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On an average of at least once a year there comes to the attention of the Institute Headquarters the activities of some individual who represents himself as a member of the Institute, and by a hard-luck story or other means secures loans or advances of money which are never returned. On one or two occasions the Institute has been able to secure the arrest and conviction of these frauds. Recently some individual has been operating in California and defrauded several members of the Institute. He is described as a man of 5 ft. 7 or 8 in. height, decidedly slim, and his weight is about 140 lb. His hair and mustache are gray, eyes blue or gray and he claims to be near-sighted. He is also said to have had a keen, furtive, "Hang-dog" look and claims to have been raised in Bethlehem, Pa. He speaks with a German accent. If a man answering this description presents himself before any members and claims to be a member of the Institute it will be to the good of the profession if he can be caught making fraudulent representations and placed where his ability to defraud will be under control. The most effective means of apprehending persons of this character is the very prompt notification to Institute Headquarters of any persons claiming to be members of the Institute in hard luck. If such persons are asked to supply their signature or photograph or both to be, forwarded to Institute Headquarters for identification this will serve as an excellent check on their operations. Reluctance to comply with such a request is in itself a suspicious circumstance.

Jan 9, 1919

FROM the first to the last meeting of t h e Rocky Mountain Club John Hays Hammond served as president. He guided its deliberations when there were any, but that always y o u n g organization was never particularly deliberate. Youth never is. And the Club was the embodiment of the youthful spirit of the West, which considers any- thing can be done if there be but the will to do it. Ham- mond and the others came out of the West, but they, brought the West with them P and in all the far countries in which he has served his profession and in all the honorable offices in which he has served his country, he lived true to the ideals under which he was raised. A Californian, born in San Francisco in 1855, the son of an army officer, Major Richard Pindell Hammond, educated in the public schools of his native city, at Yale, and at Freiburg, he turned early and quickly to mining. He served his apprenticeship as all successful mining men do, as assayer, surveyor, as assistant in ex-aminations and later as principal, and finally as mine manager. Even in those days of beginnings, his future world-wide career was foreshadowed in that Mexico as well as California served as his training school. His first major step up the ladder was in connection with the Bunker Hill and Sullivan mine, where he served in various positions finishing as president and considerable owner. It was from this great lead mine that he was called to South Africa, where he remained a number of years and was the technical expert who guided the great enterprises of Barnato Brothers and Cecil Rhodes. The story of his activity in developing the "deeps" of the Rand and in opening Rhodesia has been often told but is always an alluring one of adventure and accomplish-ment. After his famous escape from death at Johannes-burg as a member of the Reform Committee, he went first to London and later returned to the United States representing both British and American capital in the purchase and development of great mines in all parts of the world. For some years he was general man-ager, consulting engineer, and director of the Guggen-heim Exploration Co., but of recent years he has oper-ated entirely on his own account and with marked success.

Jan 4, 1928

By A. H. Tousley, L. H. Gee

Until comparatively recently, the gypsum industry has been slow to change, often clinging to old processing methods developed a generation ago. Now, however, a highly competitive market has forced gypsum companies to concentrate on devising methods to reduce material and operating costs and improve product quality. In one such effort, Kaiser Engineers recently designed and constructed two modern gypsum plants for Kaiser Gypsum Co., Inc., incorporating centralized control, automatic sequence starting, mill amperage control of the roller milling systems, automatic calcining in kettles, and rapid mechanical stucco cooling. Fig. 1 shows the control panel for the calcining departments at wallboard plants located in Jacksonville, Fla., and Delanco, N. J. In each instance the calcining department (commonly known as the "mill") sets the basis for the quality control for the entire gypsum plant.

Jan 12, 1966

INTRODUCTION Besides the European export credit agencies covered in Ted Rides' paper in this Chapter, other agencies are also active (see Appendix) but the most notable for mining projects are The Export-Import Bank of the United States ("US Exim") and the Export Development Corporation ("EDC") of Canada. Mexico's Fomex is basically a short-term trade-finance fund administered by the Central Bank. US Exim This independent agency can provide loans, guarantees, and insurance. Like all export-credit agencies, its mandate is to support the export of goods and services from the US as a means of competing against other countries' products. If a piece of mining equipment can only he made in the US, the US Exim may very well not provide any financial assistance. (It is important not to place the order for any item for which export credit is sought because, once ordered, the situation is no longer competitive in US Exim's eyes.) Direct Credits and financial guarantees ("buyer credits") are commonly in amounts greater than 85 million and for terms longer than six years. An example here is the $48.5 million provided to PT International Nickel Indonesia (see Robert de Gavre's paper in Chapter 12). US Exim usually requires a 15% downpayment and, therefore, finances up to 857 of the goods; less if the US content is lower. The dollar funding can he US prime, London Interbank Offered Rate (LIBOR), or other sources. Exim can fund in either or both of the following ways: 1. Under a US bank Letter of Credit ("L/C") 2. Reimbursement to the buyer/borrower via a US bank account. US Exim will, without charge, issue a preliminary commitment. It will, however, need to approve the various credit agreements and prefers to tie other parallel financings into one loan agreement. US Exim's total commitments are large, up to $5R billion in aggregate under various programs. US Exim has been the world's leader in medium-to long-term minerals project financings/ co-financings but suffers from (i) aggressive foreign export-credit competition whereby other nations mix in soft-loans or aid programs ("mixed credits") to increase the percentage financed and lower the interest margin and (ii) an imbalance in its own cost of funds. A common US Exim package would be as follows: 15% Banks under US Exim guarantee, floating rate over prime or LIBOR. 35% US Exim funding, fixed rate 35% Pefco funding, fixed rate 857 Drawn down pro-rata under US bank L/C 15% Cash down payment (may have been financed within a project/corporate credit) 100% Repayment usually begins six months after planned start-up in equal semi-annual instalments, with the banks usually paid out first, Pefco next, and US Exim last. Medium-term credits ("supplier credits") are issued for US equipment exports for terms up to five years, again for 85% of the equipment costs although the exporter is expected to bear at least 10% out of that 857 for its own risk. The buyer is required to be a first-class credit such as some governments or highly credit-worthy companies. Otherwise a bank L/C would be required. (This may be wrapped into an overall project-finance package for a minerals development. The project-finance banks provide an L/C to US Exim instead of funding that portion themselves.) US Exim guarantees 100% of the political risk and either 85% or 95% of the commercial risk for

Jan 1, 1985

By Keith Sutherland

AEROFLOAT 25 is a complex mixture of free cresylic acid with aryl substituted dithiophosphoric acids, sulphides, disulphides, etc. Its complete composition has not been published by the makers or patentees. It is prepared1 by the reaction between phosphorus pentasulphide and carefully selected cresylic acid. We have been informed that this acid contains no phenol and very little cresol, and that it is rich in the higher alkyl phenols, particularly the xylenols. The reaction between a phenol ROH and phosphorus pentasulphide may produce compounds of the following type:2 (i) RO S P Diaryldithiophosphoric acids RO SH (ii) R-SH Thiophenolic compounds (iii) R-S-R Diaryl sulphides (iv) R-S-S-R Diaryl disulphides (v) Substituted thianthren compounds Except for the simplest type, the thiophenols (ii), the boiling points of these compounds lie above 300° C. The amounts of the thianthren compounds formed from the five xylenols (if all these are present) will vary according to the position of the substituents. In an attempt to ascertain something of the nature of the reagent, fractional distillation under atmospheric pressure was undertaken. At the outset, hydrogen sulphide was freely evolved, and-particularly below 200° C.-the fractions had the strong odor characteristic of the

Jan 1, 1939

By C. H. Li, R. J. Stokes, T. L. Johnston

Dislocation half-loops, artificially introduced by sprinkling with carborundum, were subjected to stress using three-point loading. The different stages of loop expansion and multiplication were then correlated with the macroscopic stress-deflection curve. Loop expansion started at approximately one-third of the "yield stress," defined here as the motivation stress. Above one-half of the "yield stress" simple multiplication commenced while about two-thirds of the yield stress gross multiplication developed short slip-line segments. These values were not affected by the age of surfaces exposed to both dry and wet air. Slip was not detected on unsprinkled crystals below two-thirds of the "yield stress." Thus the stress to activate intrinsic sources, defined here as the activation stress, was approximately twice the motivation stress. This relationship was independent of the strain rate used. It is concluded that lattice resistance takes the form of a viscous drag rather than a static type of force. THE importance of surface condition and environment as one of the more significant factors controlling the mechanical properties of ionic solids has recently received renewed attention.1-4 In some materials, notably the alkali halides, exposing freshly cleaved specimens to the atmosphere results in a progressive hardening and embrittlement of the crystals. This has been attributed to the surface layer becoming "aged," thereby restricting the motion of dislocations in such a way that pileup and eventually fracture results. It is necessary therefore in studying the mechanical properties of ionic crystals to inquire first into the density and distribution of dislocations in the normal cleaved surface and to understand the role these dislocations play in the onset of plastic flow. Knowledge of the effect of environment on this behavior will then assist in understanding the mechanism of embrittlement on aging. In the work reported here a method is described for studying the initiation of plastic flow from dislocation sources in the surface of magnesium oxide crystals. Preliminary results are described of the influence of surface age on this behavior. EXPERIMENTAL TECHNIQUES The magnesium oxide used in this investigation was obtained from the Norton Co. and had a nominal purity of 99.5.pct. Single-crystal specimens, having dimensions typically 1/4 by 1/8 in. cross section and 1 in. in length, were prepared by cleavage over (100) planes from the parent crystal. They were deformed under three-point loading with 3/4 in. spacing between the two end supports and a constant rate of deflection at the center of 0.001 in. per min. The maximum strain rate therefore was 1.5 X 10-5 sec-1. Reasons for choosing this particular form of loading will become apparent in a later section. In addition, a number of confirmatory type tests have been performed at higher loading rates where the maximum strain rate was increased to 1 x 10-3 sec -1. Following deformation the crystals were etched to reveal the dislocation distribution. In a previous paper5 we described a satisfactory etching solution consisting of 5 parts of saturated ammonium chloride, one part of sulfuric acid, and one part distilled water. Immersion of the crystals for 1/4 hr at room temperature developed reproducible conical etch pits at the points where dislocations emerged through the surface. It should be mentioned that dislocations freshly introduced by room temperature deformation gave sharply pointed etch pits which generally distinguished them from the almost flat-bottomed pits obtained on "grown-in" dislocations. The distinction is obvious in the photomicrograph included in Fig. 5(b). Annealing crystals at 1000°C for 12 hr on the other hand gave sharper etch pits on the grown-in dislocations and the distinction was no lower -possible; a similar observation has been reported for lithium fluoride. We have succeeded furthermore in chemically polishing magnesium-oxide crystals. Boiling in fresh 85 pct ortho-phosphoric acid for only 1 min resulted in a microscopically smooth surface which could again be etched to reexamine the dislocation distribution. This boiling time was sufficient to remove the surface damage introduced by cleavage (see next section). SURFACE DISLOCATION SOURCES There are a number of ways by which dislocations may be introduced into cleaved surfaces to act later

Jan 1, 1960

By A. Yoshikawa, T. Sugeno

To detenmine the origin of the sharp fatigue limit in many ferrous metals, S-N curvces were determined in push-pull fatigue at 18.6 kc per sec at room temperature and - 67°C for various kinds of iron. These differed in carbon and nitrogen content and grain size (25 and 2500 grains per sq mm). Sharp knees appeared in the S-N curves of fine-grained specimens with high interstitial content at both temperatures. In coarse-gruined specimens, knees were not sharp .regardless of the interstitial content and the testing temperature. It is concluded from these results that the controlling factov for the appeavance of the sharp fatigue limit is not strain aging but grain size. It has already been mentioned that iron and some iron alloys show fatigue curves characterized by a more or less sharp knee and a fatigue limit.' Explanations of the origin of this characteristic behavior of fatigue in iron appear to fall into two broad classes. One is concerned with interstitial impurities through the aging or locking effect and the other is based on intrinsic plastic properties of iron. Levy and sinclair2 and Lipsit and Horne3 have suggested that the fatigue limit observed generally in iron and steel is due to interstitial solute aging during the course of fatigue. On the other hand, Thompson and wadsworthl have suggested that the fatigue limit may be analogous to the sharp yield point, in the sense that alternating stresses above the fatigue limit are necessary to break down the dislocation locking. However, there are some experimental results which cast doubt on the general validity of these suppositions.4-8 Ferro and Montalenti' have recently suggested that the typical form of the fatigue curve of iron seems to come from an intrinsic plastic characteristic of the iron structure. This suggestion is based on the experimental result that pure iron containing an insufficient amount of interstitial solute to alldw appreciable strain-aging effects still showed a fatigue limit at room temperature. Although systematic investigations on the effect of grain size are scarce, it is thought that this effect is important in relation to the sharp fatigue limit. In fact, sensible differences were observed by Oates and Wilson4 in fatigue behaviors of a low-carbon steel depending on grain size. Ideally, the fatigue limit will be defined as the upper limit of stress amplitudes at which the life is infinite. This ideal fatigue limit can never be determined because of the limited time available for experiments, and moreover scattered data points often leave the construction of S-N curves somewhat arbitrary. And, it is usually stated that a material has a fatigue limit when its statistical S-N curve becomes apparently parallel to the N axis with a more or less sharp knee. The meaning of the fatigue limit and the sharp knee will be discussed in detail in relation to the construction of S-N curves. The origin of this sharp knee was investigated by determining S-N curves of iron for various interstitial contents, testing temperatures, and grain sizes. EXPERTMENTAL PROCEDURE The material as received was a commercial-grade low-carbon steel in the form of 4-mm-diameter rods with the following composition in weight percent: C, 0.09; Si, 0.017; Mn, 0.43; P, 0.006; S, 0.012; Cu, 0.11. Five different groups of specimens were tested. The grain sizes and interstitial contents in each group are given in Table I. The specimens of group C-02 were decarburized by annealing for 100 hr at 700°C, followed by an additional 100 hr at 850°C in wet hydrogen. Specimens of groups N-2 and N-9 nitrided in a mixed atmosphere of ammonia and hydrogen after an initial treatment identical to group C-02. The specimens of group C-9 were prepared in a manner similar to those of group C-02, except heat treatment was carried out in a vacuum. After polishing their surface with emery paper, the specimens of all groups were given a final anneal for 30 min at 930°C and air-cooled in an evacuated quartz tube. For group C*-9 this

Jan 1, 1965

By H. G. Kok

The continuous increase in energy costs has made it necessary to consider a broader use of belt conveyors for the transportation of material from the mine pit to the processing plant. Hard rock has to be crushed before it can be moved by belt conveyors. Systems are in the planning stage for mining hard rock, such as copper and iron ore, by using high-capacity, mobile, or semi-portable crushers. The mobile crusher is located in the pit, and the crushed material is transported by energy-efficient, shiftable belt conveyors out of the pit.

Jan 1, 1983

By American Institute of Mining Engineers

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Jan 1, 1918

By Kung-Lee Wang, Brian W. Mackenzie, Warren E. Morrison, DeVerle P. Harris, George F. Sharrard

