Search Documents

By M. T. Abasov

Among a host of challenges dictated by the explosively developing scientific and technical revolution, the improvement of control and management is one of the most essential problems. This problem is also of far-reaching importance for the oil and gas industries. An oil and gas extracting complex is an involved multilink system characterized by a great number of elements and by intricate interconnections between these elements. Of paramount importance for these systems is the quality of control. Any deviation of the control from the optimum reduces the effectiveness of the system and deteriorates its basic technical and economic factors. In case of large systems, even a relatively small deviation from the optimum may result in considerable material and power losses. Optimization of control of large production systems is therefore one of the basic means to enhance their effectiveness. The present paper discusses a development control problem for a multilayer gas deposit using the method of simultaneous exploitation of several strata by means of a single well. The optimum control is achieved by determining the dynamics of changes in the number of producing wells in a reservoir with regard to the depth of occurrence of these reservoirs as well as the difference in the time of introduction of the wells from drilling and their transfer to another reservoir. A mathematical model was constructed for the problem under consideration and a method was given to solve this problem. The problem was dealt with under the assumption that either each of the reservoirs or a part of them have vertically overlying areas and that there is no hydrodynamic interference between the horizons. It was

Jan 1, 1977

By L. A. Cowan

IF the elements of personality be those characteristics in which humans differ, and if this definition be applied to the purchasing department for the Climax operations in Colorado, it must he concluded that this department has no distinguishing traits that would give it a departmental personality different from that possessed by the similar department of any progressive mining enterprise. Or, one may go further by stating that the rudimentary functions of any purchasing practice employed principally in the acquisition of maintenance, repair, and operating supplies are much alike, whether or not the industry involved be mining or milling. However, in the fact that the principal purchases of a mining company are materials for maintenance and repair and consumable operating supplies lies that essential characteristic which differentiates mining and milling purchasing functions from those of the manufacturer, the fabricator, or the ordinary processor.

Jan 1, 1946

By C. Atkinson

A method is described for the numerical solution of the diffusion equation with a composition-dependent diffusion coefficient and applied to the radial growth of a cylinder; the radial growth of a sphere, and the symmetric growth of an ellipsoid. Sample applications of the method are made to the growth of particles of proeutectoid ferrite into austenite. RECENTLY&apos; we described a method for numerical solution of the diffusion equation with a composition-dependent diffusion coefficient for the case of the growth of a planar interface. In this paper we extend this method to describe the radial growth of a cylinder, the radial growth of a sphere, and the symmetric growth of an ellipsoid. In the latter case, limiting values of the axial ratios of the ellipsoid reduces the problem to one of a cylinder, a sphere, or a plane depending on the axial ratio. A check on these limiting values is made in the results section. In all of these cases we consider growth from zero size. A natural consequence of this assumption as applied to the sphere, for example, is that the radius of the sphere is proportional to the square root of the time. This is consistent with the condition that the radius is zero initially, i.e., grows from zero size. It may be argued that it is more realistic to consider particles which grow from a nucleus of finite initial size; even in this case the analysis of this paper is likely to be applicable. This can be seen if a comparison is made of the work of Cable and Evans,2 who consider a sphere of initially finite size growing by diffusion in a matrix with a constant diffusion coefficient, with the results of Scriven3 for growth from zero size. This comparison shows that the rates of growth in each case differ trivially by the time the particle has grown to about five times its initial size." This investigation is a generalization of those of Zener,4 Ham,5 and Horvay and cahn6 to the situation often encountered experimentally, in which the diffusion coefficient varies with concentration. First let us consider each of the cases separately. I) GROWTH OF SPHERICAL PARTICLES FROM ZERO SIZE In this case the differential equation in the matrix depends only on R, the radius in spherical coordinates, and can be written: ? 1 <^\ ^13D . , dt U\dRz + R 3Rj + dR dR [ J where C is the composition, t is the time, and D is the diffusion coefficient which depends on c. The boundary conditions will be: c = c, at the moving interface in the matrix, c = c, at infinity in the matrix (and at t = 0, everywhere in the matrix), c = X, is the composition in the spherical particle. Each of the above compositions is assumed constant. In addition there is the flu condition at the moving interface which can be written: , dR0 ~/3c dt \dR/H =Ra where R,, which is a function of t, is the position of the moving interface. We make the substitution q = RI~ in [I] reducing this equation to: & - m - *ws) »i where we have written D = D,F(c) or simply D,F, and Do = D(c,). Thus F[c(q0)] = 1 where q, = ~,/a is the value of the dimensionless parameter q evaluated at the interface. Multiplying Eq. [2] by dq/dc and integrating, we find: where the lower limit of the integral has been chosen so that dc/dq — 0 as c — c,, thereby satisfying the boundary condition at infinity. We require, then, to solve Eq. [3] subject to the condition c = c, when q = q, (this follows from putting R = R, at the interface) together with the flux condition which can be rewritten in terms of q as: Eqs. [3] and [4] together with the condition c = c, at q = q0 enable us to find 77, and the concentration profile c = c(q). Numerical Method. We treat Eq. [3] in the same way as we did the corresponding equation for the planar interface problem&apos; i.e., by dividing the interval c, to c, into n equal steps so that: cr = ca -rbc [5] where r takes the values 0, 1, ... n and we call no,, q1, ... nn the values of n corresponding to the compositions c,, c,, ... c,.

