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By Arthur B. Cummins

POWDERED nonmetallic minerals and rocks of many different types are used extensively in industry for incorporation in compositions and manufactured products The term "mineral filler" is commonly employed to designate a material that is used for a specific purpose but not as an essential or reactive component Such a definition is not without objections, and it is indeed difficult to define fillers in any fully satisfactory manner, since the term has come to have so many different meanings and to cover such a wide range of uses. A filler is defined, for the purposes of this chapter, as a substantially inert material not specifically employed as a reactive or essential component, the primary function of which is to modify the properties or processing of a composition of matter or fabricated article Emery1 has emphasized that fillers change the properties of the product but are themselves unchanged in compounding or use The term "filler" appears to be rather general when referring to usages m bituminous compositions, rubber, composition floorings, fertilizers, plastics, textile finishes, and some others. In paper manufacture, in the paint industry and with insecticides, other terms are frequently employed, as is indicated, herinafter By placing emphasis on the function of the material used in modifying the properties of the composition or article, it is believed that a more useful classification of filler products and their applications may be derived. FUNCTIONS OF MINERAL FILLERS All of the manifold functions of mineral fillers cannot be listed in a summary review. A survey of the uses for these materials, however, shows that in nearly all cases the powders are employed to modify the properties of a composition of matter or those of a fabricated article, or to perform some useful function In the manufacture of either. A generalized list of these useful functions may be given is follows 1 To Modify Optical Properties Color Surface texture Opacity Brightness and gloss (as in paper and plastics) Flatness (as in lacquers and paints)

Jan 1, 1949

By A. J. Miles, A. D. Topping

in this paper, the theory of elasticity has been applied to the rock about a deep well, It is assumed that the rock has a modulus of . elasticity and a Poisson's ratio and that the theory of elasticity applies. It is necessary to know or assume the state of stress existing in the rock before it is penetrated by the well drill. The application of this theory indicates that stress concentration of shear, tensions, and compressions about the bore hole are of a high order. This is particularly true when a horizontal compressive stress exists in one direction only in the formation before drilling. If such an initial state of stress exists before drilling, then the rock will have stress concentrations of both tension and compression at the same elevation and of such magnitude that failure of the rock is likely. Accompanying these is a shearing stress of large proportion which is likely to produce spalling of the well walls. Internal pressure applied to the well bore will relieve the extreme compression but not the tension and has little effect upon the shear. Plastic deformation of the rock through a geological time tends to mitigate the stress concentrations. IntroductioN It has long been known that the stresses about holes and re-entrant corners of elastic solids under the influence of loads are different and generally more intense than those imposed upon the body else- where. Stress concentration at a re-entrant corner can be reduced by increasing the radius of the fillet at the corner. Stress concentration at the end of a crack in a plate undergoing either tension or compression Can be relieved appreciably by drilling a hole at the very end of the crack. Also, stresses can be increased in an elastic body in tension or compression by making a hole in it. The stress concentration is greatest at the edge of the hole. Considerable knowledge of the stresses which exist about the bore hole of a deep well may be had by applying our knowledge of engineering mechanics; or more particularly the theory of elasticity. It is, of course, necessary to make the assumption that the rock is elastic and behaves as an elastic solid, that is, that it obeys Hooke's law, has a modulus of elasticity, and a Poisson's ratio. It is also necessary to know, Or assume, the state of stress which exists in the rock prior to the penetration of the drill. With this knowledge it is possible to compute the stresses about the bore hole. The problem can be simplified by considering several simple cases separately and then by applying the principle of superposition to solve the more complex cases which are made up of the simpler ones. Case i—Rock Strata in Compression Penetrated by a Hole This case was first worked out by G. Kirsch* for structural material, but applies equally well to a horizontal rock strata in a state of in in one direction

Jan 1, 1949

By G. K. Manning, C. H. Lorig

TWO metallurgical tools have acquired wide use within the past several years as a means of studying the transformation characteristics of steel. One is a technique used first by Bain and Davenport for determining the transformation characteristics of a steel at constant temperature; the second is the end-quench hardenability test. Constant-temperature transformation curves like those of Bain and Davenport have done much to rationalize the metallography of steel; however, in commercial practices, constant-temperature transformation is seldom encountered, therefore only rarely can such curves be directly applied. The real reason for the determination of such curves lies in the fact that they provide a way of thinking about transformation that is both convenient and productive. The end-quench hardenability test is a more practical means of studying transformation, for, by correlating positions on the hardenability bar with shapes of different masses, an almost direct application of the results can be made. Unfortunately, the end-quench test, though practical, can do very little toward improving the metallurgists' way of thinking about transformation. These two metallurgical tools, dealing with precisely the same phenomenon, should be very closely associated in metallurgists' minds. Actually, they are frequently pushed into separate mental corners and considered as being more or less distinct and unrelated. The reason for this is that no strong connecting link between them has been developed. An attempt is sometimes made to relate these two tools by projecting the critical cooling rate on the isothermal transformation plot as illustrated in Fig. I. The critical cooling rate is considered as a constant rate-though in practical applications, cooling rates are never constant—and this constant cooling rate is given uniform significance from the Ae temperature down to the temperature of initial transformation. A little thought indicates the errors of such a procedure. Certainly the time interval spent just below point A of Fig. I cannot be as effective in promoting nucleation as is the time interval spent just above point B. Yet the procedure represented in Fig. I considers all the time spent between temperatures A and B to be just as effective in promoting nucleation as though all the time were spent at temperature B. Furthermore, change the shape of the isothermal curve between points B and C in any way desired, and the required critical cooling rate is not changed one iota. This cannot possibly be true. Such a way of thinking about critical cooling rates not only is incapable of giving any results that are quantitatively satisfactory but is likely to give very misleading qualitative results.

