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选取四川盆地长宁县双河镇上奥陶统五峰组—下志留统龙马溪组新鲜露头样品23个,渝东南黔浅1井岩心样品14个,运用氮气吸附法进行了孔径分布表征,并结合TOC、矿物组成含量和含气量在垂向上的变化及相关性分析,探讨了控制页岩孔隙发育的主要影响因素及其与页岩含气性的关系。结果表明:页岩孔隙以四周开放的具有平行板结构的狭缝孔为主,平均孔径为3.76~8.53nm,主体孔径以2~30nm的介孔为主。总体来看,BET比表面积和孔体积在五峰组—龙马溪组底部大,向上减小并趋于稳定,与TOC变化趋势一致,呈较好正相关性,表明有机质是控制龙马溪组页岩孔隙发育的主要因素。在TOC含量相近时,黏土矿物含量高的样品具有更大的比表面积,页岩中纳米孔隙的发育同时受黏土矿物的影响。四川盆地五峰组—龙马溪组底部TOC和脆性矿物含量高,有机孔发育,页岩含气性好,是页岩气储层压裂改造的优选层位。
Twenty-three new samples of the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in Shuanghe Town, Changning County, Sichuan Province, and 14 core samples of the Qian-1 well in Southeast Chongqing, were selected for pore size distribution characterization by nitrogen adsorption. Based on the vertical variation and correlation analysis of TOC, mineral composition and gas content, the main influencing factors controlling shale pore development and its relationship with shale gas content are discussed. The results show that the pores of the shale are dominated by the slit with parallel plate structure, the average pore diameter is 3.76 ~ 8.53nm, and the main pore size is 2 ~ 30nm. Overall, the BET specific surface area and pore volume at the bottom of the Wufeng Formation-Longmaxi Formation are large and upwardly decreasing and tend to be stable, consistent with the trend of TOC. There is a positive correlation between the BET specific surface area and the pore volume, indicating that the organic matter controls the shale of the Longmaxi Formation The main factor of pore development. At similar TOC content, samples with high clay mineral content have larger specific surface area, while the development of nanopores in shales is affected by clay minerals. The TOC and brittle minerals in the bottom of Wufeng-Longmaxi Formation in Sichuan Basin are high, organic pores are developed and gas content in shale is good, which is the preferred horizon for fracturing and rebuilding shale gas reservoirs.