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By Kefton H. Teague

Olivine is a mineral containing a mixture of forsterite (Mg,SiO,) and fayalite (Fe,SiO,) in solid solution. The name "olivine" was first applied by Werner in 1790 (Hunter, 1941) because of the olive-green color of the mineral. Uses The principal use of olivine is in various foundry applications. Perhaps the largest tonnage is utilized as a special foundry sand for mold-making in brass, aluminum, and magnesium foundries (Schaller, 1957, 1958; Snyder, 1957). Olivine was first used as an industrial mineral in the early 1930s for a refractory material (Anon., 1970; Hunter, 1941). As a refractory raw material, olivine was first introduced in the United States as handcobbed, selected, shaped blocks of crude olivine. This use met with limited success. More recently, finely ground olivine blended with MgO and pressed into bricks, which are then fired, have found use in glass tank furnaces and open-hearth furnaces. Ramming or gunning mixes for basic furnace linings also utilize olivine. Olivine has been used in ladle linings with varied success. In Europe, substantial tonnages of olivine are utilized in refractory brick for night storage heaters (Anon., 1970). A limited amount of olivine has been used in the past as a fertilizer (magnesium source) and has been fused with rock phosphate to produce a magnesium phosphate as a plant food. The relatively high magnesia (MgO) content of olivine also attracted attention to it as a potential source of both magnesium compounds and as a source of metallic magnesium (Bengston, 1956; Hunter, 1941). Industries using olivine have not standardized specifications. Normally, producers supply a product which meets individual customer requirements. Such requirements involve type and amount of impurities, grain size of product, refractory characteristics, etc. Geology Olivine occurs commonly as accessories in basic igneous and basic metamorphic rocks. Economic deposits are of magmatic origin and are restricted to essentially the dunite variety of periodotite. Dunites are medium to coarse- grained crystalline rocks, generally reddish brown on weathered outcrop, and are composed primarily of olivine.

Jan 1, 1975

By K. E. Gray, M. S. Seth

In Part I of this work,1 equations of elasticity were formulated for transversely isotropic, axisymmetric, homogeneous, porous media exhibiting pore fluid pressure. Equations of elasticity and the thermal analogy method were used to determine transient horizontal, tangential, and vertical stresses and radial displacement in a semi-infinite cylindrical region when either a constant rate of pressure or a constant rate of flow is maintained at the wellbore. In this paper, the approach presented earlier is extended to finite reservoirs for the cases of (1) steady-state flow, (2) constant pressures at the well bore and outer boundary and (3) constant pressure at the wellbore and no flow at the outer boundary. Results of this work show that radial and tangential stress gradients are high near the wellbore but diminish rapidt; away from the well; the vertical stress gradient behaves in the same way but is less severe. Radial stresses are compressive or neutral, whereas tangential and vertical stresses may be tensile, neutral or com-pressive, depending upon the boundary conditions, the physical Properties of the system and the radial distance involved (vertical stresses are always compressive in an unbounded system1. For constant boundary pressures, both radial and tangential stresses increase with time whereas they both decrease for a closed outer boundary and constant pressure at the wellbore. The vertical stress decreases with time for both systems. For steady-state systems, radial displacement may be positive or negative, depending upon the dimensions of the system, the pressure differential and the porosity. Radial displacement may be positive or negative for a closed outer boundary but is positive for constant pressures at both boundaries. INTRODUCTION The importance, utility and complexity of a realistic appraisal of the stress state at and local to a wellbore were indicated in Part I. In this paper the analytical approach presented earlier is extended to finite, cylindrical reservoir geometry for the cases of (1) steady-state flow, (2) constant pressures at wellbore and outer boundary and (3) constant pressure at the wellbore and no flow at the outer boundary. Other than the outer boundary of the reservoir being finite, the physical system and assumptions pertinent thereto are the same as before. The reader may wish to review the mathematical development through Eq. 49 of Part I before proceeding here. SOLUTION FOR GENERAL BOUNDARY CONDITIONS THERMAL STRESSES AND DISPLACEMENTS Since normal stresses do not exist at the free boundaries of a system subjected to thermal stresses, the boundary conditions are

Jan 1, 1969

By John A. Brown

Granules are used primarily as roofing material. From the earliest times, man has been faced with the basic problem of providing protection for himself, his family, and his property against the ravages of the weather. Basically, this problem is no different today than in the past, except that today the trend is to demand shelter which is also colorful and distinctive. There has been a gradual evolution from the thatched roof to the modem ranchstyle home. In his search for a more permanent and more attractive roof, the home owner has utilized many mineral materials. All granules, whether slate or colored granules, are referred to by the asphalt roofing industry as "Slate Granules." Early Roofing Materials The development of mineral roofing in the United States followed two trends: first, the slate industry, and second, the bituminous products. The early colonists were familiar with slab slate construction from Europe and it was natural for them to continue with this type of roofing. As early as 1780, the forerunners of the present bituminous products were finding favor. Those early products consisted of saturating burlap or similar material with crude tar or pitch. This type of roofing was soon improved by dusting a variety of materials on the surface of the roofing to prevent adhesion while in rolls. Such factors as fire resistance and protection from the actinic rays of the sun soon followed. This started the general pattern which is still followed today, that is, saturating felt materials and supplying a uniform grade of crushed mineral to the surface. In commercial and public buildings, metal roofs found early favor. The attractive green color of verdigris-coated copper became a symbol of churches and institutions of learning. Aluminum roofing has become economical for large structures and is finding limited popularity in rural areas. Tile, asbestos, and cement materials, being weather resistant, found early acclaim and are still popular. Today, by far the most widely used roofing materials in the United States are asphalt products. Two important characteristics-economy and weatherability-account for their popularity. Influence of Building Trends on Roofing The postwar building boom in 1947 had many attractive features for the American people. The ranch-style one story type of home seemed well suited for suburban developments which sprang up in such profusion. As the roof in modern home construction is one of the most conspicuous aspects of its architecture, the home owner could now express his tastes not only in paint and landscaping, but could also select an attractive and harmonious roof color. Variety of Minerals Used Many naturally occurring minerals are used today in the roofing industry. Most widely used (and most noticeable to the public) is the granulated mineral surfacing applied to asphalt products. Selected natural colored granules as well as artificially colored granules are

