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By T. S. Spice, H. L. Lovell, R. W. Utley

With the increased demand for lightweight aggregate, such materials have been manufactured from slags, clays, slates and, to a minor extent, the refuse of coal preparation processes. The latter source is attractive due to current interest in eliminating air pollution and improving the unsightly appearance of refuse piles as well as potential economic advantages, if a satisfactory product can be manufactured. A study has been made relating the composition of coal refuse, expressed as washability data, and the properties of a resulting aggregate. Three different refuse samples (bituminous and anthracite) were separated at gravities ranging from 1.4 to 2.96. Their chemical composition was determined. Aggregates were prepared in the laboratory from these fractions before and after ashing, at temperatures between 1250' and 1350°C. The specific gravity, expansion and compressive strength of the products were measured. The response of the refuse to bloat is related to the chemical composition of the ash to yield a glass of desirable viscosity and to the presence of a material which will form a gas in the appropriate temperature range. Carbonaceous material within the particle is a negative factor since after the glassy phase forms, oxygen cannot enter the mass thus inhibiting bloating. Precombustion of the refuse is also detrimental since it removes substances of gas-forming capability. The fraction sinking at 2.60 yielded an aggregate which had the lowest specific gravity, greatest expansion and greatest compressive strength. The purpose of this study was to seek and evaluate possible relationships between the composition of coal refuse, as expressed by washability data and factors affecting the production of a lightweight aggregate from refuse by bloating. The study was related to an intense program in the Department of Mineral Preparation at the Pennsyl- vania State University to study the possible elimination of air pollution from coal refuse fires by producing a low-carbon secondary refuse. Another phase of this program is considering possible uses of such a secondary refuse. Thus one study was to determine if a lightweight aggregate could be produced from this new refuse material and what effect the nature of refuse beneficiation would have upon the characteristics of a commercial aggregate product. It was hoped that these studies would assist in the design of a process and in establishing the optimum specific gravities at which refuse separation could be made in respect to the production of a low grade fuel from the float product and a raw material for lightweight aggregate from the sink product. The combination of producing a saleable low grade fuel and a lightweight aggregate, while at the same time minimizing disposal costs and air pollution contributions would be attractive to the coal mining industry. MECHANISM OF BLOATING Austin, Nunes and Sullivan,1 Ehlers,3 Everhart, 4 Riley7 and others, have stated that bloating is an expansion process in which two essential conditions exist simultaneously. These are: the development of a glassy phase over a relatively wide temperature range (the viscosity of this glassy phase plays a major role in the retention of the evolved gases) and the evolution of gases (SO2, SO3, CO2 and O2) from mineral decomposition in sufficient quantities at appropriate temperatures to form a cellular structure in the mass. Unless these two "type" reactions take place at the same time or in overlapping ranges of time and temperature, cellulation will not occur. In this event, the gas will escape or the melt will be too fluid to retain it; or if retained, the cells may be too large or the walls too thin for good strength in the product. The stages that occur when clays and shales are heated in an oxidizing atmosphere may be summarized as follows: 1) Drying and removal of free water to 200°C. 2) Absorbed water dehydration period (200 to 480°C). 3) Chemically-combined water dehydration period (480 to 700°C).

Jan 1, 1965

By Oscar Glaeser

THE United Verde Copper Company's mine is at Jerome, Ariz. The orebodies are of the schist replacement type, the main sulfide mass being a large lens-shaped body approximately 7 acres in cross-sectional area. In general, the mineralization is found along the iron schist contact, with the orebodies extending about 1000 ft. along this contact and varying from a few feet to 250 ft. in width. Three types of ore are mined; schist porphyry and the so-called "heavy" or "massive sulfide" ore. Approximately 50 per cent. of the total tonnage mined at present is of the latter class. A representative analysis of this ore indicates 42 to 46 per cent. sulfur. Because of the high sulfur content, blasting in this ore is an extremely hazardous operation. Not only does it endanger the lives of men who may be in the mine at blasting time but it also becomes a potential fire menace when timber is in close proximity to shots being fired in these massive sulfides. The origin of the fires of 38 years ago, embers of which are glowing to this day, may perhaps be attributed to dust explosions due to blasting in the massive sulfides of those, early square-set stopes.