Jan 1, 1970

OF no less importance nor less terrifying to consider than the marvelous effects of guns are those produced with fire by powder in underground mines. These are truly not only similar to fearful natural earthquakes, but it can perhaps be said that these made by art surpass the wrath of the earth with greater effect. For if the latter shakes it happens that it causes the things on the surface to shake and sometimes to fall into ruins, but the former not only shakes but always functions and destroys-surely a marvelous effect which is almost incomprehensible, and if experience did not demonstrate it, it could scarcely be believed. Who would say that the mountains, things of such great hardness, would yield to men, easily opening their bowels? Likewise, one who had not seen it would say that it was impossible for men to have a way of administering at will fearful and destructive thunderbolts which are of such a kind that, although men make them, they cannot protect themselves against them; indeed they cannot call themselves safe from the evilness of gunpowder even in mountains composed of very hard stones or in budded structures. For, as is seen, there is no seemingly impregnable fortress that does not yield when guns are brought near it. If it happens, indeed, that guns can- not be brought near to some place because of the harshness of the site,

Jan 1, 1942

LEAD and tin mixed together make an alloy through an attachment of natural affinity which they have with each other, so that when they are mixed it is difficult to recognize by the sight which one it is, if the essences of their qualities are not surpassed by more than half. If, indeed, one can be recognized, it is the tin which gives off a certain sharp odor to the sense of smell, besides having a greater hardness and whiteness. The best of these is the one that is the purest in its kind. In the alloy of tin it is the one that is the whitest and hardest, or, when it is bent or some thin end of it is held tightly by the teeth, is heard to crackle as frozen water does. Because this happens more with this than with other metals, I do not wish now to inquire into it. It is enough that it be a sign for recognizing when tin is pure or mixed. Pewterers say that it should be joined in alloy with lead and that it is better for working when it contains four or six pounds to the hundred because it makes it softer to the hammer and more fluid in casting. But I do not like to hear this, even if all they say is true, for I see that the tin that comes from England, when worked as well as in cakes that show it to be pure, is much more beautiful and better in all works than is that made in Venice. And I believe that it is not better for any work when mixed than when pure, except for the advantage of the master who, if he does nothing else, sells lead that is worth little for tin that is worth much. I find that when mixed it serves in only two things. One is when it is wished to make a solder for copper, for use when it is not worth while to solder the bottoms and large pieces of vessels with low-grade silver as should be done. The other is when master potters calcine it in order to make glazes and to apply white to their vases. I consider lead to be useless in all other works of any kind of metal, since it unites with none of the other metals of good company except tin.

