Search Documents

By F. E. Jaumot, R. L. Smith

Self-diffusion in zinc at temperatures below 200°C has been studied using both single crystal and polycrystal samples. Anomalous results were obtained for single crystal samples, the data indicating that in some cases grain boundary diffusion predominated. These anomalous results are presumed to be due to low angle lineage boundaries in the single crystals. When volume diffusion occurred in either single or polycrystal samples, the values for the diffusion coefficient were as much as several orders of magnitude larger than would be expected from high temperature data. ONSIDERABLE work has been done on self-^-*diffusion at temperatures in the neighborhood of two thirds of the melting temperature (in OK) and higher, but very little has been done at lower temperatures. This is particularly true of self-diffusion in single crystals. This paper reports work on self-diffusion in zinc at temperatures below 200 °C where both polycrystalline and single crystal samples have been used. The measurements were made using both the sectioning and absorption techniques. The experiments on diffusion at low temperatures were initiated primarily for three reasons: to obtain data from single crystal diffusion covering a wide range of temperatures, to obtain values of the activation energy for grain boundary diffusion, and to obtain, if possible, a lower limit to the temperatures at which the absorption technique may be used. It is possible to determine whether volume or grain boundary diffusion predominates at low temperatures by analyzing the manner in which the concentration of the diffusing atoms varies with the depth of penetration. The analysis is possible only for the sectioning technique. For volume diffusion and for the boundary conditions of the present experiment, the curve of the logarithm of the concentration, C, vs the square of the penetration depth, x, is a straight line with the slope proportional to — 1/D. If grain boundary diffusion predominates, Fisher' has shown that a curve of In C vs the first power of the penetration depth should be a straight line. This linear dependence of concentration on depth has been observed experimentally by several investigators. (See, for example, refs. 3 and 4.) Following Fisher's analysis, the grain boundary diffusion coefficient can be written as where 8 is the grain boundary width, D, is the volume diffusion coefficient at the temperature involved, t is the time of diffusion, C is the concentration of diffusing material, and x is the depth of penetration. A more general analysis employing the same model as Fisher's but with fewer assumptions has been given by Whipple.' In contrast to Fisher's analysis the more general analysis of Whipple does not always yield a straight line relation between In C and x. Recently Turnbull and Hoffman have discussed both analyses and have applied the Fisher-Whipple model to a more refined dislocation model of the grain boundary. They have also discussed the possibility of a large effect of grain boundary direction on diffusion. In the case of the absorption technique, for which results are also given, one simply gets a value for the diffusion coefficient with no indication of the predominating mechanism. Experimental Techniques Single crystals of 99.99+ pct Zn were grown using a modified Bridgman method. Polycrystal samples were prepared in three grain sizes (small, about 4 mm2; medium, about 9 mm'; and large, about 25 mmz) by quenching, air cooling, and furnace cooling. The grains of the polycrystalline samples tended to be columnar, with some preferred texture such that the c-axis was inclined at about 20" to 25" from the normal to the diffusion face, particularly in the medium and large grain size samples. The samples were cut from the rod, polished, and heavily etched, and faces cut accurately parallel using a jeweler's lathe. They were again etched to remove the lathe smear and annealed for 3 hr at 250" to 300°C. After annealing, they were etched, examined, and the orientation determined by Laue back reflection photographs. They were then electroplated with Zn. The plated surfaces were examined for uniformity; nonuniform coatings were removed by etching and the samples replated without additional preparation. For the diffusion anneals, the samples were placed in pairs, with active faces together, in evacuated Pyrex tubes. Constant temperature baths were used, and the variation in temperature did not exceed ±l°C, Diffusion runs were made at l00°,

Jan 1, 1957

By D. L. Martin

THAT small amounts of impurities have a harm-J- ful effect on the malleability of metals and alloys is well-known. One common type of em-brittlement involves the formation of a small quantity of eutectic at the grain boundaries, and is typified by sulfur embrittlement of nickel. Another example of eutectic embrittlement—sulfur embrittlement of cobalt—is described in this report. In the preparation of specimens for a study of Co-Pt alloys, it was observed that the hot swagabil-ity of the alloys appeared to be influenced by the grade of cobalt used as melting stock. The cause of the hot-shortness was not traced to any particular impurity, although sulfur was suspected.' The damaging action of sulfur on the malleability of cobalt has not been generally recognized,'; in spite of the fact that the Co-S phase diagram8 eveals the same basic conditions—low solubility and eutectic formation—responsible for sulfur embrittlement of iron and nickel.7, 8 Apparently sulfur embrittlement has not been a serious problem in the fabrication of cobalt alloys. One related factor is likely the limited commercial experience with high cobalt alloys, since the predominant use of cobalt has been in alloys containing less than 75 pet Co. A series of Co-S alloys was prepared and studied to establish the effect of sulfur on the hot working characteristics of cobalt. Specimens, 5/8 in. diam by 4 in. long, were prepared by vacuum melting in magnesium oxide crucibles and casting in a copper mold. Two grades of low sulfur electrolytic cobalt were used as the basic material for the study, one from Johnson, Matthey and Co. and the other from the International Nickel Co. Each contained about 99.5 pet Co and had a nominal sulfur content under 0.005 pet. The sulfur was added initially as cobalt sulfide powder. Later, some low sulfur alloys were prepared by diluting the high sulfur alloys with cobalt. Trouble was experienced in controlling the sulfur content. Apparently much of the cobalt sulfide powder was lost during melting, as most of the samples contained a lower sulfur content than was added. The alloys were evaluated for hot brittleness by heating to 1000°C in a hydrogen furnace and swaging in air. The results of these tests are summarized in Table I. All the alloys containing less than 0.008 pet S were successfully hot swaged to 1/4 in. diam. The bars containing more than 0.015 pet S could not be swaged because of the formation of intercrystal-line cracks similar to those illustrated in Fig. 1. Examination of the microstructure of the cast bars revealed cobalt sulfide eutectic at the grain boundaries, Fig. 2. The sulfide was not always continuous at grain boundaries in bars that were hot embrittled but, in general, the particles did form a network that could account for the brittleness above the eutectic temperature, 880°C. There is no question about the brittle nature of a specimen exhibiting a continuous sulfide network such as is shown in Fig. 2b, though a sulfide distribution similar to that in Fig. 2a is marginal. This particular bar cracked when hot-swaged. However, other bars with lower sulfur content but with some sulfide phase at grain boundaries were successfully worked. The reduction of area of a hot tensile test specimen was also found to be a sensitive indicator of sulfur embrittlement. The variation of reduction of area with sulfur content is shown in Fig. 3 for specimens fractured at 900°C in an evacuated capsule. The ductility of cobalt is greatly reduced when the sulfur content exceeds 0.005 pet. Similar results were obtained for alloys tested at 800°C, below the eutectic temperature. The upper sulfur embrittlement limit of 0.015 pet, Table I, agrees with the observation of Kalmus8 hat

