The Research Of Hydrocarbon Generation And Gas-bearing Of High And Over-matured Shale

In order to studying the preservation condition and gas-bearing characteristics of theblack shale of Longmaxi formation， lower Silurian system in western Zhongyanzi area， thethermal history of typical wells and profiles is fitted by PetroMod. The use of this basinmodeling software is that according to data of measured vitrinite reflectance (bitumenreflectance)，the basin thermal history is corrected by Ro inversion method. The change ruleover geologic time of organic matter maturity of Silurian hydrocarbon generation is simulated.And its maturity in different geologic period is reappeared dynamically. And the depositionaland burial history in different areas is rebuilt. In the study area，the tectono-depositional andburial type of the west Xiang-E is forepart persistent subsidence-middle part uplift style (lateindo-chinese epoch exposure)， and west E-east Yu is persistent subsidence-middle-late partuplift style (late yanshan period exposure). Combined with the thermal evolution history oforganic matter， multistage hydrocarbon generation and evolution characteristics andhydrocarbon generation potential in different geologic period of shale in Longmaxi formation，Silurian system is analyzed dynamically. The geochemical analysis results of shale samplesshow that the abundance of organic matter of the shale of Longmaxi formation is high， andthe content of TOC is0.96%~2.89%， and the average is1.79%. The type of organic mattermainly is sapropelic kerogen (Type I)， and its maturity is1.82%~3.46%， at the high-overmature stage and belonging to good-medium hydrocarbon source. The field emission scanningelectron microscope， reservoir characteristics experiment and adsorbed gas experiment of thesamples of Longmaxi formation is analyzed. The results show that the shale of Longmaxiformation possesses low porosity and tight，and meets the requirement of vast gas production.Shale adsorption quantity and TOC are positively correlated relationship， and shaleadsorption quantity and the vitrinite reflectance， shale porosity are negatively correlatedrelationship. It points out that in the shale of Longmaxi formation， organic mattermicroporous is the main factor of influencing shale gas content. In the study area，tgether withshale hydrocarbon source rock characteristics and its reservoir physical property， thepreservation condition of the shale in Longmaxi formation， lower Silurian system isevaluated comprehensively from tectonic movement，shale brittleness mