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By Dennis E. Stover

Grade control for in situ uranium leaching is maintaining, at desired levels, the uranium concentration in the pregnant lixiviant which feeds the extraction (ion exchange) circuit. This differs from grade control in conventional mining in that in situ grade control is imposed subsequent to rather than prior to leaching without the direct observation and control possible in conventional mining and milling. Grade control is a necessary engineering task through the entire project life, beginning with preliminary evaluation and design and ending only when the final wells are shut in. More specifically, this task is associated with designing the initial well field, maintaining productivity during well field operations, and planning well field expansions to compensate for the depletion of existing wells. Our aim during each of these phases is to maximize uranium productivity while ensuring that we are developing information necessary for future phases. Throughout this task, we remain cognizant of the fact that uranium productivity is a function of both the complex geologic and operational parameters of the project. A minimum list of significant geological factors must include the following: . Host formation mineralogy . Uranium mineralogy . Permeability . Ore quality (grade and thickness) Our concerns are not limited to average or general descriptions of these factors. The interactions among the factors as well as localized variations among them are far more important in obtaining high productivity from a deposit. For example, an ore body may display an average permeability of one darcy but have its high grade ore confined to regions with permeabilities less than 500 millidarcies. This relationship between ore grade and permeability must be understood early in the project life if the operation is to be successful. Similarly, the fundamental operating parameters for the well field include those items which enable us to distribute the lixiviant within the ore as well as the chemistry which will dissolve the uranium minerals. A minimum list of such factors will include: . Well design . Well efficiency . Well bore damage . Pattern size and shape . Oxidant type and concentration . Complexing agent concentration - pH The interactions between these variables and the complex geological variations create a situation which often defies quantitative analysis. Hence, we have adopted a statistical approach when correlating production history with these parameters and the quality of the correlations improves as the number of wells operated increases. However, the correlations are often specific to an ore body. We find that we must tailor the process to meet the unique geologic parameters of each ore body. PHASE 1: INITIAL WELL FIELD DESIGN Designing the initial well field is perhaps the most difficult phase because we have the smallest data base from which to predict performance. We will have conducted numerous laboratory tests and, perhaps, field pilot tests to select the lixiviant system and to characterize the geologic parameters. However, we will learn a great deal more about the deposit and its productivity during actual commercial scale operation. Fully acknowledging its limitations, we will, as a starting point, assume that uranium productivity will be directly proportional to the quality and quantity of recoverable reserves. Future deviations from this assumption will be plentiful and result from our limited understanding of the aforementioned interactions between and among the operational and geological factors. However, in planning the initial field, estimation of the quantity of leachable uranium present at levels above the economic grade and grade-thickness limitations is a priority task. (The concentration of uranium in the ore, the ore grade, is expressed in units of weight percent. The grade-thickness of the ore is the product of the average grade and ore thickness expressed in units of percent-feet.) These parameters provide a direct indication of the quality and quantity of ore. They are determined from gamma logging of closely spaced drill holes (50 to 100 foot centers being typical) accompanied by uranium core analysis or direct uranium assay logging. Gamma- logging measures gross gamma radiation which emanates from uranium decay products and indicates only the possible presence of uranium. Direct uranium assays are necessary to confirm this presence and the true location and quality of the reserve. From this information, an estimate of the in-place uranium reserve is formulated. Utilizing the above data, we begin to assess the quantity and quality of the leachable reserve. Analysis of self-potential and resistivity logs in conjunction with uranium logs will identify those zones which contain uranium and display apparent high permeabilities. Similarly, zones with extensive calcite cementation or dense clay sedimentation are located and uranium within such zones is excluded. (Interpretation of these logs should be confirmed

Jan 1, 1980

By N. T. Cotman, C. H. Pickering, P. B. Crawford

A beat-conduction model has been developed to study the flow of fluids in a stratified oil reservoir which is being subjected to unsteady-state depletion. To simulate stratification, plates of different metals were joined together so that cross flow could occur between strata. A description of the model, plate construction and necessary instruments is included. The data indicate that stratified oil reservoirs experiencing cross flow may be treated as a single, homogeneous, producing sand having properties intermediate between those of the layers making up the system. A technique for averaging core-analysis data to arrive at the proper average value of rock permeability and porosity is presented INTRODUCTION Although oil has been produced from reservoirs for 100 years and reservoir injection processes have been undertaken for 40 years, the industry is still inadequately informed on the problem of reservoir inhomogeneities. Stratification is perhaps the best-known type of reservoir heterogeneity. Urenl discussed the possible significance of this nonuniformity in his 1927 paper on the theoretical aspects of water flooding. Since this time the problem of vertical permeability variations has been the subject of much discussion and numerous papers. Levorsen2 simply describes the origin of layered beds in his Geology of Petroleum. Some beds are field-wide and may be traced from well to well, while others apparently pinch-out and become discontinuous. In addition, the physical characteristics of a layer may vary from place to place. For these reasons, a stratified system is not easily defined. In calculations involving oil reservoirs in which permeabi1ities vary, methods presently used contain many simplifying assumptions. The reservoir frequently is considered as consisting of permeable layers, each of uniform vertical and lateral permeability and each behaving as if separated from adjacent layers by thin impermeable layers. Other assumptions frequently made in reservoir calculations are steady-state flow conditions, unit mobility ratio, linear geometry, average or homogeneous porosity, and negligible capillary-pressure and gravity effects. Muskat3 has. developed solutions to the stratification problem for mobility ratios other than unity for both linear and exponential permeability distributions. He assumes lateral uniformity and continuity of all productive strata and does not consider porosity. This study will take into account transient effects, cross flow and varying porosity, as well as the variations in permeability, by means of a heat analogy. Muskat5 has shown the similarity of the equations which describe the flow of fluids in a porous medium to the flow of heat through a solid. Landrum, et al,6 made an analogy between the flow of fluid in an unsymmetrical reservoir and the conduction of heat in a similarly shaped metal plate. This analogy is summarized briefly as follows. If fluid is produced from an oil reservoir above the bubble point, the resulting pressure distribution will be identical to the temperature which would result in a metal or heat-conducting plate if heat were similarly removed. This means that a study of heat flow in stratified thermal models will behave like fluid flow in stratified oil reservoirs. For mathematical correspondencies, set- Ref. 6. The fluid mobility k/p is proportional to the thermal conductivity, and the porosity-times-compressibility product is proportional to the density times specific heat of the thermal plate. EXPERIMENTAL EQUIPMENT AND PROCEDURE The stratified reservoir model used in this study is illustrated schematically in Fig. 1. A Leeds and Northrup Speedomax Type G temperature recorder

