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By P. E. Mather, M. J. M. Krane

Uncertainty quantification is a means of articulating the reliability of model estimations. Models of copper pyrometallurgical processes have been published for decades but discussion of their reliability has typically been terse and qualitative, mitigating understanding of their exact applicability to industrial situations. This presentation shows basic uncertainty propagation and Bayesian model calibration, two powerful uncertainty quantification tools, applied to a reduced order model of copper fire/anode refining. The implications of the uncertainty quantification analyses on the applicability of the model results to industrial practice are then discussed. Finally, other possible applications of uncertainty quantification to copper extractive metallurgy are explored. INTRODUCTION Modern copper production operations, including mining operations through wire drawing factories, are ubiquitously heavily instrumented. Most mine-sites and smelters have large repositories of historical data. That said, much of this data is not exploited to its maximum effect. This proceeding provides examples of using uncertainty quantification (UQ) to maximize the informational yield of the data collected from a fire-refining operation. Anode/Fire Refining is the final pyrometallurgical step in the production of copper anodes; it is an essential and universally employed processing step at smelters (Schlesinger, King, Sole, & Davenport, 2011). Much like the smelting and converting furnaces further up the process stream, anode furnaces are difficult to instrument due to their high temperature and the corrosive and/or caking quality of their offgas. This makes continuous and accurate measurement of the streams leaving the unit operation, e.g. liquid copper, slag, and offgas very difficult. As an example, offgas flowmeters, while providing continuous draft values, could miss the actual draft value by tens of percent due to caking or corrosion. UQ methods account for the uncertainty in process measurements and parameter values; they use a process model with measurements of performance indices to provide better and better estimations of process performance. This proceeding will first introduce a surrogate model for copper fire refining, made from a 1D, transient, reacting flow model of the process presented elsewhere in these proceedings (Mather & Krane, 2019). Discussion of the data used to make the surrogate model, as well as the creation of the surrogate model, will be included. Then, a Monte Carlo simulation will be performed, showing the expected soot production rate based on the surrogate model and assumptions about the uncertainty in the model’s parameters. Finally, the surrogate model parameters will be calibrated in a Bayesian way; this will tell what the actual uncertainty in the parameters are, given a set of observed industrial data and prior assumptions of the observations’ and parameters’ uncertainty.

Jan 1, 2019

By H. Rafiei Renani, C. D. Martin

"The Cohesion Weakening Friction Strengthening (CWFS) is adopted in numerical analysis to capture the observed progressive failure of hard rock pillars. As a case study, pillars at the Elliot Lake mines with width to height ratios of 0.5 to 3 were analyzed in FLAC3D. Pillars with width to height ratios of 0.5 and 1 show a very similar strain softening behavior while with width to height ratios of 2 and especially 3 indicated prolonged strain hardening. The CWFS model successfully captured the mechanism of progressive failure observed in hard rock pillars including initiation of spalling at the corners, progress of spalling towards the centre and formation of hour-glass shaped pillar, and eventually shearing through the width of pillar. Both the CWFS model and site specific empirical formula successfully separated the stable and failed cases in the Elliot Lake mines. While both models are in reasonable agreement for width to height ratios of less than 2, the empirical formula gives increasingly lower strength values for wider pillars which may result in excessively conservative and uneconomical design.INTRODUCTIONPillars are the portion of in situ rock left between the adjacent openings to maintain the stability of excavations. Conditions of equilibrium require that the loads previously carried by the excavated rocks be transferred to the pillars resulting in elevated stresses within the pillar. Hence, prediction of the behavior of pillars under these loads is important for underground design. Determination of the strength of pillars is a classic subject in underground mining. In conventional mining methods such as room and pillar operations, economic incentives point towards higher excavation ratios i.e., leaving smaller pillars between the mined excavations, while safety and stability requirements favor wider stronger pillars. In some mining methods such as caving operations, the problem is even more challenging. On one hand, the whole operation is directly dependent on the proper continuous flow of caved ore between the drawpoints which requires optimizing the spacing between drawpoints and thereby often leaving narrower pillars. On the other hand, the pillars should be wide enough to ensure the safety of mining operation. Both the blockage of drawpoints as a result of wide pillars and uncontrolled failure of narrow pillars can jeopardize the investments and mining operation.Therefore, design of pillar poses a somewhat unique challenge to rock engineers where simple conservative approaches frequently used in other design methods are no longer acceptable. The behavior of pillar under elevated loads should be predicted accurately."

