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By W. C. Lacy

A WIDE variety of metalliferous deposits in Peru shows a close and consistent relationship to intrusive and extrusive igneous rocks. This relation- ship furnishes a clue to the composition of ore-bearing fluids and to the timing in separation of these fluids from differentiation magma. Conclusions presented here are based on ten years' study of a large number of metalliferous deposits in Peru. The most important of these areas are shown in Fig. 1.

Jan 5, 1957

By John Birkinbine

(Read at the Philadelphia Meeting, February, 1878.) IN a former paper* attention was directed to the various firms of pumping machines employed for permanent work in mining and metallurgical processes. The following is simply a collection of memoranda of work done of a temporary character, and is presented by way of comparison with other work of similar nature. In close proximity to the charcoal furnace at Pine Grove, Cumberland County, Pa., is a large deposit of superior hematite iron ore, which has been worked for a number of years, and from which many thousand tons of ore have been taken by open pit workings. In July, 1874, the furnace was blown out and operations at the bank suspended, the machinery for draining being removed except a plunger pump, 18 inches in diameter and 66 inches stroke, operated by a steam-engine by means of rods. The pit was allowed to fill with water, and no steps towards its reclamation were taken until November, 1877. At that time the pit was a pond of water at the base of the mountain, having an area of about four acres and a depth of seventy feet. As the pumps, rods, etc., had been submerged for over three years, and partially buried by the mud washed down from the banks, and as it was determined to change the location of the pump for future operations and drive it by water-power, a temporary pumping apparatus was determined upon for reclaiming the pit and keeping it drained until the permanent arrangements could be completed. By opening an old adit about 10 feet of the water was removed, and the area decreased to three acres. The inflow of springs was found to be 250 gallons per minute, and the amount of water contained in the pit was computed to be 45,000,000 gallons. As the inflow would undoubtedly increase while the water sank in the pit, provision was made for removing at least 60,000,000 gallons, at the rate of 1,500,000 to 2,000,000 gallons per day. The company determined to employ a Heald and Cisco centrifugal pump driven by an oscillating engine by means of a belt. Steam was supplied by four plain cylinder boilers, each 36 inches diameter *Transactioiis of the American Institute of Mining Engineers, vol. p. 455.

Jan 1, 1878

By John Dasher, Wilfred L. Freyberger, James H. Pannell, A. M. Gaudin

WHEN beryllium is bombarded by gamma rays under suitable conditions it evolves neutrons. This nuclear reaction, Bes + y + n + Be", [I] is utilized in the process that is described in this paper. The equation, which physicists often abbreviate to Bevy, n)Be" shows that a photon, y, is absorbed by the Be- sotope of beryllium which then emits a neutron, n, leaving Be8 as a residue." It has been determined that the threshold for this reaction is 1.63 mev; that is, gamma rays having an energy less than 1.63 million electron volts do not have enough energy to remove a neutron from the beryllium nucleus. The threshold value for the beryllium (y, n) reaction is lower than that for any other element. The next most sensitive element is heavy hydrogen (deuterium) whose gamma neutron reaction, D2 (-y, n) H1, has a threshold of 2.2 mev. Thus, gamma rays having an intensity between 1.63 and 2.2 mev will evolve neutrons from beryllium and from beryllium only. Nuclear reactions can be considered as occurring between a projectile and a target. The probability of the occurrence of any such encounter can be expressed in terms of the "cross section" of the target nucleus for the projectile and projectile energy. This cross section, then, is the area normal to the path of the projectile controlled by the target for the purpose of the reaction under consideration. Cross sections are usually expressed in barns, in which a barn is lo-" sq cm. The cross section for Eq 1 is very small, even for nuclear reactions, and of the order of 10"3 barns. It is therefore necessary that a high flux of gamma radiation at the appropriate energy be used to obtain an appreciable neutron yield. In view of the nuclear properties of beryllium it seemed that if pieces of beryllium ore on a moving belt were bombarded with an intense beam of gamma rays, those pieces which are rich in beryllium minerals would emit neutrons at a sufficiently high rate to make it possible to detect that emission, and to use it to actuate a mechanical device for removal of the active from the barren particles. The principal economic source of beryllium is the mineral, beryl. Beryl occurs mainly in pegmatites which are characteristically coarse grained. The suitability of mechanical concentration depends upon the size at which the desired mineral can be liber-