Jan 1, 1930

By C. H. Mathewson

Discussion of the paper of C. H. MATHEWSON and ARTHUR PHILLIPS, presented at the New York meeting, February, 1916, and printed in Bulletin No. 109, January, 1916, pp. 1 to 50. ZAY JEFFRIES, Cleveland, Ohio (communication to the Secretary*).¬The authors are to be congratulated for this interesting and valuable contribution. The paper as a whole shows very careful experimentation coupled with rare judgment in drawing conclusions. I have been working along similar lines for the last two years with other metals and alloys. In a short conversation with Dr. Mathewson about July 1, 1915, he mentioned the fact that different degrees of cold work greatly affect the temperature of recrystallization on annealing, Later I determined the recrystallization temperatures of iron, mild steel, and copper, with different degrees of cold work and found that the greater the degree of cold work, the lower the temperature of recrystallization on annealing. In the course of these experiments, I conceived practically the same ideas regarding the reasons for recrystallization as those advanced in the article under discussion. After a metal has been reduced by cold work to about one-fourth of its original area, the differences in orientation of different parts of a given grain can be seen plainly at a magnification of about 1,000 diameters. It is interesting to note that in Fig. A, Plate I, the lines of deformation are not parallel. For example,. in the large grain at the lower left corner of the micrograph, if the lines of deformation about 3g in. from the left edge are continued in a straight line, this line will intersect a straight line drawn as a continuation of the lines of deformation on the extreme right of the grain, at an angle of about 20°. Similarly, if the lines of deformation at the extremities of the large grain in the right central portion of the micrograph are extended, the lines intersect at an angle of about 35°. The individual lines of deformation are not straight. In some of these the parts of the broken lines intersect at angles as great as 15°.

Jan 5, 1916

NEW MEMBERS The following list comprises the names of those persons who became members during the period Sept. 10 to Oct. 10, 1914: Members ALLEN, MILTON A., Min. Engr., Alaska Gastineau Mining Co., Juneau, Alaska. ALLPORT, ROBESON H., Gent Supt Colonial Coal & Coke Co., Dorchester, Va. ALSDORF, FREDERICK C.... Murray Apartments, 1026 Orange St., Los Angeles, Cal. ANDERSON, CARL A., Min. Engr 920 Wooward Ave., Portland, Ore. ARMS, CHARLES SEELYE, Asst. Met Willys-Overland Co., Toledo, Ohio. BAILEY, PHILIP P., Min. Engr McGill University, Montreal, Canada. BECK, CHARLES SMITH, Engr Detroit Copper Co., Morenci, Ariz. BEESON, ALEXANDER G., Chief Engr., Pittsburg-Buffalo Co. and Four States" Coal & Coke Co., Washington, Pa. BINGHAM, RAYMOND A Box 173, Bridgeport, W. Va. BJORGE, Guy N., Geol., Old Dominion Copper Mining & Smelting Co.,. Globe, Ariz.

