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By George H. K. Schenck

Decisions to develop deposits of calcareous materials for cement production are based largely on anticipated markets for heavy construction which utilizes concrete. The geologist should understand the fundamental factors that underlie such management decisions, so that his field work and reports will more effectively relate to the information requirements of managers in the cement industry. The paper examines the relationships that exist between exploration and development of calcareous raw materials for cement manufacture and changing factors in the marketing of cement. Continued overcapacity, improved technology, changing distribution patterns, ease of entry, economics of scale, and the nature of product demand are some of the characteristics of the cement industry that are basic to decisions regarding exploration programs and property development.

Jan 1, 1966

By T. E. Burns

The process engineer is frequently requested to select equipment to separate brine from solids, In many cases, this is a more difficult task than the selection of most other pieces of process equipment because quite often the operation of the various types of debrining equipment cannot be predicted by calculations, One must rely to a great extent upon experience or empirical test work to predict performance - that is to say one must use a practical rather than a theoretical approach. This is not to say that the solutions to liquid-solids separating problems are wholly an art but rather it is to emphasize that the approach demands a fair knowledge of commercially available liquid-solids separating equipment, some background on the advantages and limitations of each type and in many cases might necessitate a fair amount of test work, or at least, a study of performance of equipment on similar applications.

Jan 1, 1966

By R. H. McLean

Velocity, kinetic energy and shear in crossflow beneath three-cone jet bits may influence cleaning of the bottom of the borehole and the teeth of the bit. Laboratory investigation shows that each of these parameters is a function of the diameter of the borehole and the product of the volume rate of flow and velocity through the nozzles (QVn). Increasing QV, or decreasing the diameter of the borehole increases each parameter. These functions provide means of predicting the magnitude of each parameter and of scaling the cleaning forces. INTRODUCTION In drilling operations using conventional jet-type rock bits, the impinging jels create an important flow mechanism. Called crossflow, this flow mechanism originates in the impact area of the jets, spreads across the bottom of the hole and supplies the principal source of energy to clean the teeth of the bit and most of the bottom.' Besides providing the means of cleaning cuttings from the bit and the hole bottom, crossflow may also have other, less direct, effects on the rate of penetration. The shear stress generated on the bottom by crossflow will inIluence the thickness and permeability of any filter cake of mud solids or crushed material which forms on the bottom.' These factors may affect the rate of penetration. A previous pulblication introduced some fundamental concepts of crossflow.' Crossllow was shown to occur in a thin layer adjacent to the bottom, and to cover the bottom completely. The maximum velocity in the crossflow above any position on the bottom was found to be directly proporlional to the square root of the product of the volume rate of flow and velocity through the nozzles—the jct QV,,—and inversely proportional to the diameter of the borehole. This information indicated that the effectiveness of crossllow in scavenging the bottom can be improved by maximizing the jet QV. The investigation reported herein amplifies the definition of crossflow. Complete velocity profile data above a representative position on the bottom are analyzed. These data better illustrate control of the capacity of crossflow to scavenge the bottom, and also relate shear stress on the bottom to known, controllable parameters. The conclusion reached in the previous publication that maximization of the jet QV. produces the maximunl cleaning beneath current jet bits is unchanged by these new data; rather, it is strcngthened. Data presented here show that the kinetic energy flux above a representative position on the bottom is maximized by maximizing the jet QV. The shear stress on the bottom will also be shown to be maximized in the same manner. Since the functions relating the jet QV. to velocity, shear stress and kinetic energy also involve the diameter of the borehole, means of equating, or scaling, these quantities in different sizes of boreholes will be illustrated. EXPERIMENTAL EQUIPMENT AND TECHNIQUE JET BIT MODEL Data were recorded from the same laboratory model as used in the aforementioned investigation of the flow around a jet bit.' The model consisted of a 43/4-in. three-cone, jet-type rock bit in a smooth, flat-bottomed borehole constructed of lucite. The bit had a shape and nozzle placement closely resembling larger three-cone jet bits commonly used in field operations. Fig. 1 illustrates the impact area on the bottom of a jet from this bit. Details of the orientation of the jets may be found in the previous publication. TECHNIOU'E OF MEASUREMENT Measurements of the crossflow were made by inserting a very small Pitot tube through the bottom of the simulatetl boreholc. Extreme thinness of the layer of crossflow necessitated accurate measurements of the height of the Pitot tube above the bottom to achieve close definition of the velocity profile. A cathetometer, which could be read to the nearest 0.005 cm, was used to make this measurement.