By John V. Beall

Homeland of the Republic of China, the island of Taiwan looks on the map like a seal, muzzle pointed south, resting complacently on the emerald waters of the China Sea. Any notion of placidness is quickly dispelled by going to that country where the visitor gains the impression of almost violent busyness in tearing up streets, pushing up buildings and tilling the fields. Driving from the airport downtown to Taipei, the capital city, one sees roads, streets and thorough-fares which seethe with bizarre traffic. From water buffaloes to buses, transportation takes every conceivable shape, size and color in between. The load being transported need not conform in any way to the capabilities of the vehicle. Twenty- foot lengths of pipe may be trans- ported on a bicycle. A family of five may go to town on a motor- cycle. Impossible? Count them. The streets and buildings of the city appear unrestrained, or without margins. Shops do not end at the doorway but overflow with a variety of goods onto the sidewalks and into the streets where the marginal traffic, on foot or on wheels, intertwines unconcernedly with the flotsam from the shops. Signs, dry goods, hardware and the continuous hubbub make the view colorful, lighthearted and fascinating. The island is 230 miles long by 75 miles wide with a central mountain spine. To the east, the mountains descend steeply to the ocean whereas to the west, beyond the foothills, there is a broad coastal plain. Only about 25% of the land is suitable for cultivation but the tropical climate permits several harvests a year. At the same time the mountains, which are high enough to sometimes have snow, offer an agreeable change of temperature. In this setting, society has created an economy that is growing at such a rate on all fronts that it would seem to be fairly bursting at the seams.

Jan 9, 1969

By Persifor Frazer

It has been the aim of the writer, by measuring his base line on the territory of theoretical chemistry, to attempt to fix by triangula tion certain points within the domain of mineralogy. As the barest first experiment in this direction, a few of the hydrated oxides of iron have been selected, their theoretical construe tion reduced to percentage of the constituents into which the ordinary analytical methods would resolve them, and the results compared with actual analyses compiled from the most reliable sources; the accidental errors being as much as possible eliminated. This method seems to be a simple one and one easily pursued, but, as will shortly appear, it is beset with grave difficulties, all of which the writer does not pretend to have satisfactorily surmounted. In the first place arises the important question, what are we to understand by the hydrated oxides of iron ? In all books of chemistry and lexicons of minerals, the proposition, long ago taught by the earlier chemists, that water might exist in two forms of combination, viz., as water of crystallization or as water of constitution, is tacitly assumed. There is nothing in the principles of the new chemistry which is opposed to this; for (to carry the mind's eye into the process of con struction of the least units into which a definite chemical compound is capable of being divided without losing its characteristic proper ties), however unlikely it may seem, it is, nevertheless, possible that a given molecule of iron may, under certain conditions of heat, pressure, etc., attract to itself as many molecules of the water in which it is natant as: from the relative size, shape, attractive force, etc. of either, it is capable of taking up, and this complex system of associated molecules might oscillate as a physical unit so long as the conditions on which its existence was dependent remained unchanged. Moreover, it is highly probable that the first effect upon such a mole cule produced by physical or chemical forces would be to separate it into two or more simple ones of different kinds, while a further ap plication of these forces might rend asunder the bonds of the simpler compounds themselves.

Jan 1, 1879

By Persifor Frazer

(Read at the Amenia Meeting, October, 1877.) IT has been the aim of the writer, by measuring his base line on the territory of theoretical chemistry, to attempt to fix by triangulation certain points within the domain of mineralogy. As the barest first experiment in this direction, a few of the hydrated oxides of iron have been selected, their theoretical construction reduced to percentage of the constituents into which the ordinary analytical methods would resolve them, and the results compared with actual analyses compiled from the most reliable sources; the accidental errors being as much as possible eliminated. This method seems to be a simple one and one easily pursued, but, as will shortly appear, it is beset with grave difficulties, all of which the writer does not pretend to have satisfactorily surmounted. In the first place arises the important question, what are we to understand by the hydrated oxides of iron ? In all books of chemistry and lexicons of minerals, the proposition, long ago taught by the earlier chemists, that water might exist in two forms of combination, viz., as water of crystallization or as water of constitution, is tacitly assumed. There is nothing in the principles of the new chemistry which is opposed to this ; for (to carry the mind's eye into .the process of construction of the least units into which a definite chemical compound is capable of being divided without losing its characteristic properties), however unlikely it may seem, it is, nevertheless, possible that a given molecule of iron may, under certain conditions of heat, pressure, etc., attract to itself as many molecules of the water in which it is natant as from the relative size, shape, attractive force, etc. of either, it is capable of taking up, and this complex system of associated molecules might oscillate as a physical unit so long as the conditions on which its existence was dependent remained unchanged. Moreover, it is highly probable that the first effect upon such a molecule produced by physical or chemical forces would be to separate it into two or more simple ones of different kinds, while a further application of these forces might rend asunder the bonds of the simpler compounds themselves.

Jan 1, 1878

By Sidney H. Haughton

FOLLOWING the discovery of diamonds in 1870 and the Witwatersrand gold fields in 1886 South Africa changed from a predominantly pastoral country with a scattered white population into a land whose economy came rapidly to be based primarily on mining. The total value of the mineral output of the Union in 1944 was approximately $493,000,000, to which gold contributed 84 per cent. Gold furnished some 33 per cent of the Union Government's total revenue in that year, and approximately half the country's population obtained its livelihood directly or indirectly from the gold mining industry. In any review of the Union's mining activities and in any consideration of the country's future, gold mining must occupy a prominent place. It is generally conceded that the present structure is not properly balanced and that an economy based on a preponderance of a single nonpermanent factor possesses potentialities of serious instability.

Jan 1, 1946

By AIME AIME

THE 1944 Chairman of the Institute of Metals Division might be classed as metallurgically ambidextrous ; he is teacher of theory and practice of both nonferrous and ferrous metallurgy, and he is consultant on brass and on highspred steel. Arthur Phillips was born in Troy N.Y. and attended the New Haven Connecticut high school. Upon graduation he entered Yale, receiving a degree in metallurgy in 1913. At that time Professor Mathewson was starting his plan of '"co-operation with the metal industries in metallographic work at the Hammond Laboratory of the Sheffield Scientific School, Yale University, and Arthur Phillip, became the first co-operative graduate student, working in the laboratory of the Bridgeport Brass Co., and receiving his Masters of Science degree in 1915. A little later, when the department of metallurgy at Yale was expanded. Me. Phillips was appointed assistant professor. In 1928 he was made associate professor, and in 1934 he was promoted to full professor.

Jan 1, 1944

By R. B. G. Yeo

The effects of alloy additions on the M, and A, temperatures of an Fe-22.5 pct Ni alloy have been determined. Increasing amounts of titanium, colum-bium, vanadium, and silicon raise and then lower M,while raising A, cmtinuously. Cobalt raises both M, and A,. Aluminum has little effect on Ms but raises A,. Chromium md nickel lower M, and A,. It is proposed that elements raise M, in accordance with their effect on the Ae3 temperature of iron until the lattice becomes stiffened against the shear transformation so that M, is then lowered. An anomaly, first pointed out by Zener,1 arises in steels when the addition of elements, such as molybdenum and tungsten, which raise the Ae3 temperature, also lower the M, temperature.2'3 During the development of a series of martensitic precipitation-hardening (maraging) steels, the effect of several elements on the transformation of austenite to martensite was studied. The results show that under suitable conditions several elements which raise Ae3 also raise the M, and A, temperatures. PREPARATION OF MATERIALS STUDIED A series of alloys was made in which cobalt, titanium, columbium, vanadium, silicon, aluminum, molybdenum, chromium, and nickel were added to an iron base containing 22.5 pct Ni. The compositions of the alloys prepared are given in Table I. The residual manganese contents of the heats were in the range of 0.030 to 0.35 pct, silicon 0.05 to 0.1 pct, carbon 0.0008 to 0.009 pct, and nitrogen from 0 to 0.004 uct. The allois were made as 50-lb induction heats starting with electro-iron and electro-nickel, melted in air to oxidize impurities. Additions of silico-manganese and ferro-silicon were made after which the power was turned off to allow the products of deoxidation to rise and be skimmed from the surface of the melt. The furnace chamber was pumped down to a pressure of 5 p and the charge was heated to 2900°F for the addition of other alloying elements. The heats were poured into five 10-lb ingots, making successive alloy additions to each. The ingots were soaked for 2 hr at 2300°F and hot-worked to 3/4-in.-diam bars. This stock was heated to 1500°F for 1

Jan 1, 1963

By R. I. Williams

Kennecott Copper's mining activities in Arizona are conducted by the Ray Mines Div., located in Ray, Ariz., in the Mineral Creek mining district about 60 miles southeast of Phoenix. The Ray orebody lies in a mineralized zone belted on the east, west, and north by well defined faults. The orebody consists principally of schist with intrusions of quartz porphyry and diabase. The dominant ore mineral in the schist and quartz porphyry is chalcocite, with some native copper, and in most areas the orebody has been heavily oxidized. In the diabase the dominant ore mineral is chalcopyrite. Ore deposition in the schist portion is very erratic, with no apparent structural explanation. In 1873 silver prospectors opened the mining district, but it was not until 1899 that an English company made the first major attempt to exploit the copper deposits. This venture failed because of improper sampling and limited development work. In 1904 D. C. Jackling, Seeley Mudd, and Philip Weiseman became interested in the Ray Copper Co. and the Gila Copper Co., which later merged as Ray Consolidated Copper Co. In 1926 the Nevada Consolidated Copper Co. took over Ray Consolidated and in turn was taken over by Kennecott Copper Corp. in 1933. The extensive program of surface and underground development and exploration begun in 1907 continued through successive changes of management and ownership to the present time.