Jan 11, 1914

By T. Egleston

THE ores of mercury of North California are composed of metallic mercury and cinnabar. They are found in serpentine, and are very often associated with chalcedony, in masses more or less irregular, often concentrated enough, however, to furnish ores yielding from three to ten per cent., and sometimes richer. This deposit makes its appearance in Vallejo where it has been worked. North of here the mines are more developed. Most of the quicksilver mines, how¬ever, are situated in Sonoma and Napa Counties. On its outcrop the serpentine rocks have become decomposed, and have often been washed away to a considerable depth, so that in many cases in their neighborhood, what is apparently nothing but ordinary dirt, will frequently contain from two to three per cent. of metallic mercury, with but a trace of cinnabar, in which case, as at the Sonoma mine, it is made up into adobes and distilled. Such material does not require to be mixed with dirt to be made into adobes. Very often, also, the outcrop of the rock, where it is not decomposed, is filled with metallic mercury, so that by striking a pick into it, as at the Rattle-snake mine, a pound or more of mercury at a time will sometimes spurt out. Such rock as this is found in several localities in every stage of impregnation, and usually makes very rich ore. There is generally, however, very little of it, and it is found only in the first workings ; the ore in depth is always cinnabar. At the Rattlesnake mine near Pine Flat, where large quantities of metallic mercury are found, the rock contains so much petroleum that it has been necessary to make special arrangements to burn the carbides of hydrogen, since the distillation of the petroleum causes an extra quantity of poor soot to be formed in the condensation-chambers. At the Geysers the ore is associated with large quantities of sulphur and gypsum, so that in a hand specimen there is often more sulphur than cinnabar, which is a serious impediment to working, especially for the modern style of furnace with iron condensers, and causes so much soot to be formed that it has been known to penetrate as far as the blower, and to so completely clog it as to prevent its revolution. The ore coming from the mine is more or less hand-picked. In one or two cases attempts have been made to treat the poorest, and especially the very fine ores, mechanically as at the California works.

Jan 1, 1875

By Thomas Egleston

The ores of mercury of North California are composed of metallic mercury and cinnabar. They are found in serpentine, and are very often associated with chalcedony, in masses more or less irregular, often concentrated enough, however, to furnish ores yielding from three to ten per cent., and sometimes richer. This deposit makes its appearance in Vallejo where it has been worked. North of here the mines are more developed. Most of the quicksilver mines, however, are situated in Sonoma and Napa Counties. On its outcrop the serpentine rocks have become decomposed, and have often been washed away to a considerable depth, so that in many cases in their neighborhood, what is apparently nothing but ordinary dirt, will frequently contain from two to three per cent. of metallic mercury, with but a trace of cinnabar, in which case, as at the Sonoma mine, it is made up into adobes and distilled. Such material does not require to be mixed with dirt to be made into adobes. Very often, also, the outcrop of the rock, where it is not decomposed, is filled with metallic mercury, so that by striking a pick into it, as at the Rattlesnake mine, a pound or more of mercury at a time will sometimes spurt out. Such rock as this is found in several localities in every stage of impregnation, and usually makes very rich ore. There is generally, however, very little of it, and it is found only in the first workings; the ore in depth is always cinnabar. At the Rattlesnake mine near Pine Flat, where large quantities of metallic mercury are found, the rock contains so much petroleum that it has been necessary to make special arrangements to burn the carbides of hydrogen, since the distillation of the petroleum causes an extra quantity of poor soot to be formed in the condensation-chambers. At the Geysers the ore is associated with large quantities of sulphur and gypsum, so that in a hand specimen there is often more sulphur than cinnabar, which is a serious impediment to working, especially for the modern style of furnace with iron condensers, and causes so much soot to be formed that it has been known to penetrate as far as the blower, and to so completely clog it as to prevent its revolution. The ore coming from the mine is more or less hand-picked. In one or two cases attempts have been made to treat the poorest, and especially the very fine ores, mechanically as at the California works.

By John V. Beall

Copper production in the. United States in 1972 amounted to 1,658,000 tons according to the USBM. This figure is up over 1971 but falls below 1970 production of 1,719,101 tons. This report is essentially about the status of copper mining operations in the U.S. and is an update and expansion of the report "Southwest Copper-A Position Survey" published in [A=], October 1965. At that time, the trend was toward using larger equipment to mine lower grade ore and toward the expansion of dump leaching practice. That trend continues today but, it is overlain by intensive activity to comply with existing environ¬mental legislation and uncertainty over proposed revisions of venerable laws governing mining. In the U.S. today there is, practically speaking, no excess smelting capacity so that expansion of copper production through the startup of new mines is inhibited. Owners of a large undeveloped orebody would have to decide before going into production whether to sell the concentrates offshore, which has many problems, whether to try one of several unproved chemical processes for producing refined metal from concentrates or embarking on the construction of a traditional pyrometallurgical plant in the face of considerable uncertainty over the pollution standards that eventually must be met. The situation is such that not only is the present rate of U.S. copper production threatened but the ability to meet projected increased demand in the years ahead may have been severely retarded.

