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By G. P. Demopoulos

"The recovery and separation of platinum-group metals (PGM) from primary and secondary materials currently attracts a lot of interest due to the high value of the metals and their increasing demand for high-tech applications. Thus, the traditional refining processes are gradually replaced by newer more efficient separation techniques such as solvent extraction and ion exchange. In this paper the classical and modern refining techniques are reviewed and the pertinent solution chemistry dictating proper processing strategies in each case is discussed. The technological advantages of the modern separation methods are emphasized and reference to the recovery of PGM from primary as well as secondary materials is given. INTRODUCTIONDue to their outstanding physicochemical properties, such as catalytic activity, conductivity and corrosion/oxidation resistance, precious metals now find extensive usage outside of the traditional jewellery and investment industries. The increasing use of precious metals in such areas as electronics and catalysis, as well as their increasing high value, has led to a growing interest in their recovery and separation from primary and secondary materials.Quantitatively the demand of platinum metals in the western world by area of application is described in Table I. Platinum and palladium represent 90% of the total demand, Rh and Ru 8% and the remaining is taken by Ir and Os. In terms of value the following were the average prices (US$/oz) of the metals in the second half of 1986: 500 Pt, 125 Pd, 1200 Rh, 650 Os, 400 Ir and 80 Ru. Due to these prices, exploration, mining, reclamation and refining activity were very high in South Africa, the biggest producer of Pt metals in the world, as well as in other areas: United States (Stilwater deposit), Canada (Sudbury, Marathon and Lac des Isles, Ontario; Kenly Lake, Quebec, etc.), Australia, Europe and elsewhere"

Jan 1, 1989

By M. R. KEYS

"The property is about 120 miles north of Red Lake in the Favourable Lake area, district of Kenora ( Patricia part) , Ontario. The original discovery was staked by K. Murray in December, 1927. The first development work was done by the Favourable Lake Mining and Exploration Company. In 1936 Newmont Mining Corporation acquired control of the property and developed it to production by September, 1939. Production to the end of 1945 had a value of $7,534,656 from 441,457 tons of ore, an average value of $17.04 a ton . This production was mainly from gold and silver, with lead and zinc of subordinate importance.The rocks in the vicinity of the mine trend in a north-south direction. From east to west the sequence is: (1) A dark-coloured, massive rock, presumably a flow, composed mainly of quartz and biotite. ( 2) A buff- coloured, scricitized rock locally containing quartz phenocrysts and black hornblende. This is an alteration product of the dark variety and is later than the folding. It occurs mainly within the dark rock. (3) A series of sediments comprising thin beds of greywacke, grit, quartzite, conglomerate, and iron formation. ( 4) A gabbro sill, now largely altered to amphibolite.With the exception of the buff type, these rocks dip 80°E. The buff rock has a very irregular outline in comparison with the other rocks and appears to dip somewhat more flatly east. Felsite and diorite dykes are also present. These have a general strike of S.60°E. and dip 65°S .W. A post-ore diorite dyke trending N.15°E. occurs about 2,000 feet east of the mine area."

Jan 1, 1954

By DALE MacGREGOR, VERA TUREK

lndusmin Limited acquired the St. Donat quartzite deposit in 1967 to produce high-quality silica for use in the sandblasting and silicon carbide industries. The quartzite, of Grenville age, is highly friable and porous. This is due to numerous small, kaolinite-coated cavities in the quartzite; the cavities were formed through leaching, probably by rising hot solutions.

