Search Documents

"The cleanliness and system evidenced in the accompanying photographs of the West Steward change-house will appeal to all mine operators. This design is the most efficient in use at Butte. It is the standard which will probably be used in Butte in all future construction and is the result of a long period of investigation and experimenting. It is important that such a structure be as nearly fire-proof as possible, because of the frequent fires originating within the lockers from matches, etc., in the men's clothes. The concrete floors permit the thorough washing of the building whenever necessary.The lockers are roomy and well ventilated. They are constructed of sheet steel and are warmed from below by steam pipes."

Jan 1, 1913

By Raymond Mancha

A TEST of any fan requires the determination of such data as fan pressure, air volume handled by the fan, and power input to the fan shaft. When testing operating mine fans of the centrifugal type, test methods have been employed, for the sake of convenience, that permit great latitude in detail of procedure resulting in wide variance in results by different investigators. Some controversial aspects of field fan testing are the result of past failure to define dearly the various forms of fan pressure and to a lack of understanding of the accurate procedure for the measurement thereof. Also, the anemometer for air-volume measurement, although convenient, if carelessly used and maintained is subject to a wide error range with variation in method of application and in instrument accuracy. The appearance of the axial-flow type of mine fan offers the possibility of refinements in field testing that were impractical with the centrifugal fan. First of all, the fan inlet and outlet are more sharply defined, giving loser agreement as to just where the fan begins and ends; thus there is less disagreement as to the proper location for measurements of fan pressure. The area of passage into the inlet of an axial-flow mine fan usually constricts, causing high air velocities with accompanying steadiness of flow. Thus the fan inlet offers an ideal location for accurate air-volume measurements with the Pitot tube, the proper use of which is well established by code. Thereby the controversial aspects of such measurements are eliminated. Use of the Pitot tube also facilitates a more accurate measure of fan pressure, since the individual pressures measured can be properly weighted, as will be explained later. Determination of power input to the axial-flow mine fan operating in the field is subject to the same inaccuracies as with the centrifugal fan if the axial-flow fan is also belt driven. However, because of the higher rates of rotation usual with axial-flow fans, direct-driven units are more numerous and it is unnecessary to assume a drive efficiency, thus eliminating one possible source of error. It is the purpose of this paper to define and explain the various types of pressure measurements involved in a field test of an axial-flow mine fan, and to further explain the proper use of the Pitot tube when measuring pressures and volumes. DEFINITION OF FAN PRESSURES The two fan pressures most commonly discussed are fan total and fan static pressure, each of which has the same meaning regardless of whether the fan is blowing, exhausting, or blowing and exhausting, as in the case of a fan with ducts connected to both outlet and inlet. Fan total pressure is the amount by which the total pressure of the air delivered by the fan exceeds the total pressure of the air received by the fan. This pressure is a measure of the maximum amount of the work done on the air by the fan that is available for external use.

Jan 1, 1942

By Hallan N. Marsh

The subject of this paper is apt to bring to mind wells ranging from 6000 to over 8000 ft. in depth. However, it is uncommon to pump wells at depths greater than about 5000 ft. Fig. 1 shows the number of wells being pumped at various depths by one company in Southern California. A few companies have a very few wells pumping at depths greater than this. This paper will deal with wells between 3000 and 5500 ft. in depth. Most California oils at these depths are between 25" and 35" gravity. The subject is so broad that it will be necessary to omit many interesting phases, and to treat others very briefly. Power, power transmission equipment, power efficiency, counterbalancing, sucker rods, pumps and volumetric efficiency will be discussed. Power As a source of power, the 50/20-hp. electric motor is generally preferred. Input is generally between 10 and 25 hp. Due to the uneven-ness of the load, an input of 20 hp. on the low range is generally about all that these motors will carry without overheating, in spite of their overload capacity. In some cases the capacity of the motor limits the speed

Jan 1, 1929

By C. Gutiérrez

Flotation and adsorption studies of ilmenite with technical oleic acid, pure oleic acid, and mixtures of each of them with n-hexadecane have been conducted. From them it is concluded that the depression of ilmenite caused by a too long conditioning time is due to adsorption of the collector onto the fines produced by attrition in the conditioning cell, and that fuel oil is necessary for economic flotation of non-deslimed ilmenite ore. This beneficial effect of fuel oil is attributed to van der Waals forces, of the hydro-carbon chains.