Jan 1, 1942

By S. E. Clay, G. P. Martins, P. R. Taylor

A grain model for gas-solid reactions in cylindrical pellets is formulated and solved numerically. The numerical solution demonstrates when it is safe to assume either a thin disk or a long cylinder geometry, and when the more general two dimensional geometry must be used. The numerical solution also demonstrates the solution of a two-dimensional moving boundary problem (i.e., when the reaction is diffusion controlled and the ratio of the height to diameter dictates two dimensions).

Jan 1, 1986

By Julien Deby

THE sinking of a deep shaft is always a serious undertaking, especially when the strata to be traversed are of great hardness, or when they are feebly coherent or highly saturated with water. In the, first case, that of solid rock, modern appliances, such as the rock-drill, put into motion by air-compressors, along with suitable explosives, will generally answer the purposes of the mining engineer until he has reached the main water-levels. When these have

Jan 1, 1877

By Julien Deby

The sinking of a deep shaft is always a serious undertaking, especially when the strata to be traversed are of great hardness, or when they are feebly coherent or highly saturated with water. In the. first case, that of solid rock, modern appliances, such as the rock-drill, put into motion by air-compressors, along with suitable explosives, will generally answer the purposes of the mining engineer until he has reached the main water-levels. When these have

By Robert M. Lewis

At the Scotia plant of Blue Diamond Coal Co., near Cumberland Ky., good recovery and grade can be obtained when floating deep mine coal. When the plant changes over to strip coal, flotation fails, resulting in loss of coal. A procedure was developed at the Minerals Research Laboratory in Asheville, N. C., for recovering strip coal by flotation. Laboratory results were duplicated on a batch scale at the plant. The procedure was found to be effective when tried on a continuous basis in the processing plant.

Jan 1, 1973

By R. H. Oliver

The purposes, types, preparation, and testing of flocculants are discussed. A flocculation compendium is included, indicating choice of flocculant for a given set of conditions. An economic evaluation of the process is presented. Solid-liquid separation is a major expense in most mineral processing flowsheets today. Proper use of flocculation can often lower the overall cost of a solid-liquid separation by reducing the size of sedimentation or filtration equipment. PURPOSE OF FLOCCULATION When is use of a flocculant justified in terms of overall process economy? 1) when it results in process improvement, such as producing a clear liquor for electrolysis, precipitation, ion exchange, or solvent extraction; 2) when it results in satisfying requirements of pollution abatement ordinances; 3) when it results in increased recovery of values that would otherwise be lost; or 4) when it results in considerable savings in capital expenditure due to use of smaller equipment. When can the use of a flocculant adversely effect overall process economy? 1) when it results in increased filter cake moisture, 2) when it results in decreased filtration rates, 3) when it results in considerable bulking of sedimentation underflow, 4) when it contaminates either the supernatant or sludge, or 5) when the cost of using the flocculant is greater than the savings due to its use. First step in consideration of flocculants for a given application is establishment of desired goals in terms of increased clarity of effluent, increased recovery of solids, or decreased size of equipment. The most economical solution to a solid-liquid separation problem is that combination of equipment and flocculant costs which meets the established goals at the lowest total annual expenditure. This economic decision can be made only after technical data has been obtained as outlined in next four sections. TYPES OF FLOCCULATION Flocculation is a process wherein individual particles are united into more or less tightly bound agglomerates or flocs, thereby increasing effective particle size of solids suspended in a liquid. Degree of flocculation of a suspension of finely divided solids in a liquid is controlled by a combination of probability of collision between particles and probability of adhesion after the collision has occurred.&apos; Probability of collision can be increased commercially through use of a paddle-type flocculator, combination flocculator, and clarifier or flocculating-type feedwell. Probability of adhesion usually can be increased by addition of a reagent known as a flocculant. Reagents act as flocculants through one or a combination of three possible mechanisms. The first is electrolytic neutralization of inter molecular repulsive force due to Zeta potential. This neutralization enables Van der Waal&apos;s cohesive force to hold the particles together after they collide.&apos; The second is the precipitation, within a definite pH range, of voluminous metallic hydroxide flocs which entrap fine particles. This process is known as coagulation.14 Third is the bridging of two or more particles by either natural or synthetic long-chain, high-molecular-weight organic polymers. This bridging is accomplished by adsorption of two particles at different sites on the same molecule or by bonding of two molecules, each adsorbed to a different particle. Considerable effort has been expended in explaining the action of these polyelec-trolytes and detailed accounts are available in the literature. CHOICE OF FLOCCULANTS It is impossible, at the present time, to specify the optimum type or amount of flocculant for a given application from a knowledge of the material to be treated. The standard procedure is to choose reagents or combination of reagents most likely to be effective on the slurry; then test them.&apos; The accompanying Flocculation Compendium (Table I) contains details of all currently available reagents sold as flocculants and it should be used when selecting the group of reagents for tests. This selection can be based on information listed in columns 4 and 5. Column 4 presents industries in which each floc-

Jan 1, 1961

By J. D. Hunt, D. T. J. Hurle

A uariety of eutectic structures are formed in faceted/nonfaceted eutectics. The various structures are explained in terms of the absence or presence of small facets in the liquid groove. Regular structures are produced when, for purely geometric reasons facels cannot form. The presence of a facet in the liquid groove leads to the formation of an irregular or a cell-like complex regular structure, due to the relative immobility of the groove. A classification of eutectics was proposed by Hunt and jackson, based on the presence or absence of facets on the primary phases (the absence of facets may be predicted from the dimensionless entropy of melting2). Eutectics were divided into three groups: 1) eutectics in which both phases grow in a nonfaceted manner; 2) eutectics in which one phase grows faceted, the other nonfaceted; 3) eutectics in which both phases grow faceted. It was suggested that regular1 rodlike or lamellar structures1 should be formed in the first group, that irregular or complex regular structures1 should be formed in the&apos; second, and that irregular structures1 should be formed in the third. Recently it has been shown that the structural classification is incomplete. Regular rodlike structures (InSb-NiSb eutectic3), or broken lamellar structure (Bi-Zn eutectic, Fig. 8), are formed in alloys of the second group when the faceted phase has a large volume fraction. Hunt and jackson&apos; argued that regular structures could form in faceted/nonfaceted systems, but that such structures would be unstable in the presence of microfacets on the lamella of the faceting phase, because the growth rate at a point on such a facet would depend on the kinetic undercooling at the point of nu-cleation on the facet, and not on the local kinetic undercooling. In these circumstances it would not be possible to consistently balance the compositional and kinetic undercooling over a lamellar structure and thus obtain a stable isothermal interface. In this paper we discuss in detail the origin of the various structures formed in faceted/nonfaceted systems, pointing out that the most important factor promoting the formation of a regular structure is the absence of a facet in the liquid groove. 1) FACET FORMATION IN SINGLE-PHASE MATERIALS Facets form when there is an energy barrier for the addition of a new solid layer on an existing solid. When a barrier is present,2 growth proceeds by the lateral movement of steps across a crystallographic plane. The rate-controlling stage of the process occurs when the step is first formed. Hulme and Mullin6 have shown that faceting in single-phase materials can only occur when both interface curvatures are convex with respect to the solid and when the surface is tangential to the facet plane. When even one of the curvatures is concave a facet does not form because new layers of solid from adjacent regions can always feed the facet plane, Fig. 1. Growth under these conditions is then as easy as elsewhere. Similar considerations will apply to eutectic growth; consequently the shape of the faceted phase is extremely important. 2) LAMELLAR SPACING CHANGES IN EUTECTICS Jackson and Hunt7 have shown that the interface undercooling AT of a growing lamellar interface (neglecting kinetic undercooling) is related to the lamellar spacing, A, and growth velocity, v, by an expression of the form: where m, Ql, and nL are constants of the system given in Ref. 7. Eq. [I] is plotted for fixed v in Fig. 2. Jackson and Hunt postulate that a regular eutectic grows near, but to the right of the minimum in the AT vs A curve. They argue that the spacing cannot be to the left of the minimum because the interface is then unstable to fluctuations in A. It cannot grow too far to the right, because when the spacing becomes too wide an isothermal interface can no longer be maintained over the large-volume-fraction phase.7 It is argued that during any change in growth rate the lamellar spacing remains in the permitted range by the movement of lamellar faults. When the spacing is too wide, the fault, shown in Fig. 3, moves to the left; when the spacing is too narrow it moves to the right. The faults, however, have to be formed. heir formation has been shown to occur when local regions deviate considerably from the spacing defined by the lamellar When the spacing is locally too narrow (it passes to the left of the minimum, Fig. 2), pinching off of the narrow phase occurs. When the spacing is locally too wide, the interface on the large volume-fraction phase can no longer be maintained as an iso-