Jan 1, 1957

By H. R. Shell

Of three known compounds in the ternary system K20 - PbO - SiO2, one having the composition K2Pb4Si8021 crystallizes into a structure with asbestiform properties. This compound, whose silicon-oxygen ratio is between that of the layer silicates (for example, mica) and the double-chain amphiboles, crystallizes in the tetragonal system. It malts, apparently congruently, at 779° C. The fiberized product prepared from crystals is fluffy and closely resembles natural asbestos in appearance, but is more brittle and has less strength. However, potassium-lead silicate may be separated into fibers with a uniform diameter of 200-300 A.U., and the fibers show with the electron microscope the s criteria that have been interpreted as indicating a hollow tube structure in chrysotile asbestos. Since very few inorganic crystalline compounds have such a structure, the material has unusual scientific interest. Microcrystalline potassium-lead silicate was rapidly and completely formed when powdered glass of the same composition was heated to 650° - 700° C, but macrocrystals grew only slowly from the viscous massive glass. Maximum growth rate was 0.12mm. per hour at 700° C.

Jan 1, 1957

By J. P. Powell

Systematic waterflooding was first tried in Washington County, Okla., in 1937, when a 40-acre project was begun in secs. 24, 29, 32, and 33, T. 27 N., R. 13 E., jointly by the Keener Oil Co. and the Phillips Petroleum Co. The property later was sold to Lee Morrison. A second project was begun in 1941 in sec. 14, T. 6 N., R. 12 E., by the Oklahoma Oil Corp. Both projects were abandoned by the end of 1942. A third project was begun in 1945 and the fourth in 1948, but 1949 actually was the beginning of intensive waterflooding development in Washington County. The results of previous waterflooding projects are described in Bureau of Mines Reports of Investigations.2 3 4/ Oil production in the county followed a similar trend, dropping to a low of 990,000 barrels in 1945, then steadily increasing until 1956, when more than 4 mil-lion barrels of oil was produced. Most of the increase in oil production is directly attributable to water injection.

Jan 1, 1957

By W. A. Selvig

[THE BUREAU OF MINES receives many requests for information regarding the low-temperature carbonization properties of American coals. This report presents in collected form the results of Fischer-Schrader bench-scale, low-temperature carbonization assays at 500° C. made by the Chemistry and Physics Section at the Pittsburgh station of the Bureau of Mines. Most of the assays were made of coals tested in connection with a survey of gas and coke-making properties of American coals,4 which was started in 1928 by the Bureau in cooperation with the American Gas Association. Other coals were assayed in connection with miscellaneous investigations. Since 1930 about 400 samples of coal were assayed from nearly every coal-producing State, Alaska, and British Columbia, Canada. The results of the tests on about two-thirds of the coals are scattered through more than 50 separate publications. This paper summarizes the data in the published reports as well as all unpublished data obtained to January 1, 1956. The report also includes a detailed description of the procedure used in making the assay.]

Jan 1, 1957

By L. J. Kane

While analyzing synthesis gas produced from coal, the Bureau of Mines found that conventional procedures for naphthalene determination were difficult and time consuming. The Bureau developed a rapid and sensitive turbidimetric procedure, which requires only simple instruments and hence can be used in plant-control laboratories. The gas is passed through a saturated aqueous solution of picric acid at 3° to 4° C. whose turbidity is then measured at room temperature. A dispersing agent is added to prevent coagulation of the suspension on warming. Only about 1 mg. (0.015 grain) of naphthalene need be absorbed, and precision and sensitivity are a few ten-thousandths of a grain, or a few hundredths of a grain per 100 cubic feet. The determination can be completed less than 10 minutes after absorption. INTRODUCTION One of the functions of the Branch of Coal Gasification, Bureau of Mines, Morgantown, W. Va., is to develop economical methods for manufacturing, from coal, a mixture of hydrogen and carbon monoxide for producing hydrogen, methane, and other gaseous fuels. This raw gas may contain many impurities, including naphthalene. This impurity is usually determined by first forming naphthalene picrate in a water solution of picric acid, separating the picrate, and titrating the unreacted picric acid or the picrate itself.

Jan 1, 1957

By Herty, C. H.