Jan 4, 1973

By Albert Roberts

Summary In response to a growing intolerance towards ground vibrations and noise as environmental pollutants the engineer must consider the effects of his operations as they are likely to be judged subjectively by the public at large. Much work has been done on the study of vibration damage to structures, but the damage criteria normally applied do not take into account any resonance effects, nor do they embody any subjective criterion. Mu1tiple criterion techniques of subjective appraisal have proven to be of value .in the assessment of environmental comfort in relation to ventilation, air conditioning, and lighting. One such scale, the Reiher-Meister Scale, has also been applied to ground vibrations and noise, and an attempt has been made to correlate this scale with objective criteria, using the parameters of frequency and displacement. This paper quotes examples and compares ground vibrations resulting from blasting, the operation of, vibrating and impact-hamner pi1e drivers, forge hammers, and railway and road traffic. The Reiher- Meister Scale was applied to a subjective-objective correlation in relation to vibrations from railway traffic and gave results which did not conflict with experience.

Jan 1, 1971

The phosphate pebble-bearing matrix in the Florida Phosphate Pebble Field has physical properties which make it readily adaptable to hydraulic transportation methods employing solids-handling pumps and pipelines. The abundance of water available, a practically flat terrain, low costs per ton-mile, and beneficiation of the matrix by agitation while being pumped have contributed to the popular choice of hydraulic transportation. Phosphate pebble mining in Florida, begun in the 1860's, first used high pressure water and solids-handling pumps for overburden removal about 1900. Removal of the average 25 ft of overburden was followed by hydraulic mining of the matrix, with 6-in. and 8-in. pumps handling 50 to 100 cu yds per hour being moved along the floor of the pit as they were advanced toward the face being undercut and slurried by hydraulic guns.

Jan 3, 1961

Beyond the industrial suburbs of Melbourne to the southeast are brown coal deposits just under the fertile soil of the Latrobe Valley. These deposits rank as one of the wonders of the world. The manner in which this resource is put to use is one of the great engineering accomplishments of our time and also a prime example of Australian elan. The brown coal, with over 60% water content, occurs in beds from 200 to 400 ft thick, under 50 ft of cover. Fifty thousand tons of coal per day move in a nearly continuous stream from mining face to boilers. The power plants supply two thirds of the State of Victoria's requirements, about 800 megawatts. Surge capacity between mine and power plant is sufficient for 12 hr steaming time! Victorian brown coals have been known since the middle of the 19th century. However, it took a strike of bituminous coal miners in 1915 to bring brown coal permanently into the picture as a fuel for power generation. In Australia, power generation is a State function. The great development of brown coals has been under the State Electricity Commission of Victoria.

