水敏感性对低渗油藏油水两相渗流影响实验研究

Experimental Study on Effect of Water Sensitivityon Oil-Water Two-Phase Seepage in Low Permeability Reservoir

为研究水敏对低渗储层油水两相渗流的影响,以江汉盆地XG组储层为例,结合微纳米CT、SEM开展研究,通过对比水敏前后孔隙结构、油水相对渗透率曲线、含水率曲线和无因次指数曲线评价水敏对油水两相渗流的影响。实验结果表明:岩心在发生水敏后导致黏土膨胀,在流体作用下发生分散运移,使得渗透率下降,孔喉半径和配位数分布频率有降低的趋势。从油水两相渗流中可以看出原油采收率在水敏后得到了提高,水敏后含水率上升更快,含水变化率峰值增大;水敏后的提液比水敏前提液更有效果,无因次吸水指数因岩石孔喉细小,毛细管滞留原油现象严重,注入水利用率很低,因此随着注入水的不断注入,无因次吸水指数急剧升高。

In order to study the influence of water sensitivity on oil-water two-phase seepage in low permeability reservoirs,taking the XG formation reservoir in Jianghan Basin as an example,by means of micro nano CT and SEM,the influence of water sensitivity on oil-water two-phase seepage is evaluated by comparing the pore structure,oil-water relative permeability curves,water cut curves and dimensionless index curves before and after water sensitivity.The experimental results show that the water sensitivity of the core leads to the expansion of the clay,and the clay disperses and migrates under the action of the fluid,which makes the permeability of the core decrease,and the pore throat radius and coordination number distribution frequency tend to decrease.After water sensitivity,the oil recovery is improved,the water cut rises faster,and the peak value of water cut change rate increases.The liquid extraction effect is better than that before water sensitivity.The dimensionless water absorption index is very low because the pore throat of the rock is small,the phenomenon of capillary retention of crude oil is serious,the utilization rate of injected water is very low.Therefore,with the continuous injection of injected water,the dimensionless water absorption index rises sharply.