Jan 1, 1978

By F. Cadena

HIWASSEE Dam, now under construction by the Tennessee Valley Authority on the Hiwassee River, a tributary of the Tennessee River, will require aggregate for approximately 800,000 cu. yd. of concrete. Near the damsite deposits of natural sand or gravel are not available and graywacke, a rock that is found in abundance, suggested itself as a likely source of manufactured aggregate. Graywacke is a metamorphosed sandstone composed principally of a mixture of quartz (65 per cent), mica (25 per cent), and feldspar (10 per cent). Other minerals are present in negligible amounts. The rock varies in different parts of the quarry from very fine to a coarse grain containing particles of about 1/4 in. maximum size, although the bulk of the deposit is medium grain. Extensive tests showed that graywacke would be suitable as a source of both coarse and fine aggregates. The aggregate plant available for use at Hiwassee Dam consisted of the coarse-aggregate and sand plant used on the Norris project. The coarse-aggregate plant had also been used at Chickamauga Dam. Although most of this plant equipment is now in use at Hiwassee, the present flowsheet is not only different from that at Norris and Chickamauga but is also unique as compared to the flowsheet of the average crushed-stone aggregate plant. It is hoped that this paper will show the importance of proper arrangement of equipment if the optimum in flexibility and capacity is to be attained. FLOWSHEET Rock is loaded by 3-yd. electric shovels into 12-yd. dump trucks, which carry the rock to the primary crusher, a 42-in. Superior McCully gyratory unit set at 4 ¾ in. (Fig. 1). The primary crusher discharges directly onto a 42-in. inclined belt conveyor, which carries the product to a surge storage pile with a maximum live storage capacity of approximately 3000 tons. A concrete tunnel under this storage pile houses the feed end of a 36-in. belt conveyor (conveyor B) fed by a 36 by 66-in.

Jan 1, 1939

By John E. Sherborne, William M. Newton

THE relation between the properties of electric logs and the fluid used in drilling a well is briefly discussed in this paper, and the fact that the resistivity of the drilling mud and its filtrate can appreciably affect such logs is shown. Apparatus was designed and a procedure established to determine the effect of various factors on the resistivity of drilling mud. Five muds commonly employed in California were tested and the following observations were made: I. The effect of raising the temperature from 80°F. to 180°F. is to decrease the resistivity of the mud or filtrate approximately 50 per cent. 2. The resistivity of the mud in most cases closely approximates that of its filtrate. 3. The change in the resistivities of muds caused by the addition of chemical is not the same function of the amount of chemical added for each mud. 4. The effect produced by increased sodium chloride content is to reduce markedly the resistivity of the mud and its filtrate. 5. Weighting materials, such as Baroid and limestone, tend to increase the resistivity of drilling mud. 6. Cement and counteracting reagents reduce mud resistivity.

Jan 1, 1942

By George J. Young

DURing the spring of 1910 1 visited a number of open-pit brown-coal mines and underground workings in the vicinity of Halle, Halberstadt, Leipsic, Cologne and Bonn. The notes which I took and the observations which I made at the time have been condensed and make up the principal part of this paper. Certain supplementary information has been taken from several sources which are given in the paper. The mining of brown coal is one of the important industries of Germany. The coal varies in color from dark brown to almost black and is soft like loam. Pieces of wood and strips of bark and even parts of tree trunks are frequently encountered in the excavation although the coal for the most part consists of a pulverulent, more or less matted mass of small particles of vegetal matter. It is a product between peat and lignitic coal. An analysis, taken from Coal Resources of the World shows the approximate composition of the material: Moisture, 53.73 per cent.; ash, 4.98; fixed carbon, 18.08; volatile carbon, 23.31 per cent. Thc principal characteristic is the amount of moisture. This seldom runs less than 48 per cent. The ash is usually low and ranges from 5 to 10 per cent. The sulphur content is usually less than 0.5 per cent. The heating effect of the fuel ranges from 2,000 to 2,500 calories. The commercial deposits are confined to the Tertiary period although

