延长组特低渗油藏CO₂驱储层溶蚀与结垢规律

Corrosion and Scaling of CO2 Flooding in Yanchang Ultra-low Permeability Reservoirs

王伟 赵永攀 江绍静 王维波 刘凯 赵洋

WANGWei，ZHAO Yongpan，JIANG Shaojing，WANGWeibo，LIU Kai，ZHAO Yang

针对延长组油藏地层水钙镁离子含量高、储层岩石酸敏性矿物多等特点，开展了CO2驱油藏不同部位CO2-地层水-储层岩石溶蚀与结垢模拟实验。研究结果表明，在CO2驱油过程中，在注气井近井地带和油藏深部因压力上升，CO2在地层水中的溶解量不断升高，溶液的pH值下降，CaCl2水型地层水没有沉淀产生，且CO2与储层岩石矿物会发生溶蚀反应，导致岩石渗透率增大；但在采油井近井地带，随着压力的剧烈下降，溶解于地层水中的CO2会大量逸出，原本溶解于地层水中的部分岩石矿物也会大量析出，产生碳酸钙无机垢。延长组油藏CO2驱油过程中在注气井近井地带和油藏深部不易结垢，且储层物性会被改善；而在采油井近井地带极易产生无机垢，引起特低渗储层堵塞。图7表6 参19

According to the characteristic of the higher Ca2+，Mg2+concentration in formation water and more acid sensibility mineral in reservoir rock of CO2 flooding in Yanchang formation，the corrosion and precipitation simulation experiments of CO2，formation water and rock mineral system in the different parts of reservoir was carried out. The results showed that the dissolution quantity of CO2 increasesd gradually and pH value increased in formation water，precipitation wouldn’t happen due to pressure decreased in CaCl2-type formation water and corrosion reaction would happen between CO2-water solution-reservoir mineral in the near-wellbore area of CO2 injection well and deep area of reservoir. The dissolved CO2 would escape form formation water largely，and the carbonated inorganic scale would generate in CaCl2-type formation water and some mineral that dissolved in formation water would separate out largely due to the pressure decreases quickly in the near-wellbore area of production well. Therefore，precipitation would not happen easily and the physical properties of reservoir would be improved in the near-wellbore area of CO2 injection well and deep area of reservoir；but carbonated inorganic scale would be precipitated easily and caused by reservoir blockage in the near-wellbore area of production well in Yanchang formation.

10.19346/j.cnki.1000-4092.2018.01.017