Search Documents

By Stephen L. Chryssoulis, Stamen Dimov

"Preg-robbing has been known for many years, where increased losses are suffered because dissolved gold is removed from solution by adsorption onto carbonaceous matter. In direct cyanidation circuits it is reasonable to conclude that the preg-robbed gold is either in a gold cyanide [Au(CN) - 2, AuCN] or metallic [Au°] form. However, in circuits with a pre-oxidation step possibilities increase and multiply even further because of water recycle streams containing apparent and not-so-apparent gold ligands. It is in these circuits where speciation of sorbed gold, i.e. the identification of the gold compound, is useful. The importance arises from the fact that proper identification of the sorbed gold species can be used to determine how, when, where and why gold was removed from solution, thereby identifying the exact cause of the problem and providing clues as to how it may be rectified.INTRODUCTIONTo the best of our knowledge, this is the first attempt ever to speciate gold preg-robbed by carbonaceous matter using a surface sensitive microbeam technique. This approach enables the direct determination of gold species sorbed on carbonaceous particulates, opening an entirely new field in the understanding of the chemistry of gold sorption on carbon. The reasoning behind this effort was to add to the current knowledge of the detrimental effect chloride ions have on gold recovery by the pressure oxidation and in particular why in the ensuing CIL step, gold is not being desorbed from the surface of the carbonaceous particles (Table 1)."

Jan 1, 2004

By Warnett Kennedy

"GENUINE CONCERN for the environment is a built-in attitude of mind. If you do not have it by age 40 you probably never will. Some people speak the jargon of 'environment' and 'ecology' for political reasons, others because it feeds their need and bias toward attitudes of moral indignation or dissent. Others pay lip-service for purely business reasons. Complete reactionaries equate conservationists, ecologists and environmentalists as either 'commies' or 'pinkos'. Their real credo is the old saying, ""Where there's muck there's brass."" Those who have genuine concern for good environment are not only romantics like Thoreau but realists who sense the danger to our planet if human greed is rampant and unchallenged. The cities are in real trouble. Almost 75 per cent of the population already live in and around cities. Even mining men live in cities or bring up their children in the new 'instant' towns. The ecology of cities is the concern of all. Our distinguished guest Stewart Udall, in his book ""The-Quiet Crisis,"" quoted Thoreau in 1859 as having written ""each town should have a miniature wilderness park, a primitive forest of five hundred or a thousand acres where a stick should never be cut for fuel, a common possession forever."" Mr. Udall will be glad to know that this advice was taken in at least one instance known to me. I refer to Stanley Park in Vancouver. It is a primitive forest of 1000 acres right inside our small downtown peninsula. It remains unmanicured. This month we celebrated the completion of a seawall of 4%, miles along its perimeter. The construction of this wonderful walkway started in 1910. We are very, very proud of our park."