Jan 1, 1916

By Stanley L. Lopata, Eric B. Kula

The problem of preferred orientation has been considered in quantitative phase analysis by X-ray diffraction techniques. The average intensity of a diffraction peak can be obtained by integration over the whole pole figure, or by random rotation of the specimen in the X-ray beam, or by a combination of both. For rod or wire, where the pole figure shows rotational symmetry, the intensity is measured along a radius of the pole figure. Where no symmetry is present, rotational symmetry is imparted by rapid rotation of the sheet around its surface normal during measurement. These methods are applied to the determination of aus-tenite in an Fe-31 pct Ni rod and Fe-28 pct Ni sheet. X-RAY diffraction techniques are frequently used for quantitatively determining the relative amounts of two or more phases present in a structure.1,2 Briefly, the method requires a measurement of the intensity of a Bragg reflection for each phase. The method is based on the principle that the intensity of a Bragg reflection, IA, is directly proportional to the volume fraction of the given phase present, CA: T KRACA/2µ [1] where K is a constant independent of the diffracting phase, RA can be calculated and depends on the Bragg angle ? and the particular reflection measured, and µ is the linear absorption coefficient of the mixture.' For a mixture of two phases A and B, IA = RAcA [2] IA/IB=RAcA/Rbcb and CA+ CB = 1 [3] This allows the volume fraction of a phase to be calculated directly from the measured integrated intensities of the two phases present. This method is frequently used for quantitatively determining retained austenite in steels, but can be used for the quantitative determination of in titanium alloys, as well as phases in other alloy systems. The intensities are generally measured by diffracting only from planes whose normals are perpendicular to the specimen surface, with the implicit assumption being made that this intensity is typical of reflections from planes whose normals lie at other angles to the surface. If the specimen contains a texture or preferred orientation of the crys- tallographic planes by virtue of previous mechanical working, however, this measured intensity is correct only if the intensity level fortuitously is one times random. Examination of pole figures for actual rolled sheet shows that the intensity level at the center of the figure is seldom at the random level, and can very easily differ by a factor of five or more, leading to a commensurate error in the calculated amount of the phases. Textures have been commonly found in materials which are cold-rolled or recrystallized after cold rolling. This problem is becoming of greater importance since structural materials in use today, such as the high-strength stainless steels, frequently are further strengthened by cold rolling, and hence contain textures. Although high-strength carbon-containing alloy steels generally do not contain textures, some of the newer thermomechani-cal treatments will impart a texture even in these cases. In the case of hexagonal metals, such as titanium, probably every wrought sample will show some anisotropy. Since the standard X-ray techniques are inapplicable in all these cases, there is a clear need for some method of taking this anisotropy into account. The specific problem is to obtain the integrated intensity of a Bragg reflection for each phase, averaged over all orientations of the sample with respect to the X-ray beam. This can be done either by purely mechanical means or by a mathematical averaging. Mechanically, a small spherical speci-