Jan 1, 1966

By Paul M. Buttermore

As part of a national canvass of water use the Bureau of Mines compiled data on water requirements in the petroleum and natural gas industries for the calendar year 1962, specifically in well drilling, secondary-recovery operations, and natural gas processing plants. Total new water use in the petroleum industry of the United States, excluding refining, was 5.3 billion barrels. Secondary-recovery operations and natural gas processing plants required about 2.5 billion barrels of new water input; each of these requirements was about eight times greater than that for well drilling. Total use, including recirculated water, was 45.3 billion barrels of which 3.4 billion barrels was consumed. The greatest use of recirculated water was for natural gas processing, amounting to 38.2 billion barrels. Projections of total water use show that by 1975, 75.4 billion barrels will be used by the petroleum industry, of which 10.2 billion barrels will be new water. By 1985, the total use requirement will be 92.8 billion barrels, of which 13.1 billion barrels will be new water.

Jan 1, 1966

By C. D. Stahl, R. Sandrea

This investigation was made to evaluate the comparative effects of the viscosity and the phase behavior of the buffer fluid in the composite solvent displacement of Bradford crude from waterflooded sandstone cores. Buffer slugs of propane, naphtha and other refined hydrocarbons exbihiting increasingly favorable viscosity ratios and decreasing solubility relationships, respectively, with Bradford crude, were used in long Berea sandstone cores. The secondary slug was isopropyl alcohol. The results indicate that higher oil recoveries are obtained for increasingly favorable phase relationships even when these are accompanied by unfavorable viscosity ratios within the range studied. Moreover, when propane is used as a buffer slug with an adverse viscosity ratio of 36, it gives higher oil recoveries than at a similar size slug of an any1 alcohol having a viscosity ratio of 1.09. The investigation was extended to the study of the effect of flooding rate on oil recovery. Residual Bradford crude was displaced from a 6-ft Berea sandstone core at rates varying from 0.3 to 30 ft/ day. The results show that as flooding rates were increased above or decreased below a minimum range of 1 to 2 ft /day, displacement efficiency increased considerably. INTRODUCTION In recent years, the alcohol slug process as a means of tertiary recovery has been the subject of many investigations. Gatlin and Slobod showed the advantages of the combination solvent slugs over the previous single-slug process.1 The combination slugs require less total slug material to obtain similar oil recoveries. The basic combination process involves injecting a primary or buffer solvent which is preferentially oleophilic, followed in turn by a water-driven slug of isopropyl alcohol. This procedure ensures that the buffer slug, which is miscible only with the reservoir oil, displaces and replaces the oil and is in turn displaced, together with the water, by the isopropyl alcohol slug miscible with both fluids. Likewise, for those reservoir oils that show some degree of phase incompatibility with isopropyl alcohol, as does Bradford crude, a proper buffer solvent can artificially make the alcohol process technically feasible. From an economic standpoint, propane or LPG would be the most appropriate primary solvent to be used in the field; however, Taber, et a12 have indicated that the alcohol process becomes highly inefficient in the displacement of light hydrocarbons because of the entrapment of these hydrocarbons during the stabilized bank formation. Moreover, since materials such as propane have such low viscosities, adverse viscosity ratios with most reservoir oils would be penerated, thereby possibly further reducing the efficiency of the buffer solvent. This paper presents the results of an experimental study of the comparative effects of viscosity ratio and phase relationships on the displacement efficiency of Bradford crude by means of dual solvents. The work was extended to include the effect of flooding rate on oil recovery. Rates within the range of field and laboratory values were used. EXPERIMENTAL PROCEDURE APPARATUS The porous media used in this study consisted of two 10-ft and one 6-ft Berea sandstone cores, 3-in. in diameter. These were cast in galvanized steel pipe of 31/2-in. ID and the annulus was filled with Armstrong cement. The 10-ft cores were assembled by connecting two 5-ft units, which were joined together by 8-in. steel flanges fitted to the pipe. Intimate contact between the two sections was obtained by inserting a thin disk of the same sandstone between the core faces. The outlet and inlet ends of the cores were covered with threaded pipe caps. The injected fluid was gravity fed to two variable-rate positive-displacement pumps. The fluids were filtered before entering the core and the effluent was collected in an automatic fraction collector and

