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By J. D. Vincent

During the history of man, the term concentration has had many meanings. Early in history, it may have been construed to mean sorting and smelting. Not many years ago, its definition included only the physical beneficiation processes. Today, and in this article, the term concentration is taking on the meaning of beneficiation and chemical processing, or either separately. An alternate definition could be: concentration is the process of recovering and upgrading an element or nonmetallic mineral so that the product can be used or refined for the needs of man. For the purpose of this article, concentration will have the same connotation as it does in the mineral industry, which has come to include processing methods such as leaching and chlorinization under this heading. Usually, smelting techniques and electrorefining are excluded and classified under the heading of refining. Using the broad definition of concentration, the areas of mining processing include not only the physical beneficiation processes and flotation but also hydrometallurgy and vapor-metallurgy. These methods include sorting, sizing, crushing and grinding, gravity concentrating, magnetic processing and flotation as well as hydrometallurgy and vapor- metallurgical processing.

Jan 1, 1971

By John Birkinbine

A specimen of brown hematite, taken from an iron-ore mine near Anniston, Alabama, exhibits a metallic streak or thread running throngh it. This specimen having been sent to me, I have no personal knowledge of its occurrence; but Mr. Albert E. Noble

Jan 1, 1895

By Earl Hanson

FIRES in heavily timbered mines are disastrous, involving danger to both life and property. Some mines have been completely ruined or so heavily damaged that reopening them would not pay. Though few mines are entirely free from danger of fire, the risk is minimized by proper care and good design of plant. The Tintic Standard mine is at Dividend, Utah, in the famous Tintic mining district, about 60 miles south of Salt Lake City. The development of the mine was begun in 1907 by the late Mr. E. J. Raddatz and his associates. From the beginning, the work was hampered by high rock temperatures and the presence of high concentrations of rock gases such as carbon dioxide and nitrogen. Development work was carried on with great perseverance for nine years, and resulted in the discovery of ore in 1916. The total production of the Tintic Standard mine to Jan. 1, 1936, amounted to 1,664,388 tons of ore, having a gross value of .$61,996,719.

Jan 1, 1936

By T. G. Nilan

Steels containing 0.4 and 0.8 pet C have been transformed isothermally at pressures up to 34 kbuv. Decomposilion mechanisms are so intimately related to phase equilibvia that, as the equilibria shift under high pressure, the microstruclures of the decomposition producls change, maintaining at pressure the same correspondence between a given phase equilibrium and a given microstructure as a1 1 atm. A bainitic unicvo-structure occurs in these steels at high pressure that IS observed only at 1 aim abole 1.4 pct C. This strrrcl111,e 1s ruliorzalized in terms of the effect of pressure on the transformation to lower bainite. The pressuve depetlderlce of the kinetics of pearlile formation is descrihed by an absolute rule theory amalysis. The activation volume for the transformation is 7 cu cm per mlole, which is indicative of a phase-interface transformation-rate cotntrol mechanism. This fortmulation, when expressed in terms of known solule effects on the energelics of tvansformation, gives promise of explaining the effects of alloying elemenls on hnrden-abilily, particularly that of 'coball. KINETIC processes in solids are functions of the primary thermodynamic variables of state: composition, temperature, and pressure. Until the development of high-pressure techniques' that permitted the generation of sustained high pressure at high temperatures, metallurgical studies of such reactions were largely limited to isobaric conditions at atmospheric pressure. The data so obtained, and theoretical deductions based on these data, were necessarily incomplete For the particular case of austenite decomposition, a knowledge of the phenomenology of the reaction in terms of all the state variables should lead to a clarification of the process. This deeper understanding should facilitate a decision between conflicting theories that have been proposed to rationalize these phe- nomena. An analysis, derived from an understanding of the transformation mechanisms, may aid in the optimization of alloy steel development. The first studies of the effect of pressure on transformations in steel were made by Kulin et al. in 1952.' In a study of the influence of applied stress on mar-tensite formation in a 30 pct Ni steel, they found that the martensite start (M,) was depressed 8°C per kbar* by hydrostatic pressure. Jellinghaus and Friedewold3 were apparently the first to investigate the effect of pressure on isothermal transformations above the Ms. They found that the bainite transformation rate in a 1.2 pct C, 3.8 pct Mn steel was reduced by a factor of 3 by a hydrostatic pressure of 4 kbar. In both of these investigations,2,3 the M, of the steels studied was below room temperature. Austenitizing and quenching were done at atmospheric pressure, followed by the decomposition of the metastable austenite under pressure. The maximum temperature at pressure in the bainite study3 was 350°C. Until the advent of the present high-pressure devices, it was not possible to conduct isobaric high-pressure heat treatments from austenitizing through isothermal decomposition and quenching. The exploitation of high pressure as a variable in metallurgical studies was greatly advanced by the apparatus and techniques developed by Hall4 and co-workers. Utilizing these techniques, Radcliffe et a1.5 and Hilliard6 etermined the pressure dependence of phase equilibria in the Fe-C system. Hilliard and cahn7 examined the pearlite transformation rate in an AISI 1080 steel and also in a high-purity 0.92 C Fe-C alloy at 1 atm and at 34 kbar and found a 700-fold reduction in rate at pressure in the 1080 steel but only a fivefold reduction in the high-purity alloy. In agreement with the shift of phase equilibria under pressure, the microstructures were hypereutectoid at 34 kbar pressure, whereas they are eutectoid at 1 atm. Determination of the effect of pressure on carbon diffu-