Three distinct processes take place during the conversion of iron ore to steel. First: the raw ore is reduced to metallic iron in the blast furnace and during this reduction certain constituents are dissolved in the iron, either through the solution of a solid into a liquid phase, as in the case of carbon, or by reduction of an oxide existing in the slag to the metallic element of that oxide, with subsequent solution of the metallic element in the iron. Thus by the process of solution and reduction, a pig iron results which contains about 4 per cent carbon, 1 per cent silicon, 1 to 2 per cent manganese, 0.1 to 0.4 per cent phosphorus, and 0.03 to 0.10 per cent sulfur. To obtain a sufficient yield of iron from the ore it is necessary that the reducing process be carried as far as possible, with the result that the impurities mentioned accompany the reduced iron. Second: to convert this iron into steel it is necessary to oxidize a part of the iron in eliminating the impurities to the extent desired for the particular product being made. In eliminating these impurities by oxidation a certain amount of iron oxide (FeO) dissolves in the steel. This dissolved FeO reacts with the metalloids, except sulfur, and to eliminate them to the desired extent it is necessary to leave a considerable amount of FeO in the metal. The reaction of iron oxide with silicon, manganese, and phosphorus results in the formation of the oxides of these elements. The oxides enter the slag and the extent of elimination of the elements depends on certain equilibria between the slag and the metal. The reaction of FeO with carbon results in the formation of the gases CO and CO, which, after saturating the metal, pass into the furnace gases. Third: after the iron has been purified to the desired extent as far as the elements listed are concerned, it is necessary to deoxidize the bath to remove the FeO, which is the vital factor in gas formation as the steel solidifies.

Jan 1, 1957

By F. A. Schaufelberger

METAL can be recovered from a leach solution either indirectly by precipitation as a compound that is later reduced or directly by electrolysis, cementation, or chemical reduction, for example, with hydrogen. The widely used electrowinning processes suffer from the inefficiency of converting fuel to low voltage dc and from low current efficiency when complete recovery is attempted. With the batch hydrogen reduction methods outlined here, a unit of fuel converted to hydrogen in modern gas reform plants will make two to three times as much metal as can be obtained with electrolysis. With continuous hydrogen reduction, four to six times as much metal is obtained. Precipitation by reducing a metal salt solution with H, has been known for almost 100 years.' Commercial use of the process, however, awaited the research and development program initiated by Chemical Construction Corp. Within the last few years this program has brought about construction of commercial plants, listed on page 545. Ideal hydrogen reduction will precipitate a pure metal from a solution obtained by commercial leaching methods at a rapid rate without excessive temperatures and pressures. The metal precipitate will be of desired size and density, less than a percent left in the vessel being deposited on the wetted parts. The present discussion will outline Chemical Construction Corp.'s early development program and will discuss the chemistry and mechanics of reducing copper, nickel, cobalt, and cadmium from solution by H2. Work on selective reduction of nickel from cobalt has been described earlier.' The article is not concerned with precipitation of copper by disproportionation of cuprous solutions where yield is limited3 to 50 pet.* It does not discuss use of gaseous reducing agents other than hydrogen, such as SO2,4 which may lead to contamination with sulfur, or C0,5 which is considerably more expensive than hydrogen and produces a gaseous reaction product, CO2.† The article does not include use of other nongaseous reducing agents,7 which are far more expensive than CO. Also, notes on the history, engineering design, and performance of commercial plants have been given elsewhere.' It will be shown that a pure metal can be precipitated by reduction with hydrogen from solutions obtained by commercial leaching methods when the solution composition is controlled and proper acidity, proper metal ion concentration through controlled complex formation and hydrolysis, and adequate agitation for suspension of metal and for transfer of reducing gas are maintained. Reasonable temperatures and pressures are used which are less excessive than those used by previous workers, although they are maintained at above equilibrium values because of process kinetics.' It has also been found necessary to induce nuclea-tion and to control growth and agglomeration in order to get a powder product of suitable physical properties. Review of the Literature Muller, Schlecht, and Schubardt of I. G. Farben10 claimed a successive reduction of silver, copper, nickel, cobalt, and zinc from ammoniacal solution by applying progressively higher temperatures and hydrogen pressures. Metals produced by this technique were not pure, since no attempt was made to adjust the solution composition between the different reductions. It is doubtful that the zinc product contained any metallic zinc. The major contribution to the literature" was made by the Ipatiews,12 who prepared platinum, iridium, copper, nickel, cobalt, lead, tin, arsenic, antimony, and bismuth at often extreme conditions, up to the critical temperature of water (373ºC), at 1500 to 7500 psi, for as long as several days. Even cadmium and zinc were claimed to have been observed in trace quantities precipitated together with basic salts. In the early experiments solutions were not stirred. Extensive formation of oxides and basic salts occurred, probably long before sufficient hydrogen could be supplied in the unstirred liquid to decrease the metal concentration in solution by reduction. The importance of hydrogen pressure was

