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By Frederic Benard

PRIOR to 1936, the Ontario Refining Co. received all incoming blister copper from The International Nickel Company's smelter in the usual form of 460-lb. cakes, or slabs. These were received in open cars in lots of 250 pieces. At the refinery the cakes were unloaded onto narrow-gauge cars, for convenient handling and pickup by charging cranes. In March 1936, an investigation was started on the feasibility of transferring converter copper in the molten state from the smelter to the refinery anode furnaces, a distance of 1 ¼ miles. Although common in steel practice, the transportation of blister copper in this form had not previously been attempted and a preliminary study of the various factors involved was therefore necessary. For this purpose, a series of experiments was made in which molten copper, removed at different stages during the furnace cycle, was held in a small portable holding furnace. This vessel was essentially a refractory-lined steel cylinder provided with ports for filling and emptying, heated by an oil burner. Dimensions of the steel shell were 3 ft. 10 in. diameter by 7 ft. 3 in. long, and thickness of refractories depended on the design and combination used for the particular experiment. The vessel was filled with approximately 2 ½ tons of copper at a predetermined temperature, the lining having been preheated to a definite point by means of an oil burner. All openings were well luted and temperature readings were made every 15 min. by means of an immersion-type thermocouple. In this manner the rate of heat loss resulting with different refractory design could be developed. The ratio of exterior surface to weight of metal was taken into consideration in comparing the experimental results with what might be expected for a full-sized unit, and observations were also made on type and degree of slag accretion. It was not possible to get as much information on this latter point as desirable, but all evidence showed that the problem would be control of slag build-up rather than attack on refractories. From the information derived, and in consultation with the engineering staff of the supplying company, an order was placed for the first

Jan 1, 1938

By Harry H. Power

The Specific purposes of forma! engineering education include training in the basic sciences, the engincering-prob]em method, the rudimentary development of technical skills, an appreciation of values and costs, and an understanding of the art of engineering as distinguished from its science, Two major divisions of an educational program in engineering are recognized: (I) the scientific-technological, and (2) the humanistic-social. Hence, the entire curriculum for the four-year program in specialized petroleum engineering schools must be designed to give the student an initial impetus in the directions indicated. In accordance with suggestions from the Engineering Council for Professional Development, Inore attention is being given to the fundamental approach in the undergraduate curriculum. This paper presents a cross-sectional viewpoint of the various educators in the petroleum engineering schools concerning course contents in the specialized curricula An outline is suggested for the content of the specialized courses wherein the engineering problem method or quantitative approach is emphasized. Although the particular viewpoints of the author have been stressed, yet due acknowledgment is made to a considerable number of petroleum engineering educators and in in industry interested in educational work, for their contribution of course outlines or helpful suggestions with respect to programs that will be of maximum value to students, institutions, and the industry they serve. Although "standardization" of course material is not suggested, the advantage to be gained by cooperative determination of purpose and scope are apparent paiticular1y from 'he standpoint of the proper accreditment of petroleum engineering schools by petroleum engineering educetors who have laid a basis from which to measure educational values. Petroleum engineering has "come of age" and deserves the same careful attention with respect to. curricula that has been accorded other engineering branches. Introduction Engineering schools have a major responsibility to the public, to industry and to the professions they serve. The specific purposes of formal education include training in the basic sciences, the engineering-problem method, the rudimentary development of technical skills, an reciaciation of values and costs, and an understanding of the art of engineering as distinguished from its science. Other purposes implied include the ability to read, write, and speak the English language effectively, an understanding of social and human relationships, a knowledge of the duties of citizenship, a broad appreciation of cultural interests, and an indoctrination in professional standards and relations. Throughout these educational processes is the development in the student of habits of accuracy, thoroughness, powers of analysis, creative ability and integrity with respect to all phases of his work. Major Divisions of Program In the Report of the Society for the Promotion of Engineering Education,† two † Report of Committee on Engineering Education after the War, dated January 1944.