Jan 1, 1960

By R. J. Charles

SEARCH for a consistent theory to explain the relationship between energy input and size reduction in a comminution process has accumulated, over the years, an enormous amount of plant and laboratory data. Although some correlation of these data has been possible for purposes of engineering design and for the advancement of research in fracture, there is still great need of a means of predicting behaviour of a solid when it is reduced in size by mechanical forces. The best known hypotheses proposed to describe the energy-size reduction relationships in crushing and grinding stem from a common origin. The present article analyzes problems of comminution in the light of the precepts of this origin. Its object is to reconcile points of difference between these well known hypotheses and to present relationships more widely applicable to comminution studies. Theoretical Considerations: Most existing relationships between energy and size reduction of a brittle solid stem from a single, simple, empirical proposition.&apos; Although this proposition can be demonstrated by observation and experiment, no theoretical derivation is yet possible. Mathematically, the proposition may be stated as follows: dE = -Cdx/xn [1] where dE = infinitesimal energy change, C = a constant, dx = infinitesimal size change, x = object size, and n = a constant. Eq. 1 states that the energy required to make a small change in the size of an object is proportional to the size change and inversely proportional to the object size to some power n. No stipulations are placed on the exponent n in either magnitude or sign. In 1867 Rittinger2 postulated that the energy required for size reduction of a solid would be proportional to the new surface area created during the size reduction. As far as can be determined there is as yet no physical basis for Rittinger&apos;s hypothesis. Rittinger&apos;s hypothesis can be stated mathematically as follows: E, = K(oa-a-0 . [2] Er = energy input per unit volume, K = a constant, <ti = initial specific surface, and o2 = final specific surface. In the size reduction of particles of size x, to particles of another smaller size, x2, Eq. 2 becomes the well known relation: ET = K&apos; {l/x2-l/xx) [3] where K&apos; is a constant. Eq. 3 may be arrived at from the proposition given in Eq. 1 by integrating and by assigning a value of 2 to the exponent n. J dE = J - C dx/x2 E = Kt (1x - 1x) where K&apos; = C. In 1885 Kick3 proposed the theory that equivalent amounts of energy should result in equivalent geometrical changes in the sizes of the pieces of a solid. For example, if one unit of energy reduced a number of equal-sized particles to particles of one half the size, then the same amount of energy applied to the particles resulting from the first test should result again in a size reduction of one half or a final size one quarter the original size. The Kick concept may be expressed as follows: Ek = K" log x1/x2 [41 K" = a constant and E, = energy per unit volume. The expression for Kick&apos;s law may be arrived at by again integrating Eq. 1 and in this case assigning a value of 1 to the exponent n. dE= J - C dx/x Eh = - C In {x/x2) = K" log (x,/x,) where K" = 2.3 C. Application of Kick&apos;s and Rittinger&apos;s laws to comminution has met with varied success. Gross and Zimmerley4 and Piret5 have shown that Rittinger&apos;s equation applies under certain conditions of experimentation. Walker and Shaw6 express the belief that in metal turning and shaping and in grinding of both metals and minerals the production of very fine particles (less than lP) follows Kick&apos;s hypothesis, whereas Rittinger&apos;s concept is valid for the size reduction of coarse particles. For the practical case of crushing and grinding, however, neither of the above hypotheses has received general acceptance. Bond&apos; has lately proposed that since neither Kick&apos;s nor Rittinger&apos;s hypotheses seem correct for plant design work, an energy-size reduction relationship somewhere between the two would be more applicable. The fundamental statement of Bond&apos;s work

Jan 1, 1958

By Milton Williams

A comparison is made between the amount of interstitial water found by analysis in cores and that estimated from the resistivity curve of the electric log for the corresponding strata of producing reservoirs. It is shown that while the determined and the estimated water saturations are in good agreement in some cases, this agreement may be due to a fortuitous compensation of errors. Estimates of water saturations made from the electric 1og by use of existing relations should, therefore, be employed with caution. Also presented are data on the variation of salinity of interstitial waters in reservoir sands, and on the effect of variation of salinity and porosity on the validity of estimates of water content made from the electric log. INTRODUCTION Throughout the history of electric logging there have been recurrent cycles of optimism and pessimism as to the value of the electric log in the quantitative estimation of reservoir fluid content. The very early days of electric logging were an optimistic period, in which there was widespread faith in the ability of the resistivity curve to reflect fluid content, and in the ability of the potential curve to indicate textural characteristics. In time the accumulation of exceptions to this idealistic behavior brought about a general disillusionment, and caused the more pessimistic of those dealing with electric logs to believe that the sole importance of the log lay in stratigraphic correlation. Within the last several years optimism as to the quantitative use of the electric log has been revived, primarily as the result of the stimulating work of C. E. Archie&apos; on the estimation of interstitial water in sands from resistivity data. Even though the general trend of thought on the quantitative value of the electric log reflects optimism, it is inevitable that there are some widely divergent opinions of the validity of quantitative estimates based on the electric log. A valid method of estimation of fluid content by means of the electric log and a general knowledge of the textural character of the reservoir rock would be of signal importance, not only in that it would save time and money in securing information on reservoirs now being drilled, but also because it would permit the evaluation of reserves in many fields drilled without adequate core data subsequent to the advent of electric logging. Because of this importance, Humble&apos;s Production Research Division, in cooperation with various other company divisions, initiated several years ago series of tests designed to evaluate the reliability of estimates of fluid content made from the electric log. The investigation was limited at the outset to sand reservoirs, since it was felt that the inclusion of limestone reservoirs would entail needless complications. In devising these tests it was immediately apparent that the chief difficulty in evaluating the worth of any method of estimation lay in establishing the true value of fluid content. The results of direct analyses of cores cut with ordinary mud were not sufficient, because of the probability of contamination of the fluids by filtrate from the drilling mud; the results of restored state tests on cores were deemed unsuitable because these results can hardly be said to furnish a primary standard. The method adopted was the direct analysis of cores cut with an oil-base drilling fluid. Such cores, when properly handled, are believed to afford the most precise determination of water content available at the present, and, in addition, lend themselves readily to the determination of various other properties which are pertinent to the estimation of fluid content from the electric log. Since it was desired to compare the fluid contents estimated from the electric log run in ordinary mud with cores cut in the same hole, the use of oil-base fluid necessitated the changing over, after all cores were cut, to a conventional mud. This procedure presented several advantages, one of which was that the use of oil-base fluid permitted