Jan 1, 1947

By G. K. Manning, C. H. Lorig

TWO metallurgical tools have acquired wide use within the past several years as a means of studying the transformation characteristics of steel. One is a technique used first by Bain and Davenport for determining the transformation characteristics of a steel at constant temperature; the second is the end-quench hardenability test. Constant-temperature transformation curves like those of Bain and Davenport have done much to rationalize the metallography of steel; however, in commercial practices, constant-temperature transformation is seldom encountered, therefore only rarely can such curves be directly applied. The real reason for the determination of such curves lies in the fact that they provide a way of thinking about transformation that is both convenient and productive. The end-quench hardenability test is a more practical means of studying transformation, for, by correlating positions on the hardenability bar with shapes of different masses, an almost direct application of the results can be made. Unfortunately, the end-quench test, though practical, can do very little toward improving the metallurgists' way of thinking about transformation. These two metallurgical tools, dealing with precisely the same phenomenon, should be very closely associated in metallurgists' minds. Actually, they are frequently pushed into separate mental corners and considered as being more or less distinct and unrelated. The reason for this is that no strong connecting link between them has been developed. An attempt is sometimes made to relate these two tools by projecting the critical cooling rate on the isothermal transformation plot as illustrated in Fig. I. The critical cooling rate is considered as a constant rate-though in practical applications, cooling rates are never constant—and this constant cooling rate is given uniform significance from the Ae temperature down to the temperature of initial transformation. A little thought indicates the errors of such a procedure. Certainly the time interval spent just below point A of Fig. I cannot be as effective in promoting nucleation as is the time interval spent just above point B. Yet the procedure represented in Fig. I considers all the time spent between temperatures A and B to be just as effective in promoting nucleation as though all the time were spent at temperature B. Furthermore, change the shape of the isothermal curve between points B and C in any way desired, and the required critical cooling rate is not changed one iota. This cannot possibly be true. Such a way of thinking about critical cooling rates not only is incapable of giving any results that are quantitatively satisfactory but is likely to give very misleading qualitative results.

Jan 1, 1947

By S. C. Miller, R. D. Carter, H. G. Riley

A merhod based on theoretical considerations is presented for estimating srabilized performance of gas wells from data obtained from short-term flow tests. Calculated results are presented for II gas wells evaluated with four-to five-hour flow tests. For seven wells on which comparison war available, satisfactory agreement between measured and calculated performance was obfained. Although the final results are favorable, diflerences in flow capacity k,h obtained from flow tests conducted at different rates were observed. This inconsistency did not seriously affect the calculated results in the test wells. INTRODUCTION In order to negotiate the sale of gas from newly drilled gas wells and to plan otherwise for the orderly exploitation of gas reserves, it is necessary to predict the long-term withdrawal rates physically possible for each well. Since low permeability gas wells do not stabilize except after a lengthy period of flow, the operator is unable, without wasting large amounts of gas, to measure directly the stabilized performance prior to contracting for sale of the gas and connecting the well to a pipeline. This problem is not new, but is one which has recently received considerable attention because of the rising importance of natural gas in the economy and new emphasis on the development of gas reserves. Thus, a method is needed for estimating stabilized performance from information obtained from short-flow tests in which stabilized flow is not attained. Such short tests would be suitable for wells not connected to a pipeline since the tests require only small amounts of time, labor and production of gas. Other requirements of such a method are short calculation time and use of a model of the gas well and its reservoir drainage area which is as consistent as possible with present theoretical, experimental and field knowledge. The method presented herein was developed in an effort to meet these requirements. It has been named the "two-Row method". In addition to the section on the evelopment and description of the method, a description of field application of the method and a discussion of well test results are in- cluded. Finally, there is a section on an additional consideration prompted by some of the test results. The Appendix contains certain details of the derivation of the two-flow method and a sample calculation for Test Well 1. MATHEMATICAL DEVELOPMENT AND DESCRIPTION OF THE METHOD The method is based upon the following assumptions: (1) The system can be described as a finite cylindrical gas reservoir produced by a single cylindrical well located at the center of the reservoir. Flow is strictly radial. (2) Flow obeys Darcy's law except very near the well where a quadratic flow law is assumed. (3) The system is also characterized by a laminar flow skin factor. The use of a quadratic or turbulent flow term is more fully justified in Refs. 1 and 2. When such a system is opened at the wellbore to constant rate flow from an initial condition of uniform pressure distribution, the radius or drainage quickly passes through the non-Darcy flow and "skin effect" region imrnediately surrounding the well. After the drainage radius or "transient" has passed beyond this region and before it reaches the external boundary, drawdown can be expressed by'." After the drainage radius reaches the external boundary, stabilized flow exists and drawdown is given by'," Eqs. 1 and 2 form the basis for the method. The validity of these equations will now be examined in the light of some well test data previously available. It has been found by actual measurements on gas wells that the relationship between drawdown and flow rate, that is the performance curve, is closely approximated by' Eq. 3 is a straight line on log-log graph paper. Eq. 2 and, for any lixed value of time, Eq. 1 plot as a curve which is slightly concave upward on log-log graph