Jan 1, 1945

By L. D. Frink

THOSE actively interested in mining are fully aware of the ever-increasing difficulty of making conditions such that efficient work can be clone in underground openings, especially as higher rock temperatures are encountered in depth. This is also true where an effort is being made to cut down the burden of overhead expense by working headings 24 hr. in a day if blasting is done as often as is possible in that time. That the conditions resulting from both these causes have driven the native-born Americans from the mines and that their places have been taken by less efficient foreigners is a fact that we must all admit. The great war now being fought in Europe and the educational qualification clause written into our immigration law by the last Congress will probably limit very materially the supply of labor, such as we are now using in our mines, and will force upon mine operators the necessity of making this work appeal again to Americans. Metal tubing, with blower or exhaust fans, has long been used in supplying air to dead ends where natural ventilation is impossible, or in driving the smoke from such places, or in doing both, as the need might be. Here in Butte we have now come to use canvas tubing very extensively and find that it has many advantages not possessed by the metal. The use of flexible tubing is not new, but it has not been generally used in mining operations. Recent improvements, however, in the canvas itself and in the jointing of sections and manner of suspension have so increased its usefulness that it promises to add much to the efficiency of mining. There is now on the market a product that is impervious to air, is fireproof, and has a system of jointing which, permits it to be put up or taken clown in a few seconds. In this article an effort will be made to explain the manner in which canvas tubing is being used in the North Butte company's operations at Butte, Mont. The accompanying photographs will, I hope, help make clear what may be done with this material.

Jan 1, 1918

DR. PeRsifor Frazer, Philadelphia, Pa. (communication to the Secretary):* Mr. Campbell's very interesting contribution, after complimentary mention, finally decides against the acceptance of the classification proposed by me in a paper bearing the same title and read at the Wilkes-Barre meeting, May, 1877.2 That paper was written primarily for the Second Geological

Jan 1, 1906

By A. N. Chirico

This paper reviews the three major distillation processes: multiple effect (LTV) evaporation, multi-stage flash distillation and vapor-compression forced circulation evaporation. Scale preventative measures are discussed for all saline water applications. Operational data is presented on the Freeport, Texas, demonstration plant, which is the first government facility to produce one million gallons per day of fresh water for a municipality. There has been much publicity concerning the water crisis that confronts many peoples today. There is little doubt that the arid regions - which include the Middle East, parts of Africa and the Caribbean — have suffered to no slight extent for the lack of this most precious commodity. But what about our own country? Government experts have extrapolated demands and flatly predict that by 1980 we will be faced with a shortage of 80 billion gal per day. The validity of this prediction has been disputed by others; however, it appears certain that there will always be a natural abundance in some areas, a shortage of supply in other areas. Distributing our total natural water resource equitably would be impossible. Transmission of water by means of aqueducts can be an expensive undertaking. The controversial Feather River Project in Calif. is an example. The estimated cost for this venture is a staggering three billion dollars. As our population continues to increase and our standard of living rises, agricultural and industrial requirements will be proportionate. What can be done to avoid a crisis? We can conserve and use our water for industrial and irrigation purposes more judiciously: we can attempt to eliminate pollution of our natural resources from sewage and industrial wastes; we can develop, while there is time, saline water conversion processes for the massive production of low cost fresh water. The scope of this paper will be limited to only the distillation type processes that are commercially feasible. The first step in making potable water is to find a source of raw material. An inexhaustible supply is provided by oceans in coastal regions, but the supply of water is more critical in the inland communities of our country. The source of raw material in these. regions is brackish well water and this must be utilized. There is a significant process difference when handling brackish water compared to seawater and this brings out an important fact: No single conversion method can be universally applied to solve all the water problems. Composition of the raw water and degree of distillate purity are factors which must be considered before a particular process is selected. Local conditions at the plant site, fuel costs, labor costs, disposal facilities, etc. are other equally important factors which must be evaluated. WATER CONVERSION PROCESSES Conversion processes commercially feasible today are: 1) multiple effect evaporation, 2) multiple flash distillation, 3) vapor compression distillation and 4) electrodialysis. The first three are distillation processes which take potable water out of the raw water, while the fourth is a membrane process which takes out the salt. In addition to the above there are a good number of other promising methods for production of potable water, many of them in the basic research stage. Freezing is another promising process with commercial potential. This process hinges upon the formation of ice crystals which are free of salt occulsions. Separation and washing of the crystals are problems that must be solved before this process can be considered commercially feasible. Freezing processes have several advantages mostly attributable to the low temperature of operation. This low temperature reduces the scaling and corrosion problems encountered in higher temperature operations. Several different freezing processes are being considered and will be tested in the pilot plant at Wrightsville Beach. One process is a flash freeze process, a second uses a secondary refrigerant such as butane for freezing, and a third process employs a secondary refrigerant particularly controlled to produce large ice crystals. Of the above processes, only the distillation processes are reliable when water of high purity is re-