Jan 1, 1984

By Gui Hua Wang, Xin Chang, Zhong Ying Han, Yuan Fang Cheng

"According to the geometrical characteristics of triangular meshes, Triangular Mesh Split Model (TMSM) based on a finite element method is proposed to simulate cracks propagation of fractured rock. With TMSM, stress intensity factors at the tip of cracks are obtained by far-field contour integral. Meanwhile, vector cross multiplication is adopted to fix the cracking unit, and maximum circumferential stress criterion is used to determine the crack propagation angle. Then crack dynamic propagation simulation is realized through local mesh split or node movement at crack tip. With this method, the crack can split apart a unit or extend along the mesh boundary, so the crack could extend along an arbitrary path and is not restricted by the initial mesh. The applicability of the mesh split algorithm is verified by the crack propagation examples of wing crack and multi-fractured rock mass with holes. The results show that this method not only has higher accuracy of fracture parameters calculation, but also can accurately simulate the crack initiation and propagation of rock under complex stress state such as tension, compression and shear. In addition, the far contour integral is introduced to determine the crack tip stress intensity factor and there is no need to reconstruct a singular element at the crack tip or to intensify the meshes. Compared with the existing mesh reconstruction algorithm, this method significantly improves the computational efficiency.INTRODUCTIONGenerally, rock is neither the full continuum, nor entirely discrete body, but rich in geological defects, such as joints and cracks. A large amount of geotechnical engineering practice shows that most fracture of rock is closely related to the internal joints, cracks and crack expansion (Horii et al., 1985; Wong et al., 1998). Although the classical theory of fracture mechanics established the theoretical foundation of crack initiation, propagation, so far it is still extremely difficult to characterize the propagation of airfoil-typed crack and the interference problem of multiple cracks. Up to now, the micromechanics mechanism research of crack propagation of fractured rocks has still been a hot research topic of rock fracture mechanics."

Jan 1, 2015

By A. M. Cann, C. I. Godwin

"The Kemess porphyry copper-molybdenum deposit occurs in the Intermontane Belt of north-central British Columbia. The deposit is in andesitic to basaltic flows and tuffs which may be correlated with the Savage Mountain Formation of the Upper Triassic Takla Group. Most known chalcopyrite and molybdenite is associated closely with a 500-m-diameter zone of intense quartz-sericite-pyrite alteration. A zone of supergene enrichment, up to 30 m thick, underlies a leached capping about 20 m thick. The age of mineralization and the surrounding granodiorite and quartz monzonite pluton is Early Jurassic. K-Ar and Rb-Sr analyses indicate that the mineralization and alteration is slightly younger (l82±6 Ma) than the granitic intrusion (KAr: about 205±6 Ma; Rb-Sr: 190±4 Ma). The low 87Sr/J6Sr initial ratio for the granodiorite is typical of plutons in the Intermontane Belt.IntroductionKemess is a medium to small porphyry copper-molybdenum deposit with significant gold and silver values (Pilcher and McDougall, 1976). This paper describes the lithologies and alteration at this property; geochronology by Rb-Sr and K-Ar methods defines the ages of mineralization and surrounding plutons to be Early Jurassic.The property, located in the Thutade Lake area of northcentral British Columbia (NTS Map 94E; lat. 57°04'N; long. 126°44'W), is about 425 km northwest of Prince George (Fig. 1). Closest road access is 35 km southeast of Kemess. Final access must be by float plane or helicopter. The British Columbia Railway right of way passes 70 km to the southwest of theproperty.A prominent gossan zone at Kemess was staked in 1967 by Kennco Explorations (Western) Ltd. following detection of geochemical anomalies during stream sampling the previous year. During 1968, 1969and 1971, Kennco completed 232 m of X-ray diamond drilling, conducted geological mapping and carried out geochemical sampling of silts and soils (Stevenson, 1969; B.C. Ministry of Energy, Mines and Petroleum Resources, G.E .M., 1969 and 1971). Getty Mines Ltd. optioned Kemess in 1975and 1976. They remapped the area and diamond drilled 12 BQ and NQ holes, totalling 2065 m (B.C. Ministry of Energy, Mines and Petroleum Resources, Expl. B.C., 1975)."

