人造岩心与天然岩心孔隙结构差异及对驱油剂渗流特性的影响

Difference of pore structure between artificial cores and natural cores and its influence on the seepage characteristics of oil displacement agent

为进一步了解驱油剂在人造岩心和天然岩心中的渗流特性及差异,以高分子材料学、物理化学和油藏工程等为理论指导,以仪器检测、化学分析和物理模拟等为技术手段,以大庆油田萨中开发区储层岩心和驱油剂为研究对象,开展人造岩心和天然岩心孔隙结构测试及驱油剂渗流特性实验研究。结果表明,在渗透率相近的条件下,与人造岩心相比,天然岩心孔隙结构复杂,分选较差,孔喉大小不一,连通性较差,非均质性较强。低渗透人造岩心与高渗透人造岩心孔隙结构差异主要为孔喉半径的差异。当聚合物溶液、聚合物/表面活性剂二元复合体系、强碱三元复合体系和弱碱三元复合体系在岩心中流动达到稳定时,天然岩心与人造岩心阻力系数之比平均值分别为1.69,1.73,1.78和1.65,表明在渗透率相同或相近的条件下,与人造岩心相比,驱油剂在天然岩心中滞留量较大,渗流阻力较大,注入压力较高,但压力仍趋于稳定,不会发生堵塞。

In order to further understand the seepage characteristics and differences of oil displacement agent in artificial cores and natural cores,pore structure of the artificial cores and natural cores and its effect on the seepage characteristics of oil displacement agent were tested in Sazhong reservoirs of Daqing oilfield by means of test,chemical analysis and physical simulation theoretically guided by polymer materials science,physical chemistry and reservoir engineering. The results show that the natural cores have the features of more complicated pore structure,poorer sorting system,worse connectivity,stronger heterogeneity and different pore-throat size compared with the artificial cores. The main difference of pore structure between low permeability and high permeability artificial cores is the pore-throat radius. When the flow of polymer solution,polymer/surfactant binary compound system,strong base ternary compound system and weak base ternary compound system gets stable,the average ratio of resistance coefficient of the natural cores to that of the artificial cores is 1.69,1.73,1.78 and 1.65 respectively,which indicates that the natural cores have larger hold-up volume of oil displacement agent,greater seepage resistance and higher injection pressure but the pressure value still tends to be stable and plugging will not occur in the natural cores compared with the artificial cores.