Jan 1, 2015

By Mei-Yan Yang, Ltd. Yunnan Yuntong Zinc Co., Yong-Xiang Li, Xing-Zheng Dai, Hong-Liang Wang, Meng-Yang Huang, Peng Zeng, Guo-Feng Li

"The removal of iron asgoethite from the high iron bearing solutions generated in zinc hydrometallurgy using a strong airflow device was investigated. The influence of oxygen flow, copper ion concentration, temperature and reaction time on iron precipitation as goethite was studied. The optimum conditions were: oxygen flow 0.2-0.35m3/h, copper ion concentration 0.25-0.5g/L, temperature 80-90oC, zinc oxide powder neutralizing agent and a reaction time of5to 7hours. Under the optimal conditions, the Fe2+concentration was reduced to 0.025g/L after iron precipitation, and the goethite residue contained 38.7wt.%Fe. The SEM and XRD analyses showed that the iron was present as well formed FeOOH crystals in the iron residue, and the amount of iron sulphate was very low. Production practice shows that, when the average iron concentration in the feed solution was 11.61g/L and 4.08g/L after precipitation, the weight of iron removed was 1,439kg/day. When the average iron concentration in the feed solution was 14.51g/L and 2.73g/L after precipitation, the weight of iron removed was 2,454kg/day. This represents a ~70 percent increase in iron removal.INTRODUCTIONThe objective of iron removal is to produce a small volume of iron residue, and our industrial goethite process meets this requirement. The high Fe(II) solution in our reactor isoxidized/hydrolyzed to precipitate goethite and the precipitate is sent to a pyro metallurgical furnace for final residue treatment. Some literature discusses (DengYong-guiet al., 2008;Meiguang-guiet al., 2001;Zhongzhu-qianet al., 1980) research on iron hydrolysis; one of the reported rate limiting parameters was the low availability of the oxidant when using air and another was the inhomogeneous air distribution. There are two iron hydrolysis-goethite precipitation methods; the Electrolytic Zinc process (EZ) and the Vieille Montagne process (VM) (Lei Xiang, 2006; Xuguo-qiang, 2007;ZhaoYonget al.,2005). The EZ method hydrolyzes the Fe3+directly to FeOOH. The weakness of the EZ process is the low recovery rate of the associated minor metals. The VM method reduces the iron to the ferrous state and then oxidizes the Fe(II)to Fe(III),with simultaneous hydrolysis/precipitation of the Fe(III) as FeOOH. Before iron hydrolysis, the minor metals, such as indium, could be selectively precipitated, because Fe(II)requires a high pH for hydrolysis. So the VM method has a high recovery rate for the minor metals. There levant goethite precipitation reaction is:"

Jan 1, 2016

By J. P. Aiello

"INTRODUCTIONWhile this paper deals specifically with potential coal use at the Cold Lake Project of Esso Resources Canada Limited, a majority of the technical aspects of coal conversion could apply to any oil field and industrial boilers or stearn generators. In 1962, Imperial Oil Limited's production arm (the forerunner of Esso Resources), began examining methods of extracting bitumen from a 50 m thick layer of oil sand buried 450 m below the surface in the Cold Lake area. Almost two decades of research followed to develop an in situ oil sands recovery technology that made commercial production feasible.A $13 billion mega project that would have produced 22 000 m3/d (141 000 barrels/day) of synthetic crude oil (160 000 bpd of bitumen) was shelved in 1981, and ultimately replaced by a phased development strategy, involving smaller production units, to bring blended bitumen production on stream as markets and prices permit.The first two phases came into production in 1985. There are currently a total of six phases in production with four more in the construction stage. Each phase has 130to 140production wells (initially) and a central plant with water treatment, crude treatment and stearn generating facilities capable of producing 150 m3/d (9500 bpd of raw bitumen). The stearn generation section for each phase consists of three 180millionBtulhour oil fieldsteam generators.In its natural state, the bitumen is too thick to be recovered using conventional oil recovery techniques. At the Cold Lake Project, bitumen is recovered by a method called cyclic stearn stimulation. Water is pumped to the central plant where it is treated and heated to produce high pressure, high temperature steam. During the steam cycle, this steam is transported in insulated pipelines to the wells for injection into the oil sand formation. This cycle lasts from 30 to 50 days, heating the formation and causing the bitumen to flow. Following an initial flowback period, a surface based artificial lift system pumps the heated liquid bitumen, mixed with water and gas, out of the well and back to the central plant. The water and gas are separated from the bitumen, with the gas being used to provide some of the fuel for the stearn generators and the water being treated and recycled. Approximately 5% of the water cannot be recycled and is disposed of by injection into deep formations . The bitumen is blended with a diluent and shipped by pipeline to market."

