裂缝性特低渗碳酸盐岩油藏注烃类气驱油室内实验研究

川中大安寨油田属特低孔、低渗并有裂缝的双重介质油藏，目前主要是衰竭式开发，靠自喷原油采收率只能达到3%～5%。室内实验采用人工造缝的方法模拟地层双重介质系统，在此基础上采用长岩心设备开展不同驱油方式的烃类气驱油效果对比研究，并开展注气压力敏感性试验。结果表明在裂缝性低渗油藏中，衰竭式开采原油其采收率低，无论注水还是注气均会产生水窜或气窜；单纯注水可适当提高原油采收率，但驱油效率不高；注烃气虽然不能达到混相，但注入压力越高采收率越高。大安寨油藏在目前地层压力下，注烃气比自然衰竭提高原油采收率6.21%，比注水提高3.91%，效果明显。图3表1参7(郭平摘)

Laboratory experiment of dry gas injection in super low-permeability carbonate fractured reservoir

Daanzhai is a low permeability carbonate fractured reservoir, the recovery factor is only 3-5% when it is exploited by natural energy. Seeking after good way to EOR is the key point. The autrors use matrix cores to make fractures by a manual method to replace real rock in our experiments. Based on the harmonic average principle the authors connect seventeen single cores to form a long core, and use it to study hydrocarbon injection. From comparing the different flooding methods and pressures it is concluded that for the low-permeability reservoir the recovery factor is low with depletion drive recovery, and it can cause water channeling and gas channelling in either way of water injection or gas injection; the recovery factor can be properly improved by water injection alone, but have no high sweep efficiency. Even though hydrocarbon gas injection isn't easy to form miscible, the recovery factor will be high with the increasing of the injection pressure. Under existing formation pressure of Daanzhai oil reservoir, hydrocarbon gas injection is very effective, its recovery factor is 6.21% higher than that of the natural depletion recovery, 3.91% higher than that of water injection.