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By H. Martyn Chance

I HAVE been induced to present this paper to the Institute because I have been unable to find any publication containing a discussion of this subject. In some of our technical schools and colleges the student is required to construct or copy (generally the latter) a number of profile sections as part of his routine work ; but little attention is given to the methods of projecting observed dips and exposures upon the section line, and still less to the method of con¬structing the under (or above) ground curves. As a result of this lack of instruction every engineer or geologist is compelled to invent for himself a system, or copy the style of others. Geological profile sections have frequently been used to determine underground structure from data obtained at the surface, but the experience of engineers in the anthracite coal-fields has shown that they are to be relied upon only in exceptional instances. The possibility of indicating underground curvatures from dip-angles observed at the surface has been found to be limited to a mere approximation of the larger flexures, As a means of predicting the depth and shape of minor rolls, they have been found most unsatisfactory. In the anthracite coal-fields the hypothecatod

Jan 1, 1881

By William Paxton Hewitt

The San Carlos lead deposit in northeast Chihuahua yielded approximately one million tons of galena ore from a blanket-like deposit. Countryrock, composed of Cretaceous limestones and calcareous shales as old as late Albian-early Aptian, and an underlying undated quartzite series, has been warped into a northwest trending anticline and has been invaded by a light-colored holocrystalline igneous rock. Magnetite and contact metamorphic minerals heterogeneously mixed with variable amounts of pyrite, sphalerite and galena, are concentrated along the anticlinal axis where they replaced magnesia-rich argillaceous sediments above the quartzite contact. Magnetite and associated silicates were deposited under near-contact conditions. Following a period of post-magnetite shattering, pyrite, sphalerite and galena were introduced at lower temperatures. Galena and associated dolomite or magnesite, the final phase of mineralization, are concentrated at the top of the deposit near the anticlinal crest and extend upward into isoclinally folded dolomitic argillites. INTRODUCTION AND ACKNOWLEDGEMENTS The stoped outlines of the San Carlos Mine are a pattern for a stratiform blanket-like deposit. But the close association of mineralization with an anticlinal axis, an observed relation between high grade galena mineralization and the apices of isoclinal folds, and the petrographic story of mineralization introduced into shattered areas make the deposit an example of structural control of ore de-

Jan 1, 1970

By W. R. Crandall

The southern gold-fields offer some of the most complex and trying problems encountered in mining; and their successful solution often means the success or failure of the particular enterprise involved. In vein-mining, where the values are scattered over large areas, making it necessary to handle a large tonnage of very low average grade, the successful solution has been found in some instances by a combined hydraulicking and milling; water under pressure being used as the mining agent, and also for transporting the broken material to the mills, and effecting in its passage a partial concentration of the product by washing out the lighter and looser dirt of the ore-mass. The placer-deposits of the South, which were the original localities from which gold was mined, have been extensively worked, and to any one now undertaking their development offer many difficulties. The antiquity of the industry in this field, which was the cradle (in fact, literally the rocker), in which the California '49-er was born, gives assurance that all the deposits available to water and natural drainage have been more or less extensively worked already, so that, as a rule, any placer-deposits yet remaining undeveloped may be considered to offer some difficulty beyond the ability of the " old-timer " to overcome.

Jan 1, 1897

By R. C. Hall

DEVELOPED to grow single crystals of alloys of high hardness and high melting points is a simple but effective apparatus described in this note. Growth from the melt, that is, by the Bridgman technique, hay be applied to metals or alloys which are physically hard as long as no phase transformation occurs on cooling to room temperature. The present apparatus was employed to grow single crystals of the ferromagnetic AI-Fe alloys above 1 wt pct Al and the Si-Fe alloys above 3 wt pct Si. Single Crystal Growth In a simple form, the method for growth of single crystals from the melt requires a molten metal charge in a pointed crucible which is slowly low-ered through a heated zone into a colder zone. Solidification starts at the bottom point and continues up the charge as the crucible is lowered through the heated zone. If a single crystal nucleates at the bottom, one crystal may grow throughout the charge under ideal conditions of slow growth.4,5 The presently developed method of growth was designed so that the chances that more than one crystal would grow were small. The single crystals were growth by the apparatus illustrated in Fig. 1. The charge was in the form

