基于密闭取心井的剩余油饱和度研究

Study on Remaining Oil Saturation Based on Sealed Coring Drilling Well

基于特高含水期密闭取心井单一点坝下部剩余油饱和度高的现象,从宏观储层非均质性和微观孔隙结构2个角度探求原因。宏观上,根据岩相和夹层密度,将单一点坝细分为上、中、下3段。并通过物性分析研究点坝储层宏观非均质性;微观上,通过铸体薄片、扫描电镜、X-衍射、高压压汞、核磁共振以及CT扫描技术,研究点坝储层基本特征、孔隙结构特征以及水驱前后孔隙结构变化特征。结果表明:点坝下部夹层密度大,储层非均质性强,夹层纵向上遮挡注入水向下运动,导致点坝下部注水波及厚度小,水洗程度低;点坝下部储层中黏土矿物含量高,孔隙结构差。水驱后,黏土矿物发生迁移、膨胀,堵塞孔喉,导致孔隙结构进一步变差,水驱油效率低。二者综合导致点坝下部剩余油饱和度高。

According to high remaining oil saturation under the single point bar of sealed coring drilling well in typical high water cut period,reasons are explored from the view of heterogeneity of macro reservoir and micro-pore structure.At the macro level,single point bar is divided upper part,middle part and lower part based on lithofacies and sandwich density.The macroscopic heterogeneity of reservoir was studied through physical property analysis;Microscopically,essential features of point bar reservoir,pore structure characteristics and change features of pore structure before and after water drive was studied through casting slice,scanning electron microscope,x-ray diffractions,high pressure Hg injection,magnetic resonance imaging and CT scanning technology.The results show that：The sandwich density of point bars was large,a strong heterogeneity existed in the reservoir.The sandwich sheltered from injection vertically,and water moved downward,so that water injection wave and thickness was small in the lower part of point bar,and washing level was low;Clay minerals was high in the reservoir of the lower part in point bars,and pore structure was bad.After water drive,migration and expansion happed to clay minerals,pore throat was blocked,so that the pore structure became worse,and oil-water displacement efficiency of water drive was low.The synthesis of both resulted in high remaining oil saturation at the lower part of point bar.