Jan 1, 1968

By L. Messulam, A. S. Appleton

Iwo major studies of the Fe-Cr-C system are available in the literature. The earlier one of Kinzel and crafts' forms the basis for the data most commonly quoted in works of reference (e.g., Metnls HandDook) though the later work of Bungardt el a1.' is more extensive and amenable to analysis in terms of isothermal sections and so forth. However it is evident from examination of either of these studies that the delination of phase boundaries on the basis of the data obtained can only be very approximate. Indeed in several instances the data are so inconclusive that this delineation is a matter of opinion. This note is to report an analysis of experimentally determined carbon activity data in this system, which, originally intended as a means of checking the self-consistency of the data for a number of alloys, enables some conclusions to be drawn concerning the 10503C isothermal section of the iron-rich corner of the system as deducible from the data of Bungardt

Jan 1, 1967

By E. G. De Coriolis

The development of huge production facilities and of new or improved processes for manufacturing magnesium from its raw sources has been an outstanding achievement of this war. Furthermore, at least one new method has reached a stage of pilot production that offers promise. Its potentialities seem to indicate that a reduction in cost and simplification or elimination of problems incident to the use of at least one of the present processes are quite within the realm of possibility. Although magnesium of very high purity (99.9 per cent and higher) is obtained, and the rate of recovery reasonable (60 to 70 per cent). the ferrosilicon reduction process is open to a serious objection, which at the time its use was proposed was thought to be sufficient to raise some doubts as to its success, at least on a high production basis. The temperature range at which the reaction is carried out—namely, 2100" to 2150°F.—is very close to the failure temperature of the material of which the retort is made. It is so close that for a time it was assumed it might make commercial use of the process an impossibility. However, at the time under discussion, the demand for magnesium was so great that it was felt by those who had to go ahead and produce this essential metal that the emergency warranted their taking a chance on this process. Subsequent developments have fully justified the soundness of their decision. Fortunately for the war effort, when the plants were put into operation it was discovered that although the retorts did collapse in rather short periods of time, as predicted, they could be blown back into operable shape by application of high-pressure air. This practical method of operation so relieved the situation that the problem disappeared. Nevertheless, if the process had not been successful, or the production of magnesium by the electrolytic process had not been able to keep pace with demands, our war program would have been seriously impaired. Fireless Cooker'' Process For this reason a program was set up and assigned for the development of a new method that had been suggested to the War Production Board in 1941. It is believed justifiable in terming the method "new" for several reasons: (I) while utilizing the same (ferrosilicon) process as the Pidgeon, hence involving similar reactions, the type of retort or furnace is essentially different, (2) the method of operation, reaction temperatures, etc., differ materially, and, most important of all, (3) the problems to be overcome in making the process successful were not and could not have been anticipated by anything previously known about the Pidgcon process. As will be shown later, the briquetting process, the condenser, the furnace lining