Jan 1, 1951

By James H. Pannell, John Dasher, Wilfred L. Freyberger, A. M. Gaudin

WHEN beryllium is bombarded by gamma rays under suitable conditions it evolves neutrons. This nuclear reaction, Bes + y + n + Be", [I] is utilized in the process that is described in this paper. The equation, which physicists often abbreviate to Bevy, n)Be" shows that a photon, y, is absorbed by the Be- sotope of beryllium which then emits a neutron, n, leaving Be8 as a residue." It has been determined that the threshold for this reaction is 1.63 mev; that is, gamma rays having an energy less than 1.63 million electron volts do not have enough energy to remove a neutron from the beryllium nucleus. The threshold value for the beryllium (y, n) reaction is lower than that for any other element. The next most sensitive element is heavy hydrogen (deuterium) whose gamma neutron reaction, D2 (-y, n) H1, has a threshold of 2.2 mev. Thus, gamma rays having an intensity between 1.63 and 2.2 mev will evolve neutrons from beryllium and from beryllium only. Nuclear reactions can be considered as occurring between a projectile and a target. The probability of the occurrence of any such encounter can be expressed in terms of the "cross section" of the target nucleus for the projectile and projectile energy. This cross section, then, is the area normal to the path of the projectile controlled by the target for the purpose of the reaction under consideration. Cross sections are usually expressed in barns, in which a barn is lo-" sq cm. The cross section for Eq 1 is very small, even for nuclear reactions, and of the order of 10"3 barns. It is therefore necessary that a high flux of gamma radiation at the appropriate energy be used to obtain an appreciable neutron yield. In view of the nuclear properties of beryllium it seemed that if pieces of beryllium ore on a moving belt were bombarded with an intense beam of gamma rays, those pieces which are rich in beryllium minerals would emit neutrons at a sufficiently high rate to make it possible to detect that emission, and to use it to actuate a mechanical device for removal of the active from the barren particles. The principal economic source of beryllium is the mineral, beryl. Beryl occurs mainly in pegmatites which are characteristically coarse grained. The suitability of mechanical concentration depends upon the size at which the desired mineral can be liber-

Jan 1, 1951

By Francis Donaldson

The direct injection of cement grout into water-bearing fissures as a means of checking or stopping the flow of water into shafts and tunnels has been experimented with for a decade or longer and seems to have been first attempted in Europe. The earliest application of which the writer has found a record was at a shaft sunk by the Mining Society of Lens; this is described by C. Dinoire in the Transactions of the Institution of Mining Engineers.1 It is only lately, however, that the process has been entirely successful. This success has been accomplished on the Catskill Aqueduct, now under construction by the city of New York. This aqueduct includes a number of deep pressure tunnels, reached by shafts for both waterway and construction purposes. In portions of these shafts and tunnels considerable underground water was met. The contract for the first of these deep pressure tunnels was let to the T. A. Gillespie Co.; this section is known as the Rondout Siphon. It leads under the Rondout valley at a depth of from 400 to 800 ft. and is about 5 miles long. The engineers expected that considerable water would be encountered, but fortunately this was not the case except at one shaft, known as No. 4, which penetrated the rock at a junction between limestone and conglomerate. Water-bearing fissures were encountered almost immediately. At a depth of about 200 ft. a flow of 1,500 gal. per minute was struck. The. shaft then contained as many pumps as could be used, and it seemed impossible to sink it further. After vain efforts had been made to proceed, John P. Hogan, a division engineer of the Board of Water Supply, suggested that cementation of the fissures be tried. The process was attempted for the first time in this country. Since the shaft was partly full of water it was necessary to drill grout holes with a diamond drill. Platforms were placed on the timbers at the water level, the diamond drill was installed and six 90-ft. holes were drilled in the bottom of the shaft. Several car loads of cement were pumped through these holes into the fissures, the drill casings being used for grout pipes. This largely cut off the flow of water from, the bottom and sinking could then