Jan 1, 1989

By D. Kershaw

"A world-scale surface mining operation is associated with the Syncrude Oils ands Plant. Each day over 300 000tonnes of oils and are mined and transported to the process plant to produce 129 000 barrels of synthetic crude oil.Examples of research and maintenance engineering programs which have resulted in substantial gains in dragline and bucket wheel conveyor system productivities are discussed. Two central themes within these programs, which go beyond the usual technical support associated with a large surface mining operation, are pursued:1. the approach taken to determine the causes of component failures and provide Syncrude performance specifications to allow manufacturing industry to respond with more appropriate products; and2. systems and equipment studies which have led to higher productivity in the major mining equipment and the development of an auxiliary feed system.IntroductionA world-scale open pit mining operation is associated with the Syncrude Oils ands Plant located near Fort McMurray in northern Alberta. Over 300 000 tonnes per day of oils and are mined and transported to the process plant. Fifty million barrel s of synthetic crude oil were produced in 1987, which represents 10010 of Canada's crude oil requirement.following tree clearing and surface drainage, overburden is removed by mobile equipment ahead of oils and mining. Draglines excavate the 40 m depth of feed grad e oils and which is windrowed on the dragline bench. Bucketwheels reclaim the oils and from the windrows for transport by conveyor systems to the extraction plant surge pile.The Syncrude mine is operated in four essentially equal quadrants, each serviced by a dragline and a bucketwheel conveyor system. The mining face in each quadrant is approximately 2 km long and reclaimed oils and is transported by 1830 mm shift able conveyors over distances up to 6 km. Individual conveyors vary in length up to 2500 m.The Syncrude plant started operating in late 1978, and Figure I shows the mine production history through to the end o f 1987. Annual production volumes have increased from 50 million tonnes of oils and in 1979 to 105 million tonnes in 1987.The period from 1982has seen a change in operating philosophy, away from striving for very high production rates, to operating at sustained targetted levels within the measured capacity of the equipment. Higher over-all production volumes have resulted from being able to operate for more hours at these rates. This same period has also seen much greater emphasis placed on routine inspection of the equipment and planned preventive maintenance to avoid problems which could otherwise impact on production."

Jan 1, 1990

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 R. A. Horn, S. M. Telfer

"Canada has a per capita GDP second only to Japan among the G7 countries and a positive trade balance which ranks third among the world's major economies. International trade represents a very large part of the national economy and as a proportion of GDP is larger than that of all the other G7 countries with the exception of Germany. On the negative side the Canadian current account deficit relative to the size of the economy is significantly worse than that of all major industrial countries, due mainly to the cost of servicing an immense foreign debt and to a large and worsening negative trade balance in manufacturing.The outflow of money may be reduced by increasing the productivity and competitiveness of those sectors of the economy in which Canada already has a leading competitive position and which have the potential for further growth. The mining industry is uniquely qualified in this respect in that Canada is the western world's largest producer of metals and mineral products and has the geology and the exploration skill to replenish reserves assuming that an adequate level of investment is maintained. In 1989 the minerals industry contributed $8 billion to the country's balance of payments and with the exception of forestry is the only sector of the economy which has shown consistently increasing foreign earnings over the long term.In recent years there has been a decline in exploration in Canada and a significant increase in countries such as Chile. The demand for hard currency to finance the development of the newly emerging capitalist economies of the CIS and Eastern Europe is also driving these countries to seek foreign investment to allow them to exploit their natural wealth more efficiently. Canada is therefore facing growing international competition for risk capital and in the future its trade surplus will probably decline in the face of lower cost foreign production.Canada rightly exercises a high level of environmental control on its mining operations; however a significant deterrent to investment is the fundamentally unjust application of the many provincial and federal environmental laws, under which a mining company, even if it takes every measure to protect the environment, runs the risk of eternal and unlimited future liability. If this situation is not rectified the effect will be an increase in global pollution as mines in countries with more lax application of law and regulations controlling environmental damage replace those of Canada. Tax benefits and incentives are a more efficient means than arbitrary regulations in minimizing environmental damage."