Jan 1, 1949

The President was authorized to appoint. a liaison committee to cooperate with the American Mining Congress in respect to the establishment of a Secretary of Mines and Mining in the President's Cabinet. He appointed Edwin Ludlow, Chairman; Mark L. Requa, and J. E. Johnson, Jr. It was resolved to accept the invitation from the Chicago Section to hold the. 120th meeting of the Institute in Chicago during the week of Sept. 15, 1919. The action of the Executive Committee in appointing Past President E. Gybbon Spilsbury as representative of this Institute to visit France upon the invitation of the Société des Ingénieurs Civils de France was approved. The final budget for 1918 was approved. Tile President was authorized to appoint a committee, of three members, on the Development of Activities of the Institute. The committee was requested to report at the February meeting of the Institute, and the Secretary was requested to invite each local section to have a member present to discuss the subject. The President appointed J. W. Richards, Chairman; P. N. Moore, and Allen H. Rogers. Thirty-six members, ten associates, and five junior associates were elected; one change of status from associate to member was granted; two members were reinstated; and eight resignations were accepted. An extension of time was granted to nine members. The dues of eight members were suspended on account of their being in active service.

Jan 2, 1919

By AIME AIME

SIR HENRY CORT HAROLD CARPENTER, F. R. S. professor of metallurgy at the Royal School of Mines, was presented with his Honorary Membership certificate in the A.I.M.E. on Oct. 18, at a luncheon in his honor in the Abraham Lincoln room of the Savoy Hotel in London. The presentation luncheon was attended by some thirty distinguished representatives of the academic and industrial British metallurgical world, all friends and acquaintances of Sir Harold. Frank W. Harbord and

Jan 1, 1938

By E. Maltby Shipp

E. MALTBY SHIPP.-It was the intention of the Committee on Safety anti Sanitation to collect information and useful data from the companies having well-organized safety departments and print this in pamphlet form for distribution among the small companies that have no way of employing safety engineers nor have at their disposal these data. Consequently, I took these rules and the general data, especially the rules, went over them a great many times and tried to cut out whatever duplications appeared.

Jan 4, 1917

By C. A. Heiland

IN the third year of war, geophysical oil exploration broke all records to keep pace with the demand for increased reserves. Geophysical prospecting for strategic and other minerals also grew in scope. The trend of geophysical oil exploration throughout the war is indicated in Fig. 1. This figure resembles the one presented in the last annual review issue of M&M (February 1944, p. 62), corrected for data on-operations in the last months of 1943 and extended into 1944. The average number of geophysical oil prospecting crews in the field in 1944 was 451, whereas the total in 1943 was 340. An upward trend in the use of all geophysical methods is clearly evident throughout the year. Seismic operations were 67 per cent, gravimeter surveys 28 per cent, and other methods 5 per cent of the total. Seismic reflection and refraction crews increased 181/2 per cent over the 1943 average, gravimeter operations increased 73 per cent, and other methods gained 92 per cent. The increase in seismic and gravimeter operations, particularly the latter, is probably due to an increased production of equipment and the organization of new service companies. Miscellaneous methods gained largely through a revival of magnetometer work, and an increase in the use of torsion balances and electrical equipment. In comparison with the prewar average of 1941, it is noteworthy that seismic operations increased 58 per cent, gravimeter operations 88 per cent, and miscellaneous other methods gained as much as 283 per cent. Unfortunately the expansion in the number of geophysical crews does not indicate a proportionate increase in efficiency or in areal coverage, as will be brought out later.

Jan 1, 1945

By O. Knacke, H. Barth, W. Gans

The rate of cementation was determined by measuring the time required to consume a thin electrodeposited layer of the cementating metal as indicated by a sudden increase in the electrical potential. The diffusion controlled cathodic current of the more positive metal was measured by conventional electrochemical techniques and compared with the cementation rate under the same experimental conditions. Micrographs revealed different types of crystal growth in different surroundings e.g. dendritic growth in acidic solutions.