Jan 10, 1964

By R. J. Sandrea, S. M. Farouq Ali

The results of an experimental and theoretical study of the effects of rectilinear impermeable barriers and highly permeable channels on the sweep efficiency and conductivity of a five-spot network are presented. The study was carried out using Hele-Shaw, and conductive sheet analogs for both. normal and inverted flood patterns. A functional relationship was developed which provides quantitative prediction of the above parameters; i.e., sweep efficiency and conductivity, for the nonhomogeneous system. To evaluate this, it is necessary only to measure the interference modulus of the obstacle using a simple expression. The results indicate that impermeable barriers, with an interference modulus greater than zero, always cause a decrease in the conductivity and the sweep efficiency of the pattern. On the other hand, permeability channels do not have a significant effect on these parameters, unless they are located along the streamlines. The study also discusses a method of formulating the difference equations pertaining to the two-dimensional Laplacian in a system containing rectilinear barriers. In addition, a technique is described for tracing the progress of a free surface, using marked particles, in a stream containing discontinuities SuCh as those occurring at the extremities of barriers. The above computational scheme was used in a digital computer program to simulate results of the Hele-Shaw analog. The computed values of sweep efficiency mere in good agreement with the experimental values. INTRODUCTION At the present time waterflooding remains the most widely used technique for the secondary recovery of oil. Among the numerous factors that affect the performance of a waterflood, the areal sweep efficiency constitutes one of the most critical parameters. It is a function only of the geometric distribution of the wells for a homogeneous medium and unit mobility ratio. Geological considerations, however, such as the presence of sealing faults or solution channels in the rock matrix, would generally exert an adverse effect on the areal sweep efficiency of a waterflood network. Surprisingly little information is presently available on the quantitative implications of such permeability interferences. It was the object of this investigation to consider the presence of rectilinear, impermeable and highly permeable interferences in an otherwise homogeneous five-spot pattern, and to analyze their effects on the resulting sweep efficiency and pattern conductivity. The experimental phase of the study was conducted using two different models: the Hele-Shaw flow cell and the field plotter. For experimental convenience, the geometric boundaries of the five-spot were assumed to constitute streamlines even in the case where the interference was asymmetrically placed with respect to a repeated five-spot pattern. A second object of the study was to develop a computational scheme for numerically calculating the pressure distribution in a five-spot flow pattern containing rectilinear, impermeable barriers, and to use this distribution to compute the sweep efficiency. EXPERIMENTAL PROCEDURE HELE-SHAW ANALOG The Hele-Shaw analog was used both as a visual model and for determining the sweep efficiency for systems involving impermeable barriers. The physical limitations of this model as a means of experimentally studying the motion of a fluid in porous medium have been adequately discussed elsewhere.2,7 Likewise, it can be easily verified that the analogy remains valid when a portion of the region between the plates contains an obstacle of the same thickness as the distance between the plates. The model used in this study was composed of

By V. W. Aubel

Among the iron-bearing ores of the world, the titaniferous iron sands of New Zealand are probably the least known to American engineers. This is not surprising in view of the fact that American ironmasters look with disfavor on any, even domestic, ores containing over 1 per cent. titanium. The possibilities of smelting titanium-bearing ores in the blast furnace are still undetermined, but the problem of their efficient reduction is becoming more important each year. There seems to be little inclination on the part of American furnace operators to tackle this problem, and they will no doubt continue to utilize the non-titanium ores at their command, leaving research and experiment to those countries not so fortunately endowed. New Zealand has, however, been intensely interested in her deposits of titanium-bearing iron sand, and during the last 50 years considerable English and New Zealand capital has been expended on this problem. The extent of the New Zealand iron-sand deposits is almost beyond measure. From Patea north to Manuka Heads, along almost the entire west coast of the North Island, these deposits exist. Wherever there is beach sand along this 300 mi. of coast line, the sand is iron bearing. It varies considerably in grade; but wherever the contour of the coast affords small bays and inlets, large dunes are found that are remarkably uniform in quality. Several of these large deposits, especially those at New Plymouth and Patea, are noted for their high iron content. The dune at New Plymouth runs between 55 and 60 per cent. of metallic iron; the panning action of the prevailing westerly winds and northwesterly currents has no doubt resulted in this concentration. Whatever the origin of this material may be, there is no doubt that deposition is going on continuously. At New Plymouth, a small artificial harbor, protected from the drifting sand by a large breakwall, has been dredged. Here sailing vessels have for years been loaded with iron sand for ballast by means of a crane and grab bucket operated from the wall of the breakwater. Thousands of tons of sand have been removed from this spot yet each succeeding storm renews the supply. The sand dune shown in Fig. 1 has been tested to a depth of 50 ft. (15 m.) without losing its