The term "mineral economics" is applied to a wide range of activities in the mineral industries. Earlier chapters have described the application of economic concepts to the mineral industries-supply, demand, conservation, tariffs, etc. The solution of mineral economics problems is often assisted by the application of quantitative methods. The purpose of this chapter is to describe a number of quantitative methods-econometric, operations research, and management science techniques-which find application in the analysis of mineral economics problems. These methods include input-output analysis, trend analysis, forecasting techniques, simulation, multivariate statistical analysis, mathematical programming, and market research techniques. The purpose of this introductory section is to provide a mineral economics framework for the application of these methods. Mineral economics is a subdivision of economics that is justified by a sufficient number of economic problems in the mineral industry requiring special experience and an unusual combination of skills. These problems are concerned with the conversion of minerals as geologic resources to minerals as economic goods. The mineral conversion process is outlined in Fig. 8.A.1. The physical occurrence of mineral deposits in nature and the market demand for mineral products in the economy provide the basic stimuli. The conversion process embodies a number of sequential stages-exploration, the development of mineral deposits, and mineral processing facilities and, consequently, productive activity to supply market demand. Changes in demand and the depletion of deposits illustrate the dynamics of the process. Mineral economics applies economic con-

Jan 1, 1976

An abstract of a paper from the Canadian Mining and Metallurgical Bulletin of August 1978 by E. Stamboliadis, J. McHardy, T. M. Salman, Department of Mining and Metallurgical Engineering, McGill University, Montreal, Quebec, states that: “The recovery of gold, silver and other heavy metal cyanides from mill solutions is technically possible using the ion exchange technique. However, the costs involved are greater than the costs of the zinc precipitation technique used for gold recovery. There are two main reasons for this: one, the fact that in gold ore cyanidation metal cyanides other than gold and silver occupy most of the resin capacity and hence reduce the adsorption efficiency of the resin for the Au and Ag cyanides; secondly, the high cost of the eluting agents.” Resin, therefore, cannot in most cases be efficiently used for recovery of precious metals. With copper in solution, only 1.47% of the resin capacity is used for gold and 0. 8970 for silver; the rest is occupied by unwanted metal cyanides, such as copper occupying 73.7%. On the other hand, although activated carbon will adsorb copper cyanides, they will be preferentially displaced by gold and silver cyanides. Ion exchange is by one or two orders of magnitude more expensive than the conventional method of zinc precipitation. The cost of removing impurities, such as copper from the resin, is greater than the cost of recovering gold. With an oxide ore amenable to cyanidation and with a low content of other metals, such as may occur with some of the Soviet gold deposits, ion exchange would be an efficient as Carbon-In-Pulp.

Jan 1, 1981

[NORTH AMERICA UNITED STATES ALABAMA Birmingham Cord, Richard H. Dlsmukes, Edward B. Hunter, Robert A. Citronelle Perrin, Huey P. Fairfield Pagel, Herbert Ervin Fairhope Ruffles, William R. Huntsville Eng, Harvard Kelley, Dean W. Waggoner, J. B. Weber, Thomas C. Mobile Hankins, James D. Horner, William L. Petroutson, Peter C. University Cudworth, James R. Jones, Walter B. Mason, William L.]

Jan 1, 1961

NORTH AMERICA Number Members Alaska 31 Canada 333 Mexico 186 Newfoundland 2 United States Alabama 60 Arizona 171 Arkansas 10 California 769 Colorado 196 Connecticut 106 Delaware 21 District of Columbia 139 Florida 17 Georgia 6 Idaho 72 Illinois 260 Indiana 63 Iowa 10 Kansas 33 Kentucky 38

Jan 1, 1932

By D. W. Smith, Robert F. Mehl

It has been shown by numerous studies that the orientations of new metal crystals are determined by the orientations of the crystals in the original matrix, whether these new crystals are formed by recrystalliza-tion, by precipitation from solid solutions, or by transitions in the solid state. The orientations of crystals formed by recrystallization of cold-worked metals that bear preferred orientations are occasionally simply related to the initial preferred orientation; often, however, the relationship is not simple, but complicated and obscure in origin.1 The orientations of crystals formed by precipitation from solid solutions have been shown by many studies in this and other countries to be determined by the orientation of the crystals of the solid solution stable at the higher temperatures, though here again complicated cases have been found and no general theory is available.2 Related to this latter class are the relationships found in crystals formed by suppressed transforma-