Jan 1, 1965

By George Rice

VENTILATION of underground workings to fur-nish air of good quality to workers is now the accepted practice for all kinds of mining; but in coal mining it is also a requirement vital for safety to have systematic coursing of the air to all parts of a mine so that fire damp can be diluted and carried away. These two basic needs are recognized in the codes of every country or State where coal is mined, and each has its own system of ventilation requirements. With the same fundamental requirements, varying in degree but not in kind, the surprising thing is that these and other features of regulatory codes should vary so-wide-ly that their provisions on the same subject bear hardly any resemblance to one another. This was strikingly brought out in the paper given before this institute in 1926, on "State Coal-Mining Laws Concerning Ventila-tion1. The explanation ordinarily is that the geologic forma-tions and the mining conditions and methods differ in the various coal fields. Although that is true, in most countries and States the variations in the differ-ent mining districts within each country or state vary widely, and the respective codes must be made to apply by special provisions to meet the variations in thickness of coal, depth,. dip, character of roof, and presence or absence of gas. Evidently the great diversity in codes is due to the method of formulating them. Some are prepared by political commissions in which partisan interests are a factor; others originated in the early days of mining with meager outlines and were so amended by legisla-tive acts or administrative orders from year to year as to become complicated and ambiguous, and pro-visions in different parts of a single law are often contradictory. Such laws have therefore been difficult to interpret and to enforce adequately.

Jan 5, 1928

By R. Henry Norton

The State of Oregon, although admitted into the Union February 14, 1859, is to-day, so far as any practical knowledge of its mineral resources is concerned, almost terra incognita, as compared with the other Western States and Territories. This is partly to be accounted for by the class of emigrants who first settled in the country ; they seem to have been, as they still are, a pastoral community, to whom the terms " mines " 'and " mining " are synonymous with bankruptcy and disaster, and who discourage all attempts to develop the mineral resources of the State. This statement is emphasized by the fact that Oregon has no State Geolo-

Jan 1, 1891

By J. B. Murdoch, John G. Jackson

The many mechanical, geological, and economic factors which influence the planning of a directional drilling program are thoroughly discussed and analyzed. It is demonstrated that the planning of a directionally drilled multiple-well artificial island location is a complicated undertaking and that it is imperative that complete planning and engineering analysis be undertaken before the program is started. Complete planning is profitable because all of the factors influencing the directional work are in general interrelated and many time compromises have to be made before a harmonious program results. The engineering control necessary to accomplish a complicated directional drilling program is outlined. Various means by which engineering control can be increased, such as cylinder drilling specifications, are given. A hypothetical example is developed for a complete offshore artificial island of ten wells to demonstrate the more important factors involved in the planning. Included with this example are special charts and tables which make more rapid the drafting of directional drilling proposals and maps. Introduction A petroleum engineer must consider many and varied factors when planning a long range directional drilling program for an offshore or inaccessible location on an oil structure. The basic principles of direc- tional drilling planning and operation must be reconciled with his company's drilling practices, and frequently special concessions to standard drilling and production practices should be made. The field techniques and tools used in directional drilling are well known and widely used, but the deliberate, careful planning of a complete directional program is in the main a recent innovation. This development, plus the increased demand for oil resources and the consequent exploitation of inaccessible structures and offshore locations, has placed this problem before many engineering departments for the first time. Directional drilling programs of a very complex and difficult nature have been successfully carried out in the Mid-Continent and Pacific Coast regions. The planning itself of a directional drilling project, however, has not had the careful analysis it deserves and we can reasonably expect widespread future progress along thesc lines. Data and experience gained in these programs by the directional drilling service companies and the oil producers have been studied with the objective of giving the engineer a better conception of the factors which govern the various steps in planning a series of directional wells. The newest engineering procedures are the result of recent careful analysis of years of directional drilling work accomplished under the supervision of directional drilling service companies working with the oil companies. The purpose of this paper is to illustrate