Jan 1, 1920

Page Fundamental Principles Involved in Segregation in Alloy Castings. By R. M. Brick. (With discussion)............................* Review of Factors Underlying Segregation in Steel Ingots. By B. M. LarseX.. (With discussion)............................. 4x4 Introduction to the Session on Segregation in Steel. By Earle C. Smith......436 Relation of Open-hearth Practice to Segregation in Rimmed Steel. By J. W. HaLley and G. L. Plimpton, Jr. (With discussion)................438 Segregation in a Large Alloy-steel Ingot. By S. W. Poole and J. .4. Rosa. (With discussion) .............................459

Jan 1, 1945

By R. F. Krueger, L. C. Vogel, P. W. Fischer

Previous studies have shown that the permeabilities of sandstone cores are markedly reduced following exposure to drilling fluid and subsequent clean-up with oil at high-pressure gradients. Laboratory experiments reported in this paper indicate that permeability damage from drilling mud or water can be substantially avoided through use of an initial low-pressure gradient followed by gradually increasing gradients during clean-up by reverse oil flow. On the other hand, attempts to improve the permeability of damaged Berea and oil formation cores with high-rate oil backflush (simulated well stimulation) and low-rate clean-up gave erratic results. Essentfully complete permeability repair was achieved in most of the fresh water-damaged cores from Miocene and Pliocene oil-producing formations; only minor improvement was noted generally in tests with both water-and mud-damaged Berea sandstone. Field well stimulation treatments using high-rate back-flush resulted in long-term productivity improvement when production was brought in at gradually increasing production rates and then restricted to a steady value less than the maximum possible rate. Wellbore plugging at high production rates correlated with increasing solids content in the produced oil. Observations and results from these tests agree with current concepts that formation damage in water-sensitive rocks results from movement and bridging of formation fines, rather than from clay swelling alone. INTRODUCTION Many laboratory studies1-g have shown that the permeabilities of sandstone cores are often markedly reduced following exposure to fresh water or water-base drilling mud filtrate. However, work with cores in the restored state has demonstrated that, although permeabilities to water may be very low for sandstones containing hy-dratable clays, flow of oil can often restore a substantial portion of the effective permeabilities to oi1.Neverthe- less, water invasion into water-sensitive sandstone cores results in varying degrees of permanent reduction in permeability to oil.24' Based on field data, Wade's statistical study" of well completion effectiveness also indicated a correlation between productivity damage and water invasion during completion. Similar damage can result from fluid invasion during workover. Nowak and Krueger' and Bertness4 observed in their early work (1951-53) that formation damage in water-sensitive sandstones was associated not only with swelling of expandable clays but also with movement of dispersed particles. Subsequent work by Monaghan et al." (1959), Atwood'' (19641, Mungan" (1965) and Gray and Rex'" (1965) has led to general acceptance of the hypothesis that permeability damage in water-sensitive formations is caused by migration of finely dispersed minerals and bridging in "brush heap" arrangements at pore constructions. In laboratory studies, Monaghan et al.' found the use of chemicals to be of only minor value for repairing formation damage. Atwood? however, was successful in substantially repairing damage in a number of low-permeability cores using an n-hexanol flush. In the field, except for treatments with acids, the use of chemical washes to reduce wellbore damage has had limited and sporadic success and generally is unpredictable. A statistical analysis of stimulation treatments in silt-blocked wells has shown that physical manipulation of wash materials is more important than chemical composition." The recent work reported on formation damage in water-sensitive sands brings to mind the results of some unpublished exploratory work done in 1954 in connection with drilling fluid studies.' This laboratory work and subsequent field stimulation treatments indicated a beneficial effect of controlled pressure drawdown and the associated production rate on formation clean-up. This paper reports the results of this work and more recent supplemental experiments on the clean-up of water-sensitive sandstones damaged by water or filtrate invasion. PERMEABILITY RECOVERY AFTER DAMAGE BY DRILLING MUD APPARATUS AND TEST SAMPLES A drilling mud circulating system was used to expose cores to simulated wellbore conditions. The mud flow system is the same as that described by Krueger and Voge17 except that no provision was made for scraping

