东营凹陷沙河街组页岩油储层微观孔隙结构研究

Study on Microscopic Pore Structure of Shale Oil Reservoir in Shahejie Formation in the Dongying Sag

储层微观孔隙结构研究可为页岩油勘探开发提供依据。利用氩离子抛光-扫描电镜实验和孔隙图像储层结构参数统计方法,分析了渤海湾盆地东营凹陷沙河街组18块岩芯样品的微观孔隙发育特征。结果表明,东营凹陷沙河街组页岩油层段的孔隙类型主要包括粒间孔、溶蚀孔、晶间孔和晶内孔,泥质粒间孔提供的面孔率贡献最大,溶蚀孔对有较高的面孔率贡献,晶间孔和晶内孔的面孔率贡献最低。页岩油储层孔隙的孔径属于纳米级和微米级,数量上纳米级孔隙占绝对优势,但储层面孔率主要由在数量上不占优势的微米级孔隙提供。因此,东营凹陷沙河街组页岩油层段的主要储集空间属于微米级孔隙。

The microscopic pore structure of reservoirs provides the basis for shale oil exploration and development. In our analyses of the pore development characteristics of shale oil reservoirs, we integrated the argon-ion scanning electron microscopy test and a statistical method to determine the parameters of the pore images of the reservoir. Eighteen rock-core samples of the Shahejie Formation in the Dongying Sag, Bohai Bay Basin, China, were used in the analyses. The results indicate that the main pore types of the shale oil layer in this formation are inter-particle pores, dissolved pores, inter-crystal pores, and intra-crystal pores. The largest rate of contribution to plane porosity is from the argillaceous inter-particle pores, with the dissolved pores making a high contribution, and the inter-crystal pores and intra-crystal pores making the lowest contributions. The pore diameter in the shale oil reservoir is of nano and micron scale, with the nano-scale pores being the dominant quantity. However, the non-dominant micron-scale pores provide porosity to the reservoir plane. Therefore, the micron-scale pores provide the main reservoir space to the shale oil layer in the Shahejie Formation.