Jan 1, 1957

By B. C. Mariacher

EXTRACTION of uranium from ores is being ac-complished by processes which. for the most part, subject the entire ore to acid or carbonate leaching. Ore deposits with a U 3 O 8 content below 0.10 pct U 3 O 8 are seldom considered suitable for treatment by leaching. A preliminary concentration that would enrich the uranium content of an ore by a simple, low cost process based on physical properties of the ore might result in some low grade deposits becoming commercial ores. In addition, the process might be employed in existing operations to reduce transportation and leaching costs and to increase capacity of existing leaching plants. A study to attempt the development of a preliminary concentration process for primary uranium ores was undertaken by the Colorado School of Mines Research Foundation under sponsorship of the U.S. Atomic Energy Commission. The objective of this work was to produce concentrates containing 0.25 pct U3O8 from the low grade ores tested. Ores Tested: The main effort was devoted to the low grade primary uranium ores from northwestern Saskatchewan. Samples were obtained from the Beaverlodge operation of the Eldorado Mining & Refining Ltd. Additional primary ores, obtained from deposits in Gilpin County, Colo., contained from 0.07 to 0.10 pct U3O8. Summary of Concentration Tests: The Beaverlodge ore was tested to determine amenability of the ore to concentration by magnetic, electrostatic, gravity, and scrubbing processes. None of these produced satisfactory results. Both gravity and magnetic processes produced fairly good concentrates when closely sized fractions of the ore were treated, but on the basis of treating the total ore, recovery was poor. Preparation of sized fractions and the low capacity of equipment for suitable concentration made these methods impractical. As flotation offered the advantage of treating the total ore without intermediate sizing, the main effort was in this direction. A flotation process was developed that fulfilled the concentration objectives as set by the AEC. Pilot plant testing was used to verify results obtained from laboratory batch testing. Mineralogy: A petrographic examination of the Beaverlodge ore included a study of polished sur- faces and identification of the radioactive mineral by autoradiograph and X-ray diffraction. Approximate quantitative mineral identification was as follows: quartz, 60 pct; orthoclase feldspar, 20 pct; chlorite, 10 pct; carbonates, 5 pct; and miscellaneous minerals, 5 pct. Included in this last group were plagioclase feldspar, pyrite, mica, chalcopyrite, pyroxene, sericite, magnetite, galena, and uraninite. The most general occurrence of uraninite was in the form of crusts and thin coatings on limonite-stained grains of pyrite, quartz, and pyrite-quartz intergrowth. At least 90 pct of the uraninite was still attached to other minerals in a 100 by 200-mesh size fraction. The uraninite crusts were as small as 10 to 20 µ diam, and 5 to 10 µ thick. The Flotation Process Petrographic examinations of the Beaverlodge ore had indicated the impracticability of attempting to concentrate the uranium by floating individual grains of uraninite. Liberation of the uraninite required grinding to sizes below those suitable for flotation. However, there was preferential association of the uraninite with some minerals while others were free of uraninite attachment. The approach to the development of a flotation process was, therefore, based upon an attempt to concentrate the uraninite by floating carrier minerals. The following paragraphs discuss the various stages of the process with regard to the factors tested and the conditions under which best results were obtained. Grinding: The most effective size range for flotation was —150 mesh + 13 µ. The —13 µ material in the final concentrate had a higher U3O8 content than the total ore, but not as high as the average concentrate; however, rejection of slimes before flotation was prohibitive because of the loss in uranium carried in the —13 µ fraction. Grinding techniques which contributed to a minimum production of fines, such as stage grinding, were then employed. Quartz and Silicate Depression: These minerals represented approximately 80 pct of the ore and were free to a large degree of uraninite attachment. Significant improvement in the grade of the concentrate was obtained by depression of these minerals with hydrofluoric acid or sodium fluoride. Promoter: Selective stage flotation of uraninite carrier minerals was simplified by development of a single promoter mixture. The mixture consisted of an emulsion of a fatty acid, fuel oil, and a petroleum sulfonate and was selected after a comprehensive series of tests. It contained three parts by weight of an oleic and linoleic acid such as Emersol 300,

Jan 1, 1957

MR. J. F. MYERS, Consulting J3eneficiation Engineer, Greenwich, Conn.: In the written discussion contributed by Mr. F. C. Bond in item ( 2) (page 515), speaiking about the significance of the ratio of mill diameter to the make-up ball diameter, he states: "When this ratio exceeds 100 the power and capacity of the mill are de-creased"; and the paragraph ends with a reference to the 30 per cent ball volume "with some de-crease in mill capacity". I believe this broad statement is incorrect. When we are dealing with a non-cataracting mill, pre-ceded by a good rod mill, there is a slight increase in capacity, but the power does drop. The second point that I consider needs consideration is Mr. Bond's item (8), Proper Mill Speed (page 516). This paragraph should be qualified to cover single-stage mills only. It does not apply where a rod mill is followed by a non-cataracting ball mill. The statement as is, with no qualification, gives an erroneous idea of proper mill speeds.