Jan 1, 1915

By G. W. Tracy

The material balance equation has been used for many years by engineers to determine reservoir performance. The use of this equation in general has been twofold: first, to determine the oil-in-place in a reservoir; and second, to predict the future performance. The Schilthuis form of the material balance equation, or one equivalent to it, has been used by many of the engineers. The use of the Schilthuis form in predicting future performance has proved to be laborious in that one generally must make several estimates at each step of the trial and error calculation before arriving at a check of the oil-in-place. A method is presented for expediting the calculations. The Schilthuis form of the material balance has been rearranged into a more useable form. In using the material balance to predict the future performance of a reservoir, it has become common practice to estimate the incremental oil production for each step of the calculation which corresponds to a given pressure reduction. Instead of estimating the incremental oil production, the method outlined in this paper better lends itself to estimating the instantaneous gas-oil ratio. A check of oil-in-place is more easily accomplished by estimating gas-oil ratio since it is less sensitive to small inaccuracies. This method incorporates the same self-checking feature inherent in the Schilthius form. DEVELOPMENT OF SIMPLIFlED EQUATION In the development of the simplified equation, the Schilthuis form of the material balance equation will he used. Substituting in Equation 1 for and rearranging terms In Equation 2, the cumulative oil production (n) is multiplied by a factor which is uniquely a function of pressure. Also, the cumulative gas production (G) and net water influx are also multiplied by factors which are a function of pressure alone. These factors are called and are defined as follows: Using these factors, Equation 2 becomes The equation in this form is easier to manipulate mathematically than any of the previous forms which, have been used. Sources of data for the pressure factors are a bottom-hole fluid analysis and the ratio of initial gas cap volume to oil volume in the reservoir. AID IN DETERMlNING THE ORIGINAL OIL-IN-PLACE Each of the curves and +, have a similar shape. Each is infinite at the bubble point pressure. As lhe pressure is reduced below the bubble point, the

Jan 1, 1956

By G. C. Gester

Oil has been produced in Persia and India for many years, but it was not until 1932 that Arabia entered the arena as a potential oil-producing area. In 1930 the Standard Oil Co. of California acquired a concession covering the rights of exploration and exploitation for oil in the Bahrein Islands and in June, 1932, the first commercial production was discovered by the bringing in of a well known as Jebel Dukhan No. 1 on the Island of Bahrein. Since then the Standard Oil Co. of California through its wholly owned subsidiary, The Bahrein Petroleum Co. Ltd., has been carrying on a systematic survey and development program of its concession in the Bahrein Islands. This group of islands, of which Bahrein is the largest, is in the southwestern portion of the Persian Gulf, approximately 25 miles from the mainland of Arabia. Although geographically a part of Arabia, the islands are not a part of the Kingdom of Saudi Arabia. Their government is essentially independent but certain special rights have been granted to Great Britain through a series of treaties. The Island of Bahrein is 32 miles long by 9 1/2 miles wide and covers an area of 215 square miles. Approximately three-fourths of the island is occupied by a relatively low, broad, elliptically shaped dissected hill, the central part of which is slightly depressed with inward-facing cliffs but culminating in the Jebel Dukhan (Hill of Smoke), which rises to an elevation of 443 ft. above sea level. The topography of the island is a good index of its geologic structure. Structurally the island is an elongated dome or quaquaversal fold composed of rocks of Eocene age. The major axis of the fold strikes N.5W. All of the topographic high portion of the island is a part of the structural uplift. The crest of the fold is broad and flat with the dips increasing on the flanks. How far tilted strata may continue beyond the line where the Eocene beds are covered by recent sands and detrital material is not known. Superimposed on the general structure are a few small irregularities in the form of minor folding and faulting. There is, however, no evidence of any major faults. The largest of the irregularities lies to the south of Jebel Dukhan and has the appearance of a sink

Jan 1, 1934

By Francis Donaldson

THE direct injection of cement grout into water-bearing fissures as a means of checking or stopping the flow of water into shafts and tunnels has been experimented with for a decade or longer and seems to have been first attempted in Europe. The earliest application of which the writer has found a record was at a shaft sunk by the Mining Society of Lens; this is described by C. Dinoire in the Transactions of the Institution of Mining Engineers.1. It is only lately, however, that the process has been entirely successful. This success has been accomplished on the Catskill Aqueduct, now under construction by the city of New York. This aqueduct includes a number of deep pressure tunnels, reached by shafts for both waterway and construction purposes. In portions of these shafts and tunnels considerable underground water was met. The contract for the first of these deep pressure tunnels was let to the T. A. Gillespie Co.; this section is known as the Rondout Siphon. It leads under the Rondout valley at a depth of from 400 to 800 ft. and is about 5 miles long. The engineers expected that considerable water would be encountered, but fortunately this was not the case except at one shaft, known as No. 4, which penetrated the rock at a junction between limestone and conglomerate. Water-bearing fissures were encountered almost immediately. At a depth of about 200 ft. a flow of 1,500 gal. per minute was struck. The shaft then contained as many pumps as could be used, and it seemed impossible to sink it further. After vain efforts had been made to proceed, John P. Hogan, a division engineer of the Board of Water Supply, suggested that cementation of the fissures be tried. The process was attempted for the first time in this country. Since the shaft was partly full of water it was necessary to drill grout holes with a diamond drill. Platforms were placed on the timbers at the water level, the diamond drill was installed and six 90-ft. holes were drilled in the bottom of the shaft. Several car loads of cement were pumped through these holes into the fissures, the drill casings being used for grout pipes. This largely cut off the flow of water from the bottom and sinking could then