Jan 1, 1950

By C. E. Nelson, T. E. Leontis

THE properties and casting characteristics of sand-cast Mg-Al-Zn alloys, used commercially in this country and abroad, have been discussed in a number of articles during the past few years.&apos;-" In addition, broad surveys of many compositions in the magnesium corner of the Mg-Al-Zn diagram between 0 and 12 pct A1 and 0 and 6 pct Zn have been presented by Busk and Marande7 and by Fox." The purpose of this paper is to furnish a comprehensive survey of the changes in tensile properties, micro-structure, and dimensional stability of two magnesium alloys, AZ92A and AZ63A,+ as a function of aging time and temperature after solution heat treatment. Rates of precipitation in Mg-Al-Zn alloys are slow enough so that a substantially homogeneous, supersaturated solid solution can be maintained even when these alloys are air-cooled from the heat-treating temperature. Consequently, even though it has been demonstrated9 10 that significantly higher strengths can be developed in some alloys in the aged condition by quenching rather than air cooling from the heat-treating temperature, general practice is to air-cool magnesium alloys. All the work discussed in this paper is based, therefore, on aging studies performed on material air-cooled from the heat-treating temperature. This investigation was intended to be a study of commercially practical aging cycles; the tensile properties were determined, therefore, up to aging times of 25-hr duration. The alloys, used in this investigation were prepared in the laboratory by remelting commercial ingots of the appropriate composition according to the procedures described in a previous paper" as the "crucible method." All melts were given the standard superheating treatment in order to insure the maintenance of a uniform grain size of 0.003 to 0.004 in. Standard test bars, 61/2 in. long with a 2½ in. long reduced section having a diameter of Y2 in., were cast from these melts in green-sand molds using a four-bar pattern. The alloys were heat treated according to the following schedules: AZ92A alloy: 500" to 780°F in 2 hr + 780°F (24 hr) AZ63Aalloy: 500" to740°Fin2 hr + 740°F (16hr) In commercial practice," AZ92A alloy is heat treated at 770°F for 18 hr and AZ63A alloy is heat treated at 730°F for 10 hr. The slightly higher temperatures and longer periods of heat treatment were used in order to obtain as homogeneous a solid solution as possible and thus to minimize inconsistencies in the

Jan 1, 1952

By John B. Myers

Vermiculite is the commercial name used to describe a micaceous mineral that expands appreciably when heated. This process, called exfoliation, results in a light weight material. The light weight material is also called vermiculite, or more exactly, expanded vermiculite. Practically all uses of vermiculite are for the expanded material. Composition and Properties Vermiculite, in its natural state, has the characteristic micaceous habit and a perfect basal cleavage and readily splits into thin laminae, which are soft, pliable, and inelastic. The monoclinic crystal faces are often marked by triangular lines at 60° and 120°. The hardness varies from 1.5 to 2 or more, depending on the composition. The specific gravity varies from 2.2 to 2.7; specific heat 0.2; fusion temperature 2,000° to 2,500°F; luster pearly to greasy; color amber, bronze, brown, dark green, and black. Feel is like talc and sometimes soapy when wet. When heated quickly at elevated temperatures, vermiculite exfoliates by expanding at right angles to the cleavage into long wormlike pieces (the name vermiculite is from the Latin vermiculari, to breed worms). This important characteristic of expansion is believed to be a mechanical separation of the layers when the contained water is converted to steam. The increase in bulk volume of commercially prepared material is 8 to 12 times, but individual flakes may expand as much as 30 times. There is no expansion parallel to the cleavage. Vermiculite may also be expanded by several chemical processes such as soaking in hydrogen peroxide, weak acids and other electrolytes. The color changes during expansion. Heat-treated material changes to a light golden bronze or cream color depending on composition. The conditions of heating affect color. Heating in an oxidizing atmosphere produces reddish colors and heating in a reducing atmosphere produces dull gray colors. The iron is generally not oxidized during chemical expansion. Vermiculite is hydrated magnesium-aluminum silicate. Although there has been much research on the chemical and structural composition, there is not yet complete agreement on the exact formula and composition. This is to be expected since vermiculite is not a mineral of fixed composition and different workers have examined different varieties. It has been proposed that vermiculite is not a single species but a family of related minerals. This has also resulted in many names for the particular vermiculite found in a certain deposit. All of this difficulty arises from the very nature of its crystal chemistry. Unlike most minerals, certain crystal structure properties and the chemical composition can be changed by the ordinary forces of nature or in the laboratory. This would suggest that vermiculite be thought of more as a variable mineral rather than a group of related species. It was stated on page 261 of this volume in the chapter on Clay Minerals by H. H. Murray of the Georgia Clay Co., that vermiculite is an equidimensional, expandable clay mineral. Gruner (ref. 14, Chap. 12) showed that the structure consists of a layer made up of two silica tetrahedral sheets with a central magnesium, iron octahedral sheet separated by two layers of water molecules and adsorbed magnesium and calcium ions. Mathieson and Walker,2a in a recent publication, agree that vermiculite must be regarded as a true clay mineral. The characteristic properties of the mineral, such as high cation ex-

