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中国南方下古生界海相页岩成熟度很高,且经历了后期强烈构造改造,成为有别于北美页岩的典型特征。在对比中国南方下古生界与美国页岩、中国南方下志留统与下寒武统页岩地质地球化学差异的基础上,通过对储集物性、保存条件、含气性等相关数据的综合研究,探讨了页岩气远景区的评价指标。提出等效镜质组反射率(EqRO)>3.5%的区域为页岩气高风险区,在EqRO值为2.0%~3.5%的范围内,保存条件是页岩含气性的主控因素。在此基础上,提出了抬升/褶皱区(四川盆地)及褶皱断裂区(四川盆地以外)下志留统与下寒武统页岩气远景区评价指标体系。认为:埋藏深度<1 500m的南方下古生界页岩不具备页岩气开发潜力;四川盆地下古生界页岩普遍存在流体超压,TOC>1.5%的下志留统页岩与TOC>2.0%的下寒武统页岩均具有页岩气潜力。在褶皱断裂区,预测深层页岩(下志留统>2 000m;下寒武统>2 500~3 000m)达到具经济开发价值的含气量限定值,将成为该类地区下一步重点勘探的领域。
The Lower Paleozoic marine shale in southern China is highly matured and has undergone strong post-structural tectonic transformation, becoming a typical feature different from the shale in North America. Based on the comparison of the geo-geochemical differences between Paleozoic and American shales in southern China and the shale in the Lower Silurian and the Lower Cambrian in southern China, the correlations of reservoir properties, preservation conditions, gas-bearing and other related data Comprehensively studied and discussed the evaluation index of shale gas prospect area. It is proposed that the area with equivalent vitrinite reflectance (EqRO)> 3.5% is the high risk area of shale gas. The storage conditions are the main controlling factors of shale gas content in the EqRO range of 2.0% ~ 3.5%. On this basis, the evaluation index system of the shale gas prospect in the Silurian and the Lower Cambrian shales in the uplift / fold area (Sichuan Basin) and the fold-fault area (outside the Sichuan Basin) is proposed. It is concluded that the lower Paleozoic shale with depth less than 1 500 m does not have the potential for shale gas development. The Lower Paleozoic shale in Sichuan Basin generally has fluid overpressure, and the Lower Silurian shale with TOC> 1.5% > 2.0% of the Lower Cambrian shale each have shale gas potential. In the fold-fault zone, it is predicted that deep shale (Lower Silurian> 2,000 m; Lower Cambrian> 2 500-3 000 m) will reach the limit value of gas content with economic development value and will be the key exploration target for this type of area field.