Jan 1, 1972

By Neil Campbell

"The gently-dipping Devonian dolomite beds south of Great Slave lake in northern Canada are nearly every-where concealed by a cover of glacial drift and muskeg. Nevertheless, in 1898 or earlier, four small outcropping areas of dolomite, richly mineralized with lead and zinc sulphides, were discovered. Exploration work performed here up to the end of 1930, included intensive trenching and drilling of the showings, together with mapping and wide-spaced drilling in the surrounding region. This work proved that the discoveries are isolated pockets of mineralization much too small to be commercially valuable by themselves. No evidence of orebodies elsewhere was reported.Meanwhile, mapping by the G.S.C. in the Shield far to the east disclosed major Precambrian faults, some of which can be projected southwesterly (under a cover of Paleozoic sediments) to the vicinity of Pine Point. During the period from 1940 to 1947, consideration was given, by The Consolidated Mining and Smelting Company Ltd., to evidence of a theoretical possibility that, although apparently dormant in Paleozoic times, these faults may have provided a structural control and a source of ore-bearing solutions in some post-Devonian period. From this, it was postulated that the breaks might have created, in the overlying dolomite, a linear array of orebodies concealed by overburden but lying in a belt of considerable length and in a position predictable within practical limits. A program of drilling designed to test and exploit this specific concept was conducted from 1948 to 1955.he drilling within the new, theoretically-defined search area resulted in the discovery of many lead-zinc ore-bodies, none of which was exposed at the surface. Some of these are large and (as indicated by 1965 production records) very rich. They are situated 1 to several miles distant from, and apparently not connected to, the earlier-known surface discoveries. The drilling also disclosed that the ore, which consists of disseminated sphalerite and galena replacements together with colloform sphalerite and coarse galena cavity fillings, occurs mainly at certain stratigraphic horizons within a large, coarsely-recrystallized dolomite barrier reef. Considerable fracturing and folding was found. It has been suggested that reef development was influenced by post-Precambrian tectonic movements associated with the old faults in the basement complex. The ore may have been deposited by solutions moving from distant sources to favourable structural and chemical environments in or related to the reef.In more recent exploration performed in the course of preparing for mining production, the rate of ore discovery within the same general geological context has been greatly accelerated by the use of new geophysical techniques and drilling equipment. Reserves of 21.5 million tons, averaging 4 per cent lead and 7.2 per cent zinc, were reported in 1965, and production from open pits at the rate of approximately 248,000 tons of concentrates per year is in progress"

Jan 1, 1966

By L. V. Kin, V. V. Lodeischikov, A. V. Byvaltsev, IRGIREDMET JSC, O. D. Khmelnitskaya, S. V. Petrov

"Irgiredmet Institute carried out the study on the development of gold recovery technology from refractory ore from a Russian deposit. The ore contained 1.1 g/t Au, 1.5% of pyrite and 2.4% of pyrrhotite. The recovery of gold achieved was 84.7% using gravity with generation of high grade recoverable gold concentrate and gravity middling. In the course of lime treatment, cyanidation of the middling followed by tailings detoxification the consumption of reagents was 13.0 kg/t CaO, 95 kg/t NaCN and 72 kg/t Ca(OCl)2 of the concentrate. This was capital intensive.In order to decrease the consumption of reagents, magnetic separation of the middling of the concentrates from gravity separation was added to this flow sheet. Pyrrotite recovered to magnetic fraction, which did not contain gold in accordance to this advanced flow sheet. The mass yield of pyrite goldbearing non-magnetic fraction decreased down to 1.5 times in relative to gravity middling. The slurry filtration prior to and after cyanidation allowed the organization of cyanide solution recycling.The results of pilot plant tests using the developed flow sheet showed that the content of pyrrhotite in the non-magnetic fraction decreased from 59.1% to 11.3%. The reagents consumption was 12 kg/t CaO, 3 kg/t NaCN and 16 kg/t Ca(OCl)2 of the pyrite concentrate. The total gold recovery using this flow sheet was 83.4%. Due to a decreased consumption of reagents, cost efficiency of the process was achieved. Based on the results of this research, a project design criteria was developed. A processing plant with the annual throughput of 2.6 million tonnes of ore is being designed."

Jan 1, 2016

By C. J. Brown

Controlling the level of impurities in copper refinery electrolytes is essential to achieving acceptable cathode purity. Purge of electrolyte is not an entirely satisfactory solution since the cost of neutralization, waste disposal, and replacement acid can be appreciable. The APU® process utilizes ion exchange resin to sorb sulphuric acid while rejecting metal salt impurities. Extensively employed for recovery of waste pickling and anodizing acids since 1977, the system is now being used at several refineries for removal of contaminants such as antimony, bismuth, iron, and nickel. The purified acid, which is recovered from the resin by water elution, is recycled back to the refinery tank-house, while the metals are typically recovered from the de-acidified by-product solution by precipitation.