Jan 1, 1966

By D. C. Treilhard

After a brief history of the mining and smelting operations of Kilembe Mines Limited, this paper outlines the smelter layout and describes . the. daily operations at the Jinja plant. Particular attention 1s paid to the details of the furnace and converter operation. A subsequent section of the paper deals with the significant developments in plant metallurgical practice, covering both smelting and converting.

Jan 1, 1966

By F. A. Forward

"NINETEEN sixty-six is a year of unusual significance in our Institute and in our country. It marks two-thirds of a century of service by the Institute to the people of the mineral industry and two-thirds of the century that Sir Wilfred Laurier said ""belongs to Canada."" As we meet here today within the historic walls of Canada's oldest city, a city that looks back on three hundred and fifty years of progress, I am reminded that it is almost a third of a century ago -in April, 1934 -that here in Quebec I first attended an Annual General Meeting of the Institute. It occurred to me that it might be appropriate to examine briefly the change that the middle third of this century has brought in the affairs of the mineral industry and, with some trepidation, to consider the prospect for the third that lies ahead.Opinions differ as to the relative importance of factors that have been responsible for the expansion and growth of Canada in its first hundred years. Some will say that it has been due to the abundance and fertility of agricultural land, others to the early enterprise of the railroads, and financiers believe that the banking system has been a major factor; -the fisherman -the forester -the teacher -each has his own view. I suspect, however, that most of us here would subscribe to the thesis of T. A. Rickard -miner, author, imperialist -who wrote, a gene-ration ago, ""Trade follows the flag, but the flag follows the pick,"" and thus agree that the finest contribution to progress, to wealth, to extension of frontiers and to inter-national trade has been provided by the mineral industry."

Jan 1, 1966

By A. S. Odeh

ABSTRACT A simplified model was employed to develop mathematically equations that describe the unsteady-state behavior of naturally fractured reservoirs. The analysis resulted in an equation of flow of radial symmetry whose solution, for the infinite case, is identical in form and function to that describing the unsteady-state behavior of homogeneous reservoirs. Accepting the assumed model, for all practical purposes one cannot distinguish between fractured and homogeneous reservoirs fram pressure build-up and/or drawdown plots. INTRODUCTION The bulk of reservoir engineering research and techniques has been directed toward homogeneous reservoirs, whose physical characteristics, such as porosity and permeability, are considered, on the average, to be constant. However, many prolific reservoirs, especially in the Middle East, are naturally fractured. These reservoirs consist of two distinct elements, namely fractures and matrix, each of which contains its characteristic porosity and permeability. Because of this, the extension of conventional methods of reservoir engineering analysis to fractured reservoirs without mathematical justification could lead to results of uncertain value. The early reported work on artificially and naturally fractured reservoirs consists mainly of papers by Pollard,l Freeman and Natanson,2 and Samara.3 The most familiar method is that of Pollard. A more recent paper by Warren and Root showed how the Pollard method could lead to erroneous results,4 Warren and Root analyzed a plausible two-dimensional model of fractured reservoirs. They concluded that a Horner-type pressure build-up plot of a well producing from a fractured reservoir may be characterized by two parallel linear segments. These segments form the early and the late portions of the build-up plot and are connected by a transitional curve. In our analysis of pressure build-up and drawdown data obtained on several wells from various fractured reservoirs, two parallel straight lines were not observed. In fact, the build-up and drawdown plots were similar in shape to those obtained on homogeneous reservoirs. Fractured reservoirs, due to their complexity, could be represented by various mathematical models, none of which may be completely descriptive and satisfactory for all systems. This is so because the fractures and matrix blocks can be diverse in pattern, size, and geometry not only between one reservoir and another but also within a single reservoir. Therefore, one mathematical model may lead to a satisfactory solution in one case and fail in another. TO understand the behavior of the pressure buildup and drawdown data that were studied, and to explain the shape of the resulting plots, a fractured reservoir model was employed and analyzed mathematically. The model is based on the following assumptions: 1. The matrix blocks act like sources which feed the fractures with fluid; 2. The net fluid movement toward the wellbore obtains only in the fractures; and 3. The fractures' flow capacity and the degree of fracturing of the reservoir are uniform. By the degree of fracturing is meant the fractures' bulk volume per unit reservoir bulk volume. Assumption 3 does not stipulate that either the fractures or the matrix blocks should possess certain size, uniformity, geometric pattern, spacing, or direction. Moreover, this assumption of uniform flow capacity and degree of fracturing should be taken in the same general sense as one accepts uniform permeability and porosity assumptions in a homogeneous reservoir when deriving the unsteady -state fluid flow equation. Thus, the assumption may not be unreasonable, especially if one considers the evidence obtained from examining samples of fractured outcrops and reservoirs. Such samples show that the matrix usually consists of numerous blocks, all of which are small compared to the reservoir dimensions and well spacings. Therefore, the model could be described to represent a "homogeneously" fractured reservoir. la this paper, the fundamental equation of flow

