“三低”油藏CO2水气交替驱可行性研究

Feasibility Study of CO2 WAG Flooding for“Three Low”Reservoir

L油田为典型的“三低”油藏(低孔隙度、低渗透率、低含油饱和度)。针对该油田注水开发中存在的“三低”问题(低采油速度、低采出程度、低地层压力保持水平),在系统分析试验区注CO2驱油有利条件的基础上,开展室内注气驱替实验和油藏数值模拟方案优化研究。结果表明,该油田注CO2的驱油机理应为多次接触非混相驱和近混相驱,并在注入气突破前获得的采出程度较高;水气交替驱最佳注入参数为水气比为1∶1,段塞尺寸为15%HCPV,注入速度为10000 m3/(d·井),水气交替驱的采收率相对于注水和注气开发可分别提高7.3、3.0个百分点;试验区开展CO2水气交替驱具有可行性。

L oilfield is a typical“three low”reservoir(low porosity,low permeability and low oil saturation).For the“three low”(low recovery rate,low formation pressure level and low recovery degree)problems of the oilfield in the water flooding development,based on the systematic analysis of the favorable conditions for CO2 injection development in the test area,the laboratory gas injection displacement experiment and optimization research of numerical simulation scenarios were carried out.The study results show that the oil displacement mechanism of CO2 injection in this oilfield should be multiple contact immiscible flooding and near-miscible flooding,and the recovery degree is higher before the injection gas breakthrough.The optimal injection parameters of water alternating gas(WAG)flooding,water and gas ratio is 1∶1,slug size is 15%HCPV,injection rate is 40000 m3/(d·well),and the recovery factor of WAG flooding can be increased by 7.3 and 3.0 percentage points respectively compared with water injection and gas injection only.It is feasible to carry out CO2 flooding in the test area of L oilfield.