By Robert B. Fulton

Commercially, celestite (SrSO,) is the only significant strontium mineral. Among other strontium-bearing minerals, only strontianite (SrCO,) occurs commonly; however, it is not an item of commerce. The principal production of celestite is in England, Mexico, and Spain. New production is now coming on stream in Canada. Consumption is mainly in the United States. Lesser quantities are consumed in Japan and Europe. Main uses are for the manufacture of strontium carbonate and nitrate. The carbonate is used in glass for TV tube face plates and in ferrites for magnets. The nitrate is used in pyrotechnics to which it imparts a characteristic brilliant red color, mainly in safety flares. Minor amounts of strontium compounds are used in electrolytic zinc manufacturing and very small quantities in greases, ceramics, soaps, alloys, and pharmaceuticals. Specifications and Prices Typical celestite specifications for the carbonate and nitrate markets are as follows: [ ] Celestite currently shipped from Mexico for carbonate manufacture tends to be slightly better than these industry specifications, assaying about 92-93% SrSO, with less than 1% BaSO, but it is generally below the 95% minimum required for nitrate production. Contract prices for celestite are approximately $32-34 per st at U.S. Port of Entry in 50 to 60-ton carload lots for Mexican material. Spot prices are generally reported as low as $20 per st but are for minor volumes. A recent sale of surplus from the U.S. stockpiles, announced by the General Service Administration (GSA), was 4005 st sold to Du Pont for $140- 455 or $35.07 per st. British celestite, ground, washed, and graded, 95% SrSO, bulk, ex- works, 240 mesh, is quoted at £ 28.75 per mt in British trade journals, and a recent figure quoted for crushed lump material was $36.00 per st f.0.b. vessel Bristol Channel port (1973). Specifications of manufactured carbonate made from celestite and sold in two grades, one to the glass industry, the other to the electronic industry for ferrites, are given in [Table 1]

Jan 1, 1975

By F. Cadena

Hiwassee Darn, now under construction by the Tennessee Valley Authority on the Hiwassee River, a tributary of the Tennessee River, will require aggregate for approximately 800,000 cu. yd. of concrete. Near the damsite deposits of natural sand or gravel are not available and graywacke, a rock that is found in abundance, suggested itself as a likely source of manufactured aggregate. Graywacke is a metamorphosed sandstone composed principally of a mixture of quartz (65 per cent), mica (25 per cent), and feldspar (10 per cent). Other minerals are present in negligible amounts. The rock varies in different parts of the quarry from very fine to a coarse grain containing particles of about ¼ in. maximum size, although the bulk of the deposit is medium grain. Extensive tests showed that graywacke would be suitable as a source of both coarse and fine aggregates. The aggregate plant available for use at Hiwassee Dam consisted of the coarse-aggregate and sand plant used on the Norris project. The coarse-aggregate plant had also been used at Chickamauga Dam. Although most of this plant equipment is now in use at Hiwassee, the present flowsheet is not only different from that at Norris and Chickamauga but is also unique as compared to the flowsheet of the average crushed-stone aggregate plant. It is hoped that this paper will show the importance of proper arrangement of equipment if the optimum in flexibility and capacity is to be attained. Flowsheet Rock is ioaded by 3-yd. electric shovels into 12-yd. dump trucks, which carry the rock to the primary crusher, a 42-in. Superior McCully gyratory unit set at 4¾ in. (Fig. 1). The primary crusher discharges directly onto a 42-in. inclined belt conveyor, which carries the product to a surge storage pile with a maximum live storage capacity of approximately 3000 tons. A concrete tunnel under this storage pile houses the feed end of a 36-in. belt conveyor (conveyor B) fed by a 36 by 66-in.