Dec 1, 1956

By J. R. O’Connor

Stimulated emission from Nd+3 in yttrium uanadate fYVOJ is reported. Single crystals of YVO4:Nd, obtained from Linde Col-p., have improved substantially in the last several months. Pulsed thresholds of YVO, laser rods are now approximately 2 to 3 5, cowparable to tliose for YAG:Nd. Yttrium uanadate crystalli~es irz a space group similar to zircon. All rare-earth vanadates have this structure. Rare-earth ions sucll as Nd+3 which substitutes for Y+3, aye situated irz a strong tetragonal crystal field which lacks inversion symmetry. This condition increases the p'robability of the parity-forbidden f — f transitions. Yttrium anadate has strong absorption bands beyond -1000A. These are clue to Y-O, V-O charge transfer and molecular transitions. Under 2537 and 3660A irradiation pure YVO, fluroresces u bright yel-LOLO. This fli&orescence is corrzpletely quenched in YV04:Ncl crystals. This and other evidence of energy trut~sjer from the lattice is repovted. Optzcul atz 1user pvope 1-ties o! YI'U4:E[t are brieJy described. THIS paper describes some of the optical and laser properties of Nd+3- and Eu+3-doped yttrium orthovana-date (YVO4). It reports laser action for the first time in this low-symmetry host. For some time we have pursued a research program concerning laser hosts' wherein the rare-earth (RE) ion is situated at a site of low crystal symmetry so as to increase the probability of radiative transitions. Single crystals of doped and undoped YV04 are grown from iridium crucibles in an oxyhydrogen gas-fired furnace by a modified Czochralski technique.' This material crystallizes in a D4li tetragonal space group of the zircon (ZrSiO,) type.3 All RE vanadates have the same structure and form solid solutions with YVO4. Therefore, it will be possible to investigate a variety of cross-pumped laser systems, as in the case of yttrium aluminum garnet (YAG).4 At present, ~d'~-doped YAG is one of the most efficient solid-state lasers.5 Accordingly, most of the material to follow will compare the properties of YV04 to those of YAG. Fig. 1 shows the relative transmission of YAG and two types of YVO4. "Pure" YVO4 has a normal absorption edge and is colorless. A second type has a broad absorption peaking near 4200A and is yellow. Rubin and Van uitert6 suggest the yellow material is slightly reduced. Samples of each type are being investigated by electron spin resonance,7 but these studies are so far inconclusive. The pulsed laser threshold is much lower in the yellow material than in the colorless. Therefore, the absorption at 3500 to 5000.4 transfers energy to the Ndi3 ions. Photons of wave length between 2000 and 4500A cause undoped YVO4 to fluoresce at 4800, 5250, 5460, 5540, and 5750A. This emission, previously reported by Brixner and Abramsom,8 is partially quenched by EU'~ and completely quenched by Ndt3 at room temperature due to energy transfer from the lattice to the RE ions. At low temperatures, some lattice fluorescence is present. This implies that the energy-transfer process is in part phonon-assisted. Although the YVO, single crystals used in this work were prepared from Y2O3 containing less than 0.01 pct rare-earth impurities, there is aopossibility that emission lines between 4800 and 5750A are due to dysprosium, terbium, and so forth. However, these lines are not observed in other compounds, prepared from Y2O3, such as YP04, Y2MoO6, and so forth. Furthermore, extensive absorption measurements on our "pure" YV04 single crystals between 0.4 and 5.0 failed to reveal any characteristic rare-earth lines. Fig. 2 compares the absorption spectra of Ndt3-doped YAG and YVO4from 0.6 to 1.0 . The Ndt3 absorptions are labeled according to free ion, R-S coupling. These term designationsQ are appropriate for YAG:Nd. They appear to be inappropriate for YV04:Nd. In YVO, neodymium must substitute for yttrium. The yttrium site is situated In a strong tetragonal field, where point symmetry is (42m) or possibly lower.1° However, the reduced splitting of the Stark components of the YV0,:Nd spectrum implies that the NdT3 ion is in a cubic site. The only plausible explanation for this discrepancy is that the Ndt3 ion is in a low-symmetry site, lacking inversion symmetry, so that a substantial admixture of 4f and 5d wave functions occurs. In this case, R-S coupling is not valid and J is no longer a good quantum number." Consistent with this view, the 4~ metastable level of YV04:Nd has an oscillator strength larger and a