Jan 1, 1958

By O. Chanute

In discussion of Mr. Macdonald's paper, I can say little more thau to add t~ the general acknowledgments of iguorae, and like several of the gentlemen who have preceded me, make one of those confessions which are thought to be good for the soul. Having had some experience in the erection of bridges during past years, I am aware that We yet need much information in order to proportion them to the best advantage. I would more especially like to emphasize three of the points mentioned by Mr. Macdonald, as among those upon which we lack knowledge; these are: first, the behavior of steel; second, the proportions of compression members; and, third, the influence of the size of a bar upon its strength per square inch. First, as to steel. While we all acknowledge this as the material of the future, our position map be said to be still one of expectaucy. Feu? engineers are bold enough to employ it largely in bridges, and those who do, find such serious difficulties in obtaining uniform grades of it, are so puzzled by apparent anomalies and unexpected phenomena, that it requires considerable faith and courage to apply it in large structural masses. A series of systematic experiments,

Jan 1, 1882

By Earle E. Schumacher, W. C. Ellis

For the purpose of developing combinations of higher strength and conductivity than are obtainable by heat treatment alone in the age-hardening copper alloys, an investigation has been made of the effects of combinations of heat treatment and strain hardening on the properties in question. The investigation was limited to a study of the alloys containing nickel and silicon; nickel, silicon and cadmium; and cobalt and silicon. The experiments made in the course of the study arc described in this paper in three groups: 1. The effect of hard drawing subsequent to heat trcatment on the mechanical and electrical properties of the alloys. 2. The effect of low-temperature aging on the properties of heat-treat,ed and hard-drawn alloys. 3. The effect of strain on the rate of aging of quenched nickel-silicon-copper alloys. Preparation and Compositions or the Alloys The alloys were prepared by melting cathode copper in an electric resistance furnace and adding sufficient of the hardening elements to bring the compositions to the desired values. The purities of the hardening elements were as high as could be obtained in commercial practice. The metals were what are designated in the trade as electrolytic nickel, cobalt rondelles, commercial stick cadmium and fused silicon. The alloys

Jan 1, 1931

By U. Paakkinen, P. Eerola

In connection with theoretical studies of the dynamics and control of the flotation process, flotation cells and circuits at the Pyha- computer control of selective Cu - Zn - Fe sulfide flotation in the latter half of 1969. In this paper, the practical conclusions of these studies, conducted through simulation techniques, are summarized. The application of these results for control purposes implies a knowledge of the dependence of the flotation rate coefficients and the grade of concentrate on several factors, including aeration rate, froth depth, and reagent consumption. The relationships found in laboratory and plant scale tests are described. Off-line optimization studies, based on the relation- ships, are also described. The proposed steps in executing the computer control schedule are presented. In the first stage, a stabilizing control will be carried out using feed-back loops. A feed-forward control system which utilizes simple process models will also be tested. After these elementary stages, a proposed mathematical model of the circuit will be checked out and implemented with computer- run, plant-scale process tests. Off-line simulation will be continued in advance development of the control system. As a final step in the program optimal control of the process will be carried out through this model.

Jan 1, 1969

(Butte Meeting, August, 1913.) IN metallurgical circle it is. known widely, but somewhat vaguely, that the ease of reduction of metallic .oxides. depends largely on the way they have been prepared. It is likewise known that. different forms of carbon have different and greatly varying reducing powers. It is the purpose of, this paper to show somewhat more definitely and scientifically these facts. Sonic years ago the writer published an account of pyrometric determinations of the reduction temperature of zinc oxides variously prepared and of several kinds.1 In said paper it was shown that the temperature at which zinc oxide evolves zinc according to the equation, ZnO+C? Zn+CO depends upon the nature of -the two reacting bodies. The determinations bad a range of accuracy of from 2°to 6°C.,whereas differences were found to, amount to an extreme of 90° C. So the differences are real ones and must have a definite cause. The equation of boiling water, (H2 O)4 = 4 (H20) has a fixed temperature for? equilibrium of 100° C. at 760 mm. pressure. In general, all equations reacting in the liquid or the gaseous phase have well-defined constant physical conditions which govern the equilibrium point and reaction velocities.

Jan 7, 1913

By P. K. Kaiser, C. Mackay

A circular shaft with a diameter of 6m was excavated by the conventional drilling and blasting method to a depth of 235m through 60m of glacial till, 1 Om of water bearing basal sand, 1 1 Om of clay shale (Bearpaw Formation) and finally a strata of coal, mudstone, siltstone and sandstone (Oldman Formation). The lined shaft was instrumented at three levels by multipoint extensometers to determine the displacement field near the shaft bottom, embedment strain gauges to measure the strains in the liner and IRAD-stress change gauges to observe the radial and tangential stress changes in the rock mass. The data from these gauges were used to determine the in situ stress field. An attempt to measure in situ stresses by overcoring was also made at a higher elevation. The performance of the shaft and its support was then evaluated by use of the "Convergence-Confinement Method". For this purpose the measurements of stress changes and displacements were combined to determine by extrapolation the displacements ahead of the shaft and after the liner installation. The convergence curves calculated in this fashion were then used to evaluate the performance of the cast-in-place concrete liner and of an alternate shotcrete shaft support system.