Jan 1, 2005

By Q. G. Reynolds, R. T. Jones

"Residence time distributions are well defined for batch and continuously stirred reactors. However, there exist many smelting furnaces that do not fit either of these classifications. A mathematical description is presented for the case of a furnace that is fed continuously, but where the liquid slag and metallic products are tapped intermittently. The effects of slag and metal tapping intervals and the fraction of liquid retained in the furnace, are shown to have a significant effect on the residence time distribution.INTRODUCTIONThere are some processes in which the time spent by the feed material in a smelting furnace plays a significant role in determining the extent of the reactions between metal and slag and influences the degree of settling of metal droplets from a molten slag.Residence time distributions are well defined for batch and continuously stirred reactors. However, there exist many smelting furnaces that do not fit either of these classifications. Here we will focus on producing a mathematical description for the case of a furnace that is fed continuously, but where the liquid slag and metallic products are tapped intermittently. The effects of slag and metal tapping intervals and the fraction of liquid retained in the furnace, are studied.Previous work (Jones, la Grange and Assis, 1997) has studied the effect of retention time on the degree of cobalt recovery achieved in a slag reduction process. In that work, a method was proposed for the calculation of the mean residence time of the contents of a pilot-plant furnace. That approach is to be extended here for the purposes of providing a more general design or scale-up tool.The maximum allowable depth of molten material in a given furnace is affected by such factors as the desired batch size (or the size of the ladles) and the pressure of the molten material that the tap-hole and surrounding system can withstand. Within these constraints, there might be some scope for choice of taphole position. The effects of this choice need to be understood mathematically."

Jan 1, 2012

By F. J. Alcock

The Appalachian region of Canada comprises the three maritime provinces; Nova Scotia; New Brunswick; and Prince Edward Island; and that; part of the Province of Quebec lying south and east of Logan's fault. This; major thrust runs in a gently curving line from lake Champlain to Quebec; city and thence down the valley of the St. Lawrence to pass between Anticosti; island and Gaspe peninsula. To the northwest lies the St. Lawrence; Lowland division of the Interior Plains geological province; a region underlain; largely by early Palxozoic strata; which for the most part lie horizontal; or with low dips; where faults occur they are predominantly of the normal; type; and only locally are the beds cut by intrusive rocks. To the southeast; on the other side of the fault zone; an entirely different set of conditions is; encountered. There; Lower Devonian and older strata stand at high angles; are sheared and thrust faulted; and are intruded in many places by granitic; igneous bodies. The present paper is designed to outline briefly the geological; and structural history of this geological province and to emphasize; the part that structural conditions have played in connection with mineral; deposition.

Jan 1, 1954

By T. Stergiou

An extensive research is being carried out on the shaft furnace operation in order to minimize down-times and reduce operational cost. The need to increase the scrap percentage on the charging mix, together with the need of cheaper spare parts has led to the investigation of alternative materials for the burner system on the shaft furnace. This system consists of a burner block and a flame holder. Traditionally these items are constructed either from SiC ? oxide bonded or SiC-nitride bonded. A lot of problems have been confronted over the past 8 years of operation. Usually, large cracks are formed on both flame holders and burner blocks. This resulted in leakage of combustion gases to the back of the lining and a quick erosion of it. Additionally, the burner blocks suffer from chemical erosion, due to the increased amount of scrap used in the charging mix and the presence of slag inside the furnace. Alternative materials such as stainless steel for the flame holder and alumina-chromia refractory for the burner block have been tested in terms of life-time and resistance on chemical erosion. Furthermore, additional changes have been made on the burner block design in order to alter the flame shape and improve the scrap melting operation.