Jan 1, 1914

By J. O. Nomland

Bahrein 'Island.—In 1936 the Bahrein Petroleum Co. continued drilling additional wells to further increase production. In all, 39 flowing wells have now been finished and five others are drilling. A second well has been deepened for prospecting the deeper horizons but has not been successfully completed as a commercial producer. In addition, a well has recently been drilled near the eastern limit of the producing area for edge-water observation. The present system places wells 3000 ft. apart in a rhombic grid, or about one well to 179 acres. The total production for the year was 4,644,635 barrels. It is expected that refinery capacity of 20,000 bbl. per day will have been completed by July, 1937. A new permanent and enlarged camp with office buildings is being built. A new hospital has been constructed and two additional medical men have been added to the staff. Saudi Arabia.—In eastern Saudi Arabia, the California Arabian Standard Oil Co. has continued with the program of prospect drilling started in 1935. After the gas encountered in Dammam well No. 1 had been successfully shut off, it was completed as a small flowing well of 51" gravity oil. Dammam No. 2, which had been started in 1935, tested 3840 bbl. of approximately 50" gravity oil from a depth of 2175 ft. Dammam No. 5, before being deepened for prospecting lower productive horizons, encountered a gas zone producing 30 million feet. Five other wells on the Dammam dome are in various stages of drilling or completion. Most of these have been located principally to outline the productive area and the various producing horizons of the structure. An extensive program of geological work is being continued. In June, 1936, a well was started on the El 'Alat structure about 25 miles northwest of the Dammam development. Although various tar showings have been reported, the well has not yet, at 2518 ft., reached the depth at which it has been thought that productive horizons might be encountered. A prospect well is being drilled by the Kuwait Oil Co. (jointly owned by Gulf and Anglo-Iranian Oil Companies) in the Sheikdom of Kuwait. The well is near Bahra, a few miles north of Kuwait Bay and about 240 miles northwest of El 'Alat. To date no favorable results at depth of about 6000 ft. have been reported.

Jan 1, 1937

By Frederic Benard

THE treatment of Balbach-Thum slimes at Copper Cliff by the Ontario Refining. Co. is of interest because it differs considerably from methods usually employed for the recovery of fine gold from parting-plant slimes. Owing to the comparatively high percentages of pal-ladium and platinum, wet methods are used to remove the greater proportion f these metals before electrolytic refining in the Wohlwill cells. THE PLANT The platinum-metals department, Wohlwill room, and gold-melting room extend along the north side f the silver refinery and are separated from the parting plant by a glass partition (Figs. 1 and 2). The platinum-metals department resembles a laboratory built on a large scale, with the various pieces of equipment laid out on terraces to facilitate handling. Because of the corrosive nature of the solutions, chemical stoneware is used throughout. Elevation of acids is accom-plished by means of Mariotte bottles. On the top level are three steam-jacketed stoneware kettles of 50-gal. capacity, also a packed tower. One kettle is used for digesting the slimes while the remaining kettles are used for precipitating the gold. The dissolver is equipped with a treated concrete hood, which is connected to the flue system. Gases are drawn off through the packed tower by means of a 6-in. stoneware exhaust fan. A 15 per cent solution of sodium carbonate is continually circulated through the tower. On the intermediate level are two suction filters, one for removing silver chloride and the other for the gold sand. The filter medium consists of an asbestos pad covered with a filter paper on which is a layer of twill.