Jan 1, 1980

By A. McLean, J. Hou

Waste slag is a major environmental concern within the metallurgical industry. In the steel industry, about 100 kg of slag is produced in making one tonne of liquid steel from iron in addition to that produced during ironmaking. The amount of slag from the steelmaking converter can be significantly reduced when charging hot metal with low phosphorus and sulphur contents. In this context, hot metal pretreatment is known as an effective means of preparing high quality charge material for the converter thus limiting the generation of residual slag during the steelmaking process. In the aluminum industry, about 2-4 tonnes of slag, including red mud from alumina production and dross from aluminum electrolysis and casting, are generated during the production of one tonne of aluminum. In recent years, reuse of waste slag from the aluminum industry is a topic that is receiving increasing attention. In this paper, the possibilities of using waste slag and by-products from the aluminum industry as a refining flux in the steel industry are discussed. Several successful processes to convert waste materials from the aluminum industry to steel refining fluxes are described. Some theoretical aspects of using calcium aluminate based flux for desulphurization are outlined together with results obtained from laboratory experiments on sulphur removal from hot metal. By intelligent use of waste materials, the disposal of solid waste from the metallurgical industries can be reduced.

Jan 1, 2004

By S. N. Rossovsky

"A new method for the hydrometalfurgical treatment of refractory gold arsenosulphide concentrates is presented. Themethod involves a combination of' finegrinding, intensive agitation, flotation, and cyanidation, and consists of leaching of -10u pyrite and arsenopyrite particles in alkaline solution under intensive agitation without the application of costly high-pressure and roasting techniques. Consistent extractions of gold, in excess of 96%, are achieved.IntroductionConventional methods of alkaline leaching of gold arsenosulphide concentrates in an autoclave» and under electrochemical oxidation( 2) require expensive equipment as well as high-cost energy and reagents. In other cases, processing of gold concentrates inelude: ultra-fme grinding, calcination at 200°C to 250°C with the addition of an oxidant (NH4NOJ followed by alkaline leaching of the resulting calcine with hydrogen peroxide, the latter being a complicated method yielding poor extractions of gold (89% to 90%). In this paper, a hydrometallurgical method is described for processing refractory gold arsenosulphide concentrates in which alkaline leaching is followed by cyanidation of the residue."

Jan 1, 1993

By K. John

"THE most recent estimate of minteable coal reserves in Saskatchewan was made by the Federal Royal Commission on Coal (1944- 6). Saskatchewan was then estimated to have some 24 per cent of the Canadian reserves and two-thirds of this is located in what is called the Souris-Estevan area, which lies in the southeast corner of the Province and border's on the International boundary. It is also estimated that there are some 61/2 million thousand-tons in this area of lignite coal which grades 8,000 B.t.u. or less and has a moisture content ranging from 30 to 33 per cent. Ownership of coal rights in the Province is widely dispersed between the Crown, individuals, and corporations, and a recent survey disclosed that 40 percent of ownership was vested in the Crown and 60 per cent in private individuals and corporations. Coal rights on Crown lands may be leased at an annual rental of $ 1.00 an acre. Under such leases, a royalty of 5 cents a ton is levied on all coal mined. A royalty of 7 cents a ton is levied on coal produced from lands where mineral rights were purchased from the Federal Government prior to the transfer of jurisdiction over natural resources to the Province, in 1931. An annual mineral tax of 50 cents per acre has also been imposed by the Provincial Government on all coals within a defined producing areas."

Jan 1, 1952

By J. E. Danoczi, J. A. Herbst

"Shore Gold Inc. (Shore) is presently designing a diamond processing plant for the Star and the Orion South kimberlite deposits in the Fort à la Corne (FalC) area in central Saskatchewan. The first step in the plant is diamond liberation and occurs in the comminution section. Diamond liberation is the process of breaking up the kimberlite rock, as gently as possible so as not to damage the diamonds.Autogenous grinding mills (AG mills) use a combination of impact crushing, abrasion and attrition to break up the kimberlite. The forces that occur during the actions of abrasion and attrition cause the kimberlites to break up preferentially along lines of weaknesses which offers a “diamond friendly” method of comminution.Hard competent kimberlite is commonly found in the diatreme zone as well as the root zone of the volcanic pipe and is the source of kimberlite for most of the Southern African diamond mines. Softer kimberlite is typically found in and around the crater area of a volcanic pipe and it is this kimberlite that makes up the majority of kimberlite for both the Star and Orion South deposits. These softer kimberlites can be readily broken up using abrasion and attrition imparted by AG mills. In order for Shore to benefit from the softer kimberlite found in the Star - Orion South diamond project, two large (10.97 m diameter x 7.10 m long) AG mills were designed for the comminution section based on extensive test work and simulations by Metso Minerals (Metso)."