Jan 1, 1968

By W. A. Backofen, D. Lee, F. S. Jabara

THE empirical character of plasticity analysis insures a continuing need for measurements of the yield surfaces of anisotropic materials. Recently, Wheeler and Ireland (W-I) proposed that an octahedral yield locus could be constructed on the basis of six Knoop hardness indentations. Such simplicity would have obvious appeal, if it led to consistently dependable results. In other recent work, a much more straightforward (and more tedious) method of measurement was used to establish all quadrants of the plane-stress yield loci for two substantially anisotropic titanium alloys.2,3 The same materials have since been reex-amined by the W-I method with results being reported here. A full description of the stress state under a Knoop indentor would be complex. In principle, however, this can be avoided in relating the hardness number to a plane-stress yield locus, by the expedient of superimposing the appropriate hydrostatic component on that state of stress. Six possible orientations of in-dentor on orthogonal (symmetry) planes, along (principal) coordinate directions, are illustrated in Fig. 1(0). Pictured in Fig. l(b) are normal-stress components nominally associated with indentation n: o2(H), directly proportional to the Khn in this case, together with By overlaying a hydrostatic tension, ah, that in general is equal to the stress state around the indentation is reduced to one of plane stress in the x-y plane for which the stress ratio is a The key step in the W-I yield-locus construction is to represent the Khn for any indentor orientation as a vector quantity on the octahedral plane. In the plotting, the vector is given as deviatoric stress components along the principal axes in the ratio , where represents the direction of the minor (width) diagonal and 1 that of the major (length) diagonal. There is no attempt by W-I to justify the 7/1, although it might be supposed that the value originates in the usual ratio of major to minor diagonals in a Knoop indentation of about 7/1. If that were its origin, the link to the deviatoric stress ratio would presumably be made by first taking 7/1 and then turning to the Levy-Mises equation for isotropic material: Interpreted in this way, the W-1 approach seems arbitrary and even contradictory. Yet it would still be favored by two circumstances: the deformation under a Knoop indentor approaches plane strain: when dcw/del =a; and the shape of the locus where plane strain is represented is not overly sensitive either to the exact value of dc,/dcl or to the degree of anisotropy, within a rather wide range of both variables. The second point is illustrated below, after a few additional comments on applying hardness

Jan 1, 1968

By John P. Bryant, Samuel Kincheloe

Plant nutrients are obtained by plants from both the air and the soil. Carbon dioxide, a gaseous form of carbon and oxygen, supplies the carbon which usually makes up 50% or more of plant structure. Plants are capable of absorbing carbon dioxide directly from the air. Most of this nutrient comes from the air, although some carbon dioxide is absorbed by soil water and taken into the plant as liquid. Growing plants use more water than any other substance. Plant nutrients in the soil dissolve in soil water; soil water entering the plant carries nutrients into the plant structure. Water is then given off into the air as the plant breathes or transpires. Inorganic or mineral nutrients essential to plants are supplied through the soil. Inorganic or mineral composition of plants usually is less than 5% of their weight. In most crop-growing areas, much of this nutrition is inadequately supplied from the soil and must be provided by fertilizers. Proper fertilization of a soil to improve its mineral level and productivity is the role of the fertilizer industry. The 13 essential plant nutrients which often must be added to soils or plants and are generally considered fertilizer minerals are categorized as primary minerals (nitrogen, phosphorus, and potassium); secondary minerals (calcium, magnesium, and sulfur); and micronutrients, or trace minerals (boron, iron, manganese, copper, zinc, molybdenum, and chlorine). These classifications are based on quantity of nutrients utilized by plants and have no implication as to function or degree of necessity. One point of major significance to the fertilizer industry is that not all nutrient carriers supply that nutrient in a chemical form which will be available to the plant. Thus, a product which may be considered a fertilizer mineral may require substantial processing or may require substantial processing or treatment before it becomes useful as a nutrient carrier. Fertilizer Industry Scope Until about 1900 demands for higher crop yields were met simply by bringing new agricultural lands into cultivation. Since that time great progress has been made in increasing yields through fertilization and improved varieties and cultural practices. The importance of the fertilizer industry to the economy and welfare of the US is widely recognized. Fig. 1 illustrates the relationship of lime and fertilizers to crop yields. In terms of tons of fertilizer products, the growth of the industry has been phenomenal, particularly between 1950 and 1980. Table 1 shows the increase in fertilizer usage. Primary Plant Nutrients in Fertilizers Primary minerals (nitrogen, phosphorus, and potassium) are designated as such because [ ]