Jan 1, 1973

By W. V. Swarzenski

In its effort to combat waterlogging and soil salinity, the Water and Soils Investigation Division of WAPDA (West Pakistan's Water and Power Development Authority) has carried out an extensive program of test drilling andwater sampling since 1954. Data collected during the past ten years have permitted the delineation of fresh and saline groundwater zones in the Punjab Plain. Fresh groundwater containing generally less than 500 ppm of total dissolved solids is found in wide belts paralleling the major rivers and in other areas of fresh-water recharge. Locally, fresh groundwater extends to depths of 1500 ft and more. Saline groundwater occurs down gradient from sources of recharge, particularly in the lower central parts of the interfluvial areas, and presumably underlies most of the Punjab Plain. The groundwaters of the Punjab are characterized by their evolution from calcium, magnesium bicarbonate waters near sources of recharge to waters containing a dominant proportion of sodium. The highly mineralized waters of the Punjab are generally of the sodium chloride type, whereas in the Dera Ismail Khan District, sodium sulfate waters predominate. The pattern of distribution of saline groundwater zones and the observed gradual increase in mineral content, down gradient from sources of recharge, can be explained best by a hypothesis stressing the process of evaporation from the water table and solution of minerals within the alluvial aquifer. In 1954, detailed groundwater surveys in the Punjab Plain were initiated by WASID, the Water and Soils Investigation Division of West Pakistan's Water and Power Development Authority. The investigations, undertaken under a cooperative agreement between the governments of Pakistan and the United States, were aimed at the formulation of reclamation measures to improve waterlogged and saline soils, and to assess the groundwater potential of the Punjab and other areas of West Pakistan. The nature and urgency of WASID's primary task limited the exploration of the alluvial aquifer generally to its uppermost part. About 1030 test holes drilled in 47,000 sq miles of the Punjab defined the nature of the alluvium to depths of about 600 ft and yielded data on water quality to 400 or 500 ft. A report on the hydrology of the Punjab, based on the results of these investigations was published by WASID in 1963.' The present report incorporates data obtained by WASID since 1962 in a program of deep test drilling in the Punjab and the adjacent areas of Bahawalpur and Dera Ismail Khan District, permitting the definition of fresh and saline groundwater zones to depths of 1500 ft in some areas. Groundwater in the Punjab Plain is contained in alluvial deposits, predominantly sand and silt, which extend almost everywhere to depths of 1000 ft and more. The alluvium has been deposited by the Indus River and its tributaries since late Tertiary time and is contiguous with similar deposits in India. The Indo-Gangetic Plain extends from the foothills of the Himalayas to the ancient rocks of the Peninsular Shield in central India and to the ocean. Gradients are generally very low and range from about 1% ft per mile in the upper part of the plain to less than 1 ft per mile in the south and southwest. The monotony of the alluvial plain is broken by scattered bedrock outcrops in two of the interfluvial areas, Chaj Doab and Rechna Doab. The bedrock hills are projections of the northwest-trending Delhi-Shahpur Ridge that is largely buried by alluvium. The rocks of the buried ridge, presumably of Precambrian age, are essentially impermeable and define the lower limit of the alluvial aquifer in parts of Chaj, Rechna, and Bari doabs. Elsewhere in the Punjab, there are no outcrops of other consolidated rocks and their presence below the alluvium is conjectural. The principal areas of bedrock outcrops, near Kirana and Sangla, are shown diagrammatically in Fig. 1. The movement of groundwater through the alluvial aquifer of the Punjab has been described by Green-man and others.' In most of the area, the pre-irriga-tion water table sloped from the rivers downstream and toward the central axes of the doabs, indicating that the rivers were sources of groundwater recharge. As a result of seepage from irrigation canals, water levels have risen as much as 90 ft. In 1960 they were within 5 to 15 ft of the land surface and above the