By F. D. Rosi, Walter R. Hibbard, R. I. Herron, H. T. Clark, O&apos

Introduction and Previous Work In the search to find a copper-base alloy with high strength properties, it was considered that the addition of a small amount of an age-hardening element to a binary system with useful strength properties might result in a series of alloys of theeretical and practical importance. The copper-nickel system was selected for its basic properties and chromium was added as the age-hardening element in view of the small percentage involved and its decreasing solubility with decreasing temperature. A study of the Cu-Cr binary alloys was undertaken as a preliminary investigation. However, in view of the response of these alloys to heat treatment, the scope of this phase of the investigation was widened.

Jan 1, 1949

By Oscar Aguilar, Jin-ichi Nakamura, Kazuo Nakamura

Michiquillay deposit is porphyry copper type with over 500 million tons of 0.70% Cu ore. In order to reflect the true nature of the orebody as to shape and value distribution and to compensate for insufficient data in the outer perimeter and lower portion, "Triangular Interpolation Method" is used in the computation, wherein block grades are determined by "Plane Regression". The results thus obtained are compared with the data from additional investigation and are found to match well with each other. Aside of total Cu, assays of Fe, S, MoS2 and geological data such as alterations, rock types, faults, mineralogical compositions are also stored in the computer. By this system, their distribution and relation to alteration become clear and classification of ore into types affecting recovery become possible. The outputs of this system make clear the characteristics of the orebody and furnish valuable geological data on the orebody.

Jan 1, 1976

By Dwight M. Lemmon

Encouraged by increased demand and higher prices for such metals as copper, lead, zinc, silver and tin, search was pressed in 1964 for mineral raw materials, especially in parts of the world that are relatively more stable politically and economically. New discoveries of metallic ores continued to be made, discoveries based on extensive geologic and geophysical work but nonetheless made in part because of good fortune.

Jan 2, 1965

By A. Haas, L. Bubenicek

The Lorraine deposit of minette iron ore has been mined for more than a century. During this time, the economic conditions have changed frequently, and especially during the past decade. Thus, it has become economically prudent to proceed to new iron ore reserves with consideration of many and varied parameters. In the past, only traditional mining parameters were considered. Today, the quantity of information that must be taken into account is of such magnitude that the only practical means of data processing is by use of a digital computer and a mathematical model. One such model, based on geostatistics, was developed by G. Matheron. Much of the required input information, such as the petrology of ores, has been generated through IRSID investigations. This paper deals with several aspects of data processing in mining including information recording, reserves calculation, and stages of shrinking data in the calculation of mining iron beds, variograms, kriging, and tonnages.

Jan 1, 1969

By D. A. Woodford

In a constant-load creep test, if the density of nlobile dislocations is assumed constant for strains exceeding that corvesponding to the minimum creep rate, it is shown that the creep rate may be approximated by the equation where E is the nominal strain, o0. is the initial stress, and a' the stress fov unit dislocation velocity. The constant C contains the mean density of mobile dislocations and n is a measure of the stress sensitivity of dislocation celocity. This equation is shoum to be applicable to published data on an alloy steel and on nickel. The degree of plastic instability and hence the creep ductility is dependent on the calue of n for these materials. When instability becomes gross and local macroscopic necking occurs, the assumptions are no longer valid. On the basis of this equation, and the strain-time relation derived from it, a method of predicting the creep behavior at different stresses is suggested. MOst analyses of creep data have been concerned with time-dependent transient creep or time-independ- ent secondary creep in constant-stress tests. The far more widely used constant-load test has been neglected in terms of a mechanistic approach. In general, since the strains involved are usually small, the same laws for transient creep may be applied to both types of tests. However, there is no steady-state creep in a constant-load test since the stress increases continuously. Any apparent steady state observed on a strain-time plot is either fortuitous or illusory, and is generally revealed as a continuously varying creep rate on a carefully constructed strain rate vs time plot.* Transient creep may be understood in terms of a simple differential equation representing the change in mobile dislocation density with time:' where p is the density of mobile dislocations. The first term on the right is related to first-order kinetics of dislocation multiDlication and the second to second-order kinetics of exhaustion. On the basis of this equation, several authors2-4 have found good agreement with experimental transient creep curves for a number of materials. When k1p = k2p2, a steady-state creep

