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Study on Gas Combustions In a Downhole Steam Generator by Reactive Dynamics Simulations

Luzheng Zhang1, Robert Lee1, and Adri Van Duin2. (1) Petroleum Recovery Research Center, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801, (2) Materials and Process Simulation Center, 139-74, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125

There are very large heavy oil reserves in many countries, US, Canada, etc, however, conventional primary recovery techniques are unapplicable because the high viscosity of these oils, often in excess of 1000 centipoises, prevents them from flowing freely to the surface. Various other recovery methods are used instead, the application of which is mostly depth limited. For deeper reservoirs, steam injection from the surface is used generally, but its effectiveness is limited in most cases to about a 2500 ft depth duo to the losss of heat. To overcome this limitation, various attempts have been made to locate the steam generator downhole (downhole steam generator, DSG). Comparing to a surface steam generator, the DSG are needed to opearte under different conditions, resulting in a special requirements on fuel and oxidizer for the combustion. Thus, an optimal fuel and its oxidizer has to be selected for better oil recovery in a specific resevoir condition.

To address fundamental issues (energy release, temperature increase, produced gases, etc), we experimented gas combustions of various combinations of fuels (methanol, ethanol and propane) and oxidizers (oxygen, ozone and hydrogen peroxide) at different conditions (temperature, pressure, fule/oxidizer ratio, etc.) by molecular dynamics (MD) simulations with the reactive force field (ReaxFF). System energy, temperature, pressure, produced gases and their composition as well as their overall kinetics are analysized in detail for all stuided systems. In practice, major handicaps in the DSG include the excessive rate of metal corrosion by the hot combustion products in the presence of wet steam and the possible incomplete combustion because of the limitted well diameter. A catalystic combustion may be a good approach to eliminating these problems in the DSG. Thus, we also simulated the catalytic reactions in gas comubstion for a few systems to test the possibility how a catalyst can improve the combustion in DSG. Finally, we suggest a combination of fuel and its oxidizer for the design of the DSG for a better oil recovery.