Jan 1, 1963

By Fred C., Fred C. Bond

Comminution energy is principally energy of deformation before breakage, which appears as heat. An empirical equation is presented which covers the entire comminution range. The new strain-energy theory considers comminution from the known principles of mechanics and the reduction ratio. Energy requirements according to the different theories are compared.

Jan 1, 1950

By John V. Beall

STREAM pollution caused by waste waters from mineral industry operations is a problem that has grown up with the industry. Its importance to each operator is dependent on the amount and type of waste he dumps into the rivers and streams; on whether this waste pollutes the waters sufficiently to make them unfit for potable water, irrigation, and conservation of wild life; and on whether this waste makes a safety or health hazard. Through the years our growing population and industry have made increasing demands on the mineral industries, the suppliers of the raw materials on which our industries are based; and we have met these demands at some sacrifice to the natural beauty and cleanliness of our country. However, that is often the unavoidable nature of the business, and along with the increased use of our

Jan 1, 1948

By V. Lepetic, C. C. Harris

A systematic program of investigations covering all aspects of cell hydrodynamics,1-3 flotation kinetics,4,5 surface chemistry and their interactions has as a major objective the elucidation of the flotation micromechanism and the principles of cell design and scale-up.6 Purely from the scale-up point of view, a family of reactors should enable different throughputs of the same material to be similarly treated or, at least, to be treated in a manner which differs beween reactors in a predictable way. Thus, for the same material and residence time, the recovery and grade from differently sized cells of the same family should, ideally, be similar or, at least, be related to each other in a known way. It is well known, however, that different-sized cells do not always achieve similar results, and it is necessary to enquire into the reasons for these differences. For example, it may be that the relative dimensions of different-sized cells result in hydrodynamic conditions which preclude similarity; if so, different scaling may improve the situation. The major question concerns identifying the dynamic conditions and their associated geometric requirements which govern the flotation process, and the criteria which are necessary for their fulfillment. It is to answer such questions that the program referred to earlier was instituted. In connection with this program and in order to examine data concerning the physical features and operating conditions of existing flotation cells, the following survey was carried out. This work represents an approach which is complementary to experimental investigations, for it recognizes that the design of existing cells may embody several of the principles being sought. If data for enough cells, especially families of cells, are examined, some broad requirements common to all cells may emerge.

Jan 9, 1966

By Allen J. Johnson

With a realization of the rapidly increasing importance of automatic stokers as a medium for domestic heating, the Anthracite Institute Laboratory has conducted extensive investigations, over a period of several years, to determine the various outstanding characteristics of stoker design and performance. The purpose of this paper is to summarize these findings as a guide to current practices. Stokees Investigated One or more models of the underfeed stokers listed below were included in the various phases of this investigation: Beckley Gilkoal Burnwell Iron Fireman Combustioneer Motor Stokor Electric Furnace Man Norristown Super-stoker Erie Heat Generator Whitney Fire Ball (Tests Incomplete.) Fuel Saver Principles of Construction.—The operating principle of the leading makes of underfeed stokers is similar (Fig. 1). A plunger1 or slowly revolving worm2, conveys the buckwheat or rice sizes of anthracite to the center of a specially constructed tuyere pot where air is admitted to the coal through suitable ports of varying design. As the fuel burns, it is slowly forced to the outside circumference of the tuyere by the pressure of the incoming coal; eventually the ash falls over the edge of the pot, either entirely by gravity or aided by mechanical sweepers. In at least one model, the entire firepot revolves. While various special details have been included in the design of a number of stokers, they do not affect the general principles as described above, and therefore have not been included in this discussion.

