鄂尔多斯盆地延安地区延长组页岩微观孔隙定量表征

Quantitative Characterization of Micro-pores in Shale of Yan’an Formation in Ordos Basin

页岩是一种有着特低孔渗、孔隙的结构复杂多样等特点的特殊油气储集类型。对页岩微观孔隙的表征及其分类(分级)是页岩储层分级的基础,因此针对性的孔隙类型划分及其油气地质意义研究将对页岩气的发展具有重要的指导价值。文章中由鄂尔多斯盆地孔隙成因类型将延安地区延长组页岩基质孔隙,总体可分为粒间与粒内两种孔隙类型,并对BET、BJH总孔比表面积与BJH总孔体积的关系做了分析,实验表明总孔比表面积与总孔体积二者具有较好的正相关性。目的层延长组页岩中孔径对孔比表面积与孔体积具有明显贡献的主要为1.5~5 nm之间的孔隙,大于5 nm的孔贡献较小,据此可推测到在小于5 nm的孔数量在泥页岩各级孔中所占比例最大,其总孔比表面积和总孔体积二者有着较好的相关性。

Shale is a special type of oil and gas reservoir with extremely low pore permeability and complex and diverse pore structure. The characterization and classification of shale micro-pores are the basis of shale reservoir classification, so the specific classification of pore types and the study on the significance of oil and gas geology will have important guiding value for the development of shale gas. In this paper, the matrix pores of Yanchang formation in Yan’an area were divided into two types: intergranular and intragranular pores based on pore genetic types of Ordos basin, and the relationship between BET and BJH pore specific surface area and total BJH pore volume was analyzed. The experiment results showed that there was a good positive correlation between the total pore specific surface area and total pore volume. In the shale of the Yanchang formation of the target layer, the pores with significant contribution to pore specific surface area and pore volume were mainly pores between 1.5 nm and 5 nm, and pores larger than 5 nm contributed less. Based on this, it was inferred that the number of pores less than 5 nm accounted for the largest proportion of the pores of each level in shale, and the total pore specific surface area and total pore volume had a good correlation..