Jiang Tao, Jin Zhijun, Qiu Hengyuan, Chen Xuanhua, Zhang Yuanhao, Su Zhanfei
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China.
Chinese Academy of Geological Sciences, Beijing 100037, China.
Nanomaterials (Basel). 2023 Feb 20;13(4):779. doi: 10.3390/nano13040779.
The Jurassic shale in the northeastern Sichuan Basin is one of the main target intervals for continental shale gas exploitation. Research on the pore structure and gas-bearing properties of shales is the key issue in target interval optimization. Through core observation, geochemistry, bulk minerals, scanning electron microscopy, nitrogen adsorption, and isothermal adsorption experiments, various lithofacies with different pore structure characteristics were clarified. In addition, the factors that control gas-bearing properties were discussed, and a continental shale gas enrichment model was finally established. The results show that the Jurassic continental shale in the northeastern Sichuan Basin can be classified into six lithofacies. Organic pores, intergranular pores, interlayer pores in clay minerals, intercrystalline pores in pyrite framboids, and dissolution pores can be observed in shale samples. Pore structures varied in different shale lithofacies. The contact angle of shales is commonly less than 45°, leading to complex wettability of pores in the shales. Free gas content is mainly controlled by the organic matter (OM) content and the brittleness in the Jurassic shale. The adsorbed gas content is mainly controlled by the OM content, clay mineral type, and water saturation of the shales. The enrichment mode of the Lower Jurassic continental shale gas in the northeastern Sichuan Basin is established. Paleoenvironments control the formation of organic-rich shales in the center part of lakes. The "baffle" layer helps the confinement and high pressure, and the complex syncline controls the preservation, forming the enrichment pattern of the complex syncline-central baffle layer.
四川盆地东北部侏罗系页岩是陆相页岩气开发的主要目的层段之一。页岩孔隙结构与含气性研究是目的层段优选的关键问题。通过岩心观察、地球化学、全岩矿物、扫描电镜、氮气吸附及等温吸附实验，明确了具有不同孔隙结构特征的各类岩相。此外，探讨了控制含气性的因素，最终建立了陆相页岩气富集模式。结果表明，四川盆地东北部侏罗系陆相页岩可划分为6种岩相。在页岩样品中可观察到有机孔、粒间孔、黏土矿物层间孔、黄铁矿莓粒晶间孔及溶蚀孔。不同页岩岩相的孔隙结构存在差异。页岩接触角普遍小于45°，致使页岩孔隙润湿性复杂。侏罗系页岩中游离气含量主要受有机质含量和脆性控制。吸附气含量主要受页岩有机质含量、黏土矿物类型及含水饱和度控制。建立了四川盆地东北部下侏罗统陆相页岩气富集模式。古环境控制湖中心部位富有机质页岩的形成，“隔板”层利于封闭和高压，复杂向斜控制保存，形成复杂向斜—中心隔板层富集格局。
