson, Granville Dutton

A large-scale water-injection program for the Holt Bryant reservoir of the Delhi field has been established by means of the new automatic multi-pool analyzer. The objectives of this program were to increase reservoir pressure and eliminate a cross-dip gradient of 200 psi. Pressure increases during the first 15 months of operation have allowed for increased oil production rates of 2,600 BID or 25 per cent. To determine the required water injection it was necessary to predict natural water influx ram. Elimination of the pressure gradients required the water-injection program to account for the fluid migration and pressure interaction between segments of the reservoir. An integral part of the ana1ysis included the determination of in-place volumes of oil and gas. The operation of the automatic multi-pool analyzer in determining the water-injection program is described. New features of the analyzer inc1ude an automatic maferial balance analog and a leart-squares computer for determination of unknown reservoir properties. Operational procedures are sufficiently simple to allow direct use by reservoir engineers on a routine basis. The rapidity and accuracy with which problems may be solved permit repeated ana1yses as a check upon reservoir performance. INTRODUCTION This paper describes the use of a new analog com- puter in determining the optimum injection program for a complex reservoir. The Holt-Bryant (Fig. 1) is the major reservoir in the Delhi field of Louisiana. Production is from the Tuscaloosa at subsea depths of 2,970 to 3,286 ft. The sand dips to the south and southwest from three to five degrees. The reservoir is approximately 12 miles long and varies in width from 1/2 to 2 miles. Various calculations have placed the initial volume of oil in-place in the wide range of 275 to 355 million STB. Two small gas caps were initially present in the reservoir. The Holt-Bryant reservoir was discovered in Dec.. 1944, and was fully developed with 188 producing wells by 1948. After development was completed, an east-west pressure gradient began to establish itself. This

Jan 1, 1957

By C. K. Leith

THE purpose of these conferences has been to find some basic principles to guide us in the chaos which confronts us, to arrive at elements of a national policy. None such exists, nor, as a matter of fact, have there been any concerted efforts by the public or the mineral industry to evolve one. In the absence of such a policy the administrative agencies of the government can hardly be expected to be consistent or really effective in their handling of mineral problems, domestic or foreign. Basic Facts MINERAL reserves are unequally distributed among the nations. The principal world supplies are grouped around the north Atlantic, and nearly three-fourths of the world's total is controlled politically and commercially by English-speaking people. No one nation has a complete supply of the minerals necessary for modern industry; specialization, reciprocity, and large-scale movements between the nations are inherent in nature's unequal distribution of them. The principal sources of supply are relatively few compared with the nations to be served-a fact which determines broadly certain natural outlines of the world flow. National isolation with regard to minerals can be accomplished only through backward steps in industry and lower standards of living even in the nations possessing the most of the mineral supplies. A certain measure of unified commercial control, international in scope, is a natural consequence of the limited number of the large sources of supply. Mineral supplies for the world as a whole are so large that there is little need for concern about early exhaustion, but every nation has important problems of early exhaustion of particular minerals, which must affect their policies.

Jan 1, 1933

By Franklin Moeller

Discussion of the paper of FRANKLIN MOELLER, presented at the New York meeting, February, 1916, and printed in Bulletin No. 110, February, 1916, pp. 343 to 354. K. A. PAULY, Schenectady, N. Y.-I read with interest Mr. Moeller's paper descriptive of the mechanical parts of the new electric hoist at the Granite Shaft of the North Butte Mining Co. and as the paper treats largely of the mechanical equipment I have little discussion to offer. There is, however, one question which I would like to ask and that is, why the discrepancy in hoisting cycles between the curves given in the paper read by Mr. Sykes for the American Institue of Electrical Engineers at San Francisco and those given in the paper under discussion? In Mr. Sykes' curves the acceleration period is shown to be 16 sec. for all depths from 2,000 to 4,000 ft. inclusive, while Mr. Moeller in Fig. 2 shows 25 sec. throughout the range and in Fig. 4 shows 35 sec. Mr. Moeller's curves also show the following reductions in the peak load during acceleration: Level, Feet Mr. Sykes, Horsepower Mr. Moeller, Horsepower 2,060 3,500 3,130 3,000 3,800 3,480 Fig. 2 4,000 4,100 3,800 2,250 1,595 Fig. 4 As the purchaser's specifications called for 15 or 16 sec. I would like to know whether or not any modifications have been made in the requirements since the equipment has been installed.

Jan 5, 1916

By Stanley Rajnak, John E. Dorn

The saddle-point activation energy for the nu-cleation of a pair of kinks is estimated as a function of the applied stress, the lattice constants, and the height and shape of the Peierls' hill by employing the line-energy model of a dislocation. The kinetics of disloration motion by the Peierls' mechanism are discussed and the microscopic dislocation velocities and macroscopic strain rates are formulated by the Arrkenius type of approach in terms of the activation energy for the formation of pairs of PEIERLS was the first to illustrate that a straight-dislocation line has its lowest energy when it lies in a potential valley parallel to lines of closest packing kinks. The log of the dislocation velocity is found to be approximately proportional to the log of the local applied stress. It is also shown that the low-temperature mechmical properties of several bcc metals might be explained in terms of the Peierls mechanism, good agreement being obtained between theory and experiment for the flow stress us ternperature, activation energy vs stress, and activation volume us stress curves for these metals. of atoms on the slip plane. When such a straight dislocation is moved rigidly from one valley toward the next, the atoms in the vicinity of the core of the dislocation change their positions and bond angles, causing the energy of the dislocation to increase. Midway between two adjacent valleys, the disloca-tion energy reaches a maximum value and any additional small displacement will cause the dislocation to fall down the hill into the next valley. The maximum shear stress necessary to promote such

Jan 1, 1964

By W. S. CAYPLESS, H. O. Hofman, E. E. HARRINGTON

I. INTRODUCTION. LIME-ROASTING is a term proposed by Ingalls 1 for the operation of forcing air under pressure through a mixture of galena and lime at the kindling-temperature with the object of oxidizing lead and sulphur and of fritting or fusing the charge. If, finely-divided galena were treated in this manner without the addition of lime, the heat set free by the oxidation of part of the lead and the sulphur would be sufficiently great to fuse undecomposed sulphide, and thus stop desulphurization. Besides the chemical action that the addition of lime, limestone or gypsum to the charge may have, the admixture has the physical effect that it keeps the particles of galena separated from one another and accessible to the oxidizing effect of the air. At present, three methods of lime-roasting are carried out on a working-scale, the Huntington-Heberlein, the Carmichael-Bradford and the Savelsberg2 processes. In the last, which interests us here, an 8-ton charge is made up of galena, limestone and perhaps some siliceous or ferruginous flux; the whole is crushed to pass a screen with 3-mm. holes and moistened with 5 per cent of water. It is fed gradually into a bowl-shaped converter, 6.56 ft. in diameter, supported by trunnions attached to a truck. On the .bottom the converter has a grate with blast-inlet beneath. In starting, the truck with the converter

Jan 1, 1907

By Robert T. Gdagher, Allison Butts

EDUCATIONAL trends as reflected in curricular changes are of interest and importance in engineering educa¬tion both as matters of record and as considerations for the future. The data on which the evidence of this report is based were obtained by sending questionnaires to all schools in the United States granting the undergraduate degree in mining engineering, metallurgy, or metallurgical engineering. The questionnaire had two parts, one inquiring as to the general nature of revisions made or planned, and the other asking for information on specific courses added to or dropped from the curriculum, or given more or less time than formerly. The frequency with which curricular changes are made, even in normal times, is notable. Although it was expected that the period since 1939-40 would show numerous revisions, it was somewhat surprising to find that of 62 mining or metallurgical curricula in existence in 1939-40 and reported in the present survey, 58 had been revised or are shortly to be revised, 52 having already been changed during this period. Moreover, approximately half of the mining schools that have already revised their curricula, and probably a similar proportion of the metallurgical schools, are about to make further important changes.

Jan 1, 1948

By W. Tempelaar Lietz

The Ten Section oil field is located in the San Joaquin Valley in Kern County, California. about 12 miles southwest of Bakersfield in Township 30 South, Ranges 25 and 26 East. The accumulation is in a low relief anticlinal dome and has a productive area of approximately 2,200 acres. Discovered in 1936 as a result of seismic work, it was the first field on the floor of the Valley to obtain production. It had a small primary gas cap, and since its inception has been produced by depletion with controlled withdrawal from the gas cap to minimize blowthrough. STRUCTURE AND STRATIGRAPHY The Ten Section structure is an elongated anticlinal dome with flank dips of only about 7 degrees. A map of the field, now fully developed, and a composite log are shown in Figs. 1 and 2. Contours shown on the map are on the top of the first zone, or Marker XA as indicated on the composite log. As shown, the field has a productive closure of only some 350 feet, and there apparently is no faulting in the reservoir. The productive measures in Ten Section are of Upper Miocene age and are known as the Stevens sand. They contain thin, irregular shale or siltstone streaks which vary considerably in stratigraphic position and thickness and apparently are rather discontinuous. As a result, individual sands and shales cannot be correlated over any appreciable area, which makes it difficult to subdivide the sand body into separate zones which are distinct throughout the field. However, there are two fairly persistent siltstone bodies that at the time of development were considered to divide the productive measures into three - zones. The first, or uppermost zone is productive over the entire field and has an average thickness of 180 feet, of which some 65 per cent is sand. It had a primary. gas cap in the crestal area with an areal extent of 930 acres. The second zone has a productive area somewhat smaller than the first zone, but it did not have any original gas cap. It has an average thickness of about 360 feet, of which 55 per cent is sand. The third zone has a very limited areal extent and a maximum productive thickness of 100 feet, of which 80 per cent is sand. Recently, a deeper oil accumulation, termed the "53" sand, was discovered, but it is not discussed in this analysis. In the first and second zones the water table was at 7,980 feet subsea, while in the third zone it was at 8,080 feet subsea. RESERVOIR CHARACTERISTICS Sand Characteristics The Stevens sand in Ten Section is hard and well consolidated, and numerous wells were cored for core analysis. Core data on four representative wells are shown, plotted beside the electric logs in Figs. 3 to 6. The average porosity is 20 per cent, with porosities ranging from 15 to 30 per cent. It is estimated, from cores taken with oil base muds, that the interstitial water content is about 40 per cent. The average weighted permeability is approximately 140, with measured permeabilities ranging from 10 to 3,000 md. As might be expected with practically no correlation of individual sand

