鄂尔多斯盆地长7_(3)亚段储层微观孔隙结构和固液作用力

Microscopic pore structure and solid−liquid force of Chang 7_(3)shale in Ordos basin

针对鄂尔多斯盆地长7_(3)亚段页岩储层孔隙结构和固液作用力问题,首先,通过聚焦离子束电子显微镜、计算机断层扫描技术和原子力显微镜对纯页岩储层样品开展研究;其次,结合Avizo软件建立页岩多尺度三维重构模型,定量分析页岩孔隙结构特征;最后,提出页岩储层固液相互作用黏附力测试方法,测定原油与孔隙壁面之间的黏附力。研究结果表明:长7_(3)储层发育有粒间孔、粒内孔和有机质孔隙,有机质孔隙形状主要有条状、弯月状和椭圆状;在微米尺度下,可以清晰看到层理缝;在纳米尺度下,不同页岩结构的样品孔隙结构特征无明显差异,孔喉形态多为片状和条状;有机质与原油之间的黏附力最大,长英质与原油之间的黏附力次之,层理面与原油之间的黏附力最小,3种平均黏附力分别为0.098、0.063和0.041μN,长7_(3)页岩储层中壁面原油启动难度较大,这从力学角度解释了该区为原位转化重点区域的原因。

To address the problems of the pore structure and solid-liquid force characteristics of the Chang 7_(3) submember shale reservoir in the Ordos Basin,firstly,the pure shale reservoir samples were studied by focusing ion beam electron microscopy,computed tomography and atomic force microscopy.Secondly,the multi-scale 3D reconstruction model of shale was established with Avizo software,and the pore structure characteristics of shale were quantitatively analyzed.Finally,a method for measuring the adhesion of shale reservoir by the interaction of solid and liquid was proposed,and the adhesion between crude oil and pore wall was measured.The results show that the Chang 7_(3) reservoir is developed with intergranular pores,intra granular pores,and organic matter pores.The main shapes of organic matter pores are strip shaped,crescent shaped,and elliptical.Organic matters have the highest roughness,followed by felsic,pyrite,and fillers.At the micrometer scale,the development of bedding seams can be clearly observed.At the nanoscale,there is no significant difference in the pore structure characteristics of samples with different shale structures,and the pore throat morphology is mostly sheet and strip shaped.The adhesion between organic matter and crude oil is the highest,followed by the adhesion between felsic matter and crude oil,and the adhesion between bedding planes and crude oil is the lowest.The average adhesion of the three types is 0.098,0.063 and 0.041μN,respectively.The difficulty of starting the wall crude oil in the Chang 7_(3) shale reservoir is relatively high,which explains from a mechanical perspective why this area is a key area for in-situ conversion.