Jan 1, 1942

By F. Cadena

Hiwassee Darn, now under construction by the Tennessee Valley Authority on the Hiwassee River, a tributary of the Tennessee River, will require aggregate for approximately 800,000 cu. yd. of concrete. Near the damsite deposits of natural sand or gravel are not available and graywacke, a rock that is found in abundance, suggested itself as a likely source of manufactured aggregate. Graywacke is a metamorphosed sandstone composed principally of a mixture of quartz (65 per cent), mica (25 per cent), and feldspar (10 per cent). Other minerals are present in negligible amounts. The rock varies in different parts of the quarry from very fine to a coarse grain containing particles of about ¼ in. maximum size, although the bulk of the deposit is medium grain. Extensive tests showed that graywacke would be suitable as a source of both coarse and fine aggregates. The aggregate plant available for use at Hiwassee Dam consisted of the coarse-aggregate and sand plant used on the Norris project. The coarse-aggregate plant had also been used at Chickamauga Dam. Although most of this plant equipment is now in use at Hiwassee, the present flowsheet is not only different from that at Norris and Chickamauga but is also unique as compared to the flowsheet of the average crushed-stone aggregate plant. It is hoped that this paper will show the importance of proper arrangement of equipment if the optimum in flexibility and capacity is to be attained. Flowsheet Rock is ioaded by 3-yd. electric shovels into 12-yd. dump trucks, which carry the rock to the primary crusher, a 42-in. Superior McCully gyratory unit set at 4¾ in. (Fig. 1). The primary crusher discharges directly onto a 42-in. inclined belt conveyor, which carries the product to a surge storage pile with a maximum live storage capacity of approximately 3000 tons. A concrete tunnel under this storage pile houses the feed end of a 36-in. belt conveyor (conveyor B) fed by a 36 by 66-in.

Jan 1, 1942

By F. Cadena

HIWASSEE Dam, now under construction by the Tennessee Valley Authority on the Hiwassee River, a tributary of the Tennessee River, will require aggregate for approximately 800,000 cu. yd. of concrete. Near the damsite deposits of natural sand or gravel are not available and graywacke, a rock that is found in abundance, suggested itself as a likely source of manufactured aggregate. Graywacke is a metamorphosed sandstone composed principally of a mixture of quartz (65 per cent), mica (25 per cent), and feldspar (10 per cent). Other minerals are present in negligible amounts. The rock varies in different parts of the quarry from very fine to a coarse grain containing particles of about 1/4 in. maximum size, although the bulk of the deposit is medium grain. Extensive tests showed that graywacke would be suitable as a source of both coarse and fine aggregates. The aggregate plant available for use at Hiwassee Dam consisted of the coarse-aggregate and sand plant used on the Norris project. The coarse-aggregate plant had also been used at Chickamauga Dam. Although most of this plant equipment is now in use at Hiwassee, the present flowsheet is not only different from that at Norris and Chickamauga but is also unique as compared to the flowsheet of the average crushed-stone aggregate plant. It is hoped that this paper will show the importance of proper arrangement of equipment if the optimum in flexibility and capacity is to be attained. FLOWSHEET Rock is loaded by 3-yd. electric shovels into 12-yd. dump trucks, which carry the rock to the primary crusher, a 42-in. Superior McCully gyratory unit set at 4 ¾ in. (Fig. 1). The primary crusher discharges directly onto a 42-in. inclined belt conveyor, which carries the product to a surge storage pile with a maximum live storage capacity of approximately 3000 tons. A concrete tunnel under this storage pile houses the feed end of a 36-in. belt conveyor (conveyor B) fed by a 36 by 66-in.

Jan 1, 1939

By William Marsh Baldwin

THE ROLLING OPERATION proper is applied to metals and alloys not only in the production of flat products but also in the production of shapes, rods, wire and even in specialized forms in the production of tubes. The present discussion of rolling copper and copper alloys will be [ ] limited to a consideration of rolling flat products such as strip, sheet, foil, plate, and others. In this case (as in the others listed above), the rolling operation itself is only part of an integrated sequence of operations. In Fig I such a sequence going to make up a brass strip mill is sketched out. It is seen that the rolling opera-

Jan 1, 1948

Time Now For Thinking In these turbulous times a natural restiveness is created among the younger men of the mining profession. Many of them are veterans of World War II and the question is raised in their minds as to whether or not to go back into military service. There is time to think about this question now and it is advisable to do so in order that snap decisions may be avoided if war is declared.

Jan 2, 1951

Frontino operates three underground lode mines at Segovia in the area of northwest Antioquia, Colombia, which has been an important gold producing district since the late 1800s. Auriferous pyrite, the pre-dominent sulfide, carries very finely disseminated gold. Other minor sulfides are galena, pyrrhotite, and sphalerite in quartz gangue with the host rock being granodiorite. Silver is associated with the galena and also occurs as a sulfo-salt. In 1.973 and 1974, at an annual milling rate of 145,000 mt (160,000 st), average mill heads were 7.80 g per mt (0.23 oz per st) Au; 20.0 g per mt (0.58 oz per st) Ag; and 0.37% Pb; with a production of 1,150 kg (35,700 oz) Au and 4,500 kg (141,000 oz) Ag. Over 300 mt (330 st) of Pb concentrate were shipped. The ore is crushed to minus 16 mm (5 18 in. ) and fed to a rod mill with the discharge passing over a 1.07 m by 1.07 m (42 in. by 42 in. ) jig operating in closed circuit with the underflow from a cyclone in closed circuit with two ball mills. Cyclone overflow is bulk-floated for sulfide recovery from which the tailings are sent to the river as waste with the flotation concentrate joining the jig concentrate for cyanidation. The combined gold bearing concentrates, after cyclone classification, are reground to a very fine mesh in closed circuit with cyclone classification, with the overflow going to the primary thickener. Regrinding, classification, and thickening is done in cyanide solution, and the primary thickener produces a pregnant solution for Merrill -Crowe precipitation. The thickener underflow is the feed to the agitators, thickener, and filter from which the overflow and filtrate are sent to precipitation. The washed filter cake is repulped and floated for the recovery of a galena concentrate for shipment. About 40% of the recovered silver is in this concentrate. In the refinery the precipitate is melted into a dore bullion. This 600 mt (660 st) capacity mill employs several interesting techniques. Gold recovery of 85% to 90% from a complex sulfide denotes good practice. While total power at 42 kwh per mt (46 kwh per st) is high, it would be recognized that the grinding units are small in size and the flowsheet is complicated due to the gold occurring in the sulfide minerals. The extremely low-cost electric power is generated by