Jan 1, 1949

By W. Tempelaar Lietz

The Ten Section oil field is located in the San Joaquin Valley in Kern County, California. about 12 miles southwest of Bakersfield in Township 30 South, Ranges 25 and 26 East. The accumulation is in a low relief anticlinal dome and has a productive area of approximately 2,200 acres. Discovered in 1936 as a result of seismic work, it was the first field on the floor of the Valley to obtain production. It had a small primary gas cap, and since its inception has been produced by depletion with controlled withdrawal from the gas cap to minimize blowthrough. STRUCTURE AND STRATIGRAPHY The Ten Section structure is an elongated anticlinal dome with flank dips of only about 7 degrees. A map of the field, now fully developed, and a composite log are shown in Figs. 1 and 2. Contours shown on the map are on the top of the first zone, or Marker XA as indicated on the composite log. As shown, the field has a productive closure of only some 350 feet, and there apparently is no faulting in the reservoir. The productive measures in Ten Section are of Upper Miocene age and are known as the Stevens sand. They contain thin, irregular shale or siltstone streaks which vary considerably in stratigraphic position and thickness and apparently are rather discontinuous. As a result, individual sands and shales cannot be correlated over any appreciable area, which makes it difficult to subdivide the sand body into separate zones which are distinct throughout the field. However, there are two fairly persistent siltstone bodies that at the time of development were considered to divide the productive measures into three - zones. The first, or uppermost zone is productive over the entire field and has an average thickness of 180 feet, of which some 65 per cent is sand. It had a primary. gas cap in the crestal area with an areal extent of 930 acres. The second zone has a productive area somewhat smaller than the first zone, but it did not have any original gas cap. It has an average thickness of about 360 feet, of which 55 per cent is sand. The third zone has a very limited areal extent and a maximum productive thickness of 100 feet, of which 80 per cent is sand. Recently, a deeper oil accumulation, termed the "53" sand, was discovered, but it is not discussed in this analysis. In the first and second zones the water table was at 7,980 feet subsea, while in the third zone it was at 8,080 feet subsea. RESERVOIR CHARACTERISTICS Sand Characteristics The Stevens sand in Ten Section is hard and well consolidated, and numerous wells were cored for core analysis. Core data on four representative wells are shown, plotted beside the electric logs in Figs. 3 to 6. The average porosity is 20 per cent, with porosities ranging from 15 to 30 per cent. It is estimated, from cores taken with oil base muds, that the interstitial water content is about 40 per cent. The average weighted permeability is approximately 140, with measured permeabilities ranging from 10 to 3,000 md. As might be expected with practically no correlation of individual sand

Jan 1, 1949

By A. S. Nowick, E. S. Machlin

ONE of the main criteria used to rate the heat-resisting properties of alloys is stress rupture.1 During a stress-rupture test a tensile specimen is held under a constant load at a constant temperature until it fractures. The chief measurement made during this test is the time required for rupture at the specific test stress and temperature. It was found empirically from a series of stress-rupture tests at a constant temperature that when the logarithm of the time for rupture is plotted against the logarithm of stress a straight line is obtained within experimental error.2~3 This method of showing stress-rupture data has been adopted by many investigators and the KACA.4 By interpolation and extrapolation from these plots, values of the stresses required to rupture the specimens (the rupture strengths) in 10, 100, and 1000 hr are obtained for specific temperatures. Alloys are then rated for a particular application on the basis of their rupture strengths at the rupture life that most nearly represents the application. Inasmuch as stress rupture is an important criterion in rating heat-resisting alloys, it would be advantageous to know the quantitative dependence of the time for rupture on stress, temperature, com- position, and structure. In order to obtain this information, an investigation was made at the KACA Cleveland laboratory during the spring of 1945. The theory of rate processes was used because it has been found to apply to certain processes such as chemical reactions, viscous flow, and creep that occur at a definite rate for given conditions. It was thought that stress rupture was such a process. An equation was derived that gives, for a given com- position and structure, the dependence of the time for rupture on stress and temperature. The investigation is part of a general program to provide information that will lead ultimately to the development of better alloys in order that the efficiency and power output of gas turbines used in aircraft propulsion can be increased. THEORY The theory of rate processes will first be discussed as a general theory. It will then be shown that if stress rupture of heat-resisting alloys can be treated as a rate process, certain equations must be satisfied. Later sections will then show that these equations are satisfied. General Theory of Rate Processes The theory of rate processes5 eveloped by Eyring and others has been applied to chemical reactions as well as to other processes such as viscosity of liquids and diffusion. In every case in which rate- process theory can be applied, there is a small subdivision, so that the macroscopic process is the net effect of all the small processes. This smallest subdivision is called the "unit process.'' For example, in a chemical reaction the unit process is

Jan 1, 1947

By B. W. Frazier

Jan 1, 1882