Jan 1, 1935

By D. W. Smith, Robert F. Mehl

It has been shown by numerous studies that the orientations of new metal crystals are determined by the orientations of the crystals in the original matrix, whether these new crystals are formed by recrystalliza-tion, by precipitation from solid solutions, or by transitions in the solid state. The orientations of crystals formed by recrystallization of cold-worked metals that bear preferred orientations are occasionally simply related to the initial preferred orientation; often, however, the relationship is not simple, but complicated and obscure in origin.1 The orientations of crystals formed by precipitation from solid solutions have been shown by many studies in this and other countries to be determined by the orientation of the crystals of the solid solution stable at the higher temperatures, though here again complicated cases have been found and no general theory is available.2 Related to this latter class are the relationships found in crystals formed by suppressed transforma-

Jan 1, 1935

Henry M. Parks, director of the Oregon. Bureau of Mines and Geology, has supplied the following information regarding a recent discovery .of manganese ore in Jefferson County, Oregon, about seventeen miles southeast of the railroad at Eagle Point, a station on the P. & E. Railway. The occurrence is about five miles southeast of Lake Creek Post Office and near the confluence of Lost Creek with the south fork of Little Butte Creek. The manganese ore occurs as psilomelane and pyrolusite, disseminated through a flat bed of volcanic tuff breccia; at a point where the bed was penetrated by a churn drill hole, the thickness of the ore-bearing stratum was 30 ft. Development thus far has consisted of open-cuts, one of which exposes a face about 40 ft. high and 75 ft. broad. Other smaller open-cuts have followed the bed for a. distance of 400 yards. The nodules of manganese mineral vary from a maximum of 25 to 50, lb. down to the size of beans and others as small as mustard seed. These grains, when clean, average from 55 to 58 per cent. manganese. A 12-ft. groove sample in the face of the main open-cut yielded 14.86 per cent. manganese. The peculiar occurrence of the manganese nodules should present but slight difficulty in concentration. A small experimental mill was built last winter, comprising gyratory crusher, rolls, and jigs, which,

Jan 8, 1918

By B. Ladanyi, B. Hoyaux

One of the most important problems in underground works is the assessment of the stability of underground openings and the determination of loads on eventual supporting structures. Under certain stress conditions, a hard and sound rock around an unlined opening may show a tendency to rock bursting, which can be prevented by appropriate measures. On the other hand, a less competent rock even if it fails in a less violent manner may give rise to a rock load because within limited regions surrounding the opening, the failed material may have a tendency to flow into the opening; this condition should be prevented by designing a proper supporting structure. The stability of the opening, as well as the value of the design loads acting on the supports in the latter case, depends clearly on the shape, extent, and location of the failed regions, which are often called “plastic zones.” It has been known for some time how the plastic zones develop in some very simple cases, such as in the case of a circular opening in an elastic ideally plastic medium subjected to a nongravitational stress fie1d.l However, to the knowledge of the authors, no information has been available up to now about the extent of the plastic zones in a more general case and for rocklike media. ASSUMPTIONS ON ROCK BEHAVIOR MADE IN THE CALCULATION The solution shown in this chapter is valid for a horizontal tunnel of circular cross section driven through a rock medium at a finite depth.