Jan 1, 1983

By D. L. Kelley

High-viscosity water injection has been proposed for use in reservoirs containing high-viscosity crude oils. Previous publications have largely ignored the possible effects of the connate water on the proposed process. This paper describes experimental work which indicates that the connate water will be forced ahead of the injected water to form a bank of low-viscosity water. This decreases the oil recovery which would be expected if such a bank were not formed. These effects are shown for a range of fluid mobilities and connate-water saturations for a five-spot injection system. In general, oil recoveries using viscous water are significantly greater than for untreated water even though they are less than would be expected if no connate water bank were formed. INTRODUCTION The effect of mobility ratio on the oil recovery of wa-terfloods has been known for many years. Muskat first pointed out that the fluid mobilities (k/µ) in the oil and water regions would affect the performance of the water-flood, and he estimated the general effect of these variables.' Since this early work, studies of the effect of mobility ratio on secondary recovery have been reported where mathematical,' potentiometric3 and scaled flow models' were used. These studies have shown that a reduction in the mobility ratio between the oil and the displacing fluid would cause additional oil recovery when water-flooding reservoirs containing viscous crude oils. Studies reported by Pye- nd Sandiford 8 have indicated that chemicals to increase injection water viscosity are now available and can be used to reduce the over-all mobility ratio of a waterflood. Where mobility ratios are controlled by the injection of viscous fluids, the connate water of the reservoir can play an important part in the displacement of the reservoir oil. The purpose of this study was to determine the effect of the connate-water saturation in waterfloods where viscous waters are used for injection. DISPLACEMENT OF THE CONNATE WATER Russell, Morgan and Muskat7 were the first to recognize the mobility of connate waters in waterflooding. They conducted waterfloods on oil-saturated cores containing 20 and 35 per cent irreducible water saturations, and found that from 80 to 90 per cent of the "irreducible" water was produced after only one pore volume of water was injected. However, their experiments were conducted at rates of flow significantly higher than those ordinarily occurring in waterfloods. Also, the cores were only from 4.0 to 8.5 cm long. Brown 4 studied a 100-cm linear sand pack which had been prepared to contain connate water and oil. He used 140- and 1.8-cp oils with injection water of essentially the same viscosity as the connate water. He found that all of the connate water was displaced by the injection water in both cases. However, the injection volumes required for complete displacement of the connate water were considerably higher in the case of the more viscous oil. To verify the results of the foregoing experiment, a 10-ft-long linear model was constructed by packing 250-300 mesh sand in a 1/2-in. diameter nylon tube. The model was evacuated, saturated with a brine of 1-cp viscosity, and flooded with a 41-cp mineral oil to the irreducible water saturation of 10.9 per cent. The model was then waterflooded by the injection of a water solution which had an apparent viscosity of 42.6 cp. The solution consisted of 0.5 per cent methylcellulose in distilled water. The viscosities of the oil and connate water were measured with an Ostwald viscosimeter. The viscosity of the polymer solution was calculated by Darcy's law using pressures measured during actual flow conditions. The ratio of the mobility in the oil region to the mobility in the inject ion-water region was approximately 0.32. The mobility ratio of the oil region to the connate-water bank was approximately 14. The mobility ratio between the connate-water bank and the injection water region was 0.024. Approximately 84.5 per cent of the recoverable oil was produced before water breakthrough. Immediately following breakthrough, oil and connate water were produced at an increasing water-oil ratio until the viscous injection water broke through. At viscous-water breakthrough, 96 per cent of the original connate water had been produced. After breakthrough of the viscous water, there was no additional production of connate water or oil. The near-

Jan 1, 1967

By C. Richard Tinsley

INTRODUCTION Project financing has been defined by various authors in this book. It is founded on reliance upon the project's own future cash flows and secondarily on the collateral value of the asset base developed. It is chiefly provided by the banking community who, after an assessment of the risks involved (See Chapter 9) analyse the company's presentation (See Chapter 10) in order to structure a financing package often at a leverage of up to 80% debt. This paper describes the various support and structuring techniques used to delimit and abate the risk components perceived from the banks' experience on project development especially for the period before cash flow is generated (pre completion). ADVANTAGES The advantages of project financing extend beyond the offloading of risks to banks. Among the advantages are the following: 1. Longer loan maturity than conventional, unsecured financing; 2. Loan disbursement and repayment tailored to specific mine; 3. Ability of a joint venture without a "track record" to raise financing; 4. Obtain financing where further direct borrowing (corporate credit) limited by existing indentures; 5. Possibility of arranging finance off-balance sheets; 6. Leverage return on equity; 7. Obtain tax savings with certain project financing structures; and 8. Obtain flexible loan repayment conditions. It can also be said that from the point of view of the company, project financing has certain disadvantages which can be summarised as follows: 1. Perceived higher cost (risk premium) compared with straight corporate credit; 2. More documentation; and 3. Need to negotiate risk-sharing aspects. The main attraction of project financing is the ability to pass certain risks on to the lenders within a flexibly funded transaction. (For a more detailed description of the specific risks see the author's paper at the beginning of Chapter 9. The same risk system is followed here.) The typical project financing has corporate support prior to completion and will usually carefully control the resultant cashflow after completion to ensure the bank does not unnecessarily assume further risks of an equity nature. WITHIN THE COMPANY'S CONTROL Operating Risk This is broken into three interrelated segments for ease of description. Technical Component: This must be specifically addressed if new technology or unproven adaptations are to be used. The banks will have scrutinized the sampling and bulk testing work, perhaps grilling the geological, mineral processing, metallurgical, and mining engineering staff or consultants directly. A number of supports are available such as: TECHNOLOGY GUARANTEE: Either the company itself or the process developer will guarantee that the technology will work for a period of, say, six months to two years after startup. If not, then financial penalties will apply although these are rarely sufficient to repay the loan. Many process developers are weak financially and may have little substance to back such a guarantee.

Jan 1, 1985

By Thomas L. Kesler

IF all of the 14 million tons of kaolin produced in Georgia through 1949 had been mined from a single deposit 20 ft thick, it would represent a mined-out area of less than 1 sq mile. This measure of depletion is in such strong contrast with the large size of the area shown in Fig. 1, from which most of the output has come, that there has developed an optimistic outlook concerning future supplies of kaolin equal in grade to that already mined. Dozens of mines are widely but not evenly distributed within this area, which consists mostly of parts of Twiggs, Wilkinson, and Washington counties. There are scarcely half a dozen kaolin mines elsewhere in the state that have been appreciably productive, although the areas in which they occur may have good possibilities. Most of the efforts to find new deposits, therefore, will be confined to the area shown in Fig. 1, for it is here that the industry has established its facilities, and prospecting is encouraged by relatively numerous outcrops and opened deposits of kaolin.