Jan 1, 1949

By Alex McCoy

SAMPLING of the fluid from oil wells for percentages of oil, emulsified oil, and water during the last two years has brought out some interesting facts concerning oil-water emulsion. This result led to a laboratory investigation of emulsion, which substantiated the conclusions made from the field observations. The purpose of this paper is to present the information collected, the laboratory experiments, and our interpretation of the same. In order to define emulsified oil exactly, give its synthesis and origin, and to show how and when it is formed in the wells, the work was necessarily divided into two separate lines-laboratory work and field observations. It is hoped that this study may lead to a discussion of such points so that the petroleum engineer, geologist, or technologist may be benefited by its practical bearing on oil-field management. Special credit is due Mr. Everett Carpenter, chief geologist of the Empire Gas & Fuel Co., for his assistance and cooperation in this work. LABORATORY INVESTIGATIONS ON EMULSIFIED OIL Laboratory investigations were conducted in an attempt to learn the composition and some of the properties of emulsified oil, or B. S., as it is more commonly called, also to demonstrate, by laboratory methods, how B. S. may be formed under conditions similar to those existing at the time a well is being pumped, and how it may be broken down. Literature bearing on this subject is widely scattered and very limited in scope. Bacon and Hamor define B. S., or bottom settlings, as "earthy matter, inert organic matter, or, in the case of Pennsylvanian petroleum, an emulsion of paraffin wax and water, which accompanies crude oil." In this discussion we will limit the term B. S. to that heavy,

Jan 8, 1919

By L. H. Hart

Because of a widely recognized association between breccia pipes of one form or another and many important copper deposits, conditions under which breccia pipes develop have been of great scientific interest for many years. Since these phenomena first attracted attention, many theories have been advanced to explain their origin. This is not unexpected, since it is likely that they have been formed by and under a wide range of conditions. Moreover, the entire subject is confused by the fact that the term breccia pipe is applied to a wide variety of occurrences. To discuss any part of the subject intelligently, therefore, it is necessary to start with definitions of the terms used. In their discussion of the Toquepala deposit, Richard and Courtright have carefully defined the terms they have used in their presentation of a very logical geo- logical history of Toquepala breccias. This is a real contribution, as there is no reference in the literature known to the writer where the history of a series of breccia pipe epochs, confined essentially within one channelway, may be read with the degree of certainty that appears to be possible at Toquepala.

Jan 6, 1958

By W. J. Nelson, R. B. Nance

Detailed underground geologic mapping at a scale of 1:1200 has been carried out at the Crown II Mine of Freeman United Coal Mining Co., which operates in the Herrin (No. 6) Coal Member. The roof sequence, upward from the coal, includes (1) soft, medium -to dark-gray shale; (2) hard, black, fissile shale; (3) argillaceous nodular- bedded limestone, and (4) fine-pined, shaly, water-bearing sandstone. The first unit is highly lenticular, and any or all may be missing at a given locality. The sandstone has a sheet facies and a channel facies. The Herrin Coal is eroded in channels near the Crown II Mine. Structural features mapped at Crown II include normal and strike-slip faults and limestone "bosses." Less stable roof and wet conditions are encountered where the limestone is thin or missing or where it is broken by natural fractures or by artificial openings that intersect the water-bearing strata above the limestone. Geologic mapping of the underground workings has allowed us to predict faults, fracture zones, and channels ahead of the face for this mine. Some lithologic and structural pattern apparently are random and cannot now be projected. Conventional exploratory drilling is entirely inadequate to map faults or lithology of the roof, but it does indicate the range of lithologic variability, which can be used to project needs for roof supports. Drilling also is useful in locating channels and in mapping regional variation in thickness and facies of the sandstone.