Jan 1, 1970

By Carl J. Christensen

This paper presents the development of diamond coring of the Weber sand section in the Rangely Field, Colorado. The description and operation of the diamond-coring equipment is included as well as the economics and results obtained by its use. Diamond coring is compared with the other methods used for drilling the Weber sand. Two types of diamond coring are discussed. The first and the one used most extensively is the regular 6 ?x 3¾-in. diamond bit and bottom hole 50-ft barrel. The second type, which has also been used successfully by Stanolind, consists of a 4 13/16 x 2 11/32-in. cutting bit and reverse circulation coring equipment. The first type will be referred to as regular or conventional diamond coring while the latter type will be referred to as reverse circulation diamond coring. Introduction Diamond coring has been used for many years in mines, quarries, surface coring at dam sites, laboratory work, and so on, but, until recently, had never been used very extensively in coring oil sands and other oil-bearing strata. It was demonstrated early in its development that hard forma-tions could be cut rapidly and that core recoveries far exceeded those obtained with conventional hard rock bits and quite often 100 pet recovery was obtained. However, the poorly constructed diamond-coring equipment and resulting high costs of early diamond coring slowed down its progress. Early in the development Of the Rangely Weber field, Rio Blanco County, Colorado, the Rangely Engineering Committee selected key wells that were to core the Weber section in its entirety. These cores were to be analyzed and various sections tested to gather sufficient information so that accurate reservoir studies could be made. The number of wells selected were kept at a minimum inasmuch as the productive Weber section, which is found at an approximate depth of 6000 ft, is thick, being as much as 600 to 700 ft on top of the structure. The Weber section is also comparatively hard to drill. For instance, one well took 60 days to core 490 ft of Weber sand with conventional coring equipment. It was noticed, however, that Core Labora-verse diamond plug cutter could quickly cut a plug from. one of these hard cores. This fact led to the serious consideration of diamond coring the Weber sand. The first diamond coring at Randy was performed by Stanolind in August 1946 andl although we experienced some difficulties, the results definitely indicated that diamond coring would be successful at Rangely for .coring the Weber sand. As more wells were cored and the equipment improved somewhat, diamond coring became less expensive than drilling the Weber sand with the conventional rock bit. In less than one Year diamond coring has definitely Proved its usefulness in oil-field drilling operations in the Rocky Mountain area where formations quite often drill very hard. The practice of spot coring in hard oil-bearing formations with conventional coring equipment is giving way diaimond coring of the entire sections, thus givng an operator the complete picture.

Jan 1, 1948

By Carl J. Christensen

This paper presents the development of diamond coring of the Weber sand section in the Rangely Field, Colorado. The description and operation of the diamond-coring equipment is included as well as the economics and results obtained by its use. Diamond coring is compared with the other methods used for drilling the Weber sand. Two types of diamond coring are discussed. The first and the one used most extensively is the regular 6 ?x 3¾-in. diamond bit and bottom hole 50-ft barrel. The second type, which has also been used successfully by Stanolind, consists of a 4 13/16 x 2 11/32-in. cutting bit and reverse circulation coring equipment. The first type will be referred to as regular or conventional diamond coring while the latter type will be referred to as reverse circulation diamond coring. Introduction Diamond coring has been used for many years in mines, quarries, surface coring at dam sites, laboratory work, and so on, but, until recently, had never been used very extensively in coring oil sands and other oil-bearing strata. It was demonstrated early in its development that hard forma-tions could be cut rapidly and that core recoveries far exceeded those obtained with conventional hard rock bits and quite often 100 pet recovery was obtained. However, the poorly constructed diamond-coring equipment and resulting high costs of early diamond coring slowed down its progress. Early in the development Of the Rangely Weber field, Rio Blanco County, Colorado, the Rangely Engineering Committee selected key wells that were to core the Weber section in its entirety. These cores were to be analyzed and various sections tested to gather sufficient information so that accurate reservoir studies could be made. The number of wells selected were kept at a minimum inasmuch as the productive Weber section, which is found at an approximate depth of 6000 ft, is thick, being as much as 600 to 700 ft on top of the structure. The Weber section is also comparatively hard to drill. For instance, one well took 60 days to core 490 ft of Weber sand with conventional coring equipment. It was noticed, however, that Core Labora-verse diamond plug cutter could quickly cut a plug from. one of these hard cores. This fact led to the serious consideration of diamond coring the Weber sand. The first diamond coring at Randy was performed by Stanolind in August 1946 andl although we experienced some difficulties, the results definitely indicated that diamond coring would be successful at Rangely for .coring the Weber sand. As more wells were cored and the equipment improved somewhat, diamond coring became less expensive than drilling the Weber sand with the conventional rock bit. In less than one Year diamond coring has definitely Proved its usefulness in oil-field drilling operations in the Rocky Mountain area where formations quite often drill very hard. The practice of spot coring in hard oil-bearing formations with conventional coring equipment is giving way diaimond coring of the entire sections, thus givng an operator the complete picture.

Jan 1, 1948