Because of the favorable properties of CO2 it has been used to enhance the recovery of oil for a long time. But this technology is under slow development in China for lack of rich CO2 resource until some CO2 reservoirs were found in recent years.

Using simulation and reservoir-engineering method, this paper presents the feasibility study of CO2 injection for heavy oil reservoirs following cyclic steam stimulation. Pilot tests were conducted to several wells in Lengjiabao heavy oil reservoirs in Liaohe oilfield, China. Some wells got good effect, while some wells got poor effect. And the results from the simulation and field pilot tests are evaluated economically. Study shows that for common heavy oil reservoir after cyclic steam stimulation, the higher the oil viscosity, the greater the CO2 utilization ratio, and the more feasible CO2 stimulation process; for extra-super heavy oil, 1-3 cycles steam huff-n-puff were performed as necessary, followed by CO2 stimulation process so that good benefit could be gained. These results are of significance for field operation and production of heavy oil.

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