Jan 1, 1994

By A. Galibois, H. Monette, J. L. Collins

This paper deals with the problem of caving, which occurs in varying degrees in blast holes before loading. It is shown that the distribution of the amount of caving in materials may be described by a gamma density function. A decision model to determine the optimal depth of over-drilling 'in order to minimize the expected additional cost per hole is described. Two different policies are discussed. In addition, charts which permit the mine operator to realize significant savings have been drawn for different actual situations.

Jan 1, 1971

By H. P. Dibbs

An account is given of the application of neutron activation analysis to the rapid, non-destructive determination of copper in minerals, using a 14-MeV neutron source. Elements that interfere in the determination of copper by this method are given, together with the errors in the estimation of copper that result from the presence of varying amounts of these elements. The possible use of a compact "sealed-tube" 14-MeV neutron generator for the field assay of copper in minerals is discussed.

Jan 1, 1970

By S. M. J. Mirazimi, F. Rashchi

Recovery of vanadium from LD (Linz-Donawits) converter slag was evaluated by means of microbial leaching. Vanadium leaching was performed in two stages. In the first stage, the bacteria were grown in a culture medium and in the second stage; vanadium containing slag was added to the metabolites produced by bacteria. Bioleaching was performed using heterotrophic bacteria Pseudomonas Putída. Control tests without bacteria inoculation were also performed and the results were compared with bioleaching outcomes. Optimal conditions for the bioleaching of vanadium containing slag were determined.

Jan 1, 2011

By J. A. Finch

The metallurgical performance of a flotation cell is strongly influenced by the features of the bubble population, characterized by the gas dispersion properties, a collective term including bubble size, superficial gas velocity and gas holdup. It is required that gas be well distributed throughout the cell. Gas distribution is estimated here by simultaneous measurement of gas velocity (Jg) at different distances from the center (radial Jg mapping). This communication describes a technique to perform radial Jg mapping together with fundamentals for the interpretation of the data.

Jan 1, 2009

By W. W. Cummings

The Mineral King Mine, owned and operated by Sheep Creek Mines is located in the Purcell mountain range of southeastern British Columbia. Production of lead and zinc concentrates commenced in 1954 some 60 years after the initial discovery. Low cost mining methods have been employed to extract 16,0C'O tons of ore monthly from large ore bodies formed by replacement in limestone. Extensive areas in the limestone are yet to be explored and success in the search for new ore bodies is anticipated.

Jan 1, 1960

By D. E. Keeley

lntroduction Some years ago it was general practice in Canadian mines to use the best timber available, just as it was cut from the tree. Later, to prevent 'borers' from getting into the wood while stacked in the yard, the bark was peeled off, cleaned up carefully, and burned to eliminate a breeding ground for these and other destructive insects. This practice of good housekeeping also decreased the hazard from fire in scattered bark. A few years after damage by borers had been minimized, it became apparent that increased temperatures in the mines, occasioned by deepening operations, were being accompanied by rapid growth of fungus and by decay in timber underground, greatly shortening its life. In places on upper levels where the air temperature was below 50 deg. F., untreated timber retained a large proportion of its strength for ten or more years. In other places on these levels, however; its life was short and it developed much dry rot and merulius lacrymans. In these latter places and on lower levels in the mine where temperatures ranged from 50 to 60 deg. F., approximately, the wood became infested with extensive growths of this white fungus. This development was accompanied by the production of millions of spores. Spread of infection was due mainly to the transfer of spores from the warm lower levels to the cool upper horizons by upcasting ventilation currents. So serious did this become that about twenty years ago Lake Shore, Hollinger, and McIntyre Mines decided to investigate the use of wood preservatives and the plant necessary to treat timber.

Jan 1, 1949

By N. Vayenas, G. Yuriy

"The combination of a predictive reliability assessment model and discrete-event simulation can be an effective methodology to study the impact of equipment failures on the capacity of production systems in mines. In our case, a predictive reliability assessment model using genetic algorithms is combined with a discrete-event simulation model to analyze mine equipment systems.Discrete-event simulation involves modelling of real-life systems based on variables and events that occur or change at distinct points in time. The Simul8 simulation software, by Visual Thinking, is used in this research. It is a two-dimensional (2D), discrete-event simulation/ animation software tool for creating realistic depictions of manufacturing and materials handling systems.The simulation model developed for the purpose of this research represents a typical two-level, sub-level stoping section of an underground mine in the Sudbury region in Ontario, Canada. This 2D model was created to assess the impact of equipment failures to a mine’s production throughput. In more detail, using mean time between failures (MTBF) data of scooptrams derived from a reliability assessment model based on genetic algorithms, LHD failures are incorporated into the simulation model. These failures cause production interruptions to the development cycle and consequently loss of hauling capacity.Another purpose of this research work is to demonstrate how low-cost simulation tools such as Simul8 can be successfully applied to model underground hard rock mining operations. The research discussed in this paper is carried out by the Laurentian University Mining Automation Laboratory (LUMAL)."