Jan 1, 1981

By J. H. Swisher, E. O. Fuchs

Rate equations were derived to describe the kinetics of internal oxidation of cylinders and spheres. The derived equations for cylinders were checked experimentally by means of sub scale thickness and electrical conductivity measurements on Cu-Cr alloy wires. The properties of the internally oxidized samples were examined with conductivity applications in mind. It was possible to produce uniform dispersions of Cr2O3 in copper with an initial chromium content as high as 3 wt pct. While electrical conductivities only a few pct less than that of OFHC copper were obtained, the Cr2Os particle size and spacing were too large for effective dispersion hardening. T.HE process of internal oxidation has been used widely in basic studies of the permeability of gases in metals. In a review article, Rapp1 has discussed the principles of internal oxidation in considerable detail. From a technological standpoint, internal oxidation is often considered undesirable, since it is a means by which inclusions can be introduced into an otherwise clean material. Another important aspect of internal oxidation is its use as a means of dispersion hardening a material. Broutman and Krock2 discuss this and other methods for making dispersion hardened alloys. The only internally oxidized material known to the authors which is commercially available is a Cu-BeO alloy.3'4 This alloy is made from Cu-Be alloy powder, using a so-called Rhines pack. It has a tensile strength of 80,000 psi and retains its strength at relatively high temperatures. The objectives of the present study were to derive rate equations for the internal oxidation of cylinders and spheres, to check the derived equations for cylinders experimentally, and to examine the structure and properties of internally oxidized Cu-Cr alloys. The Cu-Cr system was chosen for this study because uniform dispersions are obtainable at high alloy contents, which is a desirable characteristic in dispersion hardened materials. RATE EQUATIONS FOR VARIOUS GEOMETRIES A number of authors5--9 have derived equations to describe internal oxidation kinetics. These derivations differ somewhat in mathematical assumptions and approximations, and all except one of the derivations deal exclusively with the internal oxidation of plates. The exception is a brief treatment of cylindrical and spherical geometries given by Meijering and Druy-vesteyn9 as a part of a comprehensive paper on the general subject of internal oxidation. These authors did not obtain rate data to check their derivations, although they did show that the hardness profile across an internally oxidized sample is directly related to the rate of interface movement. For cylindrical and spherical geometries, a quasi-steady-state approximation is needed to circumvent mathematical complications in obtaining a solution to the basic differential equations. In using this approximation, we consider the concentration gradient of dissolved oxygen in the internally oxidized zone or sub-scale to be the same as the gradient which would be present if there were no movement of the subscale interface. The steady-state approximation introduces an error of about 1 pct in computing the rate of internal oxidation of an Fe-1.0 pct Mn alloy plate, if the present method is compared to the more exact method of Wagner.7'10 The details of the derivations of the rate equations for cylinders and spheres are given in the Appendix, and only the results of these derivations are given below. The final equations obtained by Meijering and Druyvesteyn9 can be shown to be equivalent to our Eqs. [1] and [2], although the two approaches are somewhat different. Cylindrical Geometry. [2] where r1 is the outer radius of the cylinder or sphere, cm, r2 is the radius of the unreacted core, cm, see Fig. l(a), D is the diffusion coefficient of oxygen in copper, cm2 per sec, %O is the concentration of dissolved oxygen at the surface of the specimen, wt pct, %Cr is the initial chromium concentration in the alloy, wt pct, and t is the reaction time, sec. Plate Geometry. The analogous rate equation for a plate has been derived previously for internal oxidation of Fe-Al alloys.8'11 For Cu-Cr alloys, we may write the same equation as follows: [3] where r1 is the half-thickness of the plate, cm, and r2 is the distance from the mid-plane to the subscale intherate is An analysis of Eqs. [1], [2], and [3] shows that for a plate the rate is completely parabolic. The initial