Jan 1, 1983

By H. M. Howe, E. C. Groesbeck

That the quiescence of a liquid while it is solidifying should favor the formation of columnar crystals, normal of the cooling surface, is seen readily on considering the mechanism of solidification. First, each particle of any composite liquid, whether it be an aqueous solution or a molten metal, in solidifying splits up into two parts, different in composition and hence in fusibility. One part is infusible at the existing temperature, and hence solidifies, and in general attaches itself to the inclosing walls of metal which have already solidified; A, Fig. 1. The other part is fusible at the existing temperature and hence remains molten. In the case of carbon steel, the part of each drop which actually solidifies is poorer in carbon than the drop itself was before it began to solidify, and this impoverishment of the solidifying half-drop enriches the other half-drop in carbon, and thus makes it unfreezable at the existing tern- By this mechanism there arises during solidification a "littoral" or shore layer of liquid B, Fig. 1, bathing the already solidified walls, and more fusible than either those walls or the great remaining central mass of liquid or " deep sea " C, from which it separates them. It is essential that we grasp clearly this conception of a fusible littoral molten layer coating the already solidified walls and separating them from the deep sea. Meanwhile heat is flowing rapidly outward through these walls, its escape cooling them, so that if any given particle of the deep sea metal could get past this littoral layer and come into contact with the solid walls, it would in turn solidify, and like its predecessors would split up in solidifying into a less fusible half-drop which would attach itself to those . walls and a more fusible one which would remain molten. Thus we see

Jan 1, 1920

By Lester Blackner

THE PROPERTY AND LOCATION THE Ray Consolidated Copper Co.'s mining property is located on Mineral Creek 6 miles north of Kelvin, at Ray, Pinal County, Ariz. (Fig.. 1) . The mining claims now owned by the company consist of 126 lode claims, comprising 2,144.9 acres, containing at the beginning of operations 82,904,368 tons of 2.19 per cent. copper ore. GENERAL CHARACTERISTICS OF THE OREBODY The main orebody is a disseminated deposit in schist and porphyry formed by secondary enrichment. Its existence was proved by churn drilling, and it is at present one of the largest proved copper deposits in the world. The orebody itself covers .205 acres with an average thickness of 121 ft., and occupies a definite belt which has a northwest direction. Its length is approximately 5,000 ft. The width varies, being about 2,000 ft. at the west end and 2,500 ft. at the east, narrowing down irregularly front both ends to a few feet in the center. The thickness of the body varies greatly along the line of lode, ranging from a few feet up to 470 ft. thick. The ore horizon is not constant, but varies, following in a broad sense the topography The body in general dips slightly to the northeast, and is broken up by numerous small faults and fractures. The ore-bearing formations, consisting of mineralized schist and mineralized granite porphyry, stand fairly well and offer no difficulty in mining operations.

