低渗透油藏裂缝动态渗吸机理实验研究

根据低渗透油藏裂缝与基质交渗流动的理论模型和物理模型,建立了裂缝与基质之间动态渗吸的实验方法并就裂缝内驱替速度、油水黏度比、润湿性,初始含水饱和度等参数对动态渗吸效果的影响进行了实验研究.对于低渗透裂缝性油藏,在压力梯度作用下水在裂缝内流动,同时由于毛细管力作用水渗吸到基质内,渗吸到基质中的水将油替换出来渗流到裂缝中,注入水再将裂缝中的油驱替到出口端,这就是裂缝与基质之间的交渗流动.动态渗吸实验结果表明:在本实验条件下,存在一个最佳驱替速度(3.0 mL/h),渗吸效率最高为35.5%;在一定的驱替速度范围内,由干毛细管力与黏性力的共同作用,渗吸效果最好.亲水岩心的动态渗吸效果最好.油水黏度比越小,动态渗吸效果越好.初始含水饱和度越高,毛细管力越小,动态渗吸效果越差.图6参20

Experimental study on dynamic imbibition mechanism of low permeability reservoirs

Based on the theoretical and physical models of the fluid flow between fracture and matrix in low permeability reservoirs, this paper establishes the experimental methods of dynamic imbibition between fracture and matrix, and studies the effect of parameters, such as displacement velocity in fracture, viscosity ratio of oil and water, wettability of matrix, initial water saturation, on dynamic imbibition. In a low permeability fracture reservoir, the water flows along fractures under pressure gradient and is imbibited into the matrix due to the capillary force during water flooding. Then, the oil in the matrix is displaced into the fracture with the imbibited water, and the oil in the fracture is displaced to the outlet with the injected water. There exists an optimal displacement velocity of 3.0 mL/h and the highest imbibition efficiency is 35.5% under the experimental condition. In a certain extent of displacement velocity, the imbibition result is best under the action of both capillary and viscosity forces. The imbibition efficiency of water wetting core is the highest. The smaller the viscosity ratio of oil to water, the higher the imbibition efficiency. The higher the initial water saturation, the lower the imbibition efficiency, because the capillary pressure becomes smaller.