Jan 1, 1970

By J. B. Wagstaff, R. A. Buchanan, J. F. Elliott

High speed photography through blast-furnace tuyeres showed coke particles moving rapidly. Model studies showed a raceway was formed and gave quantitative results which were correlated with actual blast furnaces. Another study showed the similarity between hanging and the flooding of a packed column. This was explored by models. THE combustion zone before the tuyere in an iron blast furnace is a vital region because here are generated: 1—most of the gases on which the furnace depends to carry out its basic operation of reducing iron ore to the metallic state, and 2—the major fraction of the heat required in the nearby regions of the furnace for the various reduction reactions, the fusion of the slag, and the melting of the iron. Since the greater part of the coke is consumed in this region, the descent of the burden must be greatly affected by the characteristics of the tuyere zone. This region then would seem to be a profitable field for study. Fortunately, a view into this important zone is available to the operator through the tuyere peep sight. Here he sees relatively dark pieces of coke "dancing" in the blast. What he sees is of considerable help in interpreting the behavior of the furnace at a given time but the very rapidly moving particles and the intense radiation obscures what is happening very deep in the zone. This investigation was initiated in the hope that a better understanding of the combustion region could be obtained by using a high speed camera with a maximum speed of 3000 frames per sec. It seemed the best practical method of "slowing down" this characteristically violent action within the highly luminous field. Model studies and tuyere probing also have been used to aid in explaining the observed phenomena. Above the combustion zone, but below the fusion zone, there is probably a region in which the coke is comparatively stationary. Here are zones in which the gases must flow up through the granular bed counter to descending liquid slag and metal. There is no easy way to observe this zone in a blast furnace, but model studies have been of some help in explaining the nature of the zone and the laws governing the flow of the fluids involved. The whole problem is difficult and involved and any approach to a complete solution may require long investigation. This preliminary report has been written, therefore, because it is believed that appreciable progress has already been made that would be of interest to others. Tuyere Studies, Chemistry and Kinetics It is well known from the early work of Kinney and coworkers1,2 that combustion of carbon before the tuyeres appears to occur in two zones: Zone A: C + O, = CO2; AH77°F. = — 14,108 Btu per lb of carbon [I] Zone B: CO2 + C = 2CO; H77°F = + 6,183 Btu per lb of carbon [2] Zone A (Fig. 1) is close to the tip of the tuyere and zone B is somewhat farther back; there being a transition region in which both reactions occur. It is interesting to estimate the rate at which coke is burned before a tuyere with a wind rate of 90,000 cfm in a modern furnace having 18 tuyeres. Approximately 0.55 lb of carbon is consumed by eq 1 per tuyere per sec. A like amount disappears by eq 2 for a total consumption of 1.11 Ib per sec per tuyere. Assuming the coke is 85 pct C and has a bulk density of 30 lb per cu ft, this figure can be converted to a total of 1.30 lb of coke with a bulk volume of 0.043 cu ft disappearing per sec per tuyere. At the temperatures prevailing in the combustion zone (according to Kozlovich,³ he maximum is about 3400°F), the rate at which carbon is con-

Jan 1, 1953

By AIME AIME

SCANDINAVIAN countries seem somehow to furnish an amount of talent and leadership far be- yond their population and among them Sweden is possibly at the top. The United States has many eminent citizens born in the latter, country or who are of Swedish descent and the engineers may claim their full share. In fact, the number is so large that a flourishing Swedish-American Engineering Society has been formed, including a number of A. I. M. E. members. Dr. Waldemar Lindgren is more scientist than engineer, though his work in economic geology has contributed directly to the development of many mines, and he is the valued- adviser of a number of our larger companies. Probably he, himself, values most highly the contributions he has been able to make to scientific theories of the occurrence and genesis of ore deposits. His fellow scientists have placed upon these the high mark of approval by electing him to the National Academy of Sciences, and Princeton University in 1916 recognized his position by conferring on him the degree of Doctor of Science.

Jan 1, 1931

By Willard L. Cumings, Benjamin L. Miller

The Camaguey brown iron-ore deposit covers the top of Sari Felipe hill, the nearest point of which lies 14 miles NW. of the city of Camaguey. While there are several low flat-topped hills in the vicinity covered with a more or less continuous mantle of brown iron-ore, the deposit of San Felipe hill is the only one of any size and importance, and the name " San Belipe district" is proposed for the region. The deposit extends in a NW-SE. direction for a distance of about 10 miles, with an average width of 5 miles. The location is shown in Fig. 1, a sketch-map of the eastern part of Cuba. Fig. 2 is a map of the San Felipe district. 2. Description. The district is mentioned by Spencer,' who says: " The Cubitas iron-ore fields are situated from 12 to 15 miles north of Camagueg City, in the province of Camagueg.....Within an area measuring roughly 10 miles east and west and 4 miles north and south, there are several flat-topped mesas rising 300 to 400 ft. above the level of an almost featureless plain which extends for many miles in all directions except toward the north." With the exception of the discrepancy in his statements .as to the distance from Camaguey and the area of the hill, which is over 50 sq. miles, his description is a very good one. Kemp2 has the following to say of ores in Camaguey Province:

Jan 1, 1912

By P. Barnes

(Resident Engineer, 1873-75.) SEVERAL statements have been made to the Institute, somewhat detached from each other, as to the cost of some parts of these works, but they have not included any extended description of the. buildings or machinery. The general plan of the work connected with the water supply differs, in some important details, from that which has been common either in the Pittsburgh district or elsewhere, and a somewhat extended description may be of interest to the Institute, in connection with a note of the cost of the work. The plan as a whole, and nearly all the important details, were developed by Mr. William P. Shinn, C.E., the general manager of the Company. The immediate and responsible charge of the work was in the hands of Mr. John C. Lewis, C.E., to whom had been committed all the work of this general description, including the laying-out of the whole of the foundations, the erection of the buildings, and the grading and laying down of the entire railroad system. The continuous operation of the machinery and other fixtures of these waterworks, for more than three years, has fully demonstrated the correctness and economy of the plan adopted. No casualties of any moment have befallen the apparatus, and no improvements have been suggested as important except that the gate at the river end of the conduit should have been made more completely water-tight, so that the whole length of the conduit could be pumped out dry without resort to any temporary dam in the conduit itself. In general terms the works of the Edgar Thomson Company are situated on a plateau, about 52 feet above the low-water level of the Monongahela River, and about 2000 feet from its bank. The site of the works is bordered on one side by Turtle Creek, a small stream which drains a considerable area of coal mining territory. This creek is about 100 feet from the group of buildings which have been erected, but it flows into the Monongahela River at a point, about 1200 feet further up than that selected for the entrance to the water-works conduit. It was ascertained by analysis that the water in the creek contains an important percentage of sulphate of lime, while the water of the river is of unusual purity, in respect of any salts

Jan 1, 1879

By P. G. Shewmon, H. E. Collins

A study has been made to determine the sites at which sulfur adsorption occurs on copper surfaces. measurements were made of the relative torques, Ys, at the intersection of twin boundaries with surfaces near the three low-index orientations, i.e., (100), @lo), and 011), over a range of H2S/H2 ratios. HZS concerztvations j'ro~n 3 to 1500pp)n between 830" and 1050°C were used. It is concluded that sulfur adsorption occurved preferentially though not exclusively at edge sites near the (100) and (110) surfaces in the HzS range — 700 Ppm giving rise to negative torques near these orientations. Beyond this HzS range, adsorption occurred at all sites. Near the (111) surface, 7/y little with HzS concentration up to approxiwzately 75pptn. Above this range, the results indicate adsorption is occurring OH both terrace and edge sites. SCIENTIFIC interest in surfaces and their interactions with a gaseous environment dates back to the beginning of the 19th century. The scientific luminaries of that period—Faraday, Maxwell, Rayleigh, Dewar, and Gibbs—were already concerned about such processes. However, it has only been within the past several decades that adsorption on metal surfaces has been actively studied. This increased interest in adsorption has been brought about by the advent of new and improved experimental techniques and apparatus, e.g., ultrahigh vacuum, and field-emission and ion microscopes. However, most of the work done using these techniques has been carried out at low temperatures. When adsorption studies have been made at either low or high temperatures, they usually gave no indication of the particular surface orientations or type of sites on which adsorption was occurring. In the last few years, there have been a series of studies in which the surface tension, y,, and/or its derivative with respect to orientation, 7, have been studied as a function of orientation and atmosphere.'-7 Nearly all of the work on the relative torque,* ~/y, silver annealed in hydrogen and air.6 Recently Winterbottom and Gjostein" have used a modified and more accurate Mykurian method to determine the y plot of gold in hydrogen The only work in which T/~, has been measured over a range of chemical potentials for a given solute, p2, is that of Robertson and shewmon7 on the Cu-0 system. They measured T/Y, vs Po, (10"" to 10- l3 atm) at 1000°C in various mixtures of Hz0 and HZ. From this work they estimated the value of p2 at which one half of the surface sites are occupied with oxygen, pg, as being in the range 10- l6 to 10- l5 atm of oxygen. They also found that increasing Pa increased the magnitude of ~/y, near the (111) and (100) orientations. This indicates that oxygen is not adsorbed preferentially at step edges, but uniformly over all surface sites. In addition, they did one experiment on sulfur adsorption on copper surfaces, which indicated that sulfur adsorption decreases ~/y, near the (100) orientation, while not affecting ~/y, near the (111). This could be interpreted as indicating that sulfur adsorbs preferentially at step edges near the (100). In this paper the primary objective of the work has been to carry out a study of sulfur adsorption on copper surfaces over a range of temperatures and p,. In conjunction with this work, thermal grooving at grain boundaries has been examined as a method of determining the effect of sulfur adsorption on y,. METHODS Ideally, one would like to have information on the quantity of solute adsorbed on a surface and the types of sites at which it is absorbed as a function of p2. The total quantity adsorbed or the surface excess is given by the thermodynamic equation Thus data on the variation of y, with pz indicates the value of p2 at which adsorption becomes appreciable and the quantity adsorbed. The type of adsorption site is more difficult to deduce but information on this can be obtained from the variation of rz with 8, the angular deviation of the surface orientation. This is obtained from the thermodynamic equationlg Data on t and ys as functions of p2 have been obtained by the following methods. 1) Twin Boundary Grooving—By determining the effect of adsorption on the torque, 7, where T is the variation of surface energy, y,, with orientation, it is possible to obtain some indication as to the preferred sites of adsorption. Experimentally, the torque value measured is the relative torque, 7/ys The twin boundary grooving technique suggested by Mykura'' was used in this study to determine near the three low-index orientations— (loo), (110), and (111). Mykura's equation relates 7 /yS to measurements of the di-

Jan 1, 1967

By F. G. Tickell, R. C. McCurdy, O. E. Mechem

The behavior of fluids in the voids of a rock is fundamental to the study of many of the problems of oil-field development and production. For it is by virtue of these openings between grains that oil and gas are able to move through the rock, to be contained by the rock, and to pass from the rock into the well. The capacity to contain fluids is measured by the porosity of the rock, and the ease of fluid movement is governed by the permeability. When the engineer wishes to estimate the amounts of oil and gas in an underground reservoir he is often concerned with the porosities of the rocks and, when dealing with problems relating to rate of production, he is more likely to be interested in the permeabilities of the rocks. Rocks are permeable because they are porous, but they may be porous without being permeable. Clays are very porous, and yet they are impermeable from a practical standpoint. Attempts have been made1 to correlate permeability with porosity for certain rock members but, where a definite relationship between these two properties is found to hold, it is purely fortuitous and local. Porosity and permeability do not necessarily bear any quantitative relationship to one another. The porosity of a substance is the percentage of void volume to bulk volume. The petroleum engineer is usually interested only in the inter-granular voids that are accessible to fluids. In measuring porosity he does not wish to include scaled openings. The measurement he desires is one of "available porosity," otherwise called "apparent porosity." The porosity of a natural aggregate of solid grains, such as a sandstone or clay, is governed by: (1) Grain-size distribution, (2) angularity of grain, (3) colloidal content, (4) degree of compaction. It is not difficult, for unconsolidated rocks, to measure the effect of any one of these when it alone is varied, and then to predict what the effects on porosity will be for such single variables. It is very difficult, however, if not

