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By E. B. Brauer, W. Hurst, J. D. Clark

Because of drilling, completion, and workover practices, the permeability around a wellbore generally is different from the permeability of the formation. The zone with the altered permeability is called "skin" and its effect on the pressure or flow behavior of the well is called "skin effect". Hawkinsl has shown that the radius and the permeability of this zone are related to the skin by: If the permeability in the skin zone is less than that of the formation, the skin is positive; if it is more than that of the formation, the skin is negative. If the two permeabilities are equal, s is zero; that is, there is no skin. Van Everdingen2 and Hurst3 have given mathematical solutions to the case of a zone of reduced permeability around the wellbore. This skin effect is illustrated in Fig. 1. They treat the positive skin as a zone of reduced permeability of infinitesimal thickness around the wellbore. When applied to a well with negative skin, however, their solutions lead to the calculated flowing well pressure which is smaller than the formation pressure, i.e., an injection situation. This is a physical contradiction. In this paper, it is shown that this mathematical difficulty can be overcome by assuming an effective wellbore radius larger than the actual wellbore. Existing solutions2"4 are modified to include the effect of an enlarged wellbore radius, and thus enable the engineer to deal with negative as well as positive skins. Theoretical Development Van Everdingen and Hurst,4 through the use of Laplace transformation, obtained the following expression for transient fluid influx into a wellbore: The values for QtD, reported extensively by van Everdingen and Hurst,4 are obtained from the following integral:

Jan 1, 1970

By Pat McCarran

WHEN this Government was founded, the framers of the Constitution wrote into that instrument a provision that Congress should "coin money and fix the value thereof;" and the Constitution prohibits making anything but "gold and silver" lawful money. So silver is written into our basic law. Shortly after President Washington took office in 1789 the Congress passed the first Mint Act, setting up the U. S. Mint. In that Act, signed by President Washington on April 2, 1792, the weight of the American dollar was fixed, and it was provided how much silver should be contained in a silver dollar and how much gold should be contained in a gold dollar. It was decided that 371 1/4 grains of pure silver was to be the standard dollar of America. That standard with respect to the pure silver content of the dollar has never changed.

Jan 1, 1947

By John G. McLain

OF all the zinc that the world consumed in 1936-'38 the United States took about 31 per cent, and almost 14 per cent of the world's zinc supply in that period was used for galvanizing purposes in the United States. Further examination of the statistics shows that about 71/2 per cent (147,500 tons in 1939) of the world zinc consumption goes into the galvanizing of sheets in the United States, which is what I am going to talk about in this paper. There is nothing especially new about galvanizing; in every year since 1921 somewhere between 41 and 49 per cent of the country's zinc consumption has been used for this purpose, and yet few people not specialists in its manufacture know much about how it is made. You take an iron or steel sheet and dip it in molten zinc and there you have a galvanized sheet-that about epitomizes popular knowledge of the subject even among engineers.

Jan 1, 1941

By R. J. Woody

Design of the most economic continuous counter-current decantation (CCD) circuit is based on selection of the number of stages and the wash volume that will give the minimum summation of the following items: 1) Capital and operating costs of the CCD circuit. 2) Capital and operating costs of the precipitation circuit. 3) Value of the dissolved product lost.

Jan 1, 1959

By John Boardman

THE latest metal-mine accident report available for the United States is that of the Bureau of Mines for the calendar year 1919. Quoting from Table 20, p. 53, of that report, we find that there were 468 men killed, 7 permanently totally disabled, 321 permanently partially disabled, 7848 injured seriously (more than 14 days disability), and 23,330 of 1 to 14 days disability. We have no records to show what the average days lost per case of accident is, but the records for the Anaconda Copper Mining Co. show that, leaving out the fatalities and total permanent disabilities, and counting those in which the lost time was one or more days, the actual days lost due to accidents, for the Butte mines and shops for five years, 1917-1921, were as follows: Accident Statistics, Butte Mines and Shops of A. C. M. Co. Rate Shifts Days Lost Year Accidents Total Shifts 10,000 Shifts Days Lost Per Acci-dent 1917 2,661 3,169,720 8.395 26,734 10.05 1918 2,765 3,545,149 7.799 39,199 14.17 1919 1,381 1,853,143 7.452 22,797 16.50 1920 1,376 1,879,410 7.321 20,164 14.65 1921 376 776,461 4.842 8,287 22.03 Total... 8,559 11,223,883 7.625 117,981 13.80 In order to place an economic value. on this loss, we will assume that all the 468 fatalities and the 7 total permanently disabled in the United States were com-pensated for at the rate which applies in the State of Montana, that is, $5000 each, and that the 8169 serious accidents in the United States were compensated for at an average of $70 per case, thus bringing the estimated compensation paid by metal-mining companies in the United States to the enormous total of $2,946,830 for the year 1919. The figure of $70 per case was obtained by dividing the total amount paid by metal-mining companies under Plan No. 1 of the Montana Compensation Law, for the first five years of its operation, by the total number of serious accidents for those years.