Jan 1, 1983

By F. E. Turton

THE town of Rancagua, at the junction of the state and Braden Copper Co. railroads, is located 82 km south of Santiago, the capital of Chile. From Rancagua 70 km to the east, situated in the Andes at an elevation of 7000 ft, is the town of Sewell, the location of a millsite. Two and one half km east of Sewell by underground railroad at an elevation of 7500 to 10,000 ft is the Teniente orbody. The history of El Teniente dates from the eighteenth century, when according to legend a Spanish lieutenant, or teniente, a fugitive from justice, escaped to the Andes and camped at what afterwards became known as the Mineral El Teniente. This man reputedly discovered a vein of high grade copper ore. The first official records date from 1819, when some exploitation was begun, and continue until 1870. The orebody was large and of relatively low grade and was beyond the capabilities of the small groups attempting to operate it. No effort was made to erect a concentrator until William Braden became interested in the property. In 1901 Mr. Braden promoted the necessary capital for the first practical exploitation of the orebody. Barton Sewell and E. W. Nash, both of the

Jan 1, 1952

By W. J. Tait, A. E. Craig, E. P. McCurdy

The Circuitron herein described applies current from the classifier motor circuit and energy from the sound of grinding media to move an oscillating disc. The disc through a photoelectric cell controls the speed of the ore feeder and consequently the amount of ore delivered to the mill. THE Telluride Mines, Inc. at Telluride, Colo., is operating a flotation concentrator recovering lead, zinc, and copper with some gold and silver. The nominal capacity is 500 tons per 24 hr. The ore, which comes from several different mines, is characteristic of the district, changing from extremely tough rhodonite to soft gouge. The ore is crushed and washed, recrushed, and delivered to the mill bin at about % in. to serve as ball mill feed. Details of Grinding Circuit The material from the fine-ore bin is carried over a belt feeder driven by a Reeves vari-speed device. The belt discharges to a No. 86 Marcy ball mill, which operates in closed circuit, with jigs and a 6-ft Dorr classifier. A Massco density controller holds the density of the classifier overflow at a predetermined point. The overflow, which contains about 5 pct + 48 mesh, goes to the flotation section. Manual Operation Before the adoption of automatic control for the grinding circuit, this work was all done manually by the operator. The bin gate was set to deliver 40 to 50 lb of ore per lineal foot of belt, and the speed of the belt was adjusted by the operator to deliver at the rate of about 500 tons per 24 hr. As the ore changed in hardness, specific gravity, or in the amount of moisture, or, as the size of the feed changed due to bin segregation, crusher setting, or other causes, the operator made corresponding changes in the rate of feed by manipulation of the Reeves control. Sometimes these changes occurred so rapidly that they caused sharp, pronounced surges, which created very considerable unbalance from normal conditions in the grinding circuit and, more critically, in the flotation section. Since it is not possible for the operator to anticipate or follow such changes closely, a very considerable unbalance from normal conditions may occur, which will require a drastic change in the rate of feed. These surges upset the fineness of grind and interfere radically with the balance between tonnage and reagent control. All of this tends to reduce the grade of concentrates, increase the loss in the tailing, and thus decrease the recovery of values. The Circuitron Some years ago, The Mine and Smelter Supply Co., in conjunction with the operators at the Telluride Mill, undertook to build a device that would give close control of the rate of feed from the ore bin and to coordinate with this a related device that would regulate the amount of sand load on the classifier rakes. Emphasis was strongly laid on the fact that such a control must apply to the entire grinding circuit and must include the feed to the ball mill, the classifier sand return, and the density of the classifier overflow. If this could be done successfully, we felt that the circuit could be operated under best possible conditions, with compensations

Jan 1, 1951

By George L. Montgomery

In a recent article Heckler, Elias, and woods1 have described an automatic computer technique for plotting of pole figures. To anyone who has constructed pole figures manually from raw X-ray data, the development of computer plotting techniques has been a very welcome development. The purpose of the present note is to describe an alternative computer plotting method which, if somewhat less precise than the method described by Heckler et al., has the advantages of being faster and of not requiring the availability of a plotter. The plot is made directly by the printer of the terminal system and, by its nature, has a good deal of visual impact. Each character of output symbolizes a level of intensity. For example the numerals 1 to 9 might represent intensities referred to some reference obtained from a randomly oriented sample. Should more levels be required (this is seldom necessary) alphabetic or other characters may be used in addition. When these are arranged in the proper fashion, the result is a pole figure such as is shown in Fig. 1. It is the purpose of the computer program to transform the data and carry out the arrangement in a suitable manner. The computation is carried out on a line by line basis in order to reduce the amount of storage required and thus keep the program "small". It is, thereby, well within the limitations of the time-sharing systems which are becoming increasingly available. The inaccuracies introduced are slight and the plot can easily be made as precise as the technique used to collect the data. Comparison of pole figures produced by this method with those constructed manually shows a high degree of equivalence. To the present, the technique has been applied to reflected X-ray data only. X-ray data are collected in a manner identical to that described by Heckler et al. That is, as the goniometer rotates the specimen, a series of counts, accumulated over a preset time, is recorded. The method by which the proper symbol, representing an intensity level, is assigned to each print position is up to the ingenuity of the programmer. Perhaps the simplest method is to section the stereograph in the fashion of a polar net, and to assign all print positions lying within each segment a symbol representing the level of intensity recorded at the data point nearest to the center of the segment, see Fig. 2. The number and arrangement of the segments are selected to conform more or less with the number of accumulated counts and the geometry of the goniometer path used to collect them. Since the angular distance between accumulated counts is usually not infinitely controllable, it is impossible to locate one reading within each segment and, at the same time, maintain symmetry in the sectioning of the stereograph. This latter requirement is essential to keep the computer program simple and flexible. As an expedient it was found that the number of data points could be increased to conform with the number of segments, with very little loss of

Jan 1, 1969

By C. S. Smith, K. K. Ikeuye

In an earlier paper1 one of the authors called attention to the significance of the relative free energies of grain boundaries and interphase boundaries in alloys in determining the shape and distribution of micro-constituents. The ratio of the interphase and inter-crystalline boundary energies (that is, —?12, where ?12 is the energy of the interface between a crystal of phase 1 and a crystal of phase 2, and ?11 is the energy of the boundary between two crystals of phase 1) will be denoted by F. It is this ratio that determines, by the simple triangle of forces relation, the dihedral angle, ?, of phase 2 where it adjoins a boundary between two grains of phase 1. On a metallographic sample various angles are actually obtained because of the random orientation of the plane of observation, but the statistically most frequent angle is the true one. These basic principles were discussed in detail in the earlier paper. The experiments described below show the effect of both composition and temperature on ? and T for some alloys containing a liquid phase, and provide data on the rate of approach to the equilibrium angles in both solid and liquid phases. All the alloys were melted in a graphite crucible and cast into ingots 3/4 by 11/8 in. cross-section. Some of the aluminum alloys consisted of two immiscible liquids from which uniform castings could not be obtained. The amount of liquid phase varied locally to a considerable extent and the analyses were meaningless. Nevertheless, the composition of the liquid would not differ from that in an alloy of the intended gross composition, and the synthetic composition of the alloys was therefore used in considering the surface energy results. The ingots were given initial deformation by cold-rolling to 50 pct reduction, annealed, and given a second 50 pct reduction prior to cutting into small samples for heat treatment at the times and temperatures subsequently reported. The resulting micro-samples were carefully prepared metallographically and examined at magnifications of 650, 1280, or 2500. The objectives used were 21X, 0.40 NA (dry); 41X, 0.65 NA (dry); and 80X, 1.40 NA (oil emulsion). The appropriate angles were measured by rotation of the stage of a Bausch and Lomb metallograph to align the appropriate boundaries successively with a cross-hair in a micrometer eyepiece. About 250 angles were measured on each phase. Though the angles were read to 1°, the accuracy is probably not above 3°, because of uncertainty in setting the cross-hair tangent to the sometimes curved boundary. The corners of very small particles, particularly in early stages of adjustment after cold-rolling, were difficult to measure and the results were slightly dependent on the magnification used (compare Fig 1-C and 1-D). With particles of larger size and more nearly equilibrium shape, magnification made no difference (vide Fig 1-F and 1-G). The measured angles were grouped in 10° intervals (5° if ? was less than 20°) and plotted in bar