Jan 1, 1969

By Smith, George Otis

ENGINEERING is in essence quantitative, and the engineer must deal with exact figures when he plans and, constructs. Engineering truths are not best expressed by adjectives, yet my wish, today, is not to attempt a quantitative measure of the dominant position of the mineral industry of the United States in the existing scheme of material things, but rather to seek a clualitative appraisal of what mining and metallurgical engineers are doing to promote and make secure our , national progress. Statistics help when we wish to gage material prosperity, but they fail when we desire to determine what share the engineers have in adding to the happiness and welfare of our people

Jan 1, 1928

By W. A. Boyer

HOISTS for metal mines are seldom designed for H one particular depth. They are intended for an ultimate load and depth with a given speed but are first used to hoist from a shallower depth, gradually working to the ultimate as development progresses. Sometimes the mine is not worked on the upper levels because of the kind and grade of ore, the mining of which depends on market conditions. In this case the hoist may be used in the same working shift to lift ore, for example, from the 1200 and the 4400-ft level. This means that the safety factor of the rope should be considered not only when it hoists from the greatest depth, but also when it hoists from the upper levels. According to present safety factor standards, a hoisting rope can have ample safety margin when hoisting from the lower or lowest level and still be shy of sufficient safety margin when hoisting from the upper levels. This will be shown by curves presented in this paper.

Jan 10, 1954

By Henry Otto

THE anthracite industry can be divided into two parts-the underground, or mining, and the outside, or preparation or manufacture. To understand recoveries in the two branches, some of the history of the industry and the changes that have taken place in the past century should be considered. It is a long step from 1807, when 55 tons were produced in the Wyoming field, to 1917, the peak year, when 80,841,223 tons were shipped to market from all the fields. In 1820, the Lehigh Coal Co., the predecessor of the Lehigh Coal & Navigation Co., shipped 365 tons in arks down the canal of the Lehigh Navigation Co. The Schuylkill field was not opened until 1822, when 1480 tons were shipped. The Wyoming field really became a producer in 1829, when 7000 tons were mined and shipped. It is well to note, at this time, the passing of the Coleraine colliery after a life of 88 years; in collieries of this age will be found the. romance of the region, as well as the history of the changes to date.