Jan 1, 1936

By Allen J. Johnson

With a realization of the rapidly increasing importance of automatic stokers as a medium for domestic heating, the Anthracite Institute Laboratory has conducted extensive investigations, over a period of several years, to determine the various outstanding characteristics of stoker design and performance. The purpose of this paper is to summarize these findings as a guide to current practices. Stokees Investigated One or more models of the underfeed stokers listed below were included in the various phases of this investigation: Beckley Gilkoal Burnwell Iron Fireman Combustioneer Motor Stokor Electric Furnace Man Norristown Super-stoker Erie Heat Generator Whitney Fire Ball (Tests Incomplete.) Fuel Saver Principles of Construction.—The operating principle of the leading makes of underfeed stokers is similar (Fig. 1). A plunger1 or slowly revolving worm2, conveys the buckwheat or rice sizes of anthracite to the center of a specially constructed tuyere pot where air is admitted to the coal through suitable ports of varying design. As the fuel burns, it is slowly forced to the outside circumference of the tuyere by the pressure of the incoming coal; eventually the ash falls over the edge of the pot, either entirely by gravity or aided by mechanical sweepers. In at least one model, the entire firepot revolves. While various special details have been included in the design of a number of stokers, they do not affect the general principles as described above, and therefore have not been included in this discussion.

Jan 1, 1936

By J. J. Arps

n approach to the study of the electrical properlies of drilling muds, their cakes and their filtrates was made by treating the drilling fluid as a porous medium. Lluring this study it was found that the weight pararneter was omitted from previous investigations on electrical properties. Patnode in 1949 made a similar approach to ,his investigation. His work showed that there was a variation of resistivity relationships with per cent Puid present in a given suspension. This present study ex-tends Patnode's investigation to one in terms of the solids fraction of the drilling fluids. Previous investigations were made on low weight muds where the effect of the rolids fraction was obscured. The following equationr were fitted to data taken from 94 field muds and 47 laboratory muds (see Tables I and 2). The parameter, C, is a complex function of the solidr content, or mud weight, of a drilling fluid. It was also found that for all drilling muds examined. A nomograph is presented combining Eqs. I and 2. INTRODUCTION It is generally recognized that the materials present in drilling muds affect the relationship between mud filtrate and mud resistivities. However, most electric log interpretations proceed with the assumption that the mud resistivity and temperature are the only important parameters needed to obtain a filtrate resistivity or a mud cake resistivity. Lamont1 suggests that only average relationships exist between mud cake, mud filtrate and mud resistivities. He indicates that there is limited accuracy when these intercorrelated factors are used since no other measure-able variable is apparent. A previous paper by Patnode indicates that drilling fluids may be considered to be a system of fluids in solid particles which may be correlated electrically in a manner similar to rock solids. 1 he equation for the resistivity factor. F = (per cent fluid) is satisfied for a given clay type in water, but the value of m varies as different materials are used in the water. The resistivity factor is not constant for a given amount of clay. As is suspected it varies as the solids fraction conducts electrical current. Since both weighting material and clay solids are present in commonly used drilling fluids, it is expected that both materials contribute to the variation of the m factor in Eq. 3. An extension of Patnode's work is presented in this paper to show some of the interrelations which exist between the resistivities of mud cake, mud filtrate and mud. Use of these data enable a more accurate calculation of mud filtrate and mud cake resistivities if only the mud resistivity and weight are measured. EXPERIMENTAL The measurements of mud weight, fluid and solids resistivity, alkalinity, and chloride content of mud samples were made in this research. Mud samples representing drilling fluids from 94 Louisiana and Texas wells (Table 1) and 47 laboratory-constructed systems (Table 2) were used in the experimentation. The measurements of the mud properties were made both in the field and in the laboratory. The tests on the properties of weight, alkalinity and chloride ion were standard tests as described by API specifications. The resistivity measuring devices were constructed in the laboratory for this study. For details on the resistivity equipment see Fig. 1. The fluid cell

By JAMES J. DOUGHERTY

THIS paper is a general discussion of developments in our reverberatory smelting practice during the past five years. It deals briefly kith changes in furnace types ; changes in furnace feed ; de- crease in the amount of slag produced; relation of slag assays to copper loss in the slag; increase in the grade of matte and furnace capacities. The reverberatory is but one unit in the copper plant ancl 'any discussion of it must be considered with reference to the other units and to the plant as a whole. A change in the grade of concentrates at the concentrator puts an entirely new aspect on reverberatory smelting and, likewise, a change in the grade of matte at the reverberatory affects the rate and cost of converting. The introduction of differential flotation in 1927 had a very marked influence on all smelting operations and its effect will be noted

Jan 1, 1930

By Robert D. Pike

IN November 1939, on behalf of the Harbison-Walker Refractories Co., the author undertook the study of the problem of utilizing the dolomite of northwestern Ohio for the manufacture of calcined magnesia suitable for use in refractories. Grateful acknowledgment is made of the unfailing assistance and encouragement throughout this work from the executive and technical staff of Harbison-Walker Refractories Company. The dolomite of the Niagara formation that is exposed or near the surface of a wide area in northwestern Ohio1 constitutes a vast supply of almost pure dolomite. It offers a virtually unlimited supply of cheap raw material of uniform dependable analysis for the manufacture of magnesia. A typical analysis of dolomite from the vicinity of Luckey, Ohio, follows: [ ] Brines containing magnesium chloride or sea water can be reacted with calcined dolomite to produce magnesia.2,3 In such reactions the MgCl2 of the brine supplies some of the magnesia and the amount of dolomite required is thereby reduced by an equivalent amount, but brines of commercial importance containing magnesium chloride are some distance away from the purest grades of the dolomite of northwestern Ohio. It was decided therefore to concentrate upon the development of a suitable process for separating the lime and magnesia of dolomite, depend¬ing upon the dolomite itself as the sole source of magnesia. This would make it possible to place a plant at the dolomite quarry, thus eliminating the cost of transporting the stone and also rendering the calcined magnesia available at a most convenient production point, considering the cost of delivery throughout the steel industry. The selection of a process depending solely upon the dolomite as a source of magnesia also necessarily entails production of the lime content of the dolomite as a by-product. It was recognized that if such a lime by-product could be produced in a suitable form, a plant location in northwestern Ohio would also be advantageous for marketing the lime. The problem, therefore, was the discovery and development of a low-cost process for separating the magnesia and lime of the dolomite of northwestern Ohio and producing each in a form relatively free from the other, and meeting the respective requirements of established markets. A satisfactory solution of this problem has been found, and it is the

Jan 1, 1947

By E. J. MCOAUSTLAND

THE behavior of steel after overstrain and at moderate temperatures is fairly well known. It has been made the subject of much investigation, and our knowledge is clear and definite on many points. The ultimate raising of the elastic limit, after moderate overstrain, and the consequent lowering of the ductility, seem to be well established. It is also well understood that the immediate effect of overstrain is to lower the elastic limit, possibly to zero, but that if not interfered with, this limit will subsequently rise higher than before. The "tests after moderate temperature," reported in this paper, were undertaken to verify the above statements for the particular steel under investigation, and also to determine, if possible, the total time required for complete recovery from this state of overstrain. The behavior of overstrained steel at temperatures at or below 32° F. is not so well known. Tests made by Prof E. G. Coker, at McGill University,' show that steel, overstrained and subjected to cold, will remain in a state of overstrain for an indefinite period. I am not aware of any other published results of tests along this particular line. The effect of time and temperature on the recovery of steel from overstrain was made in 1902-3 the subject of sortie investigation in the laboratories of the College of Civil Engineering of Cornell University. A general plan was outlined in connection with the regular courses of instruction in testing of materials; but the press of routine work and the demands of the schedules on the time of the students were so great as to presage long delay in the completion of the work. Not much had been accomplished up to 1904-05, when Messrs. E. C.

