黔北地区下寒武统页岩孔隙结构特征及其含气性能

The Characteristics of Pore Structure and Its Gas Storage Capability of the Lower Cambrian Shales from Northern Guizhou Province

通过对黔北地区下寒武统牛蹄塘组和杷榔组页岩岩心样品的有机碳含量、矿物组成、孔隙结构及甲烷等温吸附容量等分析,探讨了页岩孔隙结构的发育特征、影响因素以及有机质对页岩甲烷吸附容量的影响。研究表明,下寒武统页岩具有低孔低渗的特征,页岩比表面积介于5.64～28.29cm2/g之间,NLDFT微孔及中孔体积分别为0.02～0.54cm3/100g及0.53～3.38cm3/100g。孔隙度、BET比表面积以及微孔体积与TOC含量均呈正相关,显示了页岩有机质对孔隙的控制作用;而过高的TOC含量对页岩有机质孔隙可能有一定的抑制作用。此外,黏土矿物对孔隙也有一定贡献。下寒武统页岩吸附量为0.30～3.71cm3/g（12MPa）,Langmuir最大吸附量介于0.41～4.22cm3/g之间,吸附量与有机碳含量之间大体呈正相关,但高有机碳含量的页岩样品由于具有低的微孔体积及比表面积而表现出相对低的甲烷吸附量。

The organic carbon content,mineral compositions,pore structures and sorption capacity of core samples from the Lower Cambrian Niutitang Formation and Palang Formation in northern Guizhou Province were analyzed to obtain the pore structure characteristics,pore structure controlling factors and the impact of organic matter on methane sorption capacity.The results show that the study section is a tight reservoir with characteristics of low porosity and permeability.The samples have a BET surface area ranging from 5.64m2/g to 28.29m2/g and the NLDFT micropore volume and mesopore volume in the range of0.02-0.54cm3/100 g and 0.53-3.38cm3/100 g,respectively.The positive relationships between porosity,specific surface area,micropore volume and TOCcontent indicate that organic matter controls the pore structures.However,shales with high TOCcontent may have certain limitation on the development of organic matter pores.In addition,clays also contribute a portion of total porosity.The methane excess sorption at12MPa（nex12MPa）and Langmuir sorption capacity（nL）of the Lower Cambrian shales range from0.30cm3/g to 3.71cm3/g rock and 0.41cm3/g to 4.22cm3/g rock,respectively.The methane sorption capacity shows a positive correlation with TOCbut a decrease in high TOCsamples because of low micropore volume and specific surface area.