Jan 10, 1951

By L. L. Newman

As soon as the Congress recognized the alarming rate at which our domestic oil resources were being depleted during the war, it took action to step up the rate of research and development which the Bureau of Mines had been conducting for several years on the production of synthetic liquid fuels from coals. Under Public Law 290, approved April 5, 1944, funds were authorized for the Bureau to proceed with research, development, design and construction of demonstration plants for the hydrogenation of coal, the synthesis of oil from carbon monoxide and hydrogen, and the distillation of oil from shale. During the latter part of 1944, when it became evident that the collapse of Germany was near, a Technical Oil Mission was organized to study the German techniques of synthetic oil production. Since the cost of hydrogen or synthesis gas is one of the major factors of expense in the operation of hydrogenation or synthesis gas processes, the Bureau of Mines considered it of prime importance to include on the mission gas engineers whose instructions were to examine closely the methods employed by the Germans in solving the problem of providing low-cost hydrogen or synthesis gas for their very extensive operations on synthetic liquid fuels. The Solid Fuels Mission and the Utilities Mission, as well as the Army and Navy Missions, also included teams for the study of German gas production. Although their objectives naturally differed from those of the Technical Oil Mission and from each other, it was recognized that there was considerable overlapping of their fields of investigation. Duplication of effort, however, was largely avoided through the close cooperation between the group leaders of these missions. For example, although I went to Europe as a member of the Technical Oil Mission, my first Gcrman assignment was actually made by Dr. Harry F. Yancey, leader of the Solid Fuels Mission— to investigate the brown-coal gasification methods in central Germany. The art of gasification in the United States and England, and to a large extent in the proximity of the coking-coal regions of Germany and the rest of continental Europe, depends essentially on two stages of operation; namely, carbonization and intermittent water-gas generation. As far as the United States is concerned, complete gasification in a single stage of operation is rarely practiced, except in gas-producer operations where the product is a relatively lean gas consumed close to the point of manufacture, and for water-gas production with anthracite as a generator fuel. Complete gasification of bituminous coal has been the subject of numerous investigations. Many relatively simple modifications of the water-gas generator have been tried to permit the direct gasification of low-cost bituminous coal instead of high-cost coke and anthracite for the production of water gas. Although varying degrees of Success have been achieved and the water gas produced generally has been higher in

Jan 1, 1947

By L. L. Newman

As soon as the Congress recognized the alarming rate at which our domestic oil resources were being depleted during the war, it took action to step up the rate of research and development which the Bureau of Mines had been conducting for several years on the production of synthetic liquid fuels from coals. Under Public Law 290, approved April 5, 1944, funds were authorized for the Bureau to proceed with research, development, design and construction of demonstration plants for the hydrogenation of coal, the synthesis of oil from carbon monoxide and hydrogen, and the distillation of oil from shale. During the latter part of 1944, when it became evident that the collapse of Germany was near, a Technical Oil Mission was organized to study the German techniques of synthetic oil production. Since the cost of hydrogen or synthesis gas is one of the major factors of expense in the operation of hydrogenation or synthesis gas processes, the Bureau of Mines considered it of prime importance to include on the mission gas engineers whose instructions were to examine closely the methods employed by the Germans in solving the problem of providing low-cost hydrogen or synthesis gas for their very extensive operations on synthetic liquid fuels. The Solid Fuels Mission and the Utilities Mission, as well as the Army and Navy Missions, also included teams for the study of German gas production. Although their objectives naturally differed from those of the Technical Oil Mission and from each other, it was recognized that there was considerable overlapping of their fields of investigation. Duplication of effort, however, was largely avoided through the close cooperation between the group leaders of these missions. For example, although I went to Europe as a member of the Technical Oil Mission, my first Gcrman assignment was actually made by Dr. Harry F. Yancey, leader of the Solid Fuels Mission— to investigate the brown-coal gasification methods in central Germany. The art of gasification in the United States and England, and to a large extent in the proximity of the coking-coal regions of Germany and the rest of continental Europe, depends essentially on two stages of operation; namely, carbonization and intermittent water-gas generation. As far as the United States is concerned, complete gasification in a single stage of operation is rarely practiced, except in gas-producer operations where the product is a relatively lean gas consumed close to the point of manufacture, and for water-gas production with anthracite as a generator fuel. Complete gasification of bituminous coal has been the subject of numerous investigations. Many relatively simple modifications of the water-gas generator have been tried to permit the direct gasification of low-cost bituminous coal instead of high-cost coke and anthracite for the production of water gas. Although varying degrees of Success have been achieved and the water gas produced generally has been higher in