Jan 1, 1970

By J. L. Thompson

There are two basic forms of the LPG-slug process: the gas driven and the water driven. The pressure required for miscibility between gas and LPG prohibits the use of the gas-driven LPG process in shallow reservoirs. The water-driven LPG slug process normally exhibits good sweep efficiency. However, displacement of the LPG by water is poor. An improvement in this process appears possible by injecting a slug of carbon dioxide between the LPG slug and the water drive. Laboratory experiments were conducted in homogeneous linear systems to determine the effect of pressure on the various displacement zones. In the carbon dioxide-LPG displacement zone, the effect of pressure on the displacement efficiency is negligible above the miscibility pressure. However, the displacement efficiency decreases linearly with decreasing pressure below the miscibility pressure. With water displacing carbon dioxide, it was found that the recovery of carbon dioxide after water breakthrough can be predicted from its solubility in water. A displacement test was conducted with LPG and carbon dioxide slugs large enough to avoid interference between the oil-LPG, LPG - carbon dioxide and carbon dioxide - water displacement zones. Under these conditions, essentially complete oil and LPG recovery was obtained. However, a substantial amount of carbon dioxide was left in the core at water breakthrough. INTRODUCTION It has been shown in homogeneous linear systems that essentially complete oil recovery can be obtained by displacement with a miscible fluid such as LPG. Economic considerations dictate that the valuable LPG also be recovered. Methods proposed for recovering the LPG include (1) displacement with natural gas at a pressure high enough to make the two fluids miscible1 (the disadvantage of this method is that the required pressure of about 1,500 psi is too high for shallow reservoirs) and (2) displacement of the LPG with water2 (principal disadvantage is that a large amount of LPG remains in the formation because of poor displacement efficiency). This paper treats an improvement in the water-driven LPG slug process3,4 where carbon dioxide is injected between the LPG and water. Carbon dioxide is completely or at least partially miscible with propane and soluble in water; thus, displacement efficiency is improved at both ends of the carbon dioxide slug. To minimize effects of other variables, all experiments were conducted in linear core systems. GENERAL PROCESS DESCRIPTION The displacements of propane by carbon dioxide and carbon dioxide by water are considered separately, assuming enough of each is injected to prevent mutual interference. Displacement descriptions are confined only to the part of the pore volume containing mobile fluids unless otherwise specified. The schematic representation is given in Fig. 1. Starting at the producing well, a zone containing only oil is followed by a zone containing a single-phase mixture of propane and oil. The concentration of propane increases in the direction of the injection well and ultimately grades to pure propane. Then follows a zone containing a mixture of propane and carbon dioxide in continuously varying proportions until 100 percent carbon dioxide is reached. In this zone, the concentration of carbon dioxide in the immobile water phase also varies from zero to full saturation. Whether the displacement of propane by carbon dioxide is of complete or partial miscibility depends on pressure and temperature (Fig. 2). If the horizontal line representing the prevailing pressure intercepts the boundary curves of the phase envelopes for the prevailing temperature (i.e., if the pressure is lower than the critical

By W. G. Pfann

In zone-melting, a small molten zone or zones traverse a long charge of alloy or impure metal. Consequences of this manner of freezing are examined with impurerespect to solute distribution in the ingot, with particular reference to purification and to prevention of segregation. Results are expressed in terms of the number, size, and direction of travel of the zones, the initial intermsofsolute distribution, and the distribution coefficient. IF a charge of binary solid-solution alloy is melted and then frozen slowly from one end, as for example in the Bridgman method of making single crystals,' coring usually occurs, with a resulting end-to-end variation in concentration. Such coring, or normal segregation, is undesirable where uniformity is an object. On the other hand, for certain systems, it can be utilized to refine a material by concentrating impurities at one end of the ingot.'. ' In the present paper a different manner of freezing will be examined with respect to the distribution of solute in the ingot. A number of procedures will be indicated which have in common the traversal of a relatively long charge of solid alloy by a small molten zone. Such methods will be denoted by the general term zone-,melting, while the process described in the preceding paragraph will be called normal freezing. It will be shown that, in contrast to normal freezing, zone-melting affords wide latitude in possible distributions of solute. Segregation can either be almost entirely eliminated or it can be enhanced so as to provide a high degree of sttparation of solute and solvent. A number of simplifying assumptions will be invoked which, while not entirely realizable in practice, nevertheless provide a suitable point of departure for more refined treatments. Moreover, our own experience with zone-melting has shown that, for certain systems at least, the analysis holds quite well. The present paper will be confined to a discussion of principles and a general description of procedures. Comparison with experiment is planned for later publication. Normal Freezing Before considering zone-melting, segregation during normal freezing will be reviewed briefly. If a cylinder of molten binary alloy is made to freeze from one end as in Fig. 1, there usually will be a segregating action which will concentrate the solute in one or the other end of the ingot. If the constitutional diagram for the system is like that of Fig. 2, then the distribution coefficient k, defined as the ratio of the concentration in the solid to that in the liquid at equilibrium, will be less than one and the solute will be concentrated in the last regions to freeze. If the solute raises the freezing point, then k will be greater than one and the solute will be concentrated in the first regions to freeze. The concentration in the solid as a function of g, the fraction which has solidified, can be expressed by the relation: C = kC0 (1-g)k-1 [I] where C, is the initial solute concentration in the melt. Eq 1 is based on the following assumptions: 1—Diffusion in the solid is negligible. 2—Diffusion in the liquid is complete (i.e., concentration in the liquid is uniform). 3—k is constant. Concentration curves representing eq 1 for k's from 0.01 to 5.0 are plotted in Fig. 3. This equation, in one form or another, has been treated by Gulliver,³ Scheuer,4 Hayes and Chipman5 for alloys and by McFee2 for NaCl crystals. It is derived in Appendix I. It should be pointed out that the k which is calculated from the phase diagram will be valid only in the ideal case for which the stated assumptions are correct. In all actual cases, the effective k will be larger than this value for solutes which lower the melting point, smaller for solutes which raise the melting point, and will probably vary during the beginning of the freezing process. For simplification it will be assumed that the ideal k is valid. Zone-Leveling Processes The processes of this part are designed to produce a uniform, or level, distribution of solute in the ingot. Single Pass: Consider a rod or charge of alloy whose cross-section is constant and whose composition, C2, is constant, although permissibly varying on a microscopic scale." Such a charge might be a rapidly frozen casting or a mixture of crushed or powdered constituents. Cause a molten zone of

