特低渗透油藏CO2近混相驱油

NEAR-MISCIBLE FLOODING OF CO2 IN ULTRA-LOW PERMEABLE RESERVOIR

为了考察CO2近混相在大庆榆树林特低渗透油藏的驱油效果，采用经验公式计算确定实验范围，细管实验确定近混相最小混相压力，借助高温高压观测和界面张力分析细管实验结果。结果表明，随着驱替压力的增加，采收率不断提高，在20MPa左右达到近混相点。近混相点不仅是非混相到混相过程中出现的渐变点，而且是界面张力衰减过程的渐变点。得出的结论是，CO2与原油的混相过程是一个多次接触混相的过程；对于较为轻质的原油来说，驱替压力越高，动态混相段越长，混相程度越深，采收率越高。

To study CO2 near-miscible flooding effect in Yushulin Oilfield with ultra-low permeability in Daqing Oilfield, the test range is determined with empirical formulae, near-miscible MMP is determined through slim tube test, and results from slim tube test are analyzed with the help of HTHP observation and interfacial tension. Results indicate that recovery factor is continuously enhanced with increase of displacement pressure, and the near-miscible point is achieved at 20MPa. Near-miscible point is not only gradational point occurred from immiscible process to miscible process, but also gradational point of interfacial tension decay process. It is concluded that miscible process of CO2 and oil is the process of muhicontact miscibility. For lighter crude oil, the higher the injection pressure is, the longer the dynamically miscible section is, the deeper the miscible degree is, and the higher the recovery factor.