Jan 6, 1915

By A. J. Conelius, D. P. Sobocinski

This paper presents a correlation for predicting the behavior of a water cone as it builds from the static water-oil contact to breakthrough conditions. The correlation is partly empirical and involves dimensionless groups of reservoir and fluid properties and of production and well characteristics. The groups were deduced from the scaling criteria for the immiscible displacement of oil by water. The correlation is based on a limited amount of experimenfal data from a laboratory sand-packed model and on results from a computer program for a two-dimensional, incompressible system. Because the correlating groups are dimensionless, they can be used to estimate the performance of water coning cases not specifically considered in the correlation. However, despite its dimensionless nature, the correlation is not completely general and will not provide meaningful estimates of cone behavior in many situations. INTRODUCTION AND BACKGROUND The production of water from oil wells is a common occurrence which increases the cost of producing operations and may reduce the efficiency of the depletion mechanism and the recovery of reserves. We will deal with one cause of this water production, namely, coning. The coning of water into a producing well is caused by pressure gradients established around the wellbore by the production of fluids from the well. These pressure gradients can raise the water-oil contact near the well where gradients are most severe. Gravity forces that arise from fluid density differences counterbalance the flowing pressure gradients and tend to keep the water out of the oil zone. Therefore, at any given time, there is a balance between gravitational and viscous forces at points on and away from the completion interval. When the dynamic forces at the wellbore exceed gravitational forces, a cone of water will ultimately break into the well to produce water along with the oil. We can expand on this basic visualization of coning by introducing the concepts of stable cone, unstable cone and critical production rate. For instance, if a well is produced at a constant rate and the pressure gradients in the drainage system have become constant, a steady-state condition is reached. If, at this condition, the dynamic forces at the well are less than the gravity forces, then the water or gas cone that has formed will not extend to the well. Moreover, the cone will neither advance nor recede, thus establishing what is known as a stable cone. Conversely, if the pressure in the system is in an unsteady-state condition, then an unstable cone will continue to advance until steady-state conditions prevail. If the flowing pressure drop at the well is suffcient to overcome the gravity forces, the unstable cone will grow and ultimately break into the well. It is important to note that in a realistic sense, stable cones may only be "pseudostable" because the drainage system and pressure distribution generally change. For example, with reservoir depletion, the water-oil contact may advance toward the completion interval, thereby increasing chances for coning. As another example, reduced productivity due to well damage requires a corresponding increase in the flowing pressure drop LO maintain a given production rate. This increase in pressure drop may force an otherwise stable cone into a well. The critical production rate, well known in the literature, is the rate above which the flowing pressure gradient at the well causes water (or gas) to cone into the well. It is, therefore, the maximum rate of oil production without concurrent production of the displacing phase by coning. At the critical rate, a built-up cone is stable but is at a position of incipient breakthrough. Numerous papers have been published on critical rates. Some of the better known of these include the work of (1) Muskat and Wyckoff,' who first dealt with the coning problem; (2) Chaney, et al,' who developed expressions similar to those of Muskat but who presented results in a conven ient-to-use graphical form (the "Sun" method); and (3) Meyer and Garder,b hose analysis is based on radial-flow formulas. One assumption in critical production rate analyses is that the cone has built-up to just before its breakthrough into the well. But, these analyses reveal nothing directly about the time it takes for the cone to build up to this incipient breakthrough position. Thus, water-free oil can be produced from a well for prolonged periods at rates above the critical rate before the well reaches the condition to which the critical rate applies. The published literature contains little on the rate of growth of a cone. Experimentally, Meyer and Searcy studied the rate of rise of a cone in a Hele-Shaw model.' Additional related work on water breakthrough and produced water-oil ratios in water driven reservoirs was reported by Muskat," Hutchinson and Kemp," Henley, et al,' and Stevens, et a1.B Theoretically, the basic coning equations for a water-oil system can be developed by applying the conservation of mass to each of the phases, relating flow velocities with pressure by Darcy's law, and relating pressures across water-oil interfaces by capillary pressure. With the usual boundaries at the well and reservoir limits, the solution of the resulting equations for the time behavior of a water-oil interface constitutes a free-surface, boundary-value problem. The shape of the boundary depends on the internal potential distribution, while this

Jan 1, 1966

By A. D. Brokaw

The so-called "paraffin dirt" of the Gulf Coast oil fields has been considered an indication of the possible presence of oil and gas, and not a few wells have been brought in solely on the basis of such evidence. In a sense, it may be empirically justified as evidence of the presence of oil or gas, though it cannot be said to be infallible. If the writer is correctly informed, its association with oil and gas was pointed out by Lee Hager some years ago, and while it is commonly mentioned by geologists and operators in conversation, no discussion seems to have found its way into print. The present interpretation is based on laboratory study rather than on field investigation, and is put forth with the hope of stimulating discussion which shall lead to more complete understanding. The term "paraffin dirt" has been applied to soils with a peculiar texture, which has been described as "curdy" or "rubbery." When moist, the material breaks much after the fashion of "green" cheese. It is rubbery under compression, but does not resemble rubber in tenacity or cohesion. When dry, the material ranges from hard clods to a horny mass of high tensile strength. The shrinkage in drying is very great, especially in the hornlike matter. The moist material ranges in color from dark brown in the specimens rich in organic matter to grayish in specimens containing more inorganic matter. All of the specimens studied were readily attacked by molds, which in some cases grew in great profusion on the samples. Samples exhibited a rather characteristic "swampy" or "mucky" odor when wet, and a characteristic odor of humic soils when moist. If the material is brought into suspension in water, very fine sand settles out and may be recovered by successive washing and decantation. The sand is almost entirely quartz, but contains occasional fragments of feldspar—more or less kaolinized and iron-stained. Practically all of the sand passes through a 100-mesh screen and the grains are extremely sharp —possibly below the limit of rounding. A flocculent mud, of clay and organic matter, remains in suspension for days. Some material is taken into solution in the water, imparting a slight tendency to froth when vigorously shaken. The results of partial analyses of four samples of "paraffin dirt," and, for comparison, one of a coastal plain soil are given in Table I.

