多孔介质中CO_2驱油相态及驱替特征

Study on the phase behavior and displacement characteristics of CO_2 flooding in porous media

为弥补中国陆上原油在多孔介质中微观CO_2驱替特征的研究空缺,通过可视化PVT装置、CT装置和核磁共振装置,研究CO_2混相与非混相、不同注入气体积和不同注入气速度下的微观相态变化,以及不同条件下CO_2驱的相态变化特征与驱替特征,重新认识CO_2与地下流体的混相特征。结果表明:气液界面的变化规律为相间传质→传质增强→传质剧烈→混相;混相驱明显优于非混相驱,而且存在一个注入体积的最优值;当达到混相压力后,CO_2与原油几乎是一次接触混相的。由于混相形成了活塞式驱替,从而提高了驱油效率,减缓了气体指进。相同条件下增大CO_2注入速率并不能明显改善驱替效率,反而会使气体突破和驱替效率下降。

Application of a set of visible PVT device, CT device and scanning electron microscope device to the study of phase change of miscible and immiscible flooding under the condition of different injection rates and different injection volume is carried out so as to provide visualized test results and to support the reliability of the critical miscible pressure predicting method. It shows that the change rules of the gas liquid interface are as follows： interphase mass transfer mass transfer enhancement violent mass transfer miscibility. The study reveals that the miscible flooding is obviously better than the non miscible phase displacement, and there is an optimal value of the injected volume. When the oil and CO2 are miscible, they are almost the first contact miscibility. The miscible phase formed a piston displacement, increased the oil displacement efficiency and slowed down the gas fingering. Under the same conditions, Increasing CO2 injection rate can not significantly improve the displacement efficiency, but decrease the gas breakthrough and displacement efficiency.