Jan 1, 1938

By F. C. Newton

REFINERS of lead by the Parkes process have always been solicitous of recovering the zinc used in the desilverization, and justly so, as the loss in zinc constitutes one of the heavy costs in this method of refining. Part of this loss is due to the absorption of zinc by lead, and in the present state of knowledge is not recoverable as metallic zinc. The remainder of the zinc, which finds its way into the precious-metal-bearing crust, is recoverable and naturally engages the operators' most exacting attention. Careful elimination of the impurities in base bullion has enabled the refiner to produce a zinc crust better adapted to retorting, which reflects favorably in the zinc recovery; and to produce a richer crust, thereby lowering the zincking cost, as the increased efficiency of the zinc results in less of it being in circulation. It is obvious that if the ratio of concentration be increased, a lessening of the amount of crust formed will ensue, throwing less work on the retorts and diminishing the amount of retort metal sent to the cupels, thus making an actual money saving in all these operations. In the effort to obtain a rich crust, the metallurgist has increased the heat to a considerable degree, upon the assumption that at the higher temperature the zinc-silver alloy could be squeezed free from the adhering lead. A further possibility for improvement suggested itself in the freezing-point curve of Prof. H. C. Carpenter, upon zinc and silver. Study of this curve disclosed the existence of a definite chemical compound, . Zn3Ag2, with a freezing point of 665° C., a promising compound for practical application.

Jan 2, 1915

By R. G. Stickney

INTRODUCTION The Basalt Waste Isolation Project, conducted by Rockwell Hanford Operations under contract to the U.S. Department of Energy, is assessing the feasibility of the disposal of commercial radioactive spent fuel/high-level waste in deep geologic formations in basalts beneath and within the Hanford Site in southeastern Washington State. The Basalt Waste Isolation Project mission is to identify and characterize a potential geologic repository site in basalt and to develop associated facilities and technology required for the potential permanent isolation of radioactive wastes in basalt formations. In support of the Basalt Waste Isolation Project, a laboratory testing program was conducted to evaluate the performance of the Council for Scientific and Industrial Research's "Doorstopper" biaxial strain cell. To support site characterization studies and the design of repository openings, in situ stress measurements will be conducted within the reference repository horizon (~970 m). The Doorstopper is one of the instruments being considered for use in these measurements. It was selected because it requires only a small volume of work to achieve stress relief, which is important in a closely jointed basalt. Also, test durations are short, permitting a large number of measurements to be made within a given time to increase confidence in the results. Within the reference repository horizon, temperatures are expected in the range of 40º to 60°C with a humidity of up to 100%. For this testing program, test conditions were selected to closely resemble those expected within the repository horizon. The Doorstopper test, mainly developed by Leeman (1964), is a strain rosette relief method of measuring rock stress in situ. The Doorstopper consists of a four element, 45º strain gage rosette

Jan 1, 1984

By Eugene McAuliffe

The management of The Union Pacific Coal Co., which operates a group of coal mines in Southern Wyoming, believes in the value of applied psychology as a productive factor in the work of getting out coal. Operating almost wholly through the medium of mechanical loading machinery, the company has for some years paid a bonus, equivalent to one-half the labor saving made above a determined average output per shift worked, on a given machine. No penalty is attached where the established output is not obtained, but in 1933 the men on one class of machines earned an average premium of $0.633 per shift on 56.4 per cent of the tonnage loaded. On another class of machine, the men earned an average premium of $0.686 per shift on 28.4 per cent of the tonnage loaded An increase of 36 per cent in tons loaded per man-shift has resulted since the program was instituted. This coal company has also been very successful in reducing mine accidents through prizes awarded in an unusual way. At the close of the year, every man whose particular mine section passes through the year without a lost-time accident is given a ticket entitling him to participate in a safety drawing where an automobile is awarded as first prim.. There are also a number of cash safety prizes which are similarly awarded. Some 1500 persons attend the drawing, which excites much interest and attention. The particular plan employed, the payment of production bonus awards and safety prizes, is foundationed upon collective. rather than individual effort, and, once gotten under way, has proved to be substantlally self-cnforcing.