Jan 1, 1950

By E. P. McCurdy, W. J. Tait, A. E. Craig

The Circuitron herein described applies current from the classifier motor circuit and energy from the sound of grinding media to move an oscillating disc. The disc through a photoelectric cell controls the speed of the ore feeder and consequently the amount of ore delivered to the mill. THE Telluride Mines, Inc. at Telluride, Colo., is operating a flotation concentrator recovering lead, zinc, and copper with some gold and silver. The nominal capacity is 500 tons per 24 hr. The ore, which comes from several different mines, is characteristic of the district, changing from extremely tough rhodonite to soft gouge. The ore is crushed and washed, recrushed, and delivered to the mill bin at about % in. to serve as ball mill feed. Details of Grinding Circuit The material from the fine-ore bin is carried over a belt feeder driven by a Reeves vari-speed device. The belt discharges to a No. 86 Marcy ball mill, which operates in closed circuit, with jigs and a 6-ft Dorr classifier. A Massco density controller holds the density of the classifier overflow at a predetermined point. The overflow, which contains about 5 pct + 48 mesh, goes to the flotation section. Manual Operation Before the adoption of automatic control for the grinding circuit, this work was all done manually by the operator. The bin gate was set to deliver 40 to 50 lb of ore per lineal foot of belt, and the speed of the belt was adjusted by the operator to deliver at the rate of about 500 tons per 24 hr. As the ore changed in hardness, specific gravity, or in the amount of moisture, or, as the size of the feed changed due to bin segregation, crusher setting, or other causes, the operator made corresponding changes in the rate of feed by manipulation of the Reeves control. Sometimes these changes occurred so rapidly that they caused sharp, pronounced surges, which created very considerable unbalance from normal conditions in the grinding circuit and, more critically, in the flotation section. Since it is not possible for the operator to anticipate or follow such changes closely, a very considerable unbalance from normal conditions may occur, which will require a drastic change in the rate of feed. These surges upset the fineness of grind and interfere radically with the balance between tonnage and reagent control. All of this tends to reduce the grade of concentrates, increase the loss in the tailing, and thus decrease the recovery of values. The Circuitron Some years ago, The Mine and Smelter Supply Co., in conjunction with the operators at the Telluride Mill, undertook to build a device that would give close control of the rate of feed from the ore bin and to coordinate with this a related device that would regulate the amount of sand load on the classifier rakes. Emphasis was strongly laid on the fact that such a control must apply to the entire grinding circuit and must include the feed to the ball mill, the classifier sand return, and the density of the classifier overflow. If this could be done successfully, we felt that the circuit could be operated under best possible conditions, with compensations

Jan 1, 1951

By E. Stamboliadis

Dithiophosphates are reaction products of phosphorous pentasulfide with various organic compounds such as phenols, alcohols, mercaptans, dioalcohols, amines, and nitrides. The products with alcohols are commercially known as "aerofloats" and these are investigated in this presentation. It appears that the formation of insoluble metal dithio phosphates is responsible for their collecting properties with minerals." In this aspect they are very similar to xanthates.3 The solubility of metal dithiophosphates depends on the number of carbon atoms in the organic chain of the corresponding alcohol. An empirical mathematical model is presented here. It allows one to predict the number of carbon atoms necessary to ensure that a certain metal dithiophosphate will form at a selected pH value of the water solution. The Nature of Dithiophosphates Dithiophosphoric acid is the product of the reaction of phosphorus pentasulfide with an alcohol, as shown in the following equation: [P2S3 + 4 ROH - 2 (RO)2 PS2H + H2S (1)] where R stands for a hydrocarbon chain. The acid so produced can be neutralized by a base to produce the corresponding salt as shown in the following: [(RO), PS2H + NH- (RO)2 PS, NH,. (2)] In this aspect dithiophosphates are similar to xanthates, the only difference being the substitution of the tetravalent carbon atom in the xanthate polar group by a pentavalent phosphorus atom in the dithiophosphate group. This difference implies at least two characteristics: (1) that there are two hydrocarbon chains associated with the polar group so that an increase in the number of carbons of the single chain is expected to have a pronounced effect on the flotation properties, and (2) that the bond between the sulfur and the central atom is stronger than in the xanthate group. This probably leads to a decrease in both the polarizability of the electronic cloud of the sulfur and the interaction with cations.3 However, what is lost in the dithiophosphates by having a weak polar group can be gained by an increase in the number of carbons as will be seen later. Taking into account the size of the atoms involved in a dithiophosphate molecule, as listed in Table 1, It is possible to draw an approximate diagram of its structure as shown in [Fig. 1]. It is assumed here that the length of the single hydrocarbon chain is equal to that of the corresponding alcohol. Preparation and Purification Acid dithiophosphates can be prepared, as previously mentioned, in accordance with Eq. 1. The rate of this reaction is too slow at room temperature and can be improved by increasing the temperature to about 60° or 80°C7 or by evacuating the system. In our investigation evacuation was performed by a water aspiration pump. The dithiophosphoric acid so produced is liquid and dissolves in the alcohol. At the end of the reaction the product is filtered from the remaining P2S3; and dissolved in petroleum ether. By blowing anhydrous ammonia gas into the ether phase the ammonium salt forms as a white precipitate and can be sepa-