Jan 1, 1960

By D. J. Pye

Certain high molecular weight synthetic polymers in very dilute solutions decrease water mobility in porous media 5 to 20 times more than would be expected from the solution viscosity. This indicates that increasing water viscosity to reduce adverse mobility ratios in water floods is economically feasible in many situations. Laboratory results are consistent with accepted theory with respect to improved areal sweep, permeability distribution and displacement efficiencies as would be predicted from the solution mobility measured in the core. The laboratory results have been confirmed by field pilot floods which recovered 80 per cent and 100 per cent more oil than comparative water-flood pilots in fields containing 16 cp and 130 cp oil respectively. Economic analyses based on pilot data indicate the method to be profitable. INTRODUCTION The desirability of improving the water-oil mobility ratio in waterflood-ing operations has long been appreciated, especially for high viscosity crudes. Methods of reducing the oil viscosity by application of heat, gas resaturation and miscible drives have met with some success. Conversely, it has been generally conceded that increasing the water viscosity would also be effective, but the amount of thickening agent required to effect an appreciable increase in viscosity is discouragingly high. The use of such materials as glycerin, sugar, or glycols is completely out of the question economically, so that considerable attention has been given to the use of the much more efficient synthetic water-soluble polymers as viscosity improvers; but even these materials are not economically attractive. If increased water viscosity could be economically realized, marked improvements in areal sweep efficiency, as discussed by Caudle and Wittel and others, would be realized in field operations. Similarly, the improved mobility ratio would bring about increased recoveries by correcting permeability distribution problems as discussed by Stiles2 and Dykstra and Parsons,&apos; and improvements in displacement efficiency would be obtained as recognized by Buckley and Leverett4 and Welge.5 LABORATORY STUDIES THE RESISTANCE EFFECT In the course of research to develop a more efficient water-soluble polymer viscosity builder, we discovered that a very few types of water-soluble polymers exhibited a most unusual and very interesting property not previously observed. Among the earliest materials showing such activity were polymers containing acry-lamide. Fig. 1 shows a typical plot of the solution viscosity vs concentration for one of these polymer solutions as determined in an Ostwald viscometer. As usual, such a plot is an approximate straight line on semi-logarithmic paper. Now, an inspection of Darcy&apos;s law, shows that a viscosity value can also be determined in a formation sample if the pressure, flow rate and permeability are known. If the core permeability is previously determined with wa- ter or brine, then the viscosity of another aqueous fluid may be determined from the equation. The viscosities so determined for glycerin (glycol or polyvinyl alcohol solutions, for example) agree with the viscometer determinations. However, in the case of the water-soluble polymer solutions in which we are interested, the viscosities measured in the formation sample depart very markedly from the viscometer values. A typical relationship for a polymer solution is also shown in Fig. 1. This unusual departure from the expected response is referred to as a resistance property of the polymer and is quantified as "resistance factor". Since the resistance factor R can best be determined in a core under study, the term has been defined on the basis of the ratio of the brine mobility to the polymer solution mobility at residual oil saturation so that:

Jan 1, 1965

By Ernest Klepetko

A notable amount of fossil resin exists in many of the bituminous coal beds of Utah. The upper part of these show a marked concentration of resin, which occurs primarily in the fracture seams. In general, these seams are less than 1/8 in. thick, but it is not uncommon to find coal with areas as thick as 3/8 inches. The resin is of the hard kauri variety, with coloration varying from deep blood red to lemon yellow and almost colorless. There is also an almost black variety, which is not readily soluble in the same solvents as the lighter colored resins. These resins are valuable for many industrial purposes. When refined, they are suitable for uses similar to those for which lac resins are usually employed. They are particularly desirable for preparing dielectric varnishes. They are also desirable in preparing printing inks, waterproofing agents, special synthetic rubbers and rubber cements. They are especially suitable as an admixture in synthetic rubbers and cements, as they supply the essential tackiness the synthetics lack. The following chemical trade characteristics have been found by Inter-Chemical Co. research chemists in the refined resins: Specific gravity (melted)....... I .03 -I.06 Acid number.................. 6-8 Softening point, mercury method 160º-165ºC Iodine value (Wijs)............ 140-150 Refractive index............... 1.544 Color (Hellige, 25 pct toluol)... 14 Molecular weight, average...... 732 Purity, 99 + pct pure hydrocarbon "Unaffected by alkalies and resistant to one hour fusion with solid potassium hydroxide. Completely soluble in aliphatic and aromatic hydrocarbons. Insoluble in alcohols, ethyl acetate and other commonly used alcohols and esters. Compatible with natural and synthetic rubbers, chlorinated and cyclized rubbers, waxes, vegetable oils, mineral oils, rosin, ester gum, phenolic and modified phenolic resins and other natural and synthetic resins of like solvent solubility."* The recovery and refining of these fossil resins has been the subject of much research work and has intrigued many investigators. Broadly speaking, the problem involves separation of the resin from the coal into a very high-grade concentrate, and subsequent treatment of this concentrate to produce an acceptable refined resin for its various usages. Obviously it is also desirable to recover the residual coal without excessive size degradation. The late W. D. Green, concentration ennineeru for Combined Metals Reduction CO., obtained U, S. Patent No. 1773997 for the recovery of resin from coal through