Jan 1, 1968

By T. C. Boberg, R. B. Lantz

This paper presents a method for calculating the producing rate of a well as a function of time following steam stimulation. The calculations have proved valuable in both selecting wells for stimulation and in determining optimum treatment sizes. The heat transfer model accounts for cooling of the oil sand by both vertical and radial conduction. Heat losses for any number of productive sands separated by unproductive rock are calculated for the injection. shut-in and production phases of the cycle. The oil rate increase caused by viscosity reduction due to heating is calculated by steady-state radial flow equations. The response of successive cycles of steam injection can also be calculated with this method. Excellent agreement is shown between calculated and actual field results. Also included are the results of several reservoir and process variable studies. The method is best suited for wells producing from a multiplicity of thin sands where the bulk of the stimulated production comes from the unheated reservoir. The flow equations used neglect gravity drainage and saturation changes within the heated region. INTRODUCTION This paper presents a calculation method which can be used to predict the field performance of the cyclic steam stimulation process. The calculation method enables the engineer to select reservoirs that have favorable characteristics for steam stimulation and permits him to determine how much steam must be injected to achieve favorable stimulation. While the calculation represents a considerable simplification of physical reality and the results are subject to numerous assumptions which must be made about the reservoir, it has been found that realistic calculations can be made of individual well performance following steam injection. The duration of the stimulation effect will depend primarily on the rate at which the heated oil sand cools which, in turn, is determined by the rate at which energy is removed from the formation with the produced fluids and conducted from the heated oil sand to unproductive rock. A complete mathematical solution to this problem is a formidable task, and finite difference techniques would undoubtedly have to be used. The calculation method pre- sented here utilizes analytic solutions of simple related heat transfer and fluid flow problems. The method is sufficiently simplified that it can be used as a hand calculation, although the calculations are somewhat lengthy and laborious. For that reason, the analysis was programmed for an IBM 7044 digital computer. Well responses observed at the Quiriquire field in eastern Venezuela&apos; have been matched using this program after making suitable approximations for reservoir and wellbore conditions. One of the most valuable uses of this calculation method is to assess the effect of reservoir and proc-cess variables on the stimulation response. This paper contains results of several studies made of key reservoir and process parameters. Among the most important of these is the influence of prior wellbore permeability damage. If a well is severely damaged prior to stimulation, a higher stimulation response will be observed than if it is undamaged. If a portion of this damage is removed, a permanent rate improvement will occur. THEORY I)ES(:KJJ&apos;TION OF CALCULATION METHOD The process of cyclic steam stimulation is essentially one of reducing oil viscosity around the wellbore by heating for a limited distance out into the formation through the injection of steam. Suitable modifications of the calculation technique presented here can be made so that stimulation of wells by hot gas injection or in situ combustion can also be calculated. A schematic drawing of the heat transfer and fluid flow considerations included in the calculation method is shown in Fig. 1. In brief, the calculation assumes that the oil sand is uniformly and radially invaded by injected steam. For wells producing from several sands, each sand is assumed to be invaded to the same distance radially. In calculating the radius heated rn energy losses from the wellbore and conduction to impermeable rock adjacent to the producing sands are taken into account. After steam injection is stopped, heat conduction continues and oil sands with r < ra cool as previously unheated shale and oil sand at r > r, begin to warm. The effect of warming of oil sand out beyond r, has little effect on the oil production rate compared to the effect of cooling of the oil sand nearer the wellbore than ra. Thus, in computing the oil production rate, an idealized step function temperature distribution in the reservoir is assumed where the original temperature exists for r > rn and where an average elevated temperature exists for r < rn. The average temperature in the oil sand for the region r < rn is computed as a function of

Jan 1, 1967