Jan 1, 1957

By R. F. Domagala, M. Hansen, D. J. McPherson

Iodide zirconium was combined with calculated amounts of nitrided zirconium sponge and arc melted to prepare alloys in the 0 to 6 wt pct N region. Annealing treatments were carried out at 21 temperature levels. Metallographic examination of the heat-treated specimens permitted construction of the binary phase diagram from 0 to 6 pct N. Features of the diagram include the peritectic formation of both a and ß solid solutions. The maximum solubility of nitrogen is 0.8 pct in 8 zirconium and 4.8 pct in a zirconium. An X-ray study of nitrided materials was made in the range 6 to 13 wt pct N region because serious nitrogen losses were experienced when attempts were made to arc melt these high nitrogen alloys. PHASE relationships in the Zr-N system have been determined. Due to the inability to retain nitrogen in nitrogen-rich alloys subjected to arc melting, definitive work was possible only in the range 0 to 6 wt pct (0 to 30 atomic pct) N. Sufficient complementary X-ray work was done to permit construction of the binary phase diagram up to 13.3 wt pct (50 atomic pct) N (ZrN). Small ingots were prepared by arc melting master alloys with enough zirconium to produce an alloy of the desired composition. Following pretreatment, alloys were annealed at temperature levels between 600" and 2020°C. Determination of the phase boundaries was then accomplished by metallographic evaluation of specimens quenched from the various temperatures. Incipient melting techniques were used to corroborate solidus curves, and X-ray diffraction was employed to study the nitrogen-rich region of the a + ZrN phase field. Materials Westinghouse Grade 1 iodide zirconium crystal bar served as the base material for this investigation. The as-received bars were lightly sandblasted, pickled in a 20 pct HN0-5 pct HF aqueous solution, rinsed in water and acetone, and dried. They were rolled to about 1/32 in. strip and acid-pickled, followed by water and then acetone rinses. The material was sheared to approximately 1/4 in. squares, cleaned with acetone, and stored for use. Pure zirconium nitride is not commercially available, according to correspondence with possible suppliers. A literature survey indicated that nitrogen may be introduced into zirconium metal by passing nitrogen or ammonia gas over zirconium at an elevated temperature. After considerable experimentation, a train was devised whereby high quality nitrogen was passed through a series of bubblers to remove the last traces of oxygen, through an H,SO, bubbler and a cold trap to remove moisture, and finally over zirconium within a resistance furnace. Hand-picked Bureau of Mines magnesium-reduced zirconium sponge proved more amenable to nitriding than the crystal bar. The nitrogen used was extra pure gas purchased from Linde Air Products Co. The first two bubblers through which the gas was passed contained a solution suggested by L. F. Fieser" as being ideal for removing the last traces of oxygen from nitrogen. The solution contains 20 g KOH, 2 g sodium-anthraquinone ,9-sulphonate, and 15 g NaHSO, dissolved in 100 ml water. It is blood-red and turns brown when contaminated with oxygen. A saturated lead acetate solution, next in the series of bubblers, removed any H2S which might have formed in the 0, removal stage. An H,SO, bubbler and cold trap removed moisture before the nitrogen was passed over the zirconium. The zirconium was contained in a stainless steel screen within a Vycor or quartz tube in a resistance furnace. Unreacted nitrogen passed out of the system through a mercury bubbler. A nitriding run was performed in the following manner: Zirconium was placed in the screen within the furnace tube. The unit was assembled, suitably clamped off, and evacuated to remove the air and moisture within the tube and that trapped by the zirconium sponge. The unit was flushed with nitrogen and evacuated twice. After nitrogen was allowed to pass over the zirconium for about 30 min, the furnace was turned on; several hours were required to reach temperature. The reaction was allowed to continue at temperature for about 4 hr and the screen was then withdrawn from the hot zone of the furnace by means of a Nichrome or Kanthal rod. The screen and its contents were allowed to cool at the end of the tube and were then removed. At 800°C no more than about 5 pct N could be introduced into the sponge zirconium. This material was designated M-1 (master alloy No. 1) and reserved for the preparation of alloys in the dilute nitrogen region. A second set of experiments was conducted at 1000°C; no more than 7.2 pct N could be introduced into the zirconium at this temperature. Enough material (M-2) of this nitrogen content was prepared to produce a second set of alloys to complement the first and to provide alloys in the 0 to 6 wt pct N range. It was hoped that a diffusion anneal plus a re-nitriding might yield a material of higher nitrogen content. The material containing about 7 pct N was therefore given a homogenization treatment at 1000°C for 6 hr under an argon atmosphere. It was

Jan 1, 1957

By Gordon W. Hodgson, Edward Tipman

INT'RODUCTION An appreciable number of the oil fields in Western Canada are accumulations of heavy black oils in more or less unconsolidated sandstones. When the crude oils are produced by conventional means, they are frequently contaminated with both sand and oilfield water. The water is usually present as emulsified water, and the sand and other solid materials are suspended in the emulsions. The presence of the solid material in the crude oils is troublesome and, in general, little is known about the behavior of suspended solid particles in emulsions. The Stokes equation describes the behavior of suspended particles in homogeneous fluids in terms of particle size, density differential, and fluid viscosity. In the case of an emulsion, particle size and density differential introduce no difficulties, but considerable doubt centers around the viscosity term. It has been reported1 that the viscosity of an emulsion is related to the viscosity of the continuous phase by an expression of the type: n = a, (1 + a C) where n is the viscosity of the emulsion, n,, is the viscosity of the continuous phase, a is a constant, C' is the volume concentration of the disperse phase. The value of 17, the coefficient of the concentration term, has been determined for various systems, and has been found to vary from a value of 1 to 4.75. The value of 2.5 has been found to be applicable to a large number of systems, and this is the value that is widely used in the equation which then becomes the Einstein equation for the viscosity of emuls~ons. It is of considerable significance that neither the particle size nor the viscosity of the disperse phase enters the expression; the expression for the viscosity of the enlulsion is based solely upon the viscosity of the continuous phase and the concentration of the disperse phase. For crude oil emulsions the Simha equation and the data presented by Fukushima and lchimurai show a non-linear dependence of the viscosity ratio on the water concentration. While it is undoubtedly reasonable to use these data for predicting the viscosity of a specific emulsion, and while it is equally reasonable to expect the calculated viscosity to predict the settling rate of a solid spherical particle in the emulsion by means of Stokes equation, there seems to be no direct evidence that this calculation is indeed sound for describing the settling rates of solid particles in emulsions of water in crude oils. PROCEDURE A direct approach to the problem was thus indicated. Laboratory equipment was designed and built for the direct determination of the rate-of-fall characteristics of solid particles in emulsions of water in oil. Although the apparatus incorporated the basic design of conventional falling-ball viscometers, the study was concerned directly with the rate-of-fall characteristics of particles in emulsions, rather than with the viscosity of the emulsions as such. The crude oil used in this study was a very heavy black crude oil—the McMurray oil obtained from oil-soaked sands outcropping on the Athabasca River in northeastern Alberta. It was produced from the sands by strip mining followed by hot-water separation of the oil in the separation plant of the Alberta Government at Bitumount'. The primary plant product was a wet crude oil containing about 5 per cent solids and 35 per cent water. The final plant product was only slightly different from the native oil, having lost only about 4 per cent of its bulk as light ends during dehydration distillations. In the present investigation two kerosene dilutions of the McMurray oil were used in addition to the dry plant product. The McMurray oil contained 1.92 per cent solids. Analysis of the solids by X-ray diffraction showed the presence of kaolinite, pyrite, and illite as major constituents. with lesser amounts of quartz. Particle size of the pyrite and quartz was less than 10