Jan 9, 1922

By Thomas R. Stauffer

The principle that conventional schemes for taxing petroleum or mineral resources are "inefficient" is illustrated using simulation calculations tested against an "ideal" system. Inefficiency is defined as the relative success in maximizing expected government revenues from the resources. Most systems fail because: 1) they leave oil in limbo, i.e. unproduced because of excessive fiscal burden; or 2) they unnecessarily increase the variance in the explorationist'c, rate of return by undertaxing large fields and overtaxing smaller but infra-marginal fields. This increases his discount rate and reduces taxable surplus. An "ideal" tax system is specified which maximizes government revenues while minimizing risk to the operator. Two criteria are developed: 1) the tax falls to zero on fields which yield only the minimum necessary rate of return ("marginal" fields); and 2) the after-tax present value of all fields is the same for all fields above a threshhold size. In particular, marginal fields, while contrib- uting little to expected values, do contribute to reducing variance and hence risk praemia by distributing the exploration costs over a higher probability of successful outcomes.

Jan 1, 1982

IN THE past, we have, perhaps, been somewhat careless in our furnace practice, in the use of high-grade material, lowering the production costs through demanding high-grade ores, increasing the size of units, and eliminating heat losses by collecting and returning unused heat to our furnaces. Further economies would seem to be possible through keeping out of the furnace those materials that appear to serve no useful purpose and carry with them heat that should be used in reduction operations. In the manufacture of pig iron, about three tons of inert nitrogen pass through the furnace for each ton of iron produced. This nitrogen serves no useful purpose in the chemical actions involved, but when discharged into the atmosphere it carries away a considerable quantity of heat. Can not this loss be eliminated, at least in part, through the use of more oxygen in the blast? Many metallurgical chemists, during the past 20 years, have stated that they thought it can and have urged that the plan be tried. Others have expressed doubt, not being able to visualize how more oxygen could be used in present practice; they have regarded it as impracticable, without trying to conceive of an entirely new practice based on a new reagent. That more experimental work has not been done is due to the fact that no cheap oxygen has been available, but the committee believes that there is strong reason to expect that, should a demand exist, 99 per cent. oxygen may be made at a cost not to exceed $3 per ton. The theoretical studies of the committee have indicated such marked economy by using oxygenated air in various operations that its members strongly recommend experimental work to verify the anticipated economies. The committee has developed plans for experimentally determining the effects of oxygen-enriched air on the operation of an iron, blast furnace. A furnace with a height of 30 ft. has been built and it is recommended that the plans be put in, effect as the first step in the research.

Jan 11, 1924

By C. H. Mathewson

MY treatment of the subject of "Metals of the Future" is imaginative rather than statistical or scientific, because reliable information concerning useful concentrations in the form of ore deposits of by far the majority of the elements does not exist and the chemical, physical, and mechanical properties of the unfamiliar metals are recorded only in fragmentary and uncertain form or not at all.