Jan 1, 2007

By H. Wotruba, J. Heizmann

"The use of shotcrete is a mandatory means for rock support and therefore for safety in many underground mining operations. If shotcrete gets into the flotation feed though, it can negatively influence the flotation process. This especially occurs when sublevel stoping, cut-and-fill or room-and-pillar methods are applied because as the mining face moves on, formerly applied shotcrete layers are mined together with the ore.As shotcrete does not differ significantly from fluorspar ore in its physical properties it gets moved through the comminution process and is fed to the flotation plant like the ore. To prove the influence of shotcrete on the flotation process, a laboratory test series was conducted at the Unit of Mineral Processing (AMR) of the RWTH Aachen University. The shotcrete grade of the flotation feed was varied between 0 and 10% through addition of pure shotcrete. Flotation parameters and also reagent dosage were held constant apart from the addition of the pH regulator, which was dosed to reach a constant pH of 8 at the flotation start. Results showed that with increasing shotcrete grades in the flotation feed the fluorspar recovery as well as general mass recovery decreased. The enrichment factor of Fluorspar also decreased with increasing shotcrete grades in the feed.In an effort to eliminate the shotcrete contamination of the flotation feed, a feasibility study for use of sensor-based sorting prior to the comminution process was conducted. Rock sorting not only reduces the bad influence of shotcrete on the flotation process, but also reduces comminution costs. INTRODUCTIONShotcrete is used in underground mining on a regular basis. It is used for rock support and therefore to increase safety in the underground mining environment. In mineral processing the presence of shotcrete can cause difficulties for example in the concentration processes. In flotation the highly sensitive reagent mixtures can be disturbed by the chemical activity of shotcrete and therefore recovery rates and selectivity of the process can suffer.Shotcrete is a special form of concrete which is applied pneumatically with high velocities and is compressed by its impact energy. Since the process is especially suitable for work in difficult environments and overhead areas, it is established in underground mining for many years. Shotcrete is not only applied in pre-processing of the mines, but particularly of use for cut and fill, as well as room and pillar mining methods. There it is used to secure excavation chambers. When the mine face is secured with shotcrete and subsequently the mining continues, the applied shotcrete will automatically be mixed with the ore."

Jan 1, 2016

By Magdy Ibrahim

This paper presents experimental design and development of a low-cost remote sensing hardware designed to support automated site data acquisition for near real-time progress reporting of construction operations. The developed hardware utilizes open source microcontroller equipped with multiple sensors that include 3D accelerometer, GPS, Data logger and Bluetooth. The use of open source microcontroller makes the developed design cost effective; freeing it from the need for costly license fees. Its platform configuration is flexible; enabling the addition of temperature, weight and other sensors, Wi-Fi and Xbee capabilities to suit individual field applications. Pilot tests have been carried out in laboratory and outdoor environments. The results prove effectiveness and robustness of the developed configuration. The paper provides description of the individual components used in the development of this prototype hardware. It also describes the technical characteristics, capabilities and limitations of the developed hardware. The findings of comparison with alternative technologies used for outdoor tracking of construction operations are presented. The comparison is carried out with respect to range, cost and suitability for outdoor environment. The developed hardware is expected to support a wide range of applications including tracking of earthmoving operations, highway construction and onsite resources. As well, it is expected to enhance safety on construction jobsites.

Aug 1, 2013

By John R. Goode

"The year 2011 witnessed a major surge in rare earth prices as China, supplier of +95% of the world’s rare earths, reduced export quotas and increased export taxes and duties. In response, companies around the world are scrambling for alternative sources. In Canada too, there is a race to be the “first” rare earth producer. Something that is not generally realized is that Canada has a long history of rare earth production and was a major supplier from the early 1960’s to 1990. At one stage, Canada was said to be supplying more than one third of the world’s yttrium and probably supplied even more than that. Five decades ago, thorium was a key element in many non-nuclear applications and Canada became a major supplier of thorium from the late 1950’s to 1968, first as a by-product of uranium and then as a co-product of rare earths. This paper reviews the development of Canada’s original rare earth and thorium production facilities, which were located in the Elliot Lake uranium camp in Northern Ontario. The uses of these elements, geology, mineralogy, markets of the time, and processing are all discussed. Some of the lessons learned from these pioneering operations might be useful in today’s race to develop the next generation of rare earth production plants.INTRODUCTION The rare earths and thorium were first identified in the early 19th century but were little more than curiosities for the next century. However, in the mid-1960’s the invention of rare earth-based phosphors for the cathode ray tube in colour television sets launched a major demand for certain rare earths. The use of thorium as an alloying agent in aircraft and missiles grew rapidly in the late 1950’s. In the same period, demand for uranium for both weapons and power production soared. Also in the late 1950’s, the Elliot Lake uranium-thorium-rare earth deposits (also known as the Blind River deposits) were discovered. This conjugation of events led to uranium production in the Elliot Lake camp, quickly followed by the co-production of thorium and, later, the rare earths. Uranium production in the Elliot Lake camp continued from 1955 to 1996. Thorium was produced continuously from 1959 to 1969. Rare earths were produced, intermittently, from 1965 to 1990. Complete production records are not readily available for thorium and the rare earths but unquestionably Elliot Lake production made a significant contribution to world production. This paper is intended to present as much of the information that is available."

Jan 1, 2012

By Bruce K. McKnight

"The new H-W orebody was evaluated by considering its production at three technically feasible rates. Capital and operating costs were estimated f or each rate and production sequences were established using mining cutoff limits generated by an ore value algorithm. The viability of the project was then examined by conducting economic and financial analyses of each of the three production cases under various world economic scenarios. These analyses employing standard profitability measures demonstrated all three cases would be economically viable; the production case which maximized the Net Present Value of the project was the one selected for development and production.IntroductionWestmin Resources Limited and its predecessor company, Western Mines Ltd., has been continuously carrying out mining operations near Myra Falls in Central Vancouver Island since December 1966. The mining operation, whose current production rate is approximately 830 tonnes / day (t/d), based on ore derived from the Myra and Lynx Mines, produces copper, lead and zinc concentrates which contain significant quantities of gold and silver in addition to the base metals.In the late 1970s, with Lynx and Myra ore reserves slipping to unacceptably low levels, a major increase in mine-site exploration was initiated, with outside geological staff brought in to complement the efforts of the mine's geological staff. By the end of 1979, this program had resulted in the discovery of a significant new orebody on a deeper horizon some 300 metres below the one which hosts the Lynx and Myra deposits. Throughout the period 1980-1982, major drilling was carried out to evaluate the new H-W deposit and by the end of 1982, drill-indicated mineral inventory for the deposit compared with Myra, Lynx and Price ore reserves was as shown in Table I. During this same three-year period, a major development and evaluation program was underway comprising environmental monitoring and control programs, shaft sinking test mining, bulk sampling and mill testing, rock mechanics studies and preparation of the Stage I and II reports for the multidisciplinary Environmental Land Use Committee (ELUC).As a result of the preliminary engineering work and exploration drilling, it became rapidly apparent that the H-W deposit could support a considerably higher production rate than the current one. Accordingly, engineering studies including scheduling of development and production as well as capital and operating cost estimates, were focused on three possible production rates: 1350, 1800 and 2700 t/d. Our task was to select the optimum one of these three rates."

Jan 1, 1987

By Jian Deng

Rockbursts are sudden and violent failure of rocks in deep and/or high stress mines, which may destroy the excavation space and cause an accident or even the death of mining workers. This study is motivated by the pervasiveness of rockbursts all round the world. It has been found that rockbursts are often stimulated by dynamic fluctuation which is generated by mining operations or other sources of vibrations, such as blasting in adjacent stopes. This paper attempts to investigate the dynamically stimulating mechanism of pillar rockbursts in hard rock mines from an innovative point of view. Rockbursts are classified into triggered rockbursts and induced rockbursts in accordance with the magnitude of the stimulation force. Triggered rockbursts occur only when a small fraction of stress changes associated with rockbursts is accounted for by the causative excavation, whereas induced rockbursts happen where the causative factor is responsible for most of the stress changes required to produce the rockburst. By considering rockbursts as a dynamic instability problem of structures, rigorous mathematical models are set up for triggered rockbursts and induced rockbursts, respectively. By using the method of averaging and the method of eigenvalue problems, the boundaries of rockburst occurrence of a pillar are obtained for these two rockbursts. A new explanation of the failure mode of fretting or necking of pillars is given, the perturbation effect for pillar rockbursts is found, and the parametric resonance mechanism of pillar rockbursts is revealed. The quantitative relation between blasting parameters and pillar rockbursts obtained can be directly used to control the rockbursts. Contrary to conventional methods where only rock materials or rock specimen were used to study rockbursts, this investigation attaches more attention on the structural effect on rockbursts, which have strong potential applications in deep mining.

