新疆塔北地区低电阻率碎屑岩储层饱和度计算方法

从分析新疆塔北地区碎屑岩储层低电阻率的影响因素出发,认为储层电阻率低主要是在高矿化度使电阻降低的基础上,泥质等造成的微孔隙较多,进一步降低了电阻率,缩小了气层和水层的电阻率差别,较多的微孔隙是造成气层和水层电阻率差别小的主要原因。据此,建立了含有自由水和束缚水的低电阻储层“双水导电模型”。根据该模型,在参考现有饱和度方程的基础上,结合新疆塔北地区实测电阻率资料情况和侵入特性,从推导纯地层饱和度模型出发,建立了适合该地区含泥质碎屑岩低电阻储层的饱和度方程,并利用计算机系统计算了包括束缚水饱和度、可动水饱和度、可动烃饱和度和不可动烃饱和度等饱和度数据,能有效地用于低电阻储层流体性质判别,为低电阻储层识别、储量计算提供可靠参数和科学依据。最后给出了利用饱和度数据判别低阻储层流体性质的应用实例。

COMPUTATIONAL METHOD OF SATURATION OF CLASTIC RESERVOIR WITH LOW RESISTIVITY AND ITS APPLICATION IN TABEI AREA, XINJIANG

Beginning with analysis of the influential factors of the low resistivity of clastic reservoirs in Tabei area in Xinjiang, it is believed that in addition to high salinity, the micropores resulted from argillaceous components also lower reservoir resistivity, thus reduce the resistivity difference between gas and water layers. Relatively rich icropores are the main cause of small resistivity difference between gas and water layers. A "dual water conductivity model" of low-resistivity reservoir with free water and irreducible water is built. Based on the existing saturation equation and in combination with the measured resistivity and invasion characteristics in Tabei area in Xinjiang, a saturation equation suitable for the argillaceous clastic rocks with low permeability in the study area is established by using the pure saturation model. This equation is used to calculate irreducible water saturation, mobile water saturation, mobile hydrocarbon saturation and irreducible hydrocarbon saturation. It can be used to effectively discriminate fluid properties in reservoirs with low resistivity and provides a solid basis for identification of reservoirs with low-resistivity and calculation of reserves. A case study is finally presented for identifying fluid properties in reservoirs with low-resistivity by using saturation data.