Jan 1, 1944

By Robert Stefanko

With passage of the Clean Streams Act of the Commonwealth of Pennsylvania and its impact on the coal industry, considerable research has been conducted to explore various approaches to the problem, including deep-well disposal. Available drillhole data from gas and oil wells were used to develop cross -sectional maps for various portions of the state and potential disposal zones were evaluated. Bethlehem Mines Corp., faced with a severe water problem at its Marianna operation in Washington County, cooperated with the Dept. of Mining at The Pennsylvania State University in establishing a 1500-ft well into the Salt Sands for the purpose of determining the feasibility of mine water disposal. The thickness, porosity, and permeability of the formation at the well site proved to be below what had been anticipated from drillhole data. Further, subsequent hydraulic fracturing did not improve the flow characteristics of the well; pumping pressures remained in the range of 1800-2000 psig for disposing of water at the rate of 150 gpm. The legal problems of disposal at the site were very formidable. When the Salt Sands proved to be less than satisfactory, permission could not be obtained to dispose in other promising formations. The paper details many of the problems associated with the experimental well and makes an assessment of the potential for deep-well disposal of mine water. The concept of disposing of liquid industrial wastes by deep-well injection is not a new one. Brines associated with crude oil long have been disposed of in this manner, with the additional benefit of aiding secondary oil recovery. More recently, with the expansion of nuclear energy, the lethal, highly radioactive wastes which are by-products of the fission process have created severe disposal problems. During the past ten years, a variety of industries have resorted to subsurface disposal, some of the details of which are given e1sewhere.l,2 The list reveals wide variations in injection rate, pumping pressure, cost, and waste disposition. Included are successful installations in Western Pennsylvania. Enactment of more restrictive clean-water legislation in Pennsylvania recently had a great impact on the coal industry. Among its provisions was the reclassifica-tion of most mine water as industrial waste whose dis-posal is prohibited in any stream of the Commonwealth. This had the effect of accelerating research in a variety of areas, although treatment methods still retained primary interest. When a feasibility study of deep-well disposal was proposed to the Pennsylvania Dept. of Mines and Mineral Industries, the Coal Research Board (CRB) approved it. This paper summarizes the efforts on this project. Acid mine water is a chemically complex liquid. having no definite quantitative relationship among its constituents. However, it is the iron disulfide (FeS2) associated with practically all coal seams that produces the objectionable products present in acid mine water when combined with air and water. The principal contaminants are sulfuric acid (H2SO,) and ferric hydroxide (Fe(OH)2. Ferric hydroxide is a rust-colored gelatinous precipitate that coats stream bottoms and destroys aquatic life. However, other ions and bacteria are present in acid mine water in varying amounts.

Jan 1, 1971

By Paul F. Kerr, Donald M. Hausen

Fine colloidal gold near Carlin, Nevada is disseminated in leached carbonate strata of the Roberts Mountains Formation in the Lynn "window" of the Roberts Mountains thrust fault. The ore body is generally stratiform and is more or less conformable to altered beds near the top of the formation, underlying Devonian limestones. Two sequences of mineralization are recognized: ( 1) an earlier base metal-barite assemblage related to early Cretaceous intrusives (121 ± 5 m.y.), and (2) a later low temperature Au-As-Hg-Sb assemblage of near surface emplacement. The earlier sequence consisting of sparse galena and sphalerite in barite with anomalous amounts of zinc, lead, nickel and copper, associated with dikes of dacitic composition, is of little economic importance. The later sequence of gold, realgar, cinnabar, and stibnite associated with extensive silicification and argillic alteration of limestone beds, has resulted in important deposits of gold. Argillic alteration of hydrothermally leached carbonate strata has provided the environment in which the most prominent gold deposition took place. Carbonate minerals in the limestone host rock have been replaced by microcrystalline quartz and chalcedony to form stratiform silica masses and recrystallized lenses of euhedral quartz. Zones of porous silicification are light gray to white, elliptical in shape, and more or less follow bedding. Silicification is bordered by argillic alteration and pyritization. Deposition of gold usually lies in a zonal pattern that encircles chimney areas of silicification.

Jan 1, 1968

By T. F. Witheree

The Fletcherville Furnace was built in 1864 and 1865, making its first blast from August until October of the latter year, when it was blown out to prevent its " bunging-up." Repairs were made in time to enable it to be blown in again December 12th, 1865, the blast ending October 7th, 1866. Total product 1921.15 tons iron, an average of 6.8.2.5 tons per day, from ores yielding 44.8 per cent. Consumption of charcoal 223.2 bushels per ton of iron. The furnace journal up to this time shows no record of furnace dimensions, or temperature of the blast, but as near as can be ascertained, they were as follows, viz.: Height of stack, 42 feet. Diameter of bosh, 11 feet. Angle of bosh, 71/2 inches to 12 inches rise, about 58°. Diameter of open tunnel head, 42 inches. Number of tuyeres 3 ; each 3 inches in diameter. Dam 15 inches high. Tuyeres 24 inches high. Tymp 224 inches high. Diameter of steam cylinder, 20) inches. } Diameter of blast cylinder, 64 inches. } Stroke 5 feet. The engine is direct-acting horizontal non-condensing. December 26th, 1866, the furnace was again put in blast, having been considerably altered in the crucible; the height of stack, bosh, and tunnel head remaining as before. Six tuyeres were put in, three in each of the side arches. The hearth or crucible was rectangular in form, 3 feet wide x 31/2 feet long x 64 feet high. Inclination of bosh 58°. Height of tuyeres 26 inches; nozzles 21/4 inches diameter. Temperature of blast estimated to be about 500°.