Jan 1, 2012

By Robert MacPhail, Louis Racine, Bret G. Cousins

"Sodium Isopropyl Xanthate is employed in a wide variety of sulphide flotation procedures due to the specificity over other xanthates and the cost savings over other sulphide collectors such as thionocarbamates, xanthogen formates and dithiophosphates. An investigation carried out by Tennants Research Technology Applications (TRTA), has produced a chemically enhanced SIPX that has shown all the advantages of normal SIPX along with improved recoveries.Currently, FLEX 31 is manufactured at the Prospec Chemicals xanthate plant in Fort Saskatchewan, Alberta, Canada. Prospec, founded in 1983, produces approximately 4500 tonnes of xanthates per year and is presently undergoing expansion to produce approximately 6000 tonnes. The proprietary process for FLEX 31 is a new addition to plant operations that include the production of xanthates, thionocarbamates and xanthogen formates.This paper will cover the testwork on the zinc flotation circuit at the Louvicourt Mine in Val d'Or, Quebec. This testwork indicated that FLEX 31 could replace SIPX due to the ability of the FLEX to improve zinc flotation kinetics without adversely affecting final concentrate grade. FLEX has presently replaced SIPX in the zinc circuit at Louvicourt.BackgroundThe Louvicourt deposit is hosted by greenschist facies Archean volcanic rocks located in the southeast portion of the Abitibi Greenstone Belt. In the Val d'Or area, the volcanic rocks form an east-west striking, steeply dipping and south-facing sequence composed of thick mafic and ultramafic flows of the Lower Malartic Group.The joint venture has three partners-Aur Louvicourt Inc. (30%), Novicourt Inc. (45%) and Teck Corp (25%). Aur Resources holds 30% interest through Aur Louvicourt, a wholly owned subsidiary and is the operator of the project. Novicourt Inc. is 60.9% held by Noranda.Approximately 75% to 85% of Louvicourt's revenue comes from the sale of copper; 10% from gold (in the copper concentrate); 7% from zinc and 3% from silver (also in the copper concentrate) The copper at Louvicourt is fairly ""fast floating"". About 60% of the copper in the ore can be concentrated in the first flotation cells with feed grades of approximately 4% copper.The initial testwork and pilot trials had indicated that it would be difficult to achieve zinc grades over 52% and recoveries would have to be kept at a level amenable to salable concentrate grades. The actual mill results, with a fine regrind, achieved zinc grades of 55% to 56% at about 75% recovery."

Jan 1, 1996

By M. K. Aly

"ABSTRACTThis paper briefly describes the mining method proposed for the iron ore deposits in Wadi Shatti, western Libya. The iron ore produced will be used in the steel plant at Misurata on the Mediterranean coast. GeologyThe Wadi Shatti is located in the central part of western Libya. Flat iron-bearing sedimentary rocks are exposed with remarkable regularity in this valley. It occupies an area 200 km long by approximately 20 km wide trending in an eastnortheast direction between Jabal Fazzan in the north and Zel1af Sand Dunes in the south (Fig. I). Only a part of this valley has been ful1y explored by drilling on a 400- by 200-m pattern in an area of 18 km2 south of the town of Taroot. Farther to the south, no exploration by drilling can be done due to the presence of sand dunes .The iron-bearing bed is about 10to 15m thick, with a dip of 2 to 4 degrees in a southerly direction . The overburden consists mainly of clayey sandstones, 4 to 5 m thick, in the northern part, increasing to 35 m in the southern part. The iron ore bed consists of three different layers, from the floor upward: (1) Lower Reduced Ore (LRO), having a varying thickness of 1 to 7 m; (2) Magnetic Ore (MO), with a thickness varying from 4 to 12 m mainly in the central part of the area; and(3) Upper Reduced Ore (URO), with a bed thickness varying from 0 to 7 m."

Jan 1, 1980

By P. Mayer

"Determining the correct mechanism of a boiler tube failure is important for the prevention of future tube failures. Proper corrective measures can be undertaken to alleviate the root cause or causes for a failure only when the correct mechanism is known. A mechanism of boiler tube failure is defined as the process which degrades the tube and produces a failure.An expert system package was developed for use by electric utility power plant personnel during investigation into the cause of a boiler tube failure. It is intended to assist their efforts to recognize and identify a basic failure mechanism that can produce the type of boiler tube failure under investigation. The program guides the user to the most likely failure mechanism by asking simple questions, answers which can be obtained by determining the failure location, type of fuel, and from visual inspection of the failed tube. Expert systems are a form of artificial intelligence which imitate the decision-making process of experts.IntroductionBoiler tube failures (BTFs) continue to be the single largest source of forced outages in fossil fired electricity generating stations. Because of this a concentrated effort is being made to minimize boiler tube failure occurrences. Eliminating boiler tube failures could be worth $5 billion a year to the electric power industry(1).The aggressive service environment of fossil-fired boilers is largely the reason for these failures because the combined effects of stress, temperature, corrosion, erosion and vibration cause deterioration of boiler tube material properties and reduction in wall thickness.Determination of the boiler tube failure mechanism is important for the prevention of future problems. The root cause for a failure can be established and proper ameliorative measures taken only when the failure mechanism is identified correctly. The correct identification of failure mechanism is a complex process which may include many individuals and institutions. Technical specialists in metallurgy, chemistry, combustion, and boiler design frequently cooperate with the station staff in a failure investigation . These individuals rely on personal experience and numerous reports , theories, studies, private communications and investigations concerning the different failure modes and mechanisms."

Jan 1, 1990

By W. Marnette

The copper demand is booming. New epicentres with strong dynamic economic growth have arisen in China and other emerging markets. Furthermore, Europe contributes to higher copper demand due to positive economic growth. China and India are therefore expanding their smelter industries, with the backing of a coordinated policy of global raw material sourcing, which includes investments in raw material deposits and state-run measures to support their international trade and competition. Likewise, Europe faces scarcity of copper raw materials. The copper industry in Europe is historically grown and shows excellence in environmental protection and technical leadership. Recycling has always been an important sector. This reiterates the recycling-know-how which exists in the European sector. However, Europe still relies on importing a considerable amount of raw materials from foreign countries. As a result, the global competition for copper and copper raw materials has increased. Tough competition as regards industrial location and costs, the emergence of corporate concentrations and the use of protectionist trading practices by countries like China and India, which distort the markets, now determine the picture. Hence, a copper smelter in Europe is forced to develop tailor-made concepts to safeguard and improve its international competitive position. It is imperative that this is also flanked by improved conditions on the local level and a European raw material policy which takes account of the changed situation on the world market.

Jan 1, 2007

By M. Rigaud, N. Zhou, K. Sankaranarayanane, X. Zhou

The effect of amount and type of dispersants on the rheological behaviour of bauxite-based low-cement castables has been studied in detail. The rheological properties: flow resistance and torque viscosity, as measured by a rheometer, are found to be strongly influenced by the amount and type of dispersants. In the present investigation, a mix containing sodium hexametaphosphate, at an optimal level, is observed to be theologically superior at the given experimental conditions.

Jan 1, 2004

By D. C. Martin, P. M. Hawley, C. P. Acott

"In bedded deposits such as coal or sedimentary iron, economic limits of mineable reserves are clearly defined by the footwall of the seams or ore-bearing units. Where open pits are developed in dipping strata, a long, high footwall slope may result. In many cases, unbenched slopes excavated along the base of the lowest mineable seam are operationally simple, economically desirable and geotechnicalty practical, although a variety of failure mechanisms may develop. This paper examines the engineering geology and rock mechanics parameters of importance in the design of footwall slopes. Possible failure mechanisms and stability analysis methods are described. Design considerations for benched and unbenched slopes are discussed with prime consideration given to development of long high stopes without benches or with a minimum number of benches. IntroductionIn bedded deposits, the ultimate depth and economic viability of an open pit in dipping strata may be controlled by the design of the footwall slope. The stability and, hence, design of footwall slopes is strongly influenced by the engineering geology and rock mechanics parameters of the slope forming materials. A clear understanding of the structural geology, engineering geology and tectonic history of the deposit is essential to assess the behaviour of the slope. This is particularly important for long high, unbenched footwall slopes such as shown in Photo I.A rational footwall slope design requires identification and assessment of all possible slope failure mechanisms with respect to the proposed slope geometry. Stability analyses of each potential failure mechanism are used to identify the main controls on slope stability and to develop appropriate slope design criteria. The optimum slope design is based on the most economic and geotechnically practical slope geometry with due consideration of operational constraints and of the possible advantages of specific remedial measures."

Jan 1, 1986

By S. Flewelling, M. Scobie, G. R. Baiden

"SynopsisA feasibility study to develop a research program, the Mine Automation Plan (MAP), was recently completed. This was undertaken by a team comprised of Inco Ltd., Falconbridge Limited, the Canadian Centre for Automation and Robotics in Mining (CCARM) and the Centre for Resource Studies (CRS). The study was sponsored by PRECARN Associates, which is a consortium of thirty-six Canadian companies focussed on research and development in artificial intelligence and robotics. PRECARN Associates was formed in 1987 when a number of research proposals were funded in the fields of process control systems, robotics systems and intelligent engineering systems. In July 1991, PRECARN accepted the next round of proposals for research. The MAP project was one of the successful proposals, being awarded $100,000 for the development of a feasibility study defining a long-term R&D plan for underground hardrock mining automation.The development of the feasibility study started by addressing the fundamental structure of the mining process, and its relationship to the metallurgical process, over-all infrastructure support and management systems (Fig. I).Mining may be considered as comprising five subprocesses: (I) delineation; (2) development; (3) production; (4) backfilling; and (5) infrastructure support services. Within these subprocesses many applications for artificial intelligence and robotics exist. The mining process is dependent upon the interaction between the physical mining process and information. For example, the delineation process is dependent on geomechanical, geochemical and geophysical techniques to develop a model of the orebody based upon access to such data. This same relationship between the physical and information models holds true through the development, production, backfill and infrastructure support systems.The foundation for the MAP study has been the recent development by Inco Ltd. of an underground communications system (Fig. 2). The system has the ability to supply high bandwidth communications, over voice, data and video to mobile and stationary locations within the mining operation. It is seen to be the future backbone of a comprehensive, automated information system which should permit the application of the concept of Computer Integrated Manufacturing (CIM) to underground mining. CIM, through the automated flow of information, has been successful in integrating the engineering, production and various support groups in manufacturing."

Jan 1, 1994

By C. DeLong

"The Mt. Milligan porphyry copper-gold deposits are in central British Columbia, 155 km northwest of Prince George. Mineralized outcrops and float were discovered in the Mount Milligan area by prospecting. The most recent discoveries, which utilized lithogeochemistry, were in 1983. Areas containing the outcrops and float then were investigated by geological mapping, soil and lithogeochemical sampling, ground and airborne geophysical surveys, trenching and diamond drilling. This work led to the discovery of the Mt. Milligan Main deposit in 1987 and the Southern Star deposit in 1989. Extensive diamond drilling continued until 1991 and delineated a measured and indicated resource of 299 million tonnes grading 0.45 g/t Au and 0.22 % Cu from the combined deposits.The Mt. Milligan deposits lie within the Early Mesozoic Quesnel Terrane and are hosted by porphyritic monzonite stocks and adjacent volcanic rocks of the Takla Group. The Mt. Milligan Main deposit is centred around the MBX stock and Rainbow dike, and the Southern Star deposit around the Southern Star stock.Potassic alteration is extensive within the stocks and in volcanic rocks adjacent to the MBX stock and Rainbow dike. Propylitic alteration surrounds the potassic alteration and decreases in intensuy away from the stocks. Mineralization consists mostly of pyrite, chalcopyrite, lesser magnetite, and minor bornite, molybdenite and gold.Mineralogical zoning is well-developed within the deposits. A biotite-rich subzone forms the core of the potassic alteration zone and hosts most of the copper and gold. Numerous polymetallic veins lie within the propylitic alteration zone just beyond the limit of porphyry-style copper-gold mineralization."

Jan 1, 1995

By Bian Xue, Wu Wenyuan

High quality, mono-dispersed, hollow CeO2 microspheres with high surface area were produced by a spray pyrolysis method at 700oC. CeCl3 was used as the raw material of the process rather than Ce(NO3)3 because the latter is relatively difficult to obtain in industrial quantities. X-ray diffraction and electron microscopy results confirm the high quality synthesis of hollow CeO2 microspheres with narrow size distribution, good mono-disperse, and good reproducibility. The process of the formation of mono-dispersive CeO2 microspheres was investigated by chemical dynamics and a possible mechanism is proposed. This simple method for synthesis of CeO2 microspheres is easily scaled up to fabricate other metal oxide nanostructured materials at industrial scale.

Jan 1, 2014

By Songgen He, Jianchun Guo

With the development of complex, unconventional and deep reservoirs, it shows that many rocks behave plastically with the influence of clay and confining pressure. Traditional linear elastic hydraulic fracturing initiation models are not good predictors for elastic-plastic reservoirs. With the deformation theory of plasticity, a power hardening constitutive equation was developed in piecewise approximation method. Based on the nonlinear constitutive equation, a model of the stress field around the wellbore was developed considering fracturing fluid penetrating effect and in-situ stress anisotropy. At last, coupled with the maximum tensile strength criterion and Mohr-Coulomb criterion, a new elastic-plastic hydraulic fracturing initiation model was built. The following conclusions were summarized in the paper: (1)The piecewise power hardening constitutive equation based on the deformation theory of plasticity can accurately describe the nonlinearity of elastic-plastic deformation. (2)Whether the rock is yielded or not is determined by in-situ stress, yield stress, Biot coefficient and pore pressure. (3)Plastic yield has little influence on radial stress but significant impact on circumferential stress. The radius of the plastic zone is positively correlated with in-situ stress but negatively correlated with yield stress, power hardening index, pore pressure and Biot coefficient. (4)Initiation modes include tensile failure and shear failure when rock is yielded. (5) For elastic-plastic reservoir, the initiation pressure predicted by linear elastic model is much lower if the rock is yielded.

Jan 1, 2015

By John H. Fowler

"Barytes is one of the major components of drilling fluids used in oil and gas well-drilling. This mineral's close association with the petroleum industry bestows it with a commodity status not enjoyed by many other industrial minerals. Approximately 85% of world barytes production is used as a weighting agent in oil and gas well drilling while the remaining 15% is consumed mainly in the manufacture of barium chemicals, glass and as a pigment, filler or extender.Barytes mining began in Nova Scotia around 1865 and has continued until the present. Currently there are three barytes producers in the province one exporting pharmaceutical-grade barium sulphate and the other two supplying drilling mud-grade barytes to the offshore. Several barytes exploration and development programs are underway with excellent possibilities that Nova Scotia deposits will supply a significantly larger share of the drilling mud-grade barytes used in east coast drilling programs.Currently there is renewed interest in barytes activities in Nova Scotia because of its use as a weighting agent in drilling flu ids used in offshore oil and gas drilling programs.This paper reviews the use of barytes by the well drilling industry; outlines the history of barytes mining in the province, progressing to present-day exploration, development and production activities underway in Nova Scotia; and concludes with the market potential for Nova Scotia barytes."

Jan 1, 1986