Jan 1, 1957

By J. E. Dorn, L. A. Shepard

LOW and Gensamer' demonstrated a number of years ago that the yield point phenomenon in mild steels was associated with the presence of fer-rite soluble carbon or nitrogen. More recently the yield phenomenon in body-centered-cubic metals containing interstitials was rationalized by Cottrell' in terms of a simple dislocation model. Interstitial atoms interact with dislocations in two ways; they cause not only local expansions but induce local tetragonality in the lattice. Consequently, interstitial~ interact with the hydrostatic tension and shear components of the stress about dislocations. They tend to migrate toward the expanded regions of edge dislocations and to assume sites that relieve the shear stresses of screw dislocations. Thus, a dislocation saturated with solute atoms constitutes a lower free energy state than that obtained when the dislocation threads through the average composition regions of the matrix. A greater stress will be required to separate the dislocation from its atmosphere than to move the dislocation through the matrix. This factor gives rise to the upper yield stress, which is required to unleash a series of dislocations in a localized region. This local yielding is propagated across the specimen to form a thin band of plastically deformed material known as a Lueder's band, making an angle of about 45" to the stress axis. Once the band has formed, deformation continues at the lower yield stress by the spreading of the Lueder's band in the direction of the applied stress. Undoubtedly the spreading of Lueder's bands at the lower yield stress is accomplished by the high stress concentrations at the band fronts, which serve to induce continued unlocking of new dislocations in advance of the migrating band fronts. Cottrell and Bilby have shown that the dependence of the yield point on temperature can be deduced by assuming that thermal fluctuations aid the stress in unlocking small dislocation loops from their solute atmospheres. Once a loop that exceeds a critical size has been nucleated, the entire locked diqlocation is released and can migrate. Fisher4 simplified this analysis by assuming that the locking forces were short range, so that if the dislocation loop were displaced only one Burgers vector from its atmosphere, it would be unlocked. Applying his model to the special case of delayed yielding under a constant stress of the order of the upper yield strength, he demonstrated that the delay time 7 for yielding should depend on stress and temperature according to where A and B are constants, G is the shear modulus, and u and T are the resolved shear stress and absolute temperature, respectively. Cottrell and Bilby, Fisher, and Fisher and Rogers' have shown that the above deductions are at least in qualitative harmony with the experimental facts. A number of investigators5-0 have shown that the yield point phenomenon can also be induced in sub-stitutional alloys of face-centered-cubic metals. In general such yield points are not as pronounced as those encountered in body-centered-cubic metals containing interstitials. The yield point phenomenon in these materials is usually enhanced by prestrain-ing at low temperatures and aging at intermediate temperatures. Undoubtedly the yield point phenomenon induced by strain aging substitutional alloys also results from locking of dislocations. But the locking of dislocations in substitutional alloys of face-centered-cubic metals differs somewhat from interstitial locking of dislocations in body-centered-cubic metals. Substitutional elements in face-centered-cubic lattices cause only radial displacements of the adjacent lattice points. Consequently, only the edge components of dislocations can be locked by the mechanism suggested by Cottrell. Additional locking, however, can be obtained by the Suzuki mcchanism.10 In face-centered-cubic metals, dislocations exhibit lower energies when they are present in the

Jan 1, 1957

By G. W. Binkley, G. K. Dumbauld, F. A. Brooks, B. E. Morgan

In recent years, oil well cementing compositions have been developed with low densities, controlled set strengths, and satisfactory thickening times. With the introduction of the permanent-type well completion method for cementing wells, another property—that of rate of filtration or water loss to permeable formations— has become important. Laboratory data show that cement slurries prepared with oil, water, bentonite, and calcium lignosulfonate possess satisfactory thickening times, strengths, and filtration properties for primary cementing of casing and for squeeze cementing with the permanent-type well completion technique. Cementing compositions have been prepared with oil-in-water emulsions varying in composition from 60 cc water and 20 cc oil per 100 gm cement to 90 cc water and 45 cc oil per 100 gm cement. These compositions have contained from 0.4 to 5.0 per cent calcium lignosulfonate by weight of dry cement. Slurries prepared from these compositions weigh 11.4 to 13.1 lb/ga1 and have filtration rates of from 10 cc to approximately 100 cc in 30-min API tests at room temperature. The unfiltered emulsion cements develop one-day tensile strengths of 60 to 220 psi; and the filtered mass sets to tensile strengths of 60 to 150 psi in 12 hours and develops strengths of 320 to 515 psi in seven days when cured at 125° F. Field experience gained from 13 field mixing jobs demonstrates the utility of the emulsion cement for permanent-type squeeze cementing operations. INTRODUCTION In recent years, research in oil well cementing composition has been directed toward the development of cements having low densities, controlled set strengths, satisfactory thickening times, and low rates of water loss by filtration. Two well cementing compositions that have been developed with these properties are the modified cements containing, respectively, 12 and 25 per cent bentonite clay and various concentrations of calcium lignosulfonate1,2 In a search for other ways to incorporate these characteristics in a cementing composition, consideration was given to the rheological properties of oil-emulsion drilling fluids. Many of the desirable properties observed in oil-emulsion drilling fluids are equally advantageous in a cementing composition. For example, low water loss by filtration and low density, which are inherent characteristics of these oil-in-water emulsions, are desirable for many oil well cementing operations. Furthermore, oil-emulsion slurries have lubricating properties similar to those of oil-emulsion muds, a factor which should provide ease of rotation of casing during primary cementing operations. The properties of lubrication and low filtration may be of special value in both primary and squeeze cementing operations encountered in slim-hole drilling. Studies in the preparation of oil emulsion systems have pointed out the need for violent agitation in order to disperse the oil into the water phase. It was thought, therefore,

