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Results
Numerical Simulation Of Laboratory Steam Flood Experiments With Carbon Dioxide And Nitrogen Additives
Harding, T.G., Ali, S.M. Farouq, Flock, D.L.
Abstract In recent years considerable effort has been expended on the development of equipment, such as downhole steam generators, which creates mixture of steam and combustion gases for thermal oil recovery applications. Questions have been raised regarding the effect on reservoir production performance of injecting such mixtures and thus a study was undertaken to develop laboratory data and a numerical model capable of stimulating me processes. The present paper describes the development and application of a fully implicit thermal reservoir stimulation mode1. The model was used to examine parameter sensitivities which allowed determination of factors controlling the laboratory processes and better interpretation of the experimental results, The numerical model has demonstrated the relative importance of gas drive and solubility effects in the improvement over steam-only flooding observed in the steam/gas injection processes, The dominance of thermal effects on the process behaviour is also shown. Introduction A study was undertaken to examine the effects on reservoir performance of injecting mixtures of flue gas and steam as would be created when employing downhole steam generators or like equipment. A previous publication presented results from unsealed laboratory experiments conducted in a linear system originally saturated with a moderately viscous refined. oil and water. The experiments involved injection of steam/CO2 steam/CO2/N2 and steam/N2 mixtures in the approximate proportions which would result from recombination of steam and the combustion gas products created in raising the steam. The present paper describes the development and application of a fully implicit numerical simulation model which was written to aid in interpretation of the experimental results. Parameter sensitivity studies were conducted to define the controlling factors in the laboratory processes and several experiments were history matched. The results of these applications of the mathematical model are also included. Downhole steam generators have several potential advantages over conventional surface generators including :reduction in wellbore heat losses. elimination of stack and flow line heat losses. Reported. Because of the large number of equations and the resultant high computing cost for solution of thermal simulation problems, much emphasis in recent years has been placed on model stability, automatic time step selection and speed of matrix solution methods. Coats concluded on the basis of experience with steamflood modelling that total computer time for thermal simulations decreases with the degree of implicitness. Code intensive variable substitution techniques have been employed with success for handling the instabilities which commonly arise in thermal process simulation because of phase disappearance and reappearance. Powerful combinations of direct, sequential and iterative methods have been used for the solution of large scale thermal problems and error controlled time step selection assists in the minimisation of computing time(22). Weinstein presented simulation results for steam stimulation with natural gas injection in a Cold Lake reservoir. Runs were made to compare the effect of injecting gas before and after the steam. The addition of gas had a marked effect on production performance with average oil rate and oil-steam ratio increased. Gas injection following steam was found to be the best alternative.
Mine-Assisted Heavy Oil Recovery Technology
Harding, T.G. (BP Exploration Canada) | Ali, S.M. Farouq (U. of Alberta)
Members SPE-AIME Abstract A summary is made of technical considerations in underground mine assisted production of oil sand as well as a review of field experience in Canada and the U.S.S.R. An assessment is made of future prospects for the application of such technology. It is concluded that although the technology exists to construct underground shafts and tunnels, and that mine assisted methods are well suited to certain oil reservoirs, these reservoirs may not be developed in the short term in preference to other more economically attractive projects. It is also concluded that, because of large lead times required for technology development, research and development activities, and in particular piloting work, should continue in the near term in piloting work, should continue in the near term in order to establish methods and experience for certain large deposits. Introduction There are many large heavy oil and tar sands deposits in Canada, the United States, Venezuela and the Soviet Union which lie at relatively shallow depths and may be amenable to exploitation through a combination of mining and petroleum production technologies. The development of these known and accessible oil reserves offers advantages over exploration and development in hostile environments such as those of the Canadian Arctic and East Coast Offshore areas. Mine assisted heavy oil production may be the only feasible method for recovering oil in deposits which are too deep to be economically strip mined and yet too shallow to be exploited by normal in-situ recovery methods. Oil production by mine assisted methods would be achieved by sinking a vertical shaft from the surface to the oil producing horizon and constructing tunnels in the reservoir itself or in formations directly above and below the oil-bearing zone. The shafts and tunnels would have to provide safe access for men and equipment at least during the construction and drilling periods. Horizontal or inclined wells changing to horizontal would be drilled from the tunnels into the oil reservoir and these would be used for fluid injection and production. Figure 1 shows a simple schematic of a mine assisted in-situ processing (MAISP) scheme for the Athabasaca oil sands. In this deposit, it