陇东长7致密油藏气驱喉道动用半径下限

相比水驱,气驱能够波及到较小的喉道,研究气驱过程中气体所能波及到的最小喉道半径很有意义。选择常见的3种气驱用气:CO2、N2和空气,在驱替实验的不同阶段进行核磁共振测试,并选择相应岩心的平行样进行高压压汞测试。通过对比2种测试方法计算出来的喉道半径分布,计算出相应的转换系数C和n。再根据气驱过程中的T2截止值,使用各自转换系数求得对应的喉道动用半径。实验结果表明,驱替压差越大,驱油效率越高,其中CO2的变化幅度最高。同时发现,驱替压差越大,喉道动用半径越小,在驱替压差达到6MPa下,气驱动用半径基本稳定。该方法为致密油储层研究气驱可行性提供了评价依据,在实际生产过程中需要综合评价选择最优的驱替用气及驱替压差。

Developed radius limit for the throat by the gas flooding in Longdong Chang-7 tight oil reservoir

Compared with the water flooding, the gas flooding can sweep to the smaller throats, so it is meaningful to study the minimum swept throat radius during the gas flooding. Three common gas flooding gases were selected: CO 2, N 2 and air, the NMR test was performed at different stages of the displacing experiment. At the same time, the high-pressure mercury injecting test was conducted for the parallel sample of the corresponding core. By comparing the throat radius distributions calculated by the two testing methods, the transferring coefficient C and n were calculated. And then, with the help of the T 2 cutoff value in the gas flooding process, the corresponding gas-flooding developed throat radii were finally obtained by themselves respective converting coefficients. The experimental results show that the larger the displacing differential is, the higher the oil displaced efficiency will be, and the change of the CO2 is the biggest. At the same time, it is found that the larger the displacing pressure difference is, the smaller the developed throat radius will be, and the gas-flooded throat radius is basically stable when the displacing pressure difference reaches 6-8 MPa. This method provides an evaluating evidence for the study of the feasibility of the gas flooding in the tight oil reservoirs, in the actual production process, the comprehensive evaluation is needed for the selection of the optimal displacing gas and displacing pressure difference.