特低渗透砂岩油藏水驱微观机理

Micro mechanism of water drive in ultra-low permeability sandstone reservoir

为探讨特低渗透砂岩油藏水驱油的微观机理及水驱后的开发潜力,选取鄂尔多斯盆地延长组典型岩心进行水驱油实验并进行核磁共振测试.结果表明:特低渗透砂岩油藏小孔喉中赋存的石油很难被驱替出来,剩余油大部分集中于小孔道;岩心的原始含油饱和度普遍小于可动流体百分数,驱油效率小于可动油百分数;随着岩心渗透率的增大,原始含油饱和度、可动油饱和度、可动油百分数、驱油效率均有增大的趋势;且渗透率越低,随着渗透率的变化,上述参数变化的幅度越大.可动油百分数、可动油饱和度是影响驱油效率的主要参数.剩余油由剩余可动油与剩余不可动油组成,剩余可动油是油藏下一步挖潜的目标,其评价参数为剩余可动油百分数.水驱油实验中,只驱出了可动油的66.22%,还有33.78%的可动油残留在岩心中,特低渗透砂岩油藏水驱后还有很大的挖掘潜力.

In order to probe into the micro mechanism and development potentiality of the water drive-in ultra-low permeability sandstone reservoir,samples of Yanchang formation in the Ordos Basin were tested by the technology of NMR in displacement experiment.It was found that the oil in fine pore throat almost could not be displaced,and residual oil mainly existed in fine pore throat.The original oil saturation was lower than the mobile fluid percent,the displacement efficiency was lower than the percent of mobile oil. With the increase of permeability,the original oil saturation,mobile oil saturation,percent of mobile oil and displacement efficiency increased.The lower the permeability,the higher the change amplitude of these parameters were.The percent of mobile fluid and mobile oil saturation were the main parameters that influenced the displacement efficiency.The residual oil consisted of mobile oil and irreducible oil,the residual mobile oil should be the target for potential tapping of remaining oil and the appraising parameter was residual mobile oil percent.About 66.22%mobile oil was displaced in water drive oil experiment and about 33.78%mobile oil existed in reservoir.There is a certain potentiality after water displacement in the ultra-low permeability sandstone reservoir.