CO₂混相压裂液对低渗透储层岩心的微观作用机理

Microscopic Mechanism of CO₂ Miscible Fracturing Fluid on Low Permeability Reservoir Rocks

李迎辉 王长权 王启夏

LI Yinghui WANG Changquan WANG Qixia

为明确CO2混相压裂液与储层岩心的作用机理，以柳赞断块储层岩心为实例，利用岩心驱替、SEM、XRD和CT等实验方法开展CO2混相压裂液体系中不返排酸、CO2+增溶剂（或缩膨剂或降黏剂）在地层压力和地层温度下与岩心相互作用前后岩心孔隙结构、岩心矿物成分及渗透率的变化规律实验。研究表明：不返排酸和CO2与不同水溶性添加剂混合形成碳酸溶液均具有溶蚀长石和黏土矿物的作用，且优先溶蚀长石，溶蚀后可生成高岭石和石英等矿物，其中不返排酸的溶蚀作用最强，其次是CO2与增溶剂混合液、CO2与降黏剂混合液；CO2混相压裂液注入前后液测渗透率与气测渗透率呈相同的增大趋势，且液测渗透率增大幅度随气测渗透率的变化关系表现为很强的乘幂关系。该研究成果对CO2混相压裂提高采收率技术提供一定的技术支持。

The interaction mechanism between CO2 miscible fracturing fluid and reservoir core was clarified through the experiment of the change law of core pore structure，core mineral composition and permeability before and after the interaction of non flowback acid，CO2 + solubilizer（or swelling agent or viscosity reducer）in CO2 miscible fracturing fluid system with the core of Liuzan fault block under formation pressure and formation temperature by using the experimental methods such as core displacement，SEM，XRD and CT. The results showed that non flowback acid and the carbonic acid solution formed by the mixing of CO2 and different water-soluble additives could dissolve feldspar and clay minerals and preferentially dissolve feldspar to produce minerals such as kaolinite and quartz. The dissolution effect of non flowback acid was the strongest，followed by the mixture of CO2 and solubilizer and the mixture of CO2 and viscosity reducer. The liquid permeability and gas permeability showed the same increasing trend，and the increasing range of liquid permeability showed a strong power relationship with the change of gas permeability before and after CO2 miscible fracturing fluid injection. The research results provided some technical support for CO2 miscible fracturing EOR technology.

10.19346/j.cnki.1000-4092.2022.02.020