State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an, 710069, China.
No. 7 Oil Production Plant, PetroChina Changqing Oilfield Company, Xifeng, 745000, Gansu, China.
Sci Rep. 2021 Jan 28;11(1):2503. doi: 10.1038/s41598-021-82035-4.
Due to the poor situation of water-flooding mechanism research on Chang 4 + 5 reservoir of Ordos basin, the authors quantitatively studied the influence factors of water-flooding characteristics by sedimentology, casting thin sections, constant-speed mercury injection, scanning electron microscope as well as production records. The size and distribution of pore-throat were also found closely related with the water-flooding seepage law. The results show that the microscopic seepage paths of Chang 4 + 5 reservoir include uniform displacement, finger displacement and peak displacement, and their correspondent oil displacement efficiency reduces in turn under the same conditions. Reservoir heterogeneity, reservoir properties, distribution of pore structure and wettability play a decisive role in water-flooding efficiency. Generally, When the intra-layer range is greater than 4.65, the breakthrough coefficient is greater than 3.54, the coefficient of variation is greater than 0.7, the distribution frequency of inter-layer is greater than 0.5 per meter, and the distribution density is greater than 0.435%, the range between layers is greater than 6.86, the breakthrough coefficient is greater than 2.58, the coefficient of variation is greater than 0.51, and the thickness of inter-layer is greater than 7.54 m. the increasing trend of oil displacement efficiency will be obviously weakened.
由于鄂尔多斯盆地长 4+5 油藏注水驱替机理研究现状较差，作者通过沉积学、铸体薄片、恒速压汞、扫描电镜以及生产记录等定量研究了注水特征的影响因素。还发现喉道的大小和分布与注水渗流规律密切相关。结果表明，长 4+5 油藏的微观渗流路径包括均匀驱替、指进驱替和峰值驱替，在相同条件下，其对应的驱油效率依次降低。储层非均质性、储层物性、孔隙结构分布和润湿性对注水效率起着决定性的作用。一般来说，当层内幅度大于 4.65、突破系数大于 3.54、变异系数大于 0.7、层间分布频率大于每米 0.5、分布密度大于 0.435%、层间幅度大于 6.86、突破系数大于 2.58、变异系数大于 0.51 且夹层厚度大于 7.54m 时，驱油效率的增加趋势将明显减弱。