Jan 1, 1934

By William P. Blake

The attention of travellers, upon the desert bordering the Great Colorado of the West, is often arrested by broad stretches of pebble-covered plains, or mesas, glittering in the sunlight from the myriads of polished surfaces, giving, at a distance, the appearance of a sheet of water. It is not alone the well-rounded, polished surface of these pebbles which commands attention, but, in addition, their nearly black or darkbrown color; and, above all, their uniform distribution in a level sheet, covering the plain in a continuous layer or pavement like a vast mosaic without sand or soil. Hundreds of square miles along the lower Colorado, especially in Yuma county, Arizona, and on the borders of the Colorado Desert in California, are thus covered. It is evident that the former cxtent of such pebbly plains was much greater than now, for the continuity of the mesa is broken into by the numerous dry arroyos or " washes " formed during exceptional showers or deluging rains. In some places there is an underlying bed of pebbly conglomerate, a mixture of pebbles and sand; in others the pebbles rest on a sandy, earthy foundation. The rounded pebbles are distinctly alluvial in origin, and pertain to the ancient Colorado drainage system; but it is not comprehensible that such regular layers of polished pebbles could have been left by subsiding floods or river action. Attention was early directed by me to these remarkable plains, first examined in 1853, when exploring for the United States and seeking a practicable route for a railway to the Pacific coast.* The cut and polished surface of the pebbles

Jan 1, 1904

By R. H. Richards

In October, 1891,I read a paper before the Institute on a "A HandTelescope for Stadia-Work" (Bans., xx., 732), and promised to report at an early date some results showing the degree of accuracy attained with the instrument. I am now able to report on these results and also on certain improvements that I have made in the target since the first paper was read. I may say that I prefer the title, "Prismatic Stadia-Telescope," to that used in my earlier paper, for while the instrument can be used with perfect satisfaction for short sights up to, say, 300 to 600 feet when held in the hand, it is impossible to read milch longer distances without the use of a tripod, as a steady support for the instrument. Results are here given upon four combinations of prism and telescope. No. 1. A telescope made by Alvan Clark & Sons, 3-inch objective, 28 inches focal length, magnifying 60 diameters, the prism covering half the objective: Feet measured Reading of Distance reduced Reeding of rod pro by tape. the rod. to feet. portional to 100 ft. 127.66 1.1825 100 .92629 211.35 1.9585 100 .92666 326.59 3.0265 100 .92669 484.88 4.4925 100 ,92652 606.91 5.6225 100 .92641 Average,,92651 The value of this prism therefore is .92651 feet on the rod for 100 feet of distance, or 1 foot on the rod corresponds to 107.931 feet of distance. No. 2. A Bardou telescope having a 1-inch objective, magnifying 20 diameters, and a prism covering half the objective:

Jan 1, 1893

NEW YORK LOCAL SECTION Executive Committee LEWIS W. FRANCIS, Chairman WILLARD S. MORSE, Vice-Chairman. THOMAS T. READ, Secretary, Woolworth Bldg., New York, N. Y. PHILIP A. MOSMAN, Treasurer Louis D. HUNTOON WILLIAM A. POMEROY The October meeting of the New York Local Section was held on Oct. 2 at 1424 Broadway, following a beefsteak supper, at which 71 members were present. B. B. Thayer spoke briefly on present labor conditions at Butte, A. A. Blow discussed labor conditions in New Zealand, and Hennen Jennings discussed the fundamental problems of industrial unrest. Several other members joined in the informal discussion which followed. The next meeting will be held on Nov. 7. THOMAS T. READ, Secretary.

Jan 11, 1914

By O. W. Walvoord

To those working in the mineral industry, the flowsheet is a familiar and valuable tool, seldom used, unfortunately, to its fullest advantage. As with so many other commonplace and simple items, there is little or no attempt to expand on the forms, and types of flowsheets. A flowsheet or flow diagram may be defined as an illustration showing circulation of the ore stream in a concentrating plant. It may be further described as an explanatory graphic design or picture. A flowsheet is obtained by interpreting the metallurgists' research and ore test data, usually with some adjustments to suit the economies of the project. It brings together, in compact form, information from a number of sources.

Oct 1, 1956

By J. D. Livingston, Bruce Chalmers, R. L. Fleischer, R. S. Davis

INTERACTION of dislocations on intersecting slip planes has long been considered a primary cause of work hardening in metals. Easy glide and low work-hardening rates have been observed experimentally only when single-crystal specimens were oriented so that one slip plane was initially favored. When single-crystal specimens have been oriented so that initially two or more slip planes were equally favored, high initial work-hardening rates have been observed. In a polycrsstalline aggregate, glide on five systems is in general necessary for a crystal to deform in conformity with the change in the shape imposed by the other crystals.* Only a small fraction of the crystals of a polycrystal will be oriented so that two

