基于数值模拟的水淹储层原始电阻率反演方法

针对注水油藏开发中储层原始电阻率准确恢复的问题,以克拉玛依油田砾岩油藏为研究对象,基于储层纵向侵入的地层模式,利用岩石物理体积模型建立砾岩油藏原始电阻率恢复的理论模型,分析影响水淹储层电阻率变化的2个因素。在细分砾岩岩性的基础上,利用岩心分析数据、生产动态以及测井曲线等资料建立了黏土变化量、束缚水电阻率和含水体积增加等3个变量的反演模型,并且依据多元线性回归模型计算储层的原始含油饱和度,最终定义原始含油饱和度和目前含油饱和度的差值与原始含油饱和度的比值为储层的采出指数。研究结果表明:影响储层电阻率的因素主要为注入水对泥质的冲刷导致黏土体积减少,以及注入水对孔隙中原油的驱替导致含水体积升高,并且由于矿化度的差异注入水与原始地层水进行离子交换和平衡。采出指数利用相对值的原理消除了砾岩岩性和非均质对水淹层定量评价的影响,相对于含油饱和度和产水率2个传统的水淹敏感参数,采出指数的解释精度达到了82%,为油田二次开发方案的制定和井网的调整提供技术支撑。

Original resistivity inversion method of flooded reservoir based on numerical simulation

Accurate inversion of original reservoir resistivity is a important problem for waterflood development oilfield in the middle-latter period.Based on the stratigraphic model of reservoir vertical invasion,the conglomerate reservoir of Karamay oilfield was studied and the theoretical model of original resistivity recovery for conglomerate reservoir was established by petrophysical model.And two influence factors of the resistivity change with flooled reservoir were analyzed.Based on the fine identification of conglomerate lithologies,the inversion models of three variables including the amount of clay,the resistivity of irreducible water and the increasing of water bearing volume were established with core analysis data,production performance and well logging curves information,and recovered accurately original reservoir resistivity of conglomerate,and original oil saturation of reservoir was calculated according to multiple linear regression model.Finally,the produced index was defined as the ratio of the difference of the original oil saturation and current oil saturation to the original oil saturation.The results show that the reservoir resistivity change is caused by the decrease of clay volume because injecting water washes argillaceous particle and the increasing of water bearing volume because the injecting water displaces crude oil of pore space.Moreover the conductive ions of water injecting and original formation water exchange and balance because of their salinity difference;reservoir resistivity change is also influenced by them.The produced index eliminates the effects of conglomerate lithologies and heterogeneity for the quantitative evaluation of flooded layers by applying the principle of relative value.Compared with traditional flooding sensitive parameters,oil saturation and water production rate,the interpretation accuracy of the production index can achieve 82%,providing technical support for the development programs determination and the well pattern adjustment in the second development of oilfield.