Jan 1, 1925

By C. C. Hagenbuch

Machine loading of coal into mine cars is increasing rapidly. Particular reasons for its use frequently apply to certain localities, but in general, it is profitable to install mechanical coal-loading equipment: (I) when existing hand-loading contract rates prevent further cost reduction; (2) when the height of the coal bed requires that either top or bottom must be taken to place cars in rooms; (3) when labor shortage or limited house-plant capacity prevents the production of desired tonnage ; (4) when tonnage requirements are in excess of possible hand-loaded production from developed areas; (5) when working places are scattered and it is possible to concentrate production, and therefore supervision, by the installation of mechanical equipment; (6) when rapid development is essential. Having decided to install loading equipment, the problem then arises as to what type is best adapted for a particular mine or coal bed, the choice lying between mobile track equipment, pit-car loaders, scrapers, shaker conveyors, belt conveyors and drag conveyors. MajoR FactoRs Influencing Choice of Equipment In determining the type of equipment to be used, the following major factors must be studied: Grades.—Adverse grades, while permitting other types of loading equipment to work successfully, may prevent the success of a shaker conveyor installation. Thickness of Bed.—The thickness of coal governs the choice of equipment. A machine that requires 5 ft. of head room should not be selected for a 3-ft. bed where otherwise it would be unnecessary either to brush top or to lift bottom. Nature of Pavement.—Soft or scaly bottoms are unsuitable for the use of any type of digging loader, shaker conveyors or scraper loaders. nigging loaders and scraper loaders scale the bottom, mixing it with the coal and causing preparation difficulties; shaker-conveyor drives frequently work themselves loose, destroying the conveyor alignment and creating maintenance problems. Nature of Roof.—With any type of loading machine, it is policy to obtain the maximum possible tonnage per move per set-up. This must

Jan 1, 1931

By KENNETH CROPPER

USUALLY we forget about the things which move along smoothly. There are no causes for worry when there are no troubles. But when troubles arise we must put forth some thought and effort to alleviate them. No one "worries about his automobile until it begins to knock, develop flat tires, or refuses to start. However, when these ailments become apparent we get wide awake on the spot, and do our best to repair the car. So we find ourselves now. The old bus seems to hit all the ditches. There is rough ground on all sides and none of us is able to do anything toward improvement. A state of pessimism stares us in the face, and there is sufficient cause for it. With lead at 3.75 cents, copper about 8 cents, zinc under 4 cents, -and silver about 26 cents, one has a reason for grief. When we think of the 5000 or less men employed in Utah mines and smelters in 1931, as compared with about 12,000 in 1929, the calamity seems even worse. In view of the present economic crisis we cannot even think of new men getting a job.

Jan 1, 1931

By CLARENCE WM. POY

THE most common difficulty faced by an engineer or mine operator when opening a new property in a new field is the lack of roads and of cheap transportation. This one item often swings the balance of success or failure in starting a project. In Alaska, as elsewhere, such problems are more or less serious. In the boom days around the Valdez district, as well as in other parts of this territory, freighting was accom¬plished by dog teams or horses, or even by men that were willing to put their shoulders into harness, because there were virtually no roads. More important, there was only one time when supplies could be transported, and that was when there was suffi¬cient snow on the ground following a heavy wind. Then, and only then, could one depend on the snow to support horses and sleighs, and be sure that the gulleys, streams, and crevices in the glaciers were filled with snow to avoid pitfalls. These methods were used when one had no roads, no streams in the summer to float a barge, or even a trail for a pack train. If the snow was deep and soft, trans

Jan 1, 1935

Percolation infers the passage of a liquid through, the interstices of any material or materials permitting it. Leaching is the process of extracting soluble matter by percolation. Lixiviation is analogous to leaching. Percolation and leaching may occur simultaneously. A filter may be used either to strain suspended or finely divided matter from a liquid, when it is known as a clarifier, or to separate a liquid from a solid. Clarification usually infers the addition d: some settling or flocculating agent which permits the decantation of the clear supernatant liquor. The simple separation of solid from liquid, such as occurs when a thickened flotation concentrate is filtered, is usually termed dewatering. The word filtration is used more to cover the complex process of separating, as far as possible, solid from liquid by vacuum or pressure, removing the residual solution by wash, and at the same time leaching any recrystallized, absorbed, or undissolved matter, by percolation with the solvent. The final product of metallurgical treatment should be reported as a recovery when the yield is refined metal. When the metallurgical operations are incomplete and a concentrated but not refined-product is obtained, the metal content should be reported as an extraction.

