长庆油田CO2驱储层溶蚀与地层水结垢规律*

Reservoir Corrosion and Formation Water Scaling of CO2 Flooding in Changqing Oilfield

周 佩 周志平 李琼玮 戚建晶 何 淼

ZHOU Pei ZHOU Zhiping LI Qiongwei QI Jianjing HE Miao

针对长庆油田CO2先导试验驱地层水矿化度高，Ca2+、Mg2+、Ba2+、Sr2+ 含量高，储层岩石易溶蚀的特点，开展 了CO2-地层水与CO2-岩石-地层水相互作用的研究以及CO2驱对储层岩石的影响模拟实验。结果表明，在地层 水注入CO2的过程中，pH值、压力和温度的改变对地层水中阳离子浓度的影响很小，不会导致无机垢的生成。在 注气井近井地带，随着注入压力不断升高，溶解在地层水中的CO2增加，溶液pH值下降，储层岩石发生溶蚀。岩 心片与CO2作用后，岩心片更加亲水，这有利于改善储层物性，提高原油采收率。在采出井近井地带，由于压力 的降低，使原本溶解于地层水中的CO2大量逸出，地层水中的碳酸氢盐矿物分解成不溶性的碳酸盐沉淀，导致储 层渗透率降低，孔隙度减小，对储层造成伤害，不利于长8储层低渗油藏采油。图10表3参13

According to the characteristic of high salinity of formation water，high concentration of Ca2 +，Mg2 +，Ba2 +，Sr2 +，and easy corrosion of reservoir rock demonstrated in CO2 pilot test in Changqing oilfield，a study of the interactions of CO2-formation water and CO2-rock-formation water，as well as simulation experiments to present the effects of CO2 flooding on reservoir rock were carried out. The results showed that the change of pH value，pressure and temperature had little influence on the concentration of cations in formation water and did not lead to the formation of inorganic scale in the process of CO2 flooding. In the near-well zone of gas injection well，with the increase of injection pressure，the dissolved CO2 in formation water increased，and the pH value of solution decreased，resulting in the dissolution of reservoir rock. The core piece became more hydrophilic after interacting with CO2，which was conducive to improving physical property of reservoir and enhancing oil recovery. In near wellbore area of production well，due to the reduced pressure，a lot of CO2 dissolved in the formation water was escaped. The hydrogencarbonate minerals in formation water became insoluble carbonate precipitation，which led to the reducing of reservoir permeability， decreasing of porosity，and the damage of reservoir. It was not conducive to the oil recovery of long 8 low permeability reservoir.

10.19346/j.cnki.1000-4092.2020.03.012