Jan 1, 1947

By Charles Stuart

A PAPER on this subject can cover but a limited range. A thorough visualization of the subject would contemplate a comparative analysis of haulage machines and batteries of various types; the relationship of the storage-battery locomotive to other types of mine haulage should be considered and limiting factors in each case should be carefully developed. This paper will briefly deal with these factors. So far as the writer has been able to determine, the first storage-battery locomotives for mine haulage were manufactured in 1897 or 1898 and were tried out in the Pocahontas coal field, but they were not sufficiently satisfactory to justify their continued use. Battery explosions were frequent and caused serious damage to the wiring, electrical equipment, and the clothing and bodies of the motormen. Sulfuric acid was used as the electrolyte. Experiments were then conducted with locomotives bearing reels of flexible cable through which connection between the motors of the locomotive and the trolley wire was maintained. At first, these reels were turned by hand. Later, the reels were revolved by contact with the wheels of the locomotive, being raised out of contact with the wheels, by a lever, when necessary. About 1902, the plan of operating the reel, by chain and sprocket wheels, from one of the locomotive axles, as is still the practice, was devised. The popular floating motor-driven reel had its inception in the Pocahontas fields prior to 1906. The maximum radius of operation of the reel-type locomotive is about 500 ft. (150 m.) from point of connection with trolley wire. This is ample for room work and certain entry work, but the need for a machine that would operate entirely independently of the trolley wire was so great that, with the development of the storage battery, renewed efforts were made to manufacture a successful storage-battery locomotive. About 1908, the gasoline locomotive was introduced. In spite of many objections to this type of machine for such work, the fact that hun¬dreds of these machines were purchased was proof of the need for a machine operating independently of the trolley.

Jan 1, 1922

By S. A. Falconer

One of the outstanding achievements in connection with this country's war efforts has been the ability of our mining industry to supply from domestic sources many of the minerals of strategic importance that formerly were obtained principally from abroad. In order to meet the war-born demands for these scarce minerals, it has frequently been necessary to develop special methods for treating ores and waste products hitherto considered too lowgrade to be workable; and to improve the efficiency of older beneficiation processes. Important in this respect have been the recent technological advances in the field of froth flotation of nonsulphide minerals. Because of the refractory nature of many of these domestic ores, and, in many cases, the limited available technical data regarding their treatment, much research work has been necessary. The following examples describe the procedures and reagents used, and the results obtained, in certain laboratory flotation investigations conducted by American Cyanamid Company's engineers at the Cyanamid Ore Dressing Laboratory on ores containing such minerals as scheelite, manganese oxides and carbonate, ilmen-ite, brookite, kyanite, garnet, spodumene, mica, feldspar, celestite, fluorite, chromite, corundum, and cassiterite. In presenting these data, we wish to point out that many of the minerals listed have previously been tested, and their amenability to flotation reported, by other investigators—notably those of the United States Bureau of Mines. In some instances the procedures and reagents used in the treatment of some of the following described ores follow rather well-established lines, and with one or two exceptions, the reagents used were well known. However, many of the ores tested did not respond well to simple conventional procedures and it was necessary to adopt special methods of conditioning and desliming, reversal of the usual order of floatability of some of the minerals, multiple cleaning, etc., in order to secure separations. Except where otherwise noted, all numbered and trade-marked reagents mentioned in this paper are marketed by the American Cyanamid Co. or the American Cyanamid and Chemical Corporation. Tungsten ORes Tungsten minerals, vitally important in the war industries of the United States, rank high in the list of those we formerly had to import in order to supply our needs. Most of our domestic ores of tungsten contain scheelite as the valuable mineral. Today there are in the neighborhood of twelve tungsten operations in this country where flotation is used as the main or accessory form of benefication. It has, of Course, been known for some time that scheelite and other tungsten minerals respond to treatment by flotation.

Jan 1, 1947

By S. A. Falconer

One of the outstanding achievements in connection with this country's war efforts has been the ability of our mining industry to supply from domestic sources many of the minerals of strategic importance that formerly were obtained principally from abroad. In order to meet the war-born demands for these scarce minerals, it has frequently been necessary to develop special methods for treating ores and waste products hitherto considered too lowgrade to be workable; and to improve the efficiency of older beneficiation processes. Important in this respect have been the recent technological advances in the field of froth flotation of nonsulphide minerals. Because of the refractory nature of many of these domestic ores, and, in many cases, the limited available technical data regarding their treatment, much research work has been necessary. The following examples describe the procedures and reagents used, and the results obtained, in certain laboratory flotation investigations conducted by American Cyanamid Company's engineers at the Cyanamid Ore Dressing Laboratory on ores containing such minerals as scheelite, manganese oxides and carbonate, ilmen-ite, brookite, kyanite, garnet, spodumene, mica, feldspar, celestite, fluorite, chromite, corundum, and cassiterite. In presenting these data, we wish to point out that many of the minerals listed have previously been tested, and their amenability to flotation reported, by other investigators—notably those of the United States Bureau of Mines. In some instances the procedures and reagents used in the treatment of some of the following described ores follow rather well-established lines, and with one or two exceptions, the reagents used were well known. However, many of the ores tested did not respond well to simple conventional procedures and it was necessary to adopt special methods of conditioning and desliming, reversal of the usual order of floatability of some of the minerals, multiple cleaning, etc., in order to secure separations. Except where otherwise noted, all numbered and trade-marked reagents mentioned in this paper are marketed by the American Cyanamid Co. or the American Cyanamid and Chemical Corporation. Tungsten ORes Tungsten minerals, vitally important in the war industries of the United States, rank high in the list of those we formerly had to import in order to supply our needs. Most of our domestic ores of tungsten contain scheelite as the valuable mineral. Today there are in the neighborhood of twelve tungsten operations in this country where flotation is used as the main or accessory form of benefication. It has, of Course, been known for some time that scheelite and other tungsten minerals respond to treatment by flotation.

Jan 1, 1947