Jan 1, 1977

By R. D. Longyear

[Some Problems Involved in the Interpretation of Diamond-drill-hole Sampling and Surve ing (paper by J. J. Collins, Mining Tech., Jan. 1946). ............... I Geologic Interpretation of Magnetic Exploration on the Mesabi Range, Minnesota (paper by R. H. B. Jones, Mining Tech., July 1946) ................... 2] DISCUSSION R. D. LONGYEAR.*-Mr. Collins is to be commended very highly for the brief summary he has made of the currently used methods of taking diamond-drill sludge samples and the principles involved in evaluating the results. This paper should stimulate further discussion and research on this vitally important problem. It is particularly imperative that geologists and engineers know when assay results on sludge recovery can be accepted quantitatively and when they must be considered only qualitatively. In most cases where the sludge recovery is less than 95 per cent or more than 125 per cent, it is safest to consider the assays as of qualitative value only. Certain cases, however, are known where a relatively small proportion of the sludge sampling will give a reasonably accurate measure of the value of the total sample. One such case is ore in which the valuable mineral is of approximately the same specific gravity as the waste mineral, such as chalcopyrite in a massive pyrite body. The essential point is to determine the degree of accuracy of sludge sampling in any given drilling project and to weigh the results accordingly. It should be emphasized, however, that sludge sampling can be made reliable in many localities where careless practice produces unreliable results. In many instances, it is desirable to empty the core barrel in the core shack instead of at the drill, so that the engineer can examine the core as it first comes from the core barrel. It should be pointed out, however, that the drill * E. J. Longyear Co., Minneapolis, Minnesota. runner should be permitted to study the core to guide his future drilling. It is hoped that with the return of more normal conditions after the war geologists, engineers, contractors, and manufacturers will be able to carry on more research along the lines of improved core-barrel design and drilling technique with the objective of increasing core recovery so as to eliminate as far as possible the necessity of relying upon sludge samples. H. M. ROBERTS.*-Whoever in the future will have to do with the search for ore bodies and their exploration will have frequent occasion to refer to the clear and comprehensive summary on diamond-drilling methods by John Collins. His review of the experience of the last 40 years in this technique is invaluable. As Dr. L. D. Ricketts wrote in 1932, "The principles on which an art is founded are usually few and necessarily basic in nature, but he who wishes to achieve the power to select his aides and give success to important undertakings that may be intrusted to him in the future must ordinarily undergo years of drudgery in order to gain the experience that will enable him to distinguish such fundamentals through the haze of reinforcing detail that clothes and tends to disguise them."[t] Ricketts went on to say that since the beginning of the century there has been much

Jan 1, 1946

By Maynard H. Jameson

Earlier investigations of the potential-drop-ratio method of electrical prospecting have indicated that under suitable conditions this method is well adapted to the location of formation boundaries in stratified ground. A description of this development was given several years ago by H. Lundberg and Th. Zuschlag.l The curves published by these authors for the potential-drop-ratio variation above a horizontal contact indicated a definite relation of the position of the curve peak to the depth of the interface. The theory underlying this relation was subsequently studied by Z. Mitera in greater detail,' and the theoretical deductions were compared with the results of tank experiments. The investigations available at this writing were confined to studies of horizontal formation boundaries. It is the purpose of this paper to extend the scope of the previous work to the problem of dipping layers. Theory Consider the case of three media of different resistivities, whose interfaces are not parallel. If a point-source is located in one of these interfaces, its images do not lie in a straight line, but on the circumference of a circle whose center is at the hypothetical junction of the interfaces. R. F. Aldredgea determined the relation that exists between the degrees of dip of the two interfaces and the distances between the various images and the point for which the potential is to be found. As seen in Fig. I, three media of resistivities PO, p1, and p2 are involved, and the source I is located at the interface of the media Coo) and (p1). The perpendicular depth of the lower interface is h, 0 is the dip, R is the distance between source I and potential point P, and r is the distance between the images and that point. To distinguish between images lying above the ground interface and those below, the notation "odd" and "even" images will be employed; images below the ground interface will be termed "odd" and those above "even." The following relations govern the distances between either kind of images and the potential point: EvEn Odd Ta — R r1 - [rl] - [RS + 4h(h + R sin 01½ r, = [r] =. [R1 + 4h cos 0)2(h + -R sin 0)1½ ri - [r3] ={r3} [R* + 4h(4 cos2 0 - i)1 (h + R sin 0)l½ r4 = [r4] = [R2 + 4h(4 cos $ cos 30)1 (h + R sin 0)]½ r, — [r4] - [R2 + 4h(4 cos9 R cos 20 + cos 48)2 (h + R sin 01½ I RI + 4h[2 cos 30(4 cos2 0 - I)12 (h + R sin 8)1 ½ rn - [r4] - [R2 + 4hlf(cOs 0)18(h + R sin R)l½ As previously pointed out, the images of the source are on the circumference of a circle. If the angle of dip is 0, the angle measured from the horizontal to the first image is 28; to the second image it is 48, and so on. Since the limit of the reflecting interface is at its outcrop, the last possible

Jan 1, 1946

By Maynard H. Jameson

Earlier investigations of the potential-drop-ratio method of electrical prospecting have indicated that under suitable conditions this method is well adapted to the location of formation boundaries in stratified ground. A description of this development was given several years ago by H. Lundberg and Th. Zuschlag.l The curves published by these authors for the potential-drop-ratio variation above a horizontal contact indicated a definite relation of the position of the curve peak to the depth of the interface. The theory underlying this relation was subsequently studied by Z. Mitera in greater detail,' and the theoretical deductions were compared with the results of tank experiments. The investigations available at this writing were confined to studies of horizontal formation boundaries. It is the purpose of this paper to extend the scope of the previous work to the problem of dipping layers. Theory Consider the case of three media of different resistivities, whose interfaces are not parallel. If a point-source is located in one of these interfaces, its images do not lie in a straight line, but on the circumference of a circle whose center is at the hypothetical junction of the interfaces. R. F. Aldredgea determined the relation that exists between the degrees of dip of the two interfaces and the distances between the various images and the point for which the potential is to be found. As seen in Fig. I, three media of resistivities PO, p1, and p2 are involved, and the source I is located at the interface of the media Coo) and (p1). The perpendicular depth of the lower interface is h, 0 is the dip, R is the distance between source I and potential point P, and r is the distance between the images and that point. To distinguish between images lying above the ground interface and those below, the notation "odd" and "even" images will be employed; images below the ground interface will be termed "odd" and those above "even." The following relations govern the distances between either kind of images and the potential point: EvEn Odd Ta — R r1 - [rl] - [RS + 4h(h + R sin 01½ r, = [r] =. [R1 + 4h cos 0)2(h + -R sin 0)1½ ri - [r3] ={r3} [R* + 4h(4 cos2 0 - i)1 (h + R sin 0)l½ r4 = [r4] = [R2 + 4h(4 cos $ cos 30)1 (h + R sin 0)]½ r, — [r4] - [R2 + 4h(4 cos9 R cos 20 + cos 48)2 (h + R sin 01½ I RI + 4h[2 cos 30(4 cos2 0 - I)12 (h + R sin 8)1 ½ rn - [r4] - [R2 + 4hlf(cOs 0)18(h + R sin R)l½ As previously pointed out, the images of the source are on the circumference of a circle. If the angle of dip is 0, the angle measured from the horizontal to the first image is 28; to the second image it is 48, and so on. Since the limit of the reflecting interface is at its outcrop, the last possible