Jan 1, 2005

By Carl O. Nickle

"IntroductionIF I WERE ASKED what are the two most important single factors in shaping the growth of Canada to date, and in building its future, the answer would be: first, the treasure house of natural resources on and below the surface over the length and breadth of our country; and two, the pioneering spirit and 'get up and go' of many of our people. The two factors are inseparable. Without the pioneering spirit, the natural resources of land, forest, stream, and the subsurface would have continued •to be useless,. Idle assets. With the pioneering spirit, Canada's natural resources have been and are creating economic revolutions.Western Canada oil and natural gas rank high on the list of such revolutions. Calgary, your meeting place today, is the birthplace of this economic revolution, one that has already sharply altered the economy .of the middle half of Canada, particularly that of Alberta; is increasingly making its weight felt on the economy of all Canada; and is helping re-shape world thinking on sources of vital petroleum supply for both peace and war. Calgary is today the 'operation headquarters' for the great bulk of a huge exploration and development programme that now extends over a quarter of a million square miles of Canada's West. As a Calgarian, •therefore, I am particularly happy to have this privilege of talking about oil and natural gas to members of the C.I.M.M., who play a key role in the development of all Canada's varied natural resources."

Jan 1, 1952

By J. Boldy

This paper is an attempt to place Canadian Precambrian volcanogenic deposits in perspective, by examining and compiling data regarding certain neglected fundamentals of size, grade, value, frequency distribution and spatial density. The discovery roles played by various exploration methods are compared and contrasted, and. using empirical methods, the probabilities of discovery are discussed, combined with the use of an effective 'cost-per-target' program. From these basic observations, realistic exploration judgments may be made. Using similar methodology, this format may be applied to other types of deposits. Precambrian volcanogenic deposits occur in a natural geometric progression in size. They number 110, of which 70% are pre-producers, producers or past-producers. These deposits are bonanzas and generally have a 'net pre-smelter' value of between $43 and $62 per ton. The statistically typical deposit is that which occupies the modal position, has 400,000 tons of ore, a value of $20 million and occurs with a frequency of 40%. A median deposit has 1.4 million tons of ore, a value of $70 million and occurs with a frequency of 15%. An upper-decile deposit ha s 13.3 million tons of ore. a value of $750 million and occurs with a frequency of 6.5%. The major, mid-upper-decile deposits have a minimum of 50 million tons of ore, a value of $3 billion and occur with a frequency of 4%. Five major volcanogenic deposits occur in the Precambrian and account for 54% of production. This contrasts with 55 deposits (all below the median) which account for 3.9% of production.

Jan 1, 1977

By B. Pewkliang, K. Ehrig, E. Macmillan, M. Smith, V. Liebezeit, Y. Li

The Olympic Dam iron-oxide copper-gold (IOCG) uranium-silver deposit is the largest publicly declared uranium, fifth largest copper and third largest gold resource. Currently, the operation consists of an underground mine and integrated processing plant. Uranium is produced from leaching of flotation tailings and is a co-product to copper cathode with by-product gold and silver bullion. The Olympic Dam geometallurgy team began studying ore from the Southern Mine Area (SMA) in 2006 and soon discovered uranium behaviour was far more variable than the behaviour in the Northern Mine Area, which had been mined from the start of the operation in 1988. The primary objective of Olympic Dam geometallurgy is to develop metallurgical performance predictors that reliably describe the process performance of different ore types and distribute these into the resource block model for use as a fundamental input into mine planning. The nature of the uranium mineralisation (compositionally and texturally complex and highly variable) meant that classic mineralogy techniques alone could not provide the resolution required for prediction of uranium extraction. However, the combination of quantitative mineralogy, results from laboratory-scale leach tests and modelling within the geometallurgy program has enabled prediction of both uranium flotation recovery (via association with sulphides) and uranium leach extraction, including at variable leach conditions. These stope-based predictions have supported trade-off decisions between operating costs and uranium revenue, and have predicted the changing recovery as the mining operations have moved into the Southern Mine Area in recent years.