Jan 1, 1948

By Ernest Klepetko

A notable amount of fossil resin exists in many of the bituminous coal beds of Utah. The upper part of these show a marked concentration of resin, which occurs primarily in the fracture seams. In general, these seams are less than 1/8 in. thick, but it is not uncommon to find coal with areas as thick as 3/8 inches. The resin is of the hard kauri variety, with coloration varying from deep blood red to lemon yellow and almost colorless. There is also an almost black variety, which is not readily soluble in the same solvents as the lighter colored resins. These resins are valuable for many industrial purposes. When refined, they are suitable for uses similar to those for which lac resins are usually employed. They are particularly desirable for preparing dielectric varnishes. They are also desirable in preparing printing inks, waterproofing agents, special synthetic rubbers and rubber cements. They are especially suitable as an admixture in synthetic rubbers and cements, as they supply the essential tackiness the synthetics lack. The following chemical trade characteristics have been found by Inter-Chemical Co. research chemists in the refined resins: Specific gravity (melted)....... I .03 -I.06 Acid number.................. 6-8 Softening point, mercury method 160º-165ºC Iodine value (Wijs)............ 140-150 Refractive index............... 1.544 Color (Hellige, 25 pct toluol)... 14 Molecular weight, average...... 732 Purity, 99 + pct pure hydrocarbon "Unaffected by alkalies and resistant to one hour fusion with solid potassium hydroxide. Completely soluble in aliphatic and aromatic hydrocarbons. Insoluble in alcohols, ethyl acetate and other commonly used alcohols and esters. Compatible with natural and synthetic rubbers, chlorinated and cyclized rubbers, waxes, vegetable oils, mineral oils, rosin, ester gum, phenolic and modified phenolic resins and other natural and synthetic resins of like solvent solubility."* The recovery and refining of these fossil resins has been the subject of much research work and has intrigued many investigators. Broadly speaking, the problem involves separation of the resin from the coal into a very high-grade concentrate, and subsequent treatment of this concentrate to produce an acceptable refined resin for its various usages. Obviously it is also desirable to recover the residual coal without excessive size degradation. The late W. D. Green, concentration ennineeru for Combined Metals Reduction CO., obtained U, S. Patent No. 1773997 for the recovery of resin from coal through

Jan 1, 1948

By C. Perez-Rosales

A simplified method for evaluating specific surface of porous media is described. The theory takes as its point of departure a previous statistical method. Due to its simplicity, it is considered that the proposed method has certain advantages over methods currently used. By making some simplifications, the procedure for estimating specific surface is reduced to superposing, on an enlarged reproduction of a section of the sample to be analyzed, an evenly spaced grid and counting the number of intersections of the grid lines with the perimeter of pores. An indirect test of the theory is presented and the advantages of the method are discussed. INTRODUCTION The specific surface of a porous medium, defined as the surface area of the pores per unit bulk volume, is an important parameter with regard to flow of fluids through porous materials. In particular, it has long been recognized that specific surface is closely related to permeability. Since the internal surface of any porous material is extremely complex, the measurement of specific surface can only be accomplished by indirect means. It is considered that the best method&apos; in current use for determining specific surface is the statistical method of Chalkley, Cornfield and Parka who originally applied it for estimating volume-surface ratios of morphologic components, such as cells or nuclei. This method will be outlined later. A method which has been used extensively in determining specific surface is based on the adsorption of a vapor by the internal surface of porous media. However, this method does not yield the surface pertinent to fluid flow, since it includes the tiny molecular interstices which do not influence the permeability of the porous material.&apos; This method has been employed by Brooks and Purcell measure internal surface area of sedimentary rocks. The Kozeny equation, which relates the specific surface to the permeability of a porous medium, has found wide use in determination of specific surface. However, the KOzeny equation is not strictly correct. Large discrepancies have been found between theory and experiments.&apos; Consequently. the specific surface estimated by this method is subject to serious uncertainties. Finally, there are other methods for specific surface measurements which are based upon a variety of physical and chemical properties: the heat conduction by a gas, ionic adsorption phenomena and direct chemical reactions of the surface with other substances. This paper describes a simplified statistical method for determining specific surface of porous materials. It is considered that, due to its simplicity, it has certain advantages over the methods presently used. For its validity, it is required that the porous structure of the material under study be of a spatially random nature. This is not a serious limitation since the naturally occurring porous media have this characteristic. THEORY The method proposed in this paper takes as its point of departure the interesting result obtained by Chalkley et al The method shows that if a line of length r is dropped repeatedly at random over a section of a porous medium, and counts are made of the number of times the two end points fall within pore areas (denoted by h for "hits") and the number of times the line intersects the perimeter of pores (denoted by c for "cuts"), then in a very large number of throws where S is the internal surface of the sample (surface of pores) and V, the volume of the pores (Fig. 1). Since the specific surface S, and the porosity 4 are given, respectively, by S. = Sl V, and 4 = V,l V,, where V, is the total volume of the sample, it follows from Eq. 1

By E. F. Thomas

THE late George S. Rice was active in the inves--I- tigation of bumps, particularly in the last ten years of his career as chief mining engineer of the U. S. Bureau of Mines. Since most of his investigation was carried out in Great Britain, continental Europe, and—to a lesser extent—Canada, his thinking on prevention was influenced considerably by the experience of those countries. It is not surprising, therefore, that when he was called upon a few years before his retirement to investigate bumps in the U. S. and suggest ways to prevent them, he turned to longwall mining. A longwall method had been most successful in combating the bump hazard in mining coal under deep cover, especially in Great Britain, but the prevailing method there at the time was advancing longwall mining, which he knew was uneconomical under U. S. mining conditions. For this reason he proposed a modified retreating longwall system that he believed included the best features of the advancing method. As brought out by Rice,&apos; if the cover is 2000 ft and 50 pct of the coal is extracted, the static load on the remaining pillars will be about 4000 psi, which exceeds the ultimate crushing strength in most instances. If the pillar coal is overloaded before a pillar line is established, then the abutment zone preceding a line of extraction is no place to split pillars or extract them by any method other than an open-end system. Rice therefore advocated open-end mining, preferably by longwall, but he was willing to compromise with long-face mining if the longwall method was not acceptable. Rice&apos;s system was put into operation in a mine in Harlan County, Kentucky,3 but subsequent experience has shown that it did not take into account two important factors—avoidance of pillar-line points and maintenance of adequate development in advance of the pillar-line abutment area. For ten years after Rice&apos;s retirement the USBM did little investigation and research on bumps, chiefly because so few were occurring that there was not much cause for alarm. But in 1951 there were three occurrences involving fatal injuries, and the Bureau began a statistical survey in that year. C. T. Holland, head of the department of mines at Virginia Polytechnic Institute, was retained as a consultant. The resulting study&apos; of 117 case histories brought out these important conclusions: 1) Almost invariably the bump occurred in a locality affected by the abutment zones of one or more pillar lines. 2) In most cases the locality of the bump was influenced by the abutment zones of more than one pillar line. The term pillar-line point has been used for many years in the Appalachian region for such a situation. Point is used in the geographical rather than the mathematical sense. 3) In pillar-line extraction the following practices are safest in preventing bumps: a. The mine layout should provide for pillars of uniform size and shape along the extraction line. b. The mine layout should be planned so that no development need be done in the abutment zone of a pillar line. c. The layout should permit open-end extraction of pillar lines from the next goaf, so that it will not be necessary to resort to pocket mining, splitting pillars, or any practice that will involve driving in the direction of the goaf within the abutment zone. d. Pillars should be large enough to support area without undue roof and floor convergence before establishment of a pillar line. These are, of course, generalities, and while they are useful in laying out areas where bumps can be expected, they are of limited help in many mines that were committed to a system of mining before it was realized that they were subject to bumps. Under such conditions it becomes necessary to choose between the following alternatives: 1) Abandon the territory, except for pillars that offer no extraction problems. 2) Through experience select the pillars that are most heavily loaded, and, by augering, induce bumps from a safe vantage point so that impinged loads are relieved. This method was first developed at the Gary, W. Va. mines of U. S. Steel Corp. and later adapted to mining thick coal beds at Kaiser Steel&apos;s Sunnyside mine in Utah. No scientific method is available to determine where to drill within a loaded pillar. Although this method of unloading has worked very successfully at Gary—with one exception—