Jan 1, 1953

By Frederick Laist

Introduction IN a leaching process, having obtained the copper in solution, the choice of the precipitation method is influenced y the following factors: 1. Availability of precipitant. 2. Adaptability to the leaching process. 3. Final product desired. 4. Regeneration of leaching solutions. 5. Fouling of solutions. There are three general classes of precipitation methods: 1. The use of iron, scrap or sponge. 2. Electrolytic deposition. 3. The use of some gas or reagent y which the copper is obtained, usually in the form of an intermediate precipitate which requires further treatment. For example, the precipitation of the copper as Cu2Cl2 from chloride solutions, with SO2 gas. The use of iron is adapted to almost any process. It has the great advantage of extreme simplicity, and the recovery of the copper and any values present in a highly concentrated, easily treatable form. The disadvantages are the cost in isolated places, the uncertainty of the scrap-iron market, and the fouling of the leaching solutions. The latter is a serious factor, When a reagent such as salt is used in them, which makes necessary their re-use. Where applicable, electrolytic deposition is very attractive. The copper is obtained in a form directly marketable, there is a regeneration of acid amid no fouling of solutions. Unfortunately, chloride solutions do not lend themselves to electrolysis. An entirely satisfactory anode material has not yet been discovered, although magnetite, apart from being rather brittle, seems to answer the requirements fairly Well.

Jan 7, 1914

J. B. Cohen (AVCO Mfg. Co.)-The model presented by the authors is only one of several possible mechanisms for low-temperature aging. It is true that the motion of dislocations to the copper atoms, followed by diffusion along the dislocation lines, is one such mechanism. However, the details of such a process which would :result in copper-rich platelets on (100) planes in the f.c.c. matrix are not clear. Furthermore, there is at least one other mechanism that may be used to e.xplain the authors' results, so that the data do not clearly favor the Turnbull model. The zones may form by "normal" diffusion. The diffusion constants would be higher at room temperature than extrapolated data would suggest due to vacancies trapped in the specimens in the quench. The diffusivity would then be multiplied by the ratio of the number of vacancies present at the solution temperature to that present at room temperature. These vacancies could remain in the alloy specimen for long times at room temerature, due to interaction with the copper atoms. ' The activation energy for diffusion is smaller than that for bulk diffusion at elevated temperatures for it is only that for the motion of vacancies existing after the quench; after these are used up, the aging process effectively ceases. It is somewhat questionable if the laws governing transformation kinetics can be directly applied to changes in elastic moduli, especially in the case of aging where the structure and the composition of the zones may be changing during aging, If such laws are assumed, it is possible to explain the exponential factor of % with this vacancy model. It is probable that the structure of the zones and the matrix match only on (100) planes. Certainly the precipitates that form in this system after various aging treatments show orientation relationships similar to those of the zones. Strains on the edges of the zone may set up fields which do not allow the zone to grow in an edgewise manner. The exponent in the growth of a thin plate in a direction perpendicular to its face would be %. It may also be that copper atoms are attracted to dislocations. If this is the rate-controllin factor in the growth process Ifthisthen an exponent of % or % may arise. The writer would like to know if the authors have tried plotting l/a; proportional to as might be expected for "dislocation drainage." R. H. Doremus (General Electric Research Laboratory)—An important new method for following the growth of Guinier-Preston zones is presented in this paper, and I wish to congratulate the authors on their experiments. Their interpretation of the results, however, is doubtful in certain respects. To determine the exponent m in Eq. [4] the authors plotted -log at against t to various powers (their Fig. 6). The initial value of frequency used for these plots was found by extrapolating the data to zero time. In Fig. A the data from their Fig. 2 are plotted against a linear, rather than logarithmic, time scale. To obtain graphs similar to their Fig. 6 for these data one must use an initial frequency of about 52720; such a plot for m = % is shown in Fig. B. The straight line in Fig. B fits the data in an intermediate range only. The curve drawn in Fig. A was mapped from this line; comparison of