Jan 1, 1966

By d&apos, Kathleen J. Amico

This summary appears in Minerals Year-book volumes I and III, which cover mineral production in the United States, its island possessions, the Canal Zone, and the Commonwealth of Puerto Rico, as well as the principal minerals imported into and exported from the United States. The several commodity and area chapters contain further details on production. A summary table comparing world and U.S. mineral production also is included. Mineral production may be measured at any of several stages of extraction and processing. The stage of measurement used in the chapter is normally what is termed "mine output." It usually refers to minerals in the form in which they are first extracted from the ground, but customarily includes for some minerals the product of auxiliary processing operations at or near mines.

Jan 1, 1966

By M. M. Mebta, G. W. Dean, W. H. Somerton

With the advent of underground heating operations, interest has developed in the alteration of rock properties by high-temperature treatment. In the present work a number of sandstones were heated to temperatures in the range of 400°C to 800°C under both atmospheric and simulated reservoir pressures. Pertneabilities increased by at least 50 per cent and sonic velocities and breaking strerlgths decreased by an equivalent amount. Differential thermal expansion and other reactions of constituent min-era1 grains are the causes of these alterations. INTRODUCTION In the underground combustion of petroleum reservoirs, temperatures of the order of 600C are reported to have been reached in the combustion zone.' At this temperature rocks are subject to extensive thermal alteration. Temperatures of this magnitude and higher may also occur in subsurface formations when subjected to bottom-hole heating, thermal drilling operations, and underground nuclear explosions. Temperatures of this magnitude might also be generated by conventional rock drilling methods at points of bit-tooth contact. In earlier work, the permanent deformation of rocks resulting from heating was reported. Major structural damage of rocks occurs due to differential thermal expansion of mineral constituents. A number of mineral alterations including crystal inversions, loss of water of crystallization and dissociation, may also contribute to changes in physical structure and properties of rock. In the present work, samples of three typical sandstones were heated to several temperatures up to a maximum of 800C and then allowed to cool to room temperature. Heating was done under both atmospheric pressure and simulated reservoir pressure conditions. Physical properties of the samples were measured before and after heating and comparisons made. Measured properties included permeability, sonic velocity, breaking strength and fracture index. Changes in physical properties were compared to changes in mineralogical characteristics as determined by thin-section. X-ray diffraction and chemical tests. EQUIPMENT AND PROCEDURE Two outcrop sandstones (Bandera and Berea) and one sub-surface sandstone (St. Peter) were selected for the tests. These samples have a wide ranee in composition and physical properties as shown in Table 1. The first series of tests was made on 2-in. diameter by 5-in. long test specimens. Test specimens used in all later work were 3/4-in. diameter by 1 1/8-in. long, this being the specimen size required for heating at simulated reservoir pressures. After careful washing, the cores were oven dried at 100 ± 5C for a minimum of 24 hours before the tests were run. Test specimens were heated in an electric furnace at a constant rate of temperature increase of 3C per minute. When maximum temperature of the run was reached, the sample was allowed to soak for one hour. The furnace was then cooled to room temperature at the same rate of 3C per minute. The entire heating operation was designed for reproducibility without subjecting the test specimens to excessive thermal shock. For samples heated under simulated reservoir pressures, a pressure cell designed by Dean was used (Fig. 1).3 The core sample was inserted into a thin-walled (0.006 to 0.01-in.) copper cup which was then mounted in a high-pressure cell. Provisions were made for the application of internal pore pressure as well as confining pressure. Tests showed that the thin-walled copper cup closed tightly around the core and satisfactorily transmitted confining pressure to the core. The core was heated by placing the entire cell into the electric furnace. The heating program was the same as that used in the atmospheric pressure runs: tempera-ture rise of 3C per minute to maximum temperature of the test, soaking at maximum temperature for one hour, and cooling at a rate of approximately 3C per minute. The cell was designed to withstand 5,000 psi at 1,000C. However, since it was considered likely that repeated heating and cooling would in time weaken the steel, 2,000 psi at 850C was set as a working limit. In the present series of tests, the pore pressure was held constant at 750 psi and the confining pressure at 1.500 psi. The pressure source was a high-pressure nitrogen tank. The two pressures were controlled manually but are accurate well within ± 50 psi.

Jan 1, 1966

By A. W. Deurbrouck

This report describes the preparation characteristics of the significant coalbeds from which samples could be obtained in Webster County, W. Va. In 1964, approximately 825,000 tons of coal was produced in the county, of which 732,000 tons was mechanically cleaned in three preparation plants. The Sewell coal bed accounted for 94 percent of the coal produced. Twelve samples were collected from five coalbeds. Four of the samples would require upgrading to meet metallurgical requirements; two others of just over 8.0 percent ash would require some upgrading. In general the coalbed samples collected in the county were of medium-sulfur and medium-to low-ash content as received or after removal of the sink 1.58-specific-gravity material.

Jan 1, 1966

Rb-Sr measurements on total-rock samples of granitic rocks from the Mount Isa region have confirmed the existence of two periods of granite-forming activity. The Kalkadoon Granite, together with the Ewen Granite and possibly an older phase of the Sybella Granite, has been shown to belong to the earlier age-group at 1760 m.y.; the Wimberu Granite and a pegmatite associated with the Sybella Granite have been dated at 1540 m.y. The initial Sr ratio suggests that the Wimberu Granite may be new material of deep-seated origin.Further Rb-Sr measurements have confirmed previously-reported K-Ar results upon biotites from these rocks, whilst showing that, in this metamorphic terrain, biotites have lost varying amounts of radiogenic Sr and Ar, and therefore yield ages which are younger than the true age of the second event.

Jan 1, 1966

By Robert F. Shurtz

This paper discusses and compares methods of statistical analysis of the information relating to the evaluation of an asbestos deposit. From a study of 10-ft. lengths of drill core, the separate effects of visual evaluation errors were determined, as well as the deviations between evaluators and the deviations produced by a slight displacement in the center lines of the check drill holes. The importance of careful statistical analysis of such information is stressed.

Jan 1, 1966

By J. P. Hansen

Reducibility tests were run by the Bureau of Mines on an open hearth lump ore and four groups of pellets whose smelting characteristics had been deter-mined previously in the Bureau's experimental blast furnace. When reduction data from various tests were plotted on specially prepared paper l-(l-percent reduction/100)1/3 against time, the plots were linear. The iron-wustite inter-face therefore advances at a constant rate. The rate of the interface advance in mm/min was used as a reducibility index. The reducibility index measured at 900° C, using 0.45 cu ft hydrogen per minute varied inversely with the surface area of the sample. Even with carefully controlled surface areas, how-ever, duplicate reducibility indices varied considerably. When enough tests were run to give a stable mean, the mean reducibility index did correlate with blast furnace production for the four pellet groups. Results indicated that if the interface speed itself were to be used for correlation with blast furnace production, a sample size of about 180 grams of minus 0.742-plus 0.525-inch particles should be used with a test temperature of 900° C and a flow of 0.45 cu ft hydrogen per minute.