Jan 1, 1919

By L. W. Saperstein, W. W. Kaufman

Stimulated by the hearing protection clauses in the 1969 Coal Mine Health and Safety Law, attempts were made to determine what safety hazards, in terms of warning signal discrimination, are attendant upon the wearing of hearing protectors. Warning signals of dangerous roof conditions were collected and analyzed from 11 different coal mines in four different coal seams. Primarily, signals of audible level emanating from roof, floor, or coal were recorded. The interpretations of these signals were seen to be very dependent upon coincident visual and tactile signals. Acoustic character of such signals is shown to be dependent upon the spectral energy distribution of the pulses. Roof talk signals generally have broad-band spectra concentrated below 5 kHz. Reverberation times of acoustic pulses are generally less than 0.5 sec in duration. Indications have developed which link the coal mine entry dimensions with the nature of noises recorded there. Related experiments suggest that roof talk can be discriminated from background noise equally well when wearing protection as when not. This conclusion is only appropriate when noise levels warrant the wearing of protection. When quiet, the wearing of protection somewhat reduces discriminatory ability.

Jan 1, 1976

By W. M. McCardell, W. O. Winsauer

The abnormal conductivity found in shaly reservoir rocks containing an electrolyte is shown to be a consequence of the electrical double layer in the solution adjacent to charged clay surfaces. This increased conductivity results from a higher concentration of ions in the double layer than in the solution in equilibrium with the double layer. It is shown that the magnitude of the increased conductivity of a shaly reservoir material is influenced by the concentration and type of ions in the equilibrium solution as well as by the colloidal nature of the rock. INTRODUCTION An important factor in the quantitative interpretation of the electric log is the resistivity factor of reservoir rock. The resistivity factor is defined as the resistivity of the rock when completely saturated with an electrolyte divided by the resistivity of the electrolyte itself.&apos; In the normal case, the resistivity factor for a particular rock sample is independent of the resistivity of the electrolyte and reflects the pore geometry of the rock.&apos; In 1949. Patnode and Wyllie&apos; showed that in some cases the resistivity factor is not constant, but instead varies with the resistivity of the electrolytic solution. It was shown that clean sands behave normally—i.e., that the resistivity factor does not vary with resistivity of the electrolyte — but that sands con- taining shale and clay may exhibit abnormally low resistivity factors when the solution used to saturate them is of fairly high resistivity. At low resistivities of the electrolyte, the resistivity factor for a shaly sand appeared to approach a normal behavior. It is evident that the resistivity factor of a shaly sand is dependent upon factors other than pore geometry when the solution used to saturate it is of high resistivity. Patnode and Wyllie, and later de Witte,&apos; assumed that the conductivity of a shaly sand saturated with an electrolyte could be represented as the sum of two quantities. One of these was assumed, in effect, to be the conductivity which would be expected if the sample were a clean sand. and the other was assumed to be a conductivity inherent in the sample itself. The latter was supposed to be constant for a given rock sample regardless of the solution used to saturate it. The source of this added conductivity was ascribed to "conductive solids." In actual practice: the effect of the abnormal behavior of shaly sands is of minor importance except when the resistivity of a formation such as a sand is high. Thus the effect is more important when the sand is saturated with a dilute brine than when it contains a more concentrated electrolyte. The effect is also more important when the sample contains oil or gas than when it contains only saline water. Recently it has been suggested that the porosity of a stratum may be estimated from the electric log by use of the resistivity of the invaded zone." This is the zone flushed with the filtrate from mud used in drilling the well. which is ordinarily very dilute brine. When the method is applied to shaly sands, the effect of abnormal conductivity becomes of importance. This report describes an investigation of the mechanism responsible for the abnormal behavior of the resistivity of shaly rock saturated with conducting solutions. The investigation

Jan 1, 1953