Jan 1, 1960

OCHRE is a semimineral composed by Nature of earth and a tincture of yellow caused by a fumosity of lead ore. By itself it is a material without any [38] metal, although when it is used in smelting it helps to melt the harsh and sour ores of metals. I do not know that it has any other use, except to painters. Bole is also a red viscous earth which has a very astringent and drying nature. It has no very apparent smell or taste, and I think that the cause of its redness lies in the fumosities of iron ore, for it is a companion to this and is found in its mines. It is an efficacious medicine against any poison and in this capacity has an action like terra sigillata* or perhaps better. In

Jan 1, 1942

By P. P. Gregory

NATURAL petroleum gas occurring in the oil-bearing reservoirs is found to exist either as free gas associated with the oil and/or in solution in the oil. In some virgin fields practically no free gas is encountered under the reservoir conditions of pressure and temperature, although in other fields a considerable section of the ``pay" horizon is occupied by free gas. In other words, a given oil field may or may not have a gas cap before the exploitation takes place. However, when the reservoir pressure is reduced to a point below the critical saturation pressure by withdrawals of fluids from the producing formation, the gas dissolved in the oil inevitably begins to come out of solution and becomes free gas. Under the con-trolled methods of production and drilling, a portion of this gas is pro-duced with the oil to the surface and a portion of it remains within the reservoir to accumulate at higher structural levels toward which it migrates by virtue of its low specific gravity. The rate of growth of a gas cap in a-given structure depends primarily upon the rate of decline in the reservoir pressure. If the rate of pressure decline is rapid, the gas cap likewise will grog rapidly. On the other hand, shrinkage in the gas-cap area was noted in some fields in which reservoir pressures were increasing.

Jan 1, 1938

By E. H. Lee, F. J. Fayers

Problems in reservoir analysis can usually he cupressed in terms of a system of nonlinear partial difjerential equations. A rnethod for .setting physically reasonable boundary conditions for these systerrls by ayplication of the theory of characteristics is discussed. A short description i.c. given of the technique for finding chnmcteristics of general first order and second orrler equations. Specific examples are quoted jrorn eqrrations occurring in theoretical reservoir studies. The princip1e. ossocicred wit11 the use of chnracteristic to set physically realistic boundary conditions me developed, and thr method is discussed in terms of boundary condition for the noncupillary, compressible, two-phase flow problen: jor the cupillary, ir~cowlpressible, two-phase flow problems for the tlrtergent flooding prohlenl; as for the compressible. noncapillary, two-phase flow pro11letn. INTRODUCTION In most problcms in reservoir analysis the physical situation is described by a system of nonlinear partial differential equations. The general solution to the set of equations usually comprises a wide range of functions ancl a particular solution is normally selectetl by applying suitable boundary conditions to the problem. In some cases it is clear from the physical situation what form the boundary conditions should take, but it is usually desirable to have an independent mathematical check of the suitability of the chosen conditions. From the mathematical standpoint, a system of partial differential equations with boundary conditions is said to be properly set if the combination determines a unique solution which is continuously dependent on the equation and the boundary conditions. Such a solution is sometimes termed "reasonable". In investigating the properties of the mathematical representation, it is useful to determine the structure of the system by the application of the theory of characteristics. This theory determines in the space of the independent variables, lines or surfaces which play a special role in thc system's behavior. The characteristics determine the possibility and nature of the propagation of discontinuities in the derivatives of the dependent variables. Along the characteristics certain differential relations hold which for some problems allow a so- lution to be obtained analytically. In the case of hyperbolic equations the characteristics can bc used as 3 basis for a numerical solution. If a complicated nonlinear system is to be solved, a study of behavior of the characteristics will indicate what boundary conditions should be chosen. By using the method of characteristics, several advances have rccently been made in solving reservoir engineering problems. Sheldon, Zondek and Cardwell' have discussed how the the method may be used grap-phically to solve the incompressible two-phase displaccmerit problem when the gravity term is included in the equations. Fayers and Perrine' have applied the method to study the equations representing detergent flooding. When compressibility and solution-gas effects are introduced into the two-phase flow problem, the equations and their characteristics become more complicated. It will be seen that in this problem the characteristics are useful for indicating a reasonable set of boundary conditions but cannot readily be used to compute a numerical solution. This problem has been solved on the IBM 701 using normal finite difference methods hy West, Garvin and Sheldon." The material to be prcscntcd in this report is divided into three sections. The first discusses the determination of the characteristics of first and second order partial differential equations; the second describes the selection of suitable boundary conditions by the application of the principle that the future cannot affect the past; the third discusses the use of characteristics for setting the boundary conditions of the two-phase solution-gas flow problem. A useful introduction to the method of characteristics has been given by Hildebrand.' A summary of the method will be given in this section of the paper. The First Order Equation The quasi-linear equation of first order is It is linear in the partial derivations of z. The properly linear equation has the form The characteristics of are curves along which the