May 1, 1906

By Charles E. Heinrichs

IN the last decade one of our oldest and largest non-metallic metallic mineral industries has been the subject of persistent technical research, the results of which are another example of the benefits following the systematic application of scientific principles. The consequent improvement in the technique of phosphate recovery represents the greatest material advance in the industry since the discovery of phosphate in Florida in 1881. Moreover, these successes have stimulated interest and development in numerous other nonmetallic industries. Strange as it may seem, and despite the fact that the phosphate deposits of Giles County, Tennessee, together with those of Polk and Hillsborough Counties, Florida, have yielded more than 50,000,000 long tons in the last twenty years, the mineralogy of phosphates has been given scarcely any space in our technical literature. For many years it was the general consensus that these so-called phosphate rocks represented a physical mixture composed principally of tri-calcium phosphate, together with smaller quantities of calcium carbonate, calcium fluoride, iron phosphate, aluminum phosphate and other less important constituents. More recent investigations, however, led to the conclusion that these phosphates really represent a complex mineral in which calcium, iron, aluminum, phosphorus pentoxide, carbon dioxide, and fluorine all form a definite part of the molecule. Colony, after a careful study, utilizing chemical, microscopic, and X-ray diffraction methods, reported that American phosphates consist principally of calcium-carbono-phosphate of the staffalite type.

Jan 1, 1933

By James Hyslop

MECHANIZATION of American coal mining continues to make rapid progress. Economic pressure will compel abandonment of manual methods wherever possible and will also provide the incentive needed for the improvement of machines and mining systems. However, rapid progress may be made along strictly technological lines and at the same time much slower progress in approaching maximum productivly and efficiency. One can well ask, just how efficient are mechanized mines, and to what extent is productivity affected by the mental attitude of management and workers?

Jan 1, 1946

W. E. WRATHER, Wichita Falls, Tex. (written discussion*).-The appearance of Mr. Brokaw?s with-the chemical composition of "paraffin dirt" will be welcomed by oil geologists who have worked in the Gulf Coast district. It is to be hoped that it will lead to a discussion of the subject which will throw some light on the relation this peculiar substance bears to the occurrence of oil deposits. The problem of locating oil pools in advance of drilling is at the best a very intangible matter in the district along the Gulf Coast, and it is therefore desirable to make the most of any clew which may be of the least assistance to this end. Geologists have been familiar with "paraffin dirt" for a number of years, and have informally discussed its value as a surface indication of oil. But doubtless owing largely to the fact that they have been unable to define its exact composition, very little information has appeared in print on the subject. The presence of this baffling and somewhat indeterminate substance is now quite generally accepted as one of the most reliable indications of a gas seepage. The question is whether paraffin dirt necessarily indicates that the escaping gas is an emanation from an oil deposit, or whether it merely indicates that marsh gas (urethane) has here escaped from its source in "the abundant decomposing vegetation entombed in the sediments of the old Mississippi Embayment, and the Gulf Coastal Plain. The presence of this material has been relied upon to a great extent, both by oil producers and geologists, in the location of wildcat wells, since the discovery that it was associated with gas seepages. It is quite true that other surface indications were often present at such localities, but if, in addition, paraffin dirt could be found in the vicinity, this fact was accepted as the final justification for drilling a test well, despite the fact that no one seemed to understand its chemical composition or to know why it should be associated with oil. In fact, for a long time it has generally been accepted that the name is a misnomer, that very little, if any, paraffin is present in it, or, for that matter, any other known fraction of crude oil.