Jan 1, 1966

By W. W. Weller

Heat capacities of ferrous molybdate (FeMoO4) and ferrous tungstate (FeWO4) were measured over the temperature range 51° to 298.15° K. Ferrous tungstate has a lambda type heat capacity anomaly at 74° K. The 298.15° K entropies are FeMoO4) 30.9 cal/deg mole and FeW04) 31.5 cal/deg mole.

Jan 1, 1966

By F. J. West

This paper deals with Jones & Laughlin Steel Corporation's new Adams mine, near Kirkland Lake, Ontario. After a brief discussion of ore structure, type, reserve tonnages, etc., the main body of the paper discusses the establishment of an open-pit limit based on economic considerations. The method used by J & L to arrive at an economically sound open-pit boundary its outlined fully. Physical limitations to open-pit boundaries are mentioned briefly. The paper concludes with a few remarks on the mining equipment in use and on its productivity

Jan 1, 1966

By P. F. Mataich

When the subject of plant computers is brought up most people visualize the computer's controlling the entire plant with very little operator intervention. Actually, this picture is true today in only a limited number of cases and will certainly not be true in the minerals industries for many years to come. There are several ways in which a plant computer can significantly contribute to improving plant operation and closed loop control is only one of these. First of all, what are the basic ingredients for good plant control? For good plant control, two requirements must be met. First, the operator must get good information feedback from the process and then he must know what action to take in response to this information. Control information can be obtained through instruments, laboratory analyses, or through simple visual observation. If it is timely and accurate and the operator knows how to use it, then we have the makings of a good plant control system. The computer can be of help in both these areas by getting good data back to the operator and in helping to develop a good control scheme for the plant.

Jan 1, 1966

By B. A. Eaton, R. H. Jacoby

This paper presents the depletion-performance correlations developed using data from PVT studies and well-completion tests of 27 rich gas-condensate and volatile-oil reservoir fluids. The PVT behavior for each fluid war determined experimentally in the laboratory, and the depletion performance of each fluid was then calculated. Well-completion test data consisting of reservoir pressure and temperature, initial total gas-oil ratio, and stock-tank oil gravity were used with the depletion-performance data to develop general performance correlations. Three correlations are presented. The first equation shows the empirical relation of gas in place per barrel of hydrocarbon pore space with reservoir pressure and temperature, and initial total gas-oil ratio. The second equation is the correlation of stock-tank oil in place per barrel of hydrocarbon pore space. The third equation relates stock-tank oil production (to 500-psia depletion pressure) with pressure, temperature and oil gravity. All three correlations are also presented in convenient graphical form. Gas production to 500-psia depletion pressure is approximately 92.6 per cent of the gas in place for each fluid, so no correlation was developed for gas production. INTRODUCTION The rate of discovery of shallow, low-pressure and low-temperature oil reservoirs in the United States has been declining in recent years. For this reason, the search for oil has gone to greater depths where high pressures and temperatures are encountered. A high-pressure and high-temperature reservoir is the environment in which many rich gas condensates and highly volatile oils are found. Because of this trend, the performance prediction of such reservoirs has become an important task of the reservoir engineer. The need and usefulness of a performance correlation based on field data that are available from the usual well-completion tests have previously been established. These earlier attempts have shown that the phase behavior of rich gas-condensate systems and volatile-oil systems can be correlated with fluid properties, pressure and temperature. However, very little information on gas-condensate depletion performance5 was available at the time of these earlier attempts. The availability of more recent data has made possible the development of an improved correlation. The data, as listed in Tables I and 2, are for 25 gas-condensate and two volatile-oil systems that were studied. The problem was to correlate the data for in-place fluids and the production data with the initial total gas-oil ratio, initial reservoir pressure and temperature, and stock-tank oil gravity. These correlations were obtained by multiple regression analysis, whereby the data were fitted to an equation by the method of least squared error. BASIS OF THE CORRELATIONS 1. The data used in the development of these correlations were obtained from depletion-performance calculations6 and well-test or production measurements. 2. All of the independent variables used in the correlations are available from the usual well-test completion data. 3. The reservoir volume considered is 1 bbl of hydrocarbon pore space (HCPS). 4. The gas-oil ratio used is the total standard cubic feet of gas (at 14.7 psia, 60F) coming off the entire separator train per barrel of stock-tank oil. This minimizes the effect of separator conditions which might vary from system to system. 5. The correlated pressures are the actual reservoir pressures which might or might not be the saturation pressure of the reservoir fluid.

