水驱油藏转注CO_2驱油参数优化与效果评价

Parameter optimization and effect evaluation of CO_2 flooding after water flooding

以大港油田某断块为研究对象,基于正交试验设计原理,以提高采收率程度和换油率为评价指标,运用数值模拟方法,开展水驱油藏转注CO2驱油注采参数优化与效果评价研究.研究结果表明:转注CO2驱油能够有效提高水驱油藏采收率,最优注气段塞大小为0.05 PV,气水体积比为1∶2,注气速度为40 000 m3/d,注采比为1∶0.9;适当提高注采比有利于保持地层压力,增加原油与CO2混相程度,提高气体波及系数,有效改善CO2驱油效果;气水交替驱能够获得良好的CO2埋存效果,注入的CO2大约有50%被封存在油藏中.

Taking recovery factor enhancing degree and oil drainage rate as evaluation indexes,the injection-production parameters of water-CO2 gas alternation flooding in some block of Dagang Oilfield are optimized and flooding results are evaluated using the orthogonal experimental design and numerical simulation method.It is shown that the CO2 flooding after water flooding can effectively enhance recovery factor,optimal flooding parameters are the CO2 gas slug size of 0.05 PV,the gas-to-water ratio of 1∶2,CO2 injection rate of 40 000 m3/d,and the injection-production ratio of 1∶0.9.Appropriately increasing injection-production ratio is beneficial to keep the current formation pressure,increase the miscible degree of oil and CO2 and improve sweep efficiency of CO2 so as to improve the effect of CO2 flooding.Besides,in the water-gas(WAG) alternating flooding,about 50% of CO2 injected could be stored in the formation,which has the good geological sequestration effect of CO2.