Jan 1, 1959

By J. A. Clum, R. W. Heins, T. D. Tiemann

The use of Na-montmorillonite clay hinders (Western Bentonite) in the pelletizing of iron ore concentrates is well established as is the idea that alternative binders must be found. 1-6 This note summarizes work done7 in evaluating a Wisconsin montmorillonite clay binder. The clay occurs in irregualr beds overlying the Prairie du Chien Dolomite and the St. Peters Sandstone near Hersey, St. Croix County. The raw Wisconsin clay contained 65% quartz and 35% clay minerals. The Na20to CaO ratio was 0.234. Suspension viscosity tests of the raw clay gave results only slightly better than water alone, even after treatment with activator materials. Sedimentation treatment reduced the quartz in the decantate to 5% after 240 min (four hours). Twenty minutes of sedimentation produced a decantate with 27.5% quartz which was found as effective as the 5% quartz decantate in pelletizing behavior. The 20 min decantate was used in subsequent tests. The decantate was filtered and dried at 110°(230°F). The minus 200 mesh portion of this was added directly to the magnetite concentrate. Pellets were made in a laboratory sized disc pelletizer from pastes consisting of ore concentrate, balling water (9%) and binder (clay, or clay + resins, or resins). The pastes were premixed in a Waring blender. The binders were: (1) 1% of a commercially used Western Bentonite; (2) 1 % or 3% of the Wisconsin clay (raw, or 20 min decantate); (3) 20 min decantate washed with activator solutions, (to exchange Na for Ca in the clay); (4) decantate with activator added in the balling water; (5) decantate with organic resins; (6) organic resins. Measurements of the 0.46 m (18 in.) Green Drop Number, the Dry Strength and the Fired Strength (fired at 1260°C (2300°F) for 30 min) were made. The dry and fired compressive strengths were determined on an Instron testing machine using a C-load cell and a F-load cell, respectively. The cross-head speed was 0.004 m/sec (0.1 in./min) for both. The results of each measurement were averaged for 15 pellets. A summary of those results is presented in [Table 1]. More detailed results and procedures are presented in another report.7 In addition to the effects on pellet strength due to various binders the effect of varying magnetite concentrate characteristics is noted in [Table l]. There, a few comparative data are shown for Cornwall, PA Magnetite, which has a generally liner particle size than the Black River Falls magnetite which was used for most of the tests.

Jan 1, 1979

By M. D. Cooper

UNDERGRADUATES in mining engineering may be prepared for work by giving them sound instruction in the courses generally considered essential to the profession. The industry is not deeply concerned about the details of those courses. The average man in the coal industry does not wish to insist upon a rigid program. Therefore, he differs little from those in the teaching profession-who evidently are not unanimous in their opinions, or all college catalogs would be alike. For the good of the profession, it is just as well that there should be differences in regard to details. It appears that students graduating in mining engineering from the accredited institutions receive similar instruction.

Jan 1, 1950

By B. M. Larsen, T. E. Brower

IN an earlier paper1 we discussed a simple, rapid method of taking samples of liquid steel and analyzing them for oxygen, which, though possibly not absolutely accurate (as is likewise true of all other methods), certainly yields results that are satisfactorily consistent. Accordingly, samples from hundreds of heats in different shops were analyzed for oxygen, with results sufficient in number to be handled statistically and permit estimation of some general trends. Measurements were made in acid as well as in basic open hearths, throughout the refining period, to learn how stirring, blocking, adding ore or lime or sand, affects the oxygen content of the bath; we also followed the changes brought about by tapping, teeming, and deoxidizing. Some of these results, discussed in an earlier paper.2 bring out the dominant role of the carbon-oxygen reaction in regulating degree of oxidation both of metal and of slag, also the marked variability of concentration of dissolved oxygen [0] in excess of that which would be in equilibrium with carbon and with carbon monoxide at a partial pressure of one atmosphere. As a logical beginning on this complex problem, we take up in the present paper the variability of this excess oxygen, ?[O], when other factors are as constant as they ever are in open-hearth operation; namely, toward the end of the refining period, when the bath may be regarded as in the comparatively steady state it approaches in absence of disturbing factors. This condition was chosen because by that time the significant reactions, except carbon oxidation, between slag and metal have come to substantial equilibrium; this facilitates interpretation of the complex situation and thus permits more definite conclusions to be drawn. This excess concentration of oxygen, ?[0], in the metal is needed, of course, to make the steelmaking process go at a reasonable rate; alternatively it may be regarded as a measure of the virtual pressure increment above one atmosphere, or of the degree of supersaturation, of carbon monoxide in the metal. According to our measurements, the excess concentration ?[O] in liquid steel varies from about 0.009 to 0.035 per cent oxygen by weight. It is quite sensitive to change of conditions, being altered temporarily by operations such as stirring with green poles, additions of ore, lime, or sand; but as the disturbance works itself out, it resumes a level within the intermediate range characteristic of the steady state. The conditions most common in average furnace practice are covered by the following : [ ] as in a reasonably steady state-that is, when it is boiling normally, is at proper temperature with a well-shaped slag, and has been free from disturbing effects during the preceding half hour-?[O] returns from