Jan 1, 1933

By R. A. Bell, R. Schultz, P. G. Hallof

The Ballyvergin area is located in County Clare on the southwest coast of Ireland. It is one of six areas in County Clare in which mining operations were carried out during the last century. The ores mined were high grade Cu-Pb-Ag deposits in the form of small fracture fillings and gash veins in the lower Carboniferous limestones. The zone of primary economic interest is situated on the north limb of a geosyncline which plunges moderately to the southwest. The zones of mineralization previously mined were associated with local structures and folds, and the initial geophysical investigations took the form of reconnaissance induced polarization measurements around, and between, the old mines. This work located an anomaly which, on drilling, resulted in a small extension of the Pb-Cu ore at the Ballyvergin mine. However, a potentially more important zone of mineralization resulted from the drilling of another IP anomaly near Ballyvergin. This wide anomaly was found to be a domal shaped deposit of disseminated chalcopyrite located at a depth of more than 100 ft. The deposit is controlled by local folding in the sediments and is of a type previously unknown in the area. More IP investigations are under way to locate other deposits of the same type. The Ballyvergin area is located in County Clare, about 35 miles northeast of Shannon Airport, near the Atlantic west coast of Southern Ireland (Fig. 1). Interest in the area stems from a number of occurrences of small, but high grade, Pb-Ag deposits. From the summer of 1960 to the spring of 1961, Irish Base Metals carried out a comprehensive exploration program on a 38-sq mile concession in east-central County Clare in an attempt to locate additional deposits of this type. Field operations consisted of geologic mapping, geochemical soil and stream sampling, geophysical surveying and diamond drilling. The geophysical program consisted primarily of detailed induced polarization (IP) surveys in the general vicinity of old mine workings, supplemented by electromagnetic and self-potential investigations. Subsequent diamond drilling of a well defined IP anomaly close to the old Ballyvergin mine disclosed a sizeable deposit of low grade disseminated copper, a type of deposit previously unknown in this area. REGIONAL GEOLOGY Topography: The topography is of the Karst type with low regional relief. The northern parts of the area are covered almost completely with glacial deposits including a large number of drumlins. Elsewhere the overburden is patchy and only moderately deep. A close network of roads makes every part of the area readily accessible, and rail and harbor facilities are available nearby — Fig. 2. Stratigraphy: The area was mapped on a reconnaissance basis by the Geological Survey of Ireland during the latter part of the 19th century at scales of 1 and 6 in. to the mile. Mapping is complicated in

Jan 1, 1962

By F. J. Schuh

The drilling industry long has been plagued by failures in the bottom few joints of surface and intermediate casing strings. This paper presents an analysis of the various possible causes of failure and concludes that failures are caused by short-lived, high-energy torque impulses delivered from the drill string through the bit while drilling out the cementing plugs, cement and floating equipment. The magnitude of these torque impulses is shown to be a function of the rotational momentum of the drill string, and a method is derived to calculate the magnitude of these impulses. The available methods of strengthening the bottom joints are reviewed. It is concluded that, while present methods are ineffective, a combination of improved procedures for strengthening and minor restrictions on drillout practices will prevent failures. Introduction In most cases, failure in the bottom few joints of casing strings is not discovered until electric logs record that the bottom one, two or three joints have parted from the casing string and slipped down the hole. However, in some cases the parted section of casing uncovers a high-pressure or lost circulation zone, or shifts laterally restricting the passage of drilling equipment. In these instances extensive remedial work is required to realign the parted pieces and seal the exposed formations. Several methods used to strengthen the bottom joints of casing strings include locking set screws in the couplings, putting wedges in special collars, welding straps across the couplings, welding the couplings and, most recently, using epoxy resin-based, thread-locking compounds. Since none of these techniques has eliminated the problem, this study was initiated to find the cause of failures and to evaluate the available methods of prevention. Mechanics of Casing Failures An analysis of the various possible causes of failure indicates that the casing is unscrewed rather than broken and that therefore failure must occur before the shoe is drilled. Since there is no general agreement as to the causes of casing failure, some possible mechanisms were ATLANTIC RICHFIELD CO. DALLAS, TEX. considered in this analysis. Failure of the bottom joints of casing can occur by only one of three types of stress: tension, torsion or bending. The possible mechanisms of failure were evaluated by determining the forces required to cause casing failure by each of the stresses; and, where applicable, the possibility of failure by fatigue was considered. For casing to part under tension requires a downward load of more than the tensile strength of the casing. The lightest API weight H-40 grade casing requires a bit load on the bottom of the casing of 27,000 to 34,000 Ib per inch of bit diameter (Table 1). Since maximum drill collar weights seldom exceed 10,000 Ib per inch of bit diameter, it is apparent that casing strings cannot be parted by the downward load of the drill string. The second mechanism considered was failure by bending. This mechanism requires that the lowermost casing joints be free to be deflected laterally until the bending stress exceeds the strength of the pipe. To fail, the casing (at a height L above the shoe) requires a force and deflection' at the shoe of To deflect the casing shoe with the drill string obviously requires a dog-leg at the casing shoe. This dog-leg must have a rate of change equal to or greater than the change in curvature of the deflected casing, which is given by

Jan 1, 1969