may be advantageous to construct tunnels in the Devonian limestone directly below the oil bearing McMurray formation because of the more competent nature of the limestone in relation to the reservoir or overburden material. Conventional mining techniques for oil sands have also been considered. Serious questions have been raised, however, about the materials handling requirements and potential economics of such schemes. MAISP would have the advantage over a conventional mining operation of leaving the bulk of the reservoir skeleton in place which would considerably reduce materials handling problems. There would be a need in MAISP to dispose of materials removed during construction of shafts and tunnels and this could possibly be done through transport to existing open pit possibly be done through transport to existing open pit mines in the case of the Athabasca deposit. Tailings disposal problems of current strip mining and possible conventional underground mining operations would be greatly reduced in MAISP. Mine assisted techniques for conventional oil production have also been suggested. These schemes production have also been suggested. These schemes propose to increase recovery from shallow or depleted propose to increase recovery from shallow or depleted fields by gravity drainage into horizontal wells drilled from underground tunnels. In this paper, the application of mine assisted techniques for viscous oil reservoirs is addressed. In these cases, thermal energy is usually applied to reduce oil viscosity and thus promote a significant level of recovery. In planning a mine assisted heavy oil recovery project, it is necessary to consider a number of project, it is necessary to consider a number of subjects which have major implication for shaft and tunnel design. These are summarized for the specific case of mine assisted in-situ processing of Athabasca oil sands. Table 1 lists some of the technical considerations which are discussed in detail in the paper. paper. P. 555
- North America > United States (1.00)
- North America > Canada > Alberta > Athabasca Oil Sands (0.25)
- Geology > Petroleum Play Type > Unconventional Play > Heavy Oil Play (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Limestone (0.45)
- North America > Canada > Alberta > Athabasca Oil Sands > Western Canada Sedimentary Basin > Alberta Basin > McMurray Formation (0.99)
- Asia > Azerbaijan > Apsheron Peninsula > Balakhan Field (0.99)
- North America > Canada > Alberta > Western Canada Sedimentary Basin > Alberta Basin > Clearwater Formation (0.98)
- Europe > Russia > Northwestern Federal District > Komi Republic > Timan-Pechora Basin > Izhma-Pechora Basin > Yaregskoye Field (0.94)
Steamflood Performance In the Presence of Carbon Dioxide And Nitrogen
Harding, T.G. (University of Alberta) | Ali, S.M. Farouq (University of Alberta) | Flock, D.L. (University of Alberta)
Abstract The injection of mixtures of flue gas and Steam has been proposed in conjunction with the development of downhole Steam generators, the Vapor Therm process and the Wet Air Oxidation Boiler. The combined gas-steam injeclioll process may be superior to steam-only injection in terms of improved oil production performance and reduced levels of atmospheric pollution. This paper reviews previous experimental and numerical simulation work related to gas-steam injection and presents the results of an experimental study of steam-flooding with nitrogen Gild carbon dioxide additives. The experiments were conducted in linear porous media which were saturated with a moderately viscous refined oil and water. Several rests involved the injection of slugs of gas followed by steam but the majority used the simultaneous injection of The gases and Steam. It was found that for the systems studied, the addition of the gases to steam resulted in a slight improvement ill over-all recovery bill a marked improvement in the rate of production of oil. Introduction Much effort has recently been directed toward the development of downhole steam generators (DHSG) for use in thermal recovery of heavy oi1. In the high pressure direct-fired DHSG, flue gases from combustion of the fuel are injected into the oil producing formation along with the steam. This type of DHSG has several advantages over conventional surface steam generation including 1) elimination of stack, surface line and wellbore heat losses during injection; 2) reduction of atmospheric pollution; and 3) potential for improved production performance due to the presence of gases which are soluble in reservoir fluids. The elimination of wellbore heat losses by placing the DHSG just above the producing interval extends the depth to which steam may be used to perhaps 1800 metres (6000 feet) from the current limit of 800 metres (2600 feet)HI, Recent field tests of DHSG have demonstrated certain beneficial effects of the reservoir on pollutants: the elimination of particulates, an order of magnitude reduction of NO2, substantial scrubbing of SO2 and a two-fold reduction of Co. A portion of the pollutants remain in solution in residual reservoir liquids and in gas which is trapped in the reservoir. Much of the pollutant material is also recovered in solution in the produced liquids, Soluble gas injection with steam may improve recovery and production performance due to a number of mechanisms including swelling, viscosity reduction, and solution gas drive. Meldau el al,have used numerical simulation to identify the following mechanisms which assisted oil recovery in field experiments of cyclic air/steam stimulation:trapping of gas at saturations up to the critical; increased gas drive of heated oil near the wellbore; movement of heat into upper more viscous oil sands; and greater drawdown due to higher reservoir pressures. In addition to DHSG, two other processes have been proposed for enhanced oil recovery involving surface generation of mixtures of flue gases and steam: the Carmel Energy Vapor Therm Process and the Zimpro-AEC Wet Air Oxidation (WAO) Boiler.