Jan 1, 2015

By M. Krasowska, K. Malysa, M. Krzan

The paper presents fascinating, in our opinion, observations on mechanism and course of processes occurring during bubble collision with hydrophobic and hydrophilic solid surface. Hydrophobicity of particle surface is a necessary condition for the particle attachment to bubble. We have observed that even in the case of such hydrophobic solid surface as Teflon, the bubble attachment didn't occur at first collision. In distilled water the bubble bounced a few times without attachment. Influence of a-terpineol and n¬pentanol on bubble local and terminal velocity and the phenomena occurring during bubble collisions with hydrophobic and hydrophilic solid surfaces was studied. Bubble collisions with the solid surfaces were monitored and recorded using the high-speed (1182 frames per second) camera. It was found that in distilled water the velocity variations of the "approach-bounce" cycles were identical for Teflon and glass. Four distinct "approach-bounce" cycles were detected both at Teflon and glass surfaces. Moreover, the amplitude and frequency of the velocity variations were identical on collisions with the hydrophobic (polished) and hydrophilic surface. There was no immediate three phase contact formation, with the hydrophobic Teflon surface, what we found really astonishing. Roughness of Teflon surface seems to be important parameter, which affects probability of the bubble attachment as a result of a presence of micro-and/or nano-bubbles at the surface. It was detected that the presence of the micro-bubble affected attachment of the colliding bubble even in distilled water. Presence of a small amount of a-terpineol or n-pentanol affects dramatically the bubble velocity, but their role in mechanism of the bubble attachment needs further study.

Jan 1, 2004

By C. Langer

Although the existence of precious metals, particularly those of the platinum group, in the nickel ores in the Sudbury district has been known for a good many years- almost as long as the ore deposits themselves- the Mond Nickel Company were the first to effect their recovery on a commercial scale. The precious metals values of the different Sudbury ores vary considerably, and are generally higher in the copper-rich ores. These values are so very small that a direct determination in the ores gives quite unreliable results. This is not surprising if one considers that some of the ores contain on1y one unit of total precious metals in about two million units of ore, and that this one unit will consist of seven different metals, each with a different chemical behaviour. It is only after the ores have been smelted to a Bessemer matte containing about 80 per cent combined copper and nickel that the precious metals content can be determined with some degree of certainty. From the figures thus obtained, the precious metals content of the ores can be calculated, provided the tonnage of ore used to produce one ton of matte is known. The recovery of these minute quantities of precious metals out of ?such a large amount of gangue and sulphides of iron, copper, and nickel seems at first glance a commercial and technical impossibility. Nevertheless, science has found a way to conquer all the difficulties, and quite substantial quantities of the precious metals contained in the Sudbury nickel-copper ores have been regu1arly recovered for many years by the Mond Nickel Company.

Jan 1, 1927

By Guangyuan Li

A 3-D block-spring model (BSM) has been developed for simulating the behaviour of jointed rocks. The model uses a discontinuous formulation and an iterative procedure to solve the large displacements in jointed and faulted rock masses. The 3-D BSM has been used to simulate mining excavations in jointed rocks around an open pit and underground settings. The applications have demonstrated that it is a practical tool to solve complicated problems of rock mechanics in civil and mining engineering. This model has recently been modified to incorporate complex geological conditions, such as underground water flow (seepage), unstable blocks and the time-dependent behavior of backfill materials. To demonstrate the capability of the 3-D model this paper presents the fundamentals of the 3- D BSM and its application for open-pit mining. A complete computer package BSM3D has been developed based on the 3-D block-spring model. The package consists of a solving engine for numerical analysis and a Windows based processor for mesh generation and results display. The multi-functioned pre-processor provides tools and menus to help users setting up models easily and conveniently. The fully featured post-processor allows users to view the results in different windows and orientations. The graphical results include contours, vectors, animation of rock movement, and the failure state of the rock structures.

May 1, 2001

By Rakesh Kumar, Rajabrahma K., A. K. Verma, V. Mukesh

"In this study, laboratory investigation as well as numerical investigation is carried out to ascertain the transition from one mode to another for Semi-circular bend setup. Laboratory investigation is carried by varying the span length (s/2R); crack length (a/R); notch angle (a); and notch thickness (t). The specimen consists of cement, sand and water mixture in a ratio of 1:1:0.5 by weight and are prepared as per the ISRM standards (2014). Tests are conducted by a servo controlled universal testing machine at a strain rate of 0.2 mm/ min. The results are collected in terms of failure load, crack mouth opening displacement (CMOD) and images of crack initiation and propagation.Image analysis of laboratory tested samples shows that crack initiates at the notch tip when the notch inclination angle is 0°. As the notch angle increases (i.e. 30° and 60°) the fracture begins to initiate behind the notch tip. The direction of crack propagation in front and back side of the sample is same for notch inclination angle is 0° whereas it differs more and more as crack inclination increases. The transition represents the change in mode of failure from mode I (0°), mode II (30°) and mixed mode I/II fracture (60°).Finite element method used to find the transition based on MTS failure criterion. The inclination of notch is varied like 40, 42, 44, 45, and 50 deg and FEM analysis shows that the transition from mode-I to Mode-II take place at 49 deg. The same procedure can be extended to find the transition from mode-II to mode-III."

Jan 1, 2015

By Yi Yang, Mark Zoback

"We report laboratory studies of the time-dependent deformation of core samples from four different formations in the Williston Basin - the Lodgepole formation, the Middle and Lower Bakken formations and Three Forks formation. The laboratory tests reveal varying amounts of viscoplastic deformation in response to applied differential stress. The time-dependent deformation is generally greater in rocks with higher clay and organic content, and can be described by a power-law function. Because the magnitude of the creep strain is linearly proportional to the applied differential stress, we can utilize viscoelastic theory and geophysical logs to estimate the degree to which tectonic stress is affected by viscoplastic stress relaxation. We suggest that viscoplastic stress relaxation results in the Upper and Lower Bakken Formations act as frac barriers during hydraulic fracture stimulation in the Middle Bakken, but the Lodgepole and the Three Forks Formations are not frac barriers.INTRODUCTIONHorizontal drilling and multi-stage hydraulic fracturing in shale reservoirs are critical for successful exploitation of ultra-low permeability shale gas, tight gas and shale oil reservoirs. Characterization of the mechanical properties of the reservoir rocks is essential to understanding the behavior of rocks during drilling and completion. Previous laboratory studies have shown that the timedependent deformation in clay-rich shales can be characterized as linear/viscoelastic deformation (Chang et al., 1997; Hagin and Zoback, 2004a, b; Sone and Zoback, 2013b, 2013c). Sone and Zoback (2013c) showed that laboratory measurements of time-dependent deformation in various gas shale reservoir rocks, and demonstrated that the viscoplastic deformation of these rocks can be characterized by a power-law function. They interpreted the results in the framework of linear viscoelastic theory to quantitatively assess the geomechanical effect of viscous time-dependent deformation over engineering and geological time scales. (Sone and Zoback, 2014) further extended the theory and proposed a viscous relaxation model that can be applied to predict the continuous differential stress magnitude using the geophysical logs. They tested the validity of their model by comparing the stress prediction with the occurrence of drilling induced tensile fractures (DITFs) and the vertical hydraulic fracture penetration observed from microseismicity."