Jan 1, 1958

By Guillermo Hileman

Probably the outstanding feature of the oil industry in the Argentine, during the past year, was the increase in production from the Comodoro Rivadavia field. This increase was accounted for by the discovery of a deeper producing horizon in the old coastal field (zone A). The oil, derived from the deeper sands, served not only to balance the natural decline of the upper sands and increase the yield from the area, but also provided a product of comparatively superior quality. The finding of this ney- production in the old field had a special economic significance because of the pumps, tanks and pipe lines already installed to take care of it. The deep horizon is looked upon as a life

Jan 1, 1937

By T. E. Watkins, M. D. Nelson

INTRODUCTION Deeper drilling for oil is becoming more and more the rule rather than the exception. With deeper drilling come additional problems, perhaps the greatest being those brought on by the higher temperatures encountered down the hole. particularly in the Gulf Coast region of Texas and Louisiana. Temperature gradients of the order of 1.8° to 2.0°F/100 ft are not unusual, and a gradient of 2.3"F.'100 ft is found in some areas of Texas. With a mean surface temperature of 74oF, the following temperatures could be expected for a geothermal gradient of 2.0°F; 100 ft: at 10,000 it. 271°F. 12,000 ft, 314°F: 14,000 ft, 354,oF; and 16.000 ft. 394°F. Severe gelation of lime-base drilling fluid in wells that have high bottom hole temperatures has become perhaps the most serious difficulty enconntered in drilling under such conditions. Lime-base drilling fluids have been very succesefully and widely used in the drilling of wells in the Gulf Coast region because of their inherent stability toward contaminants. their ability to suppress the swelling dispersion of bentonitic shales, and their ease of maintainance. The gradual recognition: during the past few years, that these muds were. in themselve. the cause of many difficulties experienced in drilling has led to wide-pread efforts by the drilling industry. to determine the reasons for the failure of these mud systems and to develop mud systems capable of performing satisfactorily under high-temperature conditios. MANIFESTATIONS OF HIGH-TEMPERATURE GELATION it is generally possible to recognize the symptons of high-temperature gelation early enough that advance predictions can be made of serious difficulties. in mud control, and the useful life of the drilling fluids can be extended by proper treatment. Following i.; a list of the manifestations of high-temperature gelation: (1) The drill string 'takes weight' while going in the hole after a trip. In early stages of high-temperature gelation it is possible to notice a slight reduction in drill string weight as the drill pipe is lowred near the bottom of the hole. (2) Excessive pump pressure is required to .tart the circulation of drilling fluid at or near the bottom of the hole when going hack to bottom after a trip. As the severity of the gelation increases it may be necessary to break circulation a number of times when going in the hole. (3) The drilling fluid from the bottom of the hole is thick and often granular or lumpy when pumped up after making a round trip. In a severely gelled drilling fluid system such a condition may be irreversible; that is, it cannot be stirred or chemically treated to produce a satisfactory drilling fluid. (4) Completion tool.. such as logging tools or perforating guns will not sink to the bottom of the hole. On some occasions completion tools will become stuck and require a fishing job to retrieve them if the wire line attached to them is broken. It is often difficult to determine whether the condition of the drilling fluid is responsible for sticking the tool or whether the wire line becomes key seated in a crooked hole and causes the allow difficulty. When there are 110 other symptoms of high-temperature gelation. then the difficulty may usually be attributed to the latter cause. (5) In extreme cases of high-temperature gelation it is necessary to "wash" and "ream" when going back to bottom after coming out of the hole. (6) In many -instance. it has been found to be extremely difficult and expensive to 1111 production packers 2nd tubing in moderately deep oil wells which had been drilled with a lime-base drilling fluid. In such instances-the original mud had apparently "set" to a consistency approaching that of a weak cement. CAUSES OF HIGH-TEMPERATURE GELATION Extensive test; have indicated that a lime-base mud does not develop a highly gelled condition at temperatures below 250°F. whereas above that temperature such condition often develops rapidly. (Fig. 1) concurrently. the following changes are evident ill the mud: (1) The alkalinity of the mud decreases to a very low value. with both caustic soda and lime being consumed. (2) The quartz content of the mud decreases sharply. (3) The bentonitic content of the mud decreases or di-appears, with concurrent decrease or loss of base exchange capacity of mud solids. (4) New compounds formed in the mud have been found to be cal-cium silicate, calcium aluminum silicate, and calcium sodium aluminum silicate. (5) The mud loses the ability to form a filter cake of low permeability. The above characteristics have been discussed, in part. by other authors

Jan 1, 1953