Jan 7, 1918

By R. B. Basham, C. W. Macune

Very small anomalies in oil well temperatures are detected and measured by recording the difference in temperature existing between two thermally sensitive elements which are Spaced several feet apart on a small diameter carrier and lowered into the bore hole. The elements operate in a balanced electrical circuit, sending only a reference signal to the surface as long as normal gradient temperatures are encountered. When either element enters a temperature disturbance, the circuit is unbalanced and produces large recorder deflections for minute anomalies. The system is highly sensitive to small changes in thermal gradients caused by gas or fluid movements and to the boundaries between beds of different thermal conductivities. Typical logs show successful applications of the process to locating gas and water leaks in casing, gas entry. and gas-oil contact. INTRODUCTION Temperature measurements in oil wells have been made for many years in the search for additional sub-surface data. It has been generally agreed that many conditions in the bore hole cause temperature anomalies which, if located and measured, could yield useful information. But it has been recognized also that many of the irregularities, such as those produced by small water and gas leaks in casing, might be very small and therefore difficult to detect with certainty.' Although tem-perature measurements have been made which show anomalies of less than one degree deviation from normal gradient temperatures, the results are usually uncertain and unconvincing. The general practice, therefore. has been to apply temperature surveys only to well conditions known to produce appreciable disturbances, such as large gas movements and cement hydration. The recent demand for additional data has focused attention on the problem of making dependable temperature measurements in the many instances when anomalies are small but none the less significant. It was for the purpose of detecting these minute irregularities in bore hole temperature that the program described in the following text was undertaken. It is emphasized that this presentation is not offered as a complete study, for the process is still partially experimental. But it is believed that the results obtained thus far will be of interest to the industry and will indicate some of the system's potential usefulness. DIFFERENTIAL MEASUREMENT The chief value of differential measurement lies in the fact that a difference between two factors can be measured with a scale of values best suited to that difference, a scale that might be cumbersome or impractical if applied to the factors themselves. When it is known that all factors will be nearly equal in value, and therefore the differences consistently small, it is possible to select a scale which will permit very accurate measurement of the differences. This advantage is in contrast to the difficulty of measuring small increments of a single variable, where the increment must be measured by a large scale which is suitable for measuring the entire factor. Gradient temperatures are usually measured under this latter condition where temperature measuring apparatus must have a scale extending over the range of expected temperatures, say 50' to 25O°F, and it becomes almost impossible to detect small irregularities of less than one degree. The use of large strip chart recorders and divided multiple ranges tend to amplify the small anomaly and make it more pronounced. But the instability of instruments, both

Jan 1, 1952

By H. C. H. Darley

Particles of montmorillonite-type clays consist of plate-like clay crystals stacked face to face. Under certain conditions in a suspension, these particles disperse to individual platelets with the formation of diffuse double layers round each platelet. This action has a profound influence on the rheo-logical and other properties of the suspension. This paper describes a test for degree of dispersion and uses this test to correlate changes in dispersion with changes in viscosity and gel strength. The test is of practical value in determining and controlling dispersion in drilling muds. INTRODUCTION It has long been recognized that the hydration and dispersion of clays, particularly those of the montmoril-loilite type, strongly influences the rheological and other properties of drilling muds, but little has been done to measure either of these phenomena under conditions that exist in drilling muds. The hydration of clays as such has been extensively studied by those interested in clay mineralogy, but in drilling muds it is to be expected that dispersion is at least as important a factor as hydration because of the much higher water-to-clay ratios and the very high degree of mechanical agitation. The term dispersion as generally applied to colloidal systems means the subdivision of large particles to small. Particles of montmorillonitic clays, however, consist of plate-like particles stacked face to face. Dispersion of these aggregates to individual platelets may be expected to have an unusually large influence on the properties of the suspension because of the shape factor, the enormous increase in specific surface, and the pronounced surface phenomena exhibited by the crystal surfaces. It is this form of dispersion that is particularly considered in this paper, -and the term degree of dispersion is used to imply the number of platelets per particle. The term aggregation is used to denote the opposite of dispersion, the association of individual platelets face to face to form stacks. It is important, as Garrison' has pointed out, to distinguish between the deflocculation-flocculation phenomenon and the dispersion-aggregation phenomenon. Flocculation of clay suspensions is characterized by the formation of voluminous sediments that are stable under quite high centrifugal fields. This indicates an edge to plate association of particles to form an open network type of structure, which obviously will have quite a different influence on the properties of the suspension than aggregation of the platelets face to face. The work described in this paper was primarily concerned with developing a test for degree of dispersion in clay suspensions and by means of this test to follow changes of dispersion brought about by addition of electrolytes and to show the influence of dispersion on the rheological properties. The Clay-Volume Test This test is based on the assumption that the greater the number of particles per unit weight of clay in a suspension the greater will be the volume of sediment when it is flocculated under standard conditions and centrifuged. After considerable experimentation the following procedure was established: 1 cc of the test mud vigorously shaken with 100 cc of 1-N NaCl in an ASTM oil centrifuge tube and centrifuged for five minutes in an International No. 2 centrifuge at 2,000 rpm. When drilling fluids of different solids content are being compared, the clay volume is expressed in cc per gram of clay solids, but generally changes in dispersion in a given mud are being compared and it is more convenient to report as cc of sediment. The test is strictly a comparative test, so that it is not necessary to adhere to the conditions specified above, e.g., with field muds a stronger flocculant such as Al2(SO4)3 may be preferable to NaCl.