Jan 1, 1920

By George Young

DURING the spring of 1910 I visited a number of open-pit brown-coal mines and underground workings in the vicinity of Halle, Halberstadt, Leipsic, Cologne and Bonn. The notes which I took and the observations which I made at the time have been condensed and make up the principal part of this paper. Certain supplementary information has been taken from several sources which are given in the paper. The mining of brown coal is one of the important industries of Germany. The coal varies in color from dark brown to almost black and is soft like loam. Pieces of wood and strips of bark and, even parts of tree trunks are frequently encountered in the excavation although the coal for the most part consists of a pulverulent, more or less matted mass of small particles of vegetal matter. It is a product between peat and lignitic coal. An analysis, taken from Coal Resources of the World shows the approximate composition of the material: Moisture, 53.73 per cent.; ash, 4.98; fixed carbon, 18.08; volatile carbon, 23.31 per cent. The principal characteristic is the amount of moisture. This seldom runs less than 48 per cent. The ash is usually low and ranges from 5 to 10 per cent. The sulphur content is usually less than 0.5 per cent. The heating effect of the fuel ranges from 2,000 to 2,500 calories.

Jan 2, 1916

By James H. Courtright, Kenyon Richard

L. H. Hart (Chief Geologist, American Smelting & Refining Co.)— Because of a widely recognized association between breccia pipes of one form or another and many important copper deposits, conditions under which breccia pipes develop have been of great scientific interest for many years. Since these phenomena first attracted attention, many theories have been advanced to explain their origin. This is not unexpected, since it is likely that they have been formed by and under a wide range of conditions. Moreover, the entire subject is confused by the fact that the term brec-cia pipe is applied to a wide variety of occurrences. To discuss any part of the subject intelligently, therefore, it is necessary to start with definitions of the terms used. In their discussion of the Toquepala deposit, Richard and Courtright have carefully defined the terms they have used in their presentation of a very logical geological history of Toquepala breccias. This is a real contribution, as there is no reference in the literature known to the writer where the history of a series of breccia pipe epochs, confined essentially within one channelway, may be read with the degree of certainty that appears to be possible at Toquepala. Although the following comments are intended primarily to emphasize points brought out in the article by Richard and Courtright, certan subsequent detailed mapping by Hollister and Houston7 within the main central mineralized area of the Toquepala deposits not only supports most of Richard's and Courtright's con- clusions but also contributes additional facts that strengthen and broaden the whole concept of the origin of the Toquepala breccia pipes. In detailed mapping by Hollister and Houston,' the most significant feature disclosed is a well developed system of concentric fracturing in rocks peripheral to the main breccia pipe throughout an arc of 300°, interrupted only by the late dacite agglomerate in the north quadrant. Although Richard and Courtright noted that such fractures were developed in the southern and southeastern areas, continuity in the east and west quadrants is established by consistent orientation of the stronger set of fractures and joints. The existence of these structural weakness trends is emphasized by the emplacement of dike-like phenomena in and along members of this fracture system. Richard and Courtright described one of these dikes in the southeast quadrant. They referred to it as a ring-dike, composed of dacite porphyry. This suggests an apparent structural control of at least a part of the dacite porphyry intrusion by features related to the Toquepala breccia pipe center. This raises a perplexing question, since the dacite porphyry intrusion had been presumed to antedate breccia pipe activity. However, if this ring-dike is related to the breccia pipe center, it may indicate that some part of the dacite porphyry intrusion advanced in a manner resulting in an intensely localized stress center, which produced the concentrically arranged fracture system. The ring-dike would then appear to be evidence strongly sug-

Jan 1, 1959