渝东北城口地区Y1井页岩有机地球化学特征及勘探前景

Organic Geochemical Characteristics of the Shale from Y1 Well in Chengkou Area of Northeastern Chongqing and Exploration Prospects

基于钻井资料,以总有机碳(TOC)、干酪根显微组分、等效镜质体反射率(Ro)及碳同位素等测试数据系统分析了渝东北城口地区Y1井五峰组—龙马溪组页岩的有机地球化学特征,利用页岩流体包裹体的显微特征、均一温度及激光拉曼数据深入分析了Y1井页岩气成藏特征。结果表明:Y1井上奥陶统五峰组—下志留统龙马溪组炭质页岩发育,TOC含量>2%的富含有机质页岩厚度达83 m,干酪根类型以Ⅰ型干酪根为主,处于湿气生烃阶段。页岩裂缝脉体中大量烃包裹体和富含甲烷气体的含烃盐水包裹体证实城口地区五峰组—龙马溪组页岩发生了充足页岩气供给,具有高均一温度、高盐度的伴生盐水包裹体表明城口地区页岩气成藏时期的保存条件良好。这些Y1井页岩有机地球化学特征研究成果揭示了城口地区下古生界具备良好的页岩气勘探前景。

A study has been conducted based on the drilling data and geochemical data from the Y1 Well in Chengkou of Northeastern Chongqing,including total organic carbon(TOC),kerogen microcomponent,equivalent vitrinite reflectance(Ro) and carbon isotope composition,which are the organic geochemistry characteristics of Wufeng—Longmaxi Formation shale.The characteristics of shale gas accumulation were determined by analyzing the microstructure,homogenization temperature and laser Raman data of fluid inclusions in the shale.Results show that carbonaceous shale is well developed in Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation in the Y1 Well.Organic-rich shale(TOC > 2%) has a thickness up to 83 m.The kerogen type of the samples is mainly Type Ⅰ,belonging to the moisture hydrocarbon generation stage.Numerous hydrocarbon inclusions and hydrocarbon-rich brine inclusions with methane gas in the fractured veins of shale indicate that the shale of Wufeng Formation—Longmaxi Formation in the Chengkou area has been supplied with sufficient shale gas.The associated brine inclusions with high homogenization temperature and high salinity indicate good preservation conditions during the shale gas accumulation period in the Chengkou area.The exploration results of the Y1 Well reveal good exploration prospects for shale gas in the lower Paleozoic strata in the Chengkou area.