Jan 1, 1958

By J. J. Taber

The turbulent flow drag coefficients, or friction factors, have been experimentally determined for the cut-tings normally encountered in drilling operations. The gas law and average drag coefficients for characteristically flat particles (limestones and Shales) and for angular to sub-rounded particles (sandstones) were used to extend Newton's equation to a more useful form. The resulting equations are expressions for the slip velocity of a particle as a function of the particle size and shape, the bottom-hole injection Pressure, and the Bottom-hole temperature. The velocities necessary to lift actual rock cuttings as observed in the laboratory were compared with velocities predicted from the derived equations. Results indicate that there is no single correct circulating velocity and that the commonly used 3,000 ft/min linear velocity may he sufficient to lift only very mall particles. The advantage, in terms of horsepower requirements, of cycling high pressure air to obtain lower compression ratios was shown. INTRODUCTION A promising departure from standard rotary hydraulic drilling is air or gas drilling. In many instances the rate of penetration and bit life increases resulting from this method have been very substantial. Further the application of air drilling in areas of lost circulation or water sensitive pay zones has been highly successful. Purpose For the drilling contractor, the practical question remains, "How much air pressure and volume should I have?' lt is necessary to have a reasonable knowledge of the air velocities and pressures required in air drilling operations for the proper design and most advantageous use of surface equipment and for adequate removal of cuttings from the borehole. Eased on experience, most operators agree that at least 3,000 ft/min linear velocity is necessary for satisfactory hole cleaning.' It was the purpose of this investigation to evaluate the drag coefficients, or friction factors, for the cuttings normally encountered in drilling operations, i.e., sandstones, limestones and shales, and to utilize the values obtained to develop an expression for the minimum velocities and pressures (hence the volumes) necessary to lift these cuttings. THEORY Several investigators have done extensive work on the ability of drilling mud to lift bit cuttings. They conclude that the ability of a drilling mud to lift cuttings is dependent on the density difference between the rock being drilled and the drilling mud, the cutting size and shape, the mud flow constants, and the flow state (laminar, transitional or turbulent) of the mud. However, drilling muds are not true fluids but have a variation of viscosity with velocity in laminar flow and a constant apparent viscosity in turbulent flow. A survey of the literature revealed that no experimental work had been done to determine the velocities necessary to lift actual rock cuttings using a compressible fluid such as air or gas. In 1953, Nicolson6 stated that in air drilling fluid mechanics the particles could be assumed spherical in shape and that ; constant drag coefficient of 0.5 could be used due to the highly turbulent flow of the circulating air. By equating the turbulent resistance on the particle to the gravitational force on the particle, he obtained the expression, ^ = 2.67^y ,.......(1) where V, is slip velocity of spherical particle, ft/sec; D is particle diameter, in.; p, is particle density, 1b/ft8; and p, is fluid density, lb/ft3. However, as stated earlier, most operators seem to agree that adequate hole cleaning can be obtained by circulating a sufficient volume of air to give a linear velocity of 3,000 ft/rnin in the annular space. Basic Equation The velocity with which a solid particle freely falls through a fluid will increase until the accelerating force, gravity, is equal to the resisting forces, buoyancy due to the fluid displaced by the particle and friction due to the relative motion of the particle through the fluid. When the accelerating and resisting forces become equal,