By Edward H. Robie

Jan 1, 1971

The following record of the important responsibilities already shouldered by Dr. Ricketts will give some indication of the trust and confidence reposed in him by his colleagues. The Institute is to be congratulated that a man who is already so much engaged should be willing to assume the further responsibility of guiding the Institute's Ship of state during the ensuing year. Louis Davidson Ricketts, who is brother of Professor Palmer or Chamberlaine Ricketts, President of Rensselaer Polytechnic Institute, was born at Elkton, Md., Dec. 19. 1859, was graduated from Princeton University in 1881 with the degree, Bachelor of Science, chosen a Fellow in Chemistry and W. S. Ward Fellow in Economic Geology, and after two years' study given the degree Doctor of Science. Following the completion of Iris work at Princeton, Dr. Ricketts went to Colorado and started to work as a mine surveyor. For the 15 years following, his time was chiefly occupied in reconnaissance work, geological work and mine examination. From 1887 to 1890 Dr. Ricketts was Geologist for Wyoming, and at, the end of that period transferred his operations to the Southwest. where he has since been steadily engaged in large mining projects. He was identified with the acquisition of the property now owned by the Moctezuma Copper Co., a , subsidiary of Phelps, Dodge & Co., at Nacozari, Sonora, Mex. From 1899 to 1901 he was General Manager of the property and during his administration the concentrator and reduction works were completed and the mines put on a dividend-paying basis

Jan 3, 1916

By Mark Eisner

ONE'S JOB is the watershed down which the rest of one's life tends to flow write the Lynds in the first pages of their classic social study, "Middletown in Transition." Certainly engineers will confirm this statement after a check among those in their own profession with whose lives they are at all familiar. I have no hesitancy in acknowledging the truth of their observation for the men and women who are engaged in the profession of the law. It has been often remarked that American public life is overrun with members of the law profession. The highest public office in the land, that of President. has been occupied by lawyers almost to the exclusion of citizens of any of the other professions. Twenty-two Presidents of the United States out of the total of 31, were members of the bar. For the most part, members of Congress, the governors of the states, the state legislators and the mayors and other local leaders, men who occupy important positions of responsibility and public trust, have had legal training. Now this fact is no mere accident. Those who were fitted for the "job" of the practice of the law are favorably placed with respect to their participation in public life. Thus public service and public office is the watershed down which the "lawyer's" life tends to flow.

Jan 1, 1940

By G. C. Stone

AS the term "hardness" is used with many different meanings, it should be understood that it here means resistance to deformation by compression. It was determined by measuring the pressure, in pounds per square inch, necessary to reduce by 20 per cent., the length of cylinders 1 in. (25 mm.) in diameter by 2.6 in. (66 mm.) long. The tests were made at Columbia University on an Olsen 400,000-lb. machine, the load being applied at a constant rate of speed 0.0319 in. per min. The results were obtained by Messrs. Rigg and Williams, and some of them were given in a paper read at the Sixteenth Annual Meeting of the American Society for Testing Materials, in June, 1913. The remainder of the results were obtained in subsequent experiments by the same authors. In all cases, the results given are the averages of three or more closely concordant tests. All of the spelters tested were of standard commercial grades and all were of compositions making them good deliveries. The accompanying table gives the results arranged in the order of increasing hardness:

Jan 1, 1919

By Cyril Stanley Smith

ARCHEOLOGISTS, by use of the terms Bronze Age and Iron Age, indicate that metals have in the past determined the character of civilization. The relatively simple discovery by a primitive metallurgist that the addition of tin to copper both facilitated the production of castings and increased the durability of the product enabled hunter, warrior, and housewife alike to do things never dreamed of before. Similarly, the smelting of iron and the discovery of hardening methods greatly changed the arts of peace and war. Discoveries of low-melting-point alloys for joining and for making household utensils, and perhaps the adornment of a feminine form by sparkling precious-metal jewelry, have at times changed the destiny of a country. Bronze cannon, the cast and wrought iron Watt engine, copper transmission lines, and aluminum alloy aircraft, are cases of particular metals making possible the realization of an improved engineering design. Perhaps of the greatest influence of all upon civilization was the development of type metal. The rapid increase in the rate of dissemination of knowledge dates from the day that the technique of the pewterer was utilized in making rapidly reproducible and accurately sized letters for printing. It was not movable type, but metal type that was important, for metal castings could be made of identically the same shape and size at an enormous rate, and possessed excellent inking and wearing characteristics.