Jan 1, 1957

By J. C. Holm

ALTHOUGH the main constituents of Portland cement are the oxides of calcium, silicon, aluminum, and iron, characteristics of the cement are seriously affected by such contaminants in the raw materials as magnesium, phosphorus, sodium, potassium, sulfur, and others of lesser importance. Sources of cement raw materials comprise a long list of minerals occurring in nature in various degrees of purity. The calcareous raw materials are generally limestone of purity varying from calcite to cement rock (a low-grade limestone of natural, almost correct chemical composition), chalk, marl, seashells, coral, and coral sand. The argillaceous raw materials supplying silicon, aluminum, and iron are mainly various forms of clay and shale, to which may be added silicious sand, iron ore, bauxite, or kaolin for minor adjustment of the chemical composition. The quality of Portland cement in this country, as in most parts of the world, is controlled by rigid specifications limiting both its chemical and physical characteristics, and cement manufacturers must comply with these specifications to market their products. Brandon Raw Materials: An unusual deposit of marl, limestone, and clay occurs 12 miles east of Jackson, Miss., near the village of Brandon. The deposit is of sedimentary origin and of relatively young geological age. Layers of marl vary from putty-like consistency to such hardness that it can be cut with a knife. Interspersed between the layers of marl are bands of limestone varying from very soft to hard. the compressive strength of the hardest layers exceeding 15,000 lb per sq in. The layers of marl range in thickness from a few inches to about 25 ft. The limestone bands seldom exceed 2 to 3 ft but often occur in thinner veins in the quarry face. Above the top layer of the deposit, which may be marl or limestone, a layer of clay ranges in thickness from a few inches to more than 20 ft. Part of this clay is harvested with the raw material to supply part of the argillaceous components, but most of it is stripped as overburden and wasted. A highly silicious clay of extreme fineness, harvested from the bottom of the quarry below the marl and limestone bands, is to correct the silica content. Fig. 1 shows typical examples of the interrelation of the various materials, based on drill logs obtained during exploration of the deposit. The marls vary in moisture content in the bank from 15 to 30 pct and contain up to 70 pct -200 mesh particles and up to 40 pct —10 p particles. A large percentage of the fine fraction is within the colloidal range, making the marl extremely sticky. The limestone beds range in hardness from that of the hardest marl to a medium hard limestone and in moisture content from 2 pct to approximately 14 pct. The line of demarcation is often difficult to draw and the moisture content is possibly the best means of classification. The ratio of soft to hard material is not constant throughout the deposit, but the average is approximately 70 pct soft to 30 pct hard material. Through the years this deposit had been repeatedly explored by cement companies and rejected as unsuitable for cement manufacture, mainly because of physical characteristics. In 1950, after careful exploration of the deposit and comprehensive laboratory and pilot plant tests of the raw materials, officials of Marquette Cement Mfg. Co. of Chicago were convinced that a practical and economical method of processing the raw materials had been devised and authorized construction of a new plant that began production in December 1951. Marl and limestone, common raw materials for Portland cement, usually occur in such a manner that they can be worked separately. Their harvesting and processing normally have presented no difficult problems, as standard equipment and methods are available for handling either sticky or hard materials. No other cement plant utilizes a deposit of the nature of that at Brandon, however, and for this reason no prior art was available for design. When properly blended, the raw materials produced an excellent cement without additives. Basic problems to be solved in designing the cement plant were:

Jan 1, 1957

WHEN Magma Copper Company in 1952 set about finding $100,000,000 to finance the project of developing and equipping the property of its lusty progeny, the San Manuel Copper Corporation, A. J. McNab, president and guiding genius for both companies (and incidentally a mining engineer by profession), determined that he would avoid the mistake frequently made in such circumstances, of underestimating the cost, and thereby running short of funds before the job was completed. The fear that this might happen was one of the reasons why insurance companies, one potent source of "big" money, were reluctant to finance the enterprise. How, they asked themselves, would Magma, a relatively small company, get additional money in such a contingency? Insurance officials' thumbs were turned down. Conditions Imposed by R.F.C. The upshot was the negotiation by Mr. McNab for San Manuel of a contract with the Reconstruction Finance Corporation, dated July 10, 1952, whereby needed monies in amount up to $94,000,000 would be advanced as a loan, bearing 5 per cent interest. Arrangements were made for the separate financing of the new $10,000,000 town, needed for the project, through the Del E. Webb Construction Company of Phoenix, Arizona, and M.O.W. Homes, Incorporated, of Los Angeles. Thus the $94,000,000 drawing account was believed ample to provide for building the railroad, the mine plant, the concentrator, and the smelter, as well as for the underground development of the mine needed to start production. As a matter of fact, only