Jan 1, 1966

By F. I. Stalkup

Vapor-liquid phase equilibrium experiments have been conducted in a static equilibrium cell on mixtures of a light, 45 API stock- tank gravity reservoir fluid and a rich hydrocarbon gas containing approximately 55 mole per cent of intermediate hydrocarbons. Both apressure-vs-composition study of the gas and a simulated reservoir fluid, and a multiple-batch contact simulation of the condensing-gas-drive oil recovery process were performed. In the latter experiments equilibrium gas and liquid compositions were analyzed. Also, conventional, "condensing-gas-drive", long-tube displacement experiments of the reservoir fluid and gases of various richness were performed. The results of these experiments could not be satisfactorily interpreted by the conventional pseudo-ternary-diagram representation of multicom-ponent phase behavior. The results seem to be explained better by considering a bubble-point surface and a dew - point surface joined in a plait-point locus. Portions of the plait-point locus cannot be "seen" directly by the rich hydrocarbon gas because of curvature of the dew-point surface. In such a system, continuous injection of the rich gas over stationary reservoir fluid might form a zone of contiguously miscible compositions from pure rich gas to pure reservoir fluid by: (1) saturating the reservoir fluid with injected gas to the bubble-point surface; (2) creating by mass transfer with fresh injected gas a path of contiguously miscible compositions along the bubble - point surface to the plait-point locus; and (3) creating by mass transfer with additional injected gas a path of gas compositions along the dew-point surface up to the point where direct miscibility results between dew-point fluid and the injected rich gas. INTRODUCTION The use of the pseudo-ternary-phase diagram to illustrate miscible displacement phase behavior has been discussed by several authors.5,7 Such a representation of phase behavior is not rigorous, but the ternary diagram nevertheless gives a qualitative picture of what actually occurs in a miscible displacement process. Fig. 1 is a typical illustration of miscible displacement phase behavior by a ternary diagram. The multicomponent hydrocarbon system is divided into three pseudo-components: a light fraction containing methane and nitrogen, an intermediate fraction containing ethane through hexanes plus carbon dioxide, and a heavy fraction containing heptane and heavier components. A two-phase region is bounded by a dew-point curve and a bubble-point curve, which are joined at the critical point. The concept deduced from such a representation for miscible displacement by a condensing-gas-drive process is as follows: a rich gas G, which lies to the right of the limiting tie line through the critical point C, is injected into the reservoir and contacts reservoir fluid L, saturating the reservoir fluid to give bubble-point fluid L1 and equilibrium dew-point gas GI. Continued injection of rich gas changes the composition of the saturated liquid L1 through a series of liquid compositions lying along the bubble-point curve, until the critical composition C is reached, at which point direct miscibility with the rich gas is achieved. Some equilibrium gas with compositions lying along the dew-point curve from G1 to C is also formed in this process. Thus, continuous injection of rich gas forms a

Jan 1, 1966

By R. E. Coleman

The molecular species occurring at the mineral-reagent interface of the galena-aqueous potassium ethyl xanthate system was studied by developing a technique for using an attenuated reflection method in conjunction with standard infrared spectroscopy procedures. Lead ethyl xanthate was detected from the infrared spectra of all galena surfaces treated in the pH range of 7 to 11. At pH 8.5, lead ethyl xanthate formed as a film chemically bonded to the galena surface. A solvent extraction sampling method was employed with infrared spectroscopy to obtain quantitative data on the lead ethyl xanthate removed from the galena surface. The data showed that between pH 7 and 11 thy quantity of lead ethyl xanthate physically adsorbed decreased as the pH was decreased; in the same pH range, the quantity of free lad ethyl xanthate in the aqueous medium remained constant, and the amount of unreacted xanthate varied.

Jan 1, 1966