水驱后油藏CO2驱提高采收率评价研究

我国注水提高采收率技术已成熟，但注水开发到后期仍有大量的剩余油无法开采出来。详细分析了油藏水驱后的储层变化特征，长期水驱后粘土矿物膨胀、渗透率降低、注入压力过高，无法进一步提高采收率。介绍了CO2驱驱油方式混相驱与非混相驱，对比分析了连续注CO2、重力稳定驱和水气交替注入三种CO2注入方式各自的优缺点及油藏适应性，优选了适合油藏水驱后CO2的最优注入方式为水气交替注入方式。水气交替注入方式不仅具有降低原油粘度、使原油膨胀、降低油水界面张力、改善油层渗透率及抽提和萃取原油中轻质组分等作用，还可以降低黏性指进，防止气体早期突破等作用，能很好的提高水驱油藏采收率。并进行了现场应用的可行性分析，研究表明注CO2提高我国水驱后开发后的油藏具有很好的应用前景。

Research and evaluation of CO2 injection in waterflooding reseroirs

Water injection has been mature, however, oil recovery by watenqooding is usually low.In this paper, elaborating the variation characteristics of reservoir after waterflooding, ex- pansion of clay minerals,permeability reduction, injection pressure is too high,which makes recovery could not been improved much flooding technology,comparative analysis more. Introducing C02 miscible and non-miscible of injection means：continuous C02 injection,water alternating C02 injection etc. and water alternating C02 injection is the best injection method after waterflooding.It not only can reduce crude oil viscosity,make oil swelling,decrease boundary tension etc,also can reduce viscous fingering,prevent gas breakthrough in the early. By feasibility analysis of field application,shows that C02 injection has a good applicationprospect for oil reservoir after waterflooding in China.