Jan 1, 1946

By C. E. Westley, R. R. Beebe

Recent works by Plaksh et al.,1,2 Glembotsky,3 and others have renewed interest in the effects of oxidation on the surface activity of the sulfides. Since considerable supporting data are available on galena-potassium ethyl xanthate, this system is being studied at South Dakota School of Mines and Technology by contact angle measurement, using the technique of McGlashan and McLeod.4 The contact-angle method is well adapted to investigation of the influence of small amounts of oxygen on the establishment of a stable contact angle on galena in potassium ethyl xanthate solution. Samples of massive galena containing less than 0.001 pct Cu, 0.001 pct Ag, and 0.01 pct Zn are mounted in castable plastic and ground and polished manually in a glove box containing the desired proportions of oxygen and purified nitrogen. Oxygen and nitrogen contents of the test atmosphere are determined with an Orsatt analyzer. In this way a reproducible surface is created in contact with whatever oxygen concentration is desired. Water and all reagents are prepared and stored in the test atmosphere. An absorbent is used to control carbon dioxide that might be present. Final polishing is done with levigated alumina on a glass plate. The prepared sample is placed in the test solution and transferred to the contact angle apparatus in a sealed box, and the test is conducted while both sample and solution are maintained under a slight positive pressure of the test atmosphere. Table I gives the results of contact angle measurements made at various 02-Nz concentrations.5 Each value of contact angle is the average of at least six individual measurements made with different bubbles at different locations on the sample surface. A period of 20 to 25 min has been found by preliminary tests to be sufficient to permit develop- ment of maximum angle, and all measurements are made after at least this much time has elapsed. Exposure of prepared samples to pure water under the test atmosphere before exposure to the xanthate results in a small but measureable and consistent reduction in contact angle. This is particularly true in the oxygen-deficient atmospheres; for example, at 2.2 pct O2 such water contact reduces the average angle about 8" from that obtained by immediate testing in xanthate. The general trend of increasing contact angle with increasing oxygen concentration corresponds to the results of Plaksin et a12 The absence of diminish-ment of contact angle at very high oxygen concentration has been attributed to the high concentration of xanthate per unit of galena surface: At oxygen concentrations below 1 pct (the limit of accuracy of the Orsatt analyzer), no contact angle is obtained. Furthermore, no contact angle is obtained at any oxygen concentration in the absence of xanthate. This result seems to be in disagreement with those cited by Plaksin.1 Further work on the interaction of galena and potassium ethyl xanthate or a similar collector as influenced by oxygen is contemplated. The true nature of the interrelation is as yet unknown. For example, it is not known whether the governing oxygen reaction is with the mineral, with the reagent, or with both.

Jan 1, 1961

By J. P. Heller, H. B. Bradley, A. S. Odeh

It is an accepted procedure to represent oil field displacement problems in which the pressure is relatively constant by a potentiometric model. Variations in reservoir permeability thickness product are represented in the model by proportional variations in electrolyte depth. It is shown that significant errors are present wherever these variations are of such magnitude that the consequent differences in the electrolyte depth in the model or any regions therein are appreciable in comparison with their respective horizontal dimensions. To demonstrate the order of magnitude of this error, a hypothetical linear oil field in which permeability varies linearly with distance was treated both analytic.ally and by potentiometric model. The results obtained from the model are compared with the exact solution for various configurations of linear geometry. Deviations in flow times up to 11 per cent were observed. It is confirmed that these discrepancies can be reduced by increasing the areal scale and/or decreasing the vertical scale of the model. It is the purpose of this work to assist in the design of potentiometric models by indicating the relationship between this error and the chosen scale factors. INTRODUCTION The fundamental geometrical criterion which determines whether the pressure distribution in an oil or gas reservoir may be simulated in a conventional potentiometric model is the requirement that all reservoir parameters be constant along any vertical line between its upper and lower boundaries. This situation never obtains exactly; nevertheless, it is usually assumed that there is no permeability stratification within the section of interest, that all wells completely penetrate the sand, that there are no gravitational effects, and that variations in thickness of the sand are small compared to the horizontal extent of the field. In these ways the reservoir problem is reduced to two dimensions in which there is no variation of pressure in the vertical direction within the limits of the sand. Variations in sand thickness and/or horizontal pesmeability may be taken into account as described by Muskat, by considering the fluid conductivity of the reservoir in its horizontal plane to be proportional to the product of permeability and sand thickness. If the variations in sand thickness are small compared to the horizontal dimensions of the reservoir, then it is a good approximation to consider the reservoir problem to be essentially two dimensional. The same approximation, however, is made in the simulation of the assumed two-dimensional reservoir by the electrolytic model. The model, if it is to take into account variations of permeability-thickness product, must of necessity be made in three dimensions, that is, with variable depth. Most potentiometric model studies and theoretical treatments reported in the literature to date2,3,4,5,6,7,8 are those in which either an average permeability was used or a constant permeability was assumed. This is understandable since detailed permeability data are not usually available for the majority of reservoirs. Many investigators have recognized that the failure to incorporate permeability variations within a reservoir in model studies leads to serious error in predictions made

Jan 1, 1957