Jan 1, 1946

By R. H. Atkinson, R. N. Rhoda

An improved technique has been developed for the deoxidation of palladium with aluminum which is especially suitable for use in making small castings with an induction-melting and casting machine. The effect of various crucible linings on the efficiency of the residual deoxidizer and accompanying oxide film in protecting palladium against oxidation during remelting also has been examined; the preferred crucible lining consists of zirconia cement. THE objective of this work was to develop a simple method of deoxidizing induction-melted palladium which would be suitable for use by manufacturers of jewelry and other small castings. In a common method of deoxidizing torch-melted palladium a piece of aluminum foil is dropped on the surface of the molten metal. If a film is present, which is usually the case, it must first be removed by oxidizing the molten metal thoroughly because it would interfere with the entry of the aluminum into the melt. Removal of the film is probably facilitated by a mild fluxing action of the silica crucibles which are used for torch-melting. However, removal of an alumina film from molten palladium in the crucibles normally used for induction melting is a much slower process and it became necessary to modify the de-oxidation procedure. In the modified procedure the charge is simply melted and the desired amount of aluminum, crimped to one end of a tungsten wire, is plunged through the film into the palladium and the wire immediately withdrawn. The trace of tungsten which dissolves along with the aluminum can be avoided, if considered objectionable, by using a palladium wire. In view of the persistence of the alumina film under the conditions of induction-melting it also was decided to ascertain the efficiency of this film in protecting palladium against oxidation during repeated remelting and casting. Melting Equipment and Materials The equipment used for melting and casting consisted of an Ecco GC:6, 6 to 8-kva high-frequency converter and an Ecco M34B centrifugal casting machine. This unit is being increasingly used for making jewelry and dental castings and it also has been found useful in making exploratory melts of a variety of nickel alloys, for which purpose it is well suited on account of its speed of melting and economy of material. A description of the machine and its operation will be published elsewhere.' A common palladium jewelry alloy, 95.5 palladi-um-4.5 ruthenium (referred to as "palladium" in the trade), was selected for the deoxidation tests. It was available as melting stock which had been melted in air to free it from oxidizable impurities, and also as clean scrap from previous melts which had been deoxidized with aluminum. The latter was thought to be typical of clean "palladium" scrap to be found in a manufacturing jeweler's establishment and it is also similar to one brand of "casting palladium." By the same token, the oxidized melting stock corresponds to "casting palladium" after the latter has been melted and thoroughly oxidized: Pure aluminum wire (99.9 pet), 0.032 in. diam; 1 in. = 0.036 g. Scrap tungsten wire, 0.014 to 0.020 in. diam. Argon, commercial water-pumped; 99.9 pet pure Experimental Procedure Samples of about 50 to 75 g of the palladium alloy were melted in a crucible lined with a proprietary refractory alumina cement. Some charges were melted in air, others in argon. The oxidized melting stock was melted and solidified a number of times in order to remove as much oxygen as possible before deoxidizing, but this treatment was unnecessary in the case of scrap. In either case the metal was deoxidized with aluminum (0.01 to 0.05 pet) by the

Jan 1, 1959

By D. E. Stephenson. Discussion by R. G. K. Morrison, L. Obert

R. G. K. Morrison (Chairman, Dept. of Mining Engineering and Applied Geophysics, McGill University, Montreal, Que., Canada) - The discing of drill core has been a recognized pressure phenomenon for many years but only recently has an interest been taken in the mechanism involved. The work of Jaeger and Cook is referred to in the text. The authors have now advanced the study to establish, within certain loading limitations, a direct relationship between axial and radial stress at failure. This is an important contribution. In mines generally, where pressure conditions result in the spalling of openings, the faces of drifts and crosscuts, on scaling, usually show a concavity with respect to the opening very similar to the face of the drill hole after the separation of the stub. The same holds for shaft sinks. This suggests a similarity between the mechanism of the discing of core and that of the spalling of an opening, under pressure, to develop a more stable outline. The latter, commonly regarded as shear, is the most conspicuous type of failure observed in

Jan 1, 1967

By H. J. Wasson

WITH the close of 1932 and the third year of the depression, the activity of oil production presents, amidst the general wreckage and chaos of industrial society, a somewhat unique picture of rationalized economic effort. East Texas still dominates the contemporary horizon, but it has become, at least for the time being, a definitely known factor. With its 9500 wells it is approximately 90 per cent drilled up. So long as production control obtains, it is merely one important factor of the national oil reserve. Each succeeding month of stabilized production tends to lull the industry's fears and the menace, both actual and psychological, of this giant field becomes ever more remote.

Jan 1, 1933

By R. J. Woody

DESIGN of the most economic continuous counter-current decantation (CCD) circuit is based on selection of the number of stages and the wash volume that will give the minimum summation of the following items: 1) Capital and operating costs of the CCD circuit. 2) Capital and operating costs of the precipitation circuit. 3) Value of the dissolved product lost.

Jan 7, 1958