Jan 1, 1946

By F. M. Stewart

A paper by Hurst and van Ever-dingen in 1949 led to the practical solution of many nonsteady-state flow problems.&apos; Subsequently, applications of this material have been discussed by several authors. The purpose of this note is to outline a simplified direct procedure for water-influx pressure predictions for pressures above the bubble point. The prcposed procedure is unique in that after the "time-conversion factor" and the "influx constant" are obtained, predictions are made without trial and error. The elimination of trial and error is made possible by expressing certain PVT characteristics as explicit functions of pressure. The procedure is applicable to fields producing at pressures above the bubble point and under radial water drive from an infinite aquifer. In the usual applications it is required to predict (1) withdrawals given future pressure history or (2) reservoir pressure, given future withdrawals or production. The theory, assumptions and conditions under which the nonsteady-state solutions hold are covered in the references and are not repeated. The simplified direct procedure outlined here has been developed from published solutions for the so-called "pressure case". A similar direct procedure for the same special conditions has been developed for the "rate case"; however, in this instance the procedure is lengthy and offers no advantage over the trial-and-error solution. Consequently, this paper covers only the procedure based on the pressure case. DISCUSSION Under the pressure case prediction of withdrawals from a water-drive field, given the future pressure history, involves the use of a nonsteady-state water-influx term together with the material balance equation. The solution of a particular problem requires the following steps: (1) division of past pressure and production data into equal time intervals; (2) computation of cumulative water influx vs pressure drop for each time interval of past history using the material balance equation; (3) determination of the best values for the "time-conversion factor" and the "influx constant" by equating the nonsteady-state influx term with the influx computed in Step 2 (this requires a trial-and-error procedure); (4) prediction of influx for a given pressure drop using the influx term and the computed factors from Step 3; and (5) calculation of fluids produced using the predicted influx in the material balance equation. A forecast of the water-oil ratio or water production rate is required to complete the calculation. It is assumed that a reliable estimate of original oil in place is available, as well as the production and pressure history, and data on reservoir fluid characteristics. If the original oil in place is unknown, it may be computed simultaneously with the tinie-conversion influx factors2,3. However, the oil in place so computed may be considerably in error3; consequently, it is usually preferable to use oil in place estimated from pore-volume data unless there is considerable doubt as to its accuracy. The Material Balance Equation Above the Bubble Point Above the bubble point the simpli-

By F. L. Ruhlman, Max C. Eastman

The termination of the recent war marked a major changc in the oil-field operations at. Elk Hills. Production was greatly curtailed, various experimental production projects were started, and a long-range exploratory program was inaugurated. Production was reduced from the wartime peak of 65,000 bbl per day to the current rate of about 8ooo bbl per day in order to maintain an available source of crude that can be drawn upon during a national emergency. The existing production rate is deemed essential to carry on the experimental production projects. These projects are being conducted to determine the best methods and means of maintaining the Reserve, shut in, but in a state of readiness to produce the maximum quantity of oil in the most expeditious manner. Projects now being investigated include: (I) protection of surface equipmerit; (2) repair of wells that might damage the reservoir; (3) gas injection; (4) water eneroachment, (5) gravity drainage. An exploratory program is being carried on to determine the amount of recoverable oil in the unexplored portions of the Reserve. The Shallow-zone exploration is practically completed, but owing to the complexity of the Stevens structure and the magnitude of the oil discoveries in the Stevens, exploration will probably continue in that zone for another two years. Introduction Summary of Development History of Elk Hills Although a detailed history of Elk Hills oil field is presented in various publications,1,2 a summary of its unusual development and production history will be given in order that the present problems may be more readily understood. The first development that resulted in commercial production was in the central part of the Reserve. The first well, Hay No. I, in sec 36-R,* was completed in January I9I9, and was soon followed by 37 Others in the same general area. It is commonly referred to as the Hay-Carman area and was shut in in stages from 1925 to 1934 as a result of litigation regarding the title to the land. Not being highly producti,, only about 6½ million barrels of oil with a large volume of gas was produced from the area prior to the shutdown. Shortly after the start of the development of the Hay-Carman area, drilling was started 6 miles east in sec 36-S&apos; Tupman NO. I came in for 5000 bbl per day early in I92o, It was followed by more than 200 others in the next few years, and the field became one of major importance. Produc-