Jan 1, 1957

By A. J. de Witte

INTRODUCTION The importance of determining dips of subsurface formations in wells, especially in wildcat wells, is self-evident and need not be enlarged upon. Various dipmeter instruments have been described in technical literature1,2,3,4 over the years. The introduction of the continuous dip-meters3,4 has made the earlier types obsolete. Continuous dipmeter logs are run by at least two different major service companies. Included as part of the service are a limited number of dip calculations—usually 10—made at different levels from the log. Very frequently this is the total result of a dip survey. It is believed that dipmeter surveys would be of considerably more advantage if geologists and engineers were able to make their own calculations from the original records. Determination of dips from the dipmeter record starts with the correlation of three log curves taken at different sides of the borehole. It cannot be over-emphasized that the quality of the results hinges primarily on this correlation. Nobody should be better qualified to correlate logs than a subsurface geologist or field engineer. The next requirement is to have an easy yet accurate way of computing the dip from the correlated points. Service companies use a mechanical device for this purpose. Directions for a graphical method were given in a recent article by B. 0. Prescotts. This paper describes a different graphical technique which, in our experience, is simpler, faster and at least as accurate. The entire manipulation is carried out on the stereonet in a number of easy moves. The paper is divided into two parts. This first part contains the introductory sections and full explanation of the geometry involved. The second part reviews the reading of data from an actual field log and summarizes the practical rules for computation of dips, the whole process being illustrated by an example. Following the outlined procedure, one could calculate a good many levels in a relatively short time, thus being able in particular to check suspected anomalies such as fault zones or unconformities in as close detail as the log will permit. GENERAL EXPOSITION OF THE METHOD Prnciple of the Dipmeter The position of a plane in space is defined by the location of three points, not on a straight line. Referring to Fig. I, if a borehole traverses a bedding plane, we can determine the strike and dip of the bed by finding three points which are not in line along this plane. Such points as A, B, and C are obtained with the dipmeter. The device consists of three electrodes (or caliper arms)1, 2, and 3 spaced at 120 angles, as schematically indicated, whose readings are separately recorded (Curves 1, 11, 111, to the right). When electrode 1 passes the boundary of the bed, Curve I will kick, etc. From these curves, we know the relative distances of points A, B, C, measured along the axis of the hole. If A is at zero, then B and C are at levels d1 and d2 up the hole,

Jan 1, 1957

By C. F., Christopher

The purpose of any steel-making process is to convert the two raw materials iron and scrap into steel. The chemical analysis of the steel is set within certain limits which involve the physical proper- ties desired by the consumer. In addition to tensile properties a large number of other properties are at the present time desired, such as impact resistance, grain size regulation, specific degrees of hardenability, resistance to creep at high temperatures, resistance to expansion on heat treatment, the ability of the product to undergo extreme amounts of cold deformation without failure, and many other properties which are not directly related to the specified chemical analysis. Variations in many of the properties of plain-carbon steels are due to elements and compounds not included in the ordinary "five element"§ composition. Such variations result primarily from variations in oxidation of the metal in the furnace and from the deoxidation method employed. The steel-making problem therefore resolves itself into two distinct sections: (I) the elimination of certain elements from the charge (the iron and scrap entering the furnace) and the addition of materials to meet the chemical specifications for the heat; (2) the manipulation of the slag and metal and the process of deoxidation to give certain desired properties in the steel entirely apart from the chemical analysis specified. Each of 'these two ends must be attained

Jan 1, 1957

By G. D. Hobson, I. Mrosovsky

Material balance relationships for expansion-type reservoirs above the bubble point have been discussed in recent years by H. N. Hall and M. F. Hawkins, Jr. The former drew attention to the effects of rock compressibility, and the latter to the effects of the compressibility of any interstitial water. Hawkins derived a general relationship which took note of oil, water and rock compressibilities, and then by assuming first, the absence of interstitial water and secondly, no effects due to interstitial water or rock compressibility, obtained relationships symbolically of the same form as those previously derived directly by Hall. Hawkins defined his terms clearly, and noted an approximation, due to the omission of a term involving the product of two compressibilities, made in reaching his final equation. There is, however, possible ambiguity with regard to Hall's written definition of the oil production term. One interpretation would mean that the produced oil and initial oil-in-place, if both required as stock tank barrels, would be obtained by using different formation volume factors in the conversion in order to satisfy the conditions implicit in Hall's formulae. The other would involve an approximation which, if used, was not stated. In both Hall's and Hawkins' studies the effect of the approximation or inconsistency is very slight. Nevertheless, it may be justifiable to give a somewhat more consistent derivation, since the complexity of the final relationships is not thereby greatly increased. Let the initial pore volume be Vi and the volume after a pressure drop of Ap, V. Then V = V, (1 - ?p . cr), where c, is the rock compressibility expressed as change in pore volume/unit pore volume/unit pressure change, and is defined with the initial pressure as base. Suppose that the interstitial water saturation under the initial conditions is Sw. The total volume of interstitial water under those conditions will be ViSw. If the volume of the water after dropping the pressure by ?p is V., this will be given by Vw = ViSw (1 + ?p.c,w), the compressibility of the water being c, which is ex- pressed using the volume at the initial pressure as base. If Boi is the reservoir volume factor of the crude oil for the initial reservoir conditions, and B. the equivalent factor when the pressure has dropped by ?p, with N the initial amount of oil expressed as stock tank barrels. N.Boi = Vi - V,Sw If n is the amount of oil produced (in terms of stock tank barrels) as a result of the pressure drop ?p, the remaining subsurface volume of oil at the lower pressure will be Bw, and Bc can be related to the compressibi:ity of oil and the pressure drop, and if c, is the compressibility factor based on the initial conditions, The relationship derived by Hawkins was case to a standard at the lower pressure, while a term (Ap) had been dropped, because of its smallness arising from its dependence on the products of two compressibility factors. When there is no interstitial water and rock compressibility can be ignored, Eq. 1 reduces to:

Jan 1, 1957

By B. W. Naugle

Twenty-nine sole-heated-oven expansion teats were made on 9 different coals, and apparent specific-Brevity tests were made on 12 of the resultant cokes. The coals, which ranged in dry, mineral-matter-free fixed-carbon content from 58.7 to 81.1 percent, were tested over a rather wide range of moisture content and dry-coal bulk density to determine the separate effects of these variables on linear coal expansion. The experimental data support the follow expression relating "as-tested" coal bulk density, moisture content, and linear expansion, [ER = (1-MR) (1+Et) - 1; BDt] where ER = fractional expansion at a reference bulk density of 55.0 lb. of 1 percent moisture coal per cu. ft., Et = fractional expansion at Mt and BDt, MR = reference moisture content = 0.01, Mt = moisture content, "as-tested", BDR = reference bulk density = 55.0 lb. per cu, ft., BDt = bulk density, "as-tested", 1b. per cu. ft.

Jan 1, 1957