Jan 1, 2015

By Manqiu Xu, Joe Holmes, Peter Wells, Peter Langlois, Germain Labonté, Jim Barrett

"The flowsheet for the Voisey’s Bay mill had to meet the challenge of processing an ore containing high pentlandite and chalcopyrite values in a largely pyrrhotite/troilite matrix. In the 1994-97 period, circuit development focused on making a high-grade copper concentrate and a relatively low-grade nickel concentrate. However, in 1998 a circuit with copper concentrate, high-grade nickel concentrate and a Ni/Cu middlings concentrate was specified. Following a three year project delay, work resumed on the flowsheet in 2001, and the target for the overall grade of the nickel concentrate was raised from 14% to 20% nickel. To achieve this target triethylamine tetramine (TETA) and sulfite pyrrhotite depressants were used in an all lime circuit. It later became evident that, with appropriate selection of collector and adjustment of the circuit by the addition of a scavenger on the scavenger cleaner, it would be possible to approach the grade of concentrate required without the use of pyrrhotite depressants. The recycle of water and the contained thiosalts was also proven to be instrumental in raising the grade.Construction and commissioning of the mill were fast-tracked with start-up of the mill in September 2005 some six months ahead of the original schedule. Ramp-up of both throughput and metallurgy was faster than any other recent nickel installations with tonnage being limited mainly by concentrate dewatering due to the higher than initially planned ore grades.INTRODUCTIONNickel was discovered in the vicinity of Voisey’s Bay by Chislett and Verbiski working for Diamond Field Resources in 1993 and the Ovoid deposit was delineated in the winter of 1994/95. By the end of 1995 the Ovoid had been well explored and at that time was thought to have a reserve of at least 30 million tonnes with an average grade of 2.83% Ni and 2.0% Cu. Drilling to the east of the Ovoid had indicated the presence of significant mineralization. In June of 1995, Inco Limited bought a 25% share in the Voisey’s Bay Nickel Company (VBNC) which was a subsidiary holding company set up by Diamond Fields. Inco also bought 8% of Diamond Fields and negotiated the right to sell all the nickel produced from VBNC for twenty years as part of this agreement. In April 1996, Inco bought the 75% of VBNC shares that it did not own."

Jan 1, 2007

By Ken Dyck Sr.

"Construction of the Cigar Lake uranium mine in northern Saskatchewan is well under way. Production is anticipated to begin in the first half of 2007. When in full production, the mine is projected to produce a net 18,000,000 pounds of U3O8 per annum from a high grade ore averaging approximately 20% U3O8.Water management was a major issue that required substantial effort in the Cigar Lake design. Not only is effluent quality controlled, a tight water balance to minimize effluent volume is also designed into processes in order to minimize environmental impact. This paper focuses on the water treatment process and water handling equipment, as well as the operating philosophies that will reduce fresh water consumption to a minimum. An overview of the mining and ore handling systems, as well as aspects of controlling water production from the ore formation and the mine development areas will also be discussed.INTRODUCTIONThe Cigar Lake ore body has proven and probable reserves that total 232 million pounds U3O8. Cigar Lake is the world’s largest undeveloped high-grade deposit. It is the second largest highgrade deposit surpassed only by the McArthur River deposit another Cameco - operated mine in the Saskatchewan Athabasca Basin. Cigar Lake is owned 50% by Cameco Corporation, 37% by AREVA (COGEMA Resources Inc.), 8% by Idemitsu Uranium Exploration Canada Ltd. and 5% by TEPCO Resources Inc. When production starts in 2007, ground ore slurry from Cigar Lake will be shipped to the McClean Lake mill (owned by AREVA) some 80 km away. All of the Cigar Lake uranium will be leached from the ore at McClean Lake. During initial production ramp up, all uranium will be processed at McClean Lake to yellow cake (uranium oxide). After the average production has exceeded a 10 million pound per year rate, Cigar Lake uranium will begin to flow from the McClean Lake Mill to the Rabbit Lake Mill. At this point, subject to regulatory approval, 57% of the Cigar Lake uranium, in a uranium rich solution, will be transported to Rabbit Lake mill (owned by Cameco) for purification to yellow cake. A complete summary of the flow of uranium from the Cigar Lake ore body through to product at both McClean Lake and Rabbit Lake can be found in a recent paper titled “The Cigar Lake Project – Mining, Ore Handling and Milling” in the March 2004 issue of the CIM Bulletin. The paper was written by C.R. Edwards."

Jan 1, 2006