Jan 1, 1949

By Floyd C. Kelly

A. HUltgren, .Söderfors, Sweden (written discussion*).—From the results obtained in his own experiments as well as those of Austin and of Grube Mr. Kelley derives a general law, expressed tentatively in the following words: "whenever two metals are brought into intimate contact at a temperature at which diffusion takes place, a comparatively rapid, or abnormal, grain growth results." It is suggested that,, in order adequately to represent the facts, this definition should he restricted by the following qualifications: a and b are the two metals, b diffusing into a. A. At the temperature in question a should exist as phase a 1 having a limited solubility for b. B. The supply of b by diffusion should be sufficient, in view of the rate of diffusion into a 1, to increase the concentration of b above the saturation value in a 1 so as to cause a new phase a2 to form. (7. The phase a2 should have a range of solubility for 6, thus rendering continued diffusion possible. D. In order that the columnar grains may be preserved in the structure the phase a2 should, of course, not suffer transformation on cooling. The phenomenon thus defined may be described as progressive transformation by diffusion. Its mechanism would appear to he as follows: Fig. 17 shows a portion of the equilibrium diagram a-b, Fig. 18 the distribution of b in solution after various periods of diffusion, Fig. 19 represents the structure in cross-section of a cylindrical rod of a at the end of heating period 3. 1. The first effect of diffusion of b into a will be to establish a concentration gradient in phase a1 (1, Fig. 18). When the saturation value for the temperature of the experiment (m, Fig. 17) is reached at the surface, nuclei of, a2 of composition n will form here, and later develop into a continuous layer. Assuming that diffusion proceeds without irregularities and that transformation at any point sets in without lag—i. e., in the moment saturation is exceeded—the transformation a1-a2 will advance inwards on a cylindrical surface concentric with the surface of the rod. The discontinuity of composition at the transformation surface in the position it happens to have at the end of the treatment (3, Fig. 18) will be preserved at room temperature, if the cooling is not particularly slow, and be recorded in the structure as a marked, smooth line, in agreement with Grube&apos;s and the author&apos;s observations. The shape of the distribution curves in Fig. 18 is also corroborated by the analyses given by Grube. 2. During diffusion, since the secondary phase a2 is always in immediate contact with the saturated part of the primary phase a1, there should be very little lag in the transformation. This means that the first a2 grains formed should grow in preference to the formation of independent nuclei; in other words, columnar growth results. It does not seem necessary to assume, with Green,&apos; whose conception of the phenomenon

Jan 1, 1929

By Floyd C. Kelly

A. HUltgren, .Söderfors, Sweden (written discussion*).—From the results obtained in his own experiments as well as those of Austin and of Grube Mr. Kelley derives a general law, expressed tentatively in the following words: "whenever two metals are brought into intimate contact at a temperature at which diffusion takes place, a comparatively rapid, or abnormal, grain growth results." It is suggested that,, in order adequately to represent the facts, this definition should he restricted by the following qualifications: a and b are the two metals, b diffusing into a. A. At the temperature in question a should exist as phase a 1 having a limited solubility for b. B. The supply of b by diffusion should be sufficient, in view of the rate of diffusion into a 1, to increase the concentration of b above the saturation value in a 1 so as to cause a new phase a2 to form. (7. The phase a2 should have a range of solubility for 6, thus rendering continued diffusion possible. D. In order that the columnar grains may be preserved in the structure the phase a2 should, of course, not suffer transformation on cooling. The phenomenon thus defined may be described as progressive transformation by diffusion. Its mechanism would appear to he as follows: Fig. 17 shows a portion of the equilibrium diagram a-b, Fig. 18 the distribution of b in solution after various periods of diffusion, Fig. 19 represents the structure in cross-section of a cylindrical rod of a at the end of heating period 3. 1. The first effect of diffusion of b into a will be to establish a concentration gradient in phase a1 (1, Fig. 18). When the saturation value for the temperature of the experiment (m, Fig. 17) is reached at the surface, nuclei of, a2 of composition n will form here, and later develop into a continuous layer. Assuming that diffusion proceeds without irregularities and that transformation at any point sets in without lag—i. e., in the moment saturation is exceeded—the transformation a1-a2 will advance inwards on a cylindrical surface concentric with the surface of the rod. The discontinuity of composition at the transformation surface in the position it happens to have at the end of the treatment (3, Fig. 18) will be preserved at room temperature, if the cooling is not particularly slow, and be recorded in the structure as a marked, smooth line, in agreement with Grube&apos;s and the author&apos;s observations. The shape of the distribution curves in Fig. 18 is also corroborated by the analyses given by Grube. 2. During diffusion, since the secondary phase a2 is always in immediate contact with the saturated part of the primary phase a1, there should be very little lag in the transformation. This means that the first a2 grains formed should grow in preference to the formation of independent nuclei; in other words, columnar growth results. It does not seem necessary to assume, with Green,&apos; whose conception of the phenomenon

Jan 1, 1929

By C. D. King

THE key to maximum production of ingots for the war effort is maximum production of pig iron. For any given furnace and ore, the most important single influence on blast-furnace production is the quality of the furnace coke. It is generally recognized that undoubtedly deterioration of Pittsburgh coking coals will be accelerated by the depletion of some of the better grades of coal; the extension of mine mechanization, with attendant degradation of coal quality; and the opening of new coal fields, some of which are known to be fairly high in sulphur. All of these factors, contributing as they do to higher ash and sulphur, and not infrequently to inferior quality of coke, made it desirable that an extensive study be undertaken to determine the effect of washing some coals that closely approximate the average chemical composition of coking coals to be expected in the future by the subsidiaries of the United States Steel Corporation in the Pittsburgh district. It was deemed advisable to study the improvement obtained by washing such coals and to determine the need for supplementing the existing coal washery at Clairton to assure continued maximum production of pig iron from presently available furnace stacks. The existence of the coal washer at Clairton made it possible to conduct tests on coals used in raw form and on similar coals after washing. This study covers an investigation of the quality of furnace coke as affected by washing coking coals, and is confined to the use of IOO per cent high-volatile Pittsburgh seam coals from Fayette and Greene Counties in the manufacture of furnace coke. It covers the improvement in chemical and physical properties as well as the degree of uniformity in coke obtained by washing these coals, and includes the effect on blast-furnace production and practice. The test period involved is four months; the plants, Clairton by-product coke plant, and the Carrie No. I and No. 2 blast furnaces at Rankin, Pa., Carnegie- Illinois Steel Corporation. Clairton By-Product Coke Plant And Coal Washer The Clairton by-product coke plant carbonizes 30,800 net tons of coal daily in 22 batteries containing 1482 ovens. Three oven sizes are used, commonly known as wide, medium, and narrow types, recognizing the difference in oven width. These ovens also differ in height and length. The present coal washer has a daily capacity of approximately 14,000 tons, leaving 16,800 tons to be carbonized in raw form. Washed coal is used on all the narrow ovens and on three of the six batteries with ovens of medium width, raw coals being used on all the remaining ovens. The customary arrangement is

Jan 1, 1944