Jan 1, 2020

By J. H. Parliament

"The 15,000-tpd Similkameen open-pit copper mine, 10 miles south of Princeton, B.C., started production during 1972. The two main ore zones are separated by the deep canyon of the Similkameen River, with the Ingerbelle or western deposit being mined first. The location, design and construction of the plant were complicated by the steep terrain and the situation of the orebodies. Mining, utilizing 10-cu.yd electric shovels and 100-ton electric-wheel trucks, is conventional. Closely integrated with the preproduction mining was the construction of a 4-mile section of main highway to bypass the Ingerbelle pit. This entailed a very large fill, placed with mine equipment. Ore is crushed to minus 9 inches, stockpiled and reclaimed for direct delivery to three 32-ft-diameter by 14• ft single-stage autogenous grinding mills, each driven by two 4000-hp motors. Because of the friable ore in the upper part of the mine, 4-inch balls are added, with higher than design throughput attained. Classification is by 91>-inch spiral classifiers and cyclones. The flotation section comprises three parallel lines of ten 400-cu.ft rougher- scavenger cells and a single line of 100-cu.ft cleaner and recleaner cells. Concentrate is transported in end dump, closed trucks to Vancouver for dockside storage prior to shipment to the smelter. Tailings are piped across the canyon on a suspension bridge and through a tunnel to an empoundment area. Water is reclaimed and returned to the concentrator, forming a closed system. Dams are raised with cycloned ands, with the downstream section compacted."

Jan 1, 1973

By Mohammadreza Jalali

Alberta contains over 400 billion barrels of viscous crude oil in fractured carbonates but there is no viable extraction technology as yet. Petroleum geomechanics has become a vital part of the assessment of such hydrocarbon reserves, especially for naturally fractured cases, which are particularly challenging in terms of accurate recovery prediction because of joint fabric complexity and lithological heterogeneity. As a result of interconnected fractures, transport properties of fractures (mostly permeability issues rather than thermal effects) are affected by production and injection activities that change the pore pressures, temperatures, saturations, and effective stresses. Enhanced oil recovery methods involving massive amounts of fluid injection (hot or cold) at high pressure (pinj) may be used to mobilize and produce the oil; therefore, deeper understanding of the fractured systems is desirable. Pressure and temperature variations in a fractured reservoir change the in situ stresses in the reservoir and surrounding rocks; this affects fracture apertures, radically changing the bulk flow properties because flux rate is highly sensitive to aperture. Hence, coupled pressure, temperature and effective stress changes must be considered for fractured reservoirs under a thermo-hydro-mechanical (THM) coupling approach.A hybrid FDM/DDM coupled method is presented to couple pore pressure and stress around a fracture in an impermeable matrix block. Deformation and stresses are calculated in each time step and then fracture permeability, which is the most sensitive petrophysical parameter in fractured reservoirs, is updated based on the fracture aperture variation. This model is then verified with UDEC (Universal Distinct Element Code) which uses a discrete approach to cope with fractured rock mass behavior.

Jun 1, 2012

By M. A. Rabah

This study aims to recover europium, yttrium metals, some valuable salts or oxides from the white powder (apatite) coating the inner surface of spent florescent lamps (SFLs). Pressure leaching using sulphuric/nitric acid successfully dissolved the metals of interest. Europium or yttrium metals were obtained by hydrogen reduction of their oxides. Addition of potassium thiocyanate converted the dissolved sulphates to thiocyanates. Selective separation of Eu and Y was then carried out by solvent extraction from the thiocyanate solution. The used solvent was trimethyl-benzylammonium chloride. N-trihutylphosphate in 1 M nitric acid was used to strip the metal loaded in the organic phase. Results showed that the quality of the cleaned glass tubes of the SFL met the standard requirement for the lamp manufacture. The white powder (WP) is composed of calcium sulphate 35.2%, phosphate 61.5% and oxides of europium and yttrium 1.65%wt. respectively. Autoclave digestion of the WP for 4 h at 120°C and 500 kPa in sulphuric acid/nitric acid mixture dissolved 96.4% of yttrium and 92.8% of europium. The conversion rate of sulphate to thiocyanate was favoured at low temperature. Stripping of Eu and Y from the loaded organic phase behaved in an opposite way. A metal separation factor of 9.4 was obtained. ate recovered europium and yttrium salts were selectively separated using ethyl alcohol or dilute nitric acid. Yttrium was very soluble while europium was not. Europium and yttrium metals were obtained by hydrogen gas reduction at 850°C and 1575°C respectively.

Jan 1, 2004