河流相储层渗透率对水驱微观驱替效果的影响及挖潜方向研究

Influence of micro displacement effect of permeability on water flooding and the direction of tapping potential of fluvial reservoir

海上河流相沉积储层地质条件十分复杂,注水开发过程中,不同渗透率储层吸水不同,剩余油分布分散,开发难度大。为指导各储层后期剩余油的挖潜方向,从微观孔喉尺度,采用压汞实验和微观水驱可视化实验,分别研究了不同渗透率储层的孔喉分布特征和微观渗流特征。结果表明,平均孔喉半径与渗透率有着良好的对数相关性关系,相关性系数为0.9635,随着储层渗透率增加,平均孔喉半径逐渐增大;随着储层渗透率逐步增大,水驱微观指进现象的减少,逐渐向指状—网状—均匀驱替转变,各模型的波及系数和采收率均呈逐渐增大的趋势,连片状剩余油比例呈逐渐减小的趋势;当渗透率增大至2228.7×10^(-3)μm^(2)时,波及系数和采收率均达到最大值,波及系数82.97%,采收率66.1%,连片状剩余油比例达到最小值45.82%;渗透率在(73.1~1005.2)×10^(-3)μm^(2)的储集层后期应以提高驱替液黏度、提高波及系数作为挖潜主方向,渗透率在(1005.2~3509.6)×10^(-3)μm^(2)的储集层后期应以提高驱油效率作为挖潜主方向,渗透率在(3509.6~4040.6)×10^(-3)μm^(2)的储集层后期适宜以增加注水压力或封堵见水大孔道,使注入水改向,从而提高波及系数作为挖潜主方向。

The geological conditions of marine fluvial sedimentary reservoir are very complex.In the process of water flooding development,the remaining oil distribution is dispersed and it is difficult to develop due to different water absorption in the same permeability reservoir.In order to guide the exploration direction of remaining oil in the later stage of each reservoir,the pore throat distribution characteristics and micro percolation characteristics of different permeability reservoirs are studied based on the micro pore throat scale by the mercury injection experiment and micro water drive visualization experiment.The results show that there is a good logarithmic correlation between the average pore throat radius and permeability,and the correlation coefficient is 0.9635.With the increase of the reservoir permeability,the mean pore throat radius increases gradually,whereas the micro fingering phenomenon of water drive is reduced,and the water flooding process is gradually changing to finger-network-uniform displacement.Both the sweep efficiency and recovery efficiency of each model show an increasing tendency,and the proportion of continuous remaining oil is gradually decreasing.When the permeability increases to 2228.7×10^(-3)μm^(2),both the sweep efficiency and recovery efficiency reach their maximum value,the for is 82.97%,the latter is 66.1%,and the proportion of continuous remaining oil reaches the minimum value of 45.82%.For the reservoirs with permeability of(73.1~1005.2)×10^(-3)μm^(2),the main direction of potential tapping in the later period should be to increase the viscosity of displacement fluid and increase sweep.For reservoirs with permeability of(1005.2~3509.6)×10^(-3)μm^(2),it turns to be improving oil displacement efficiency.For reservoirs with permeability of(3509.6~4040.6)×10^(-3)μm^(2),it is appropriate to increase water injection pressure or block large water breakthrough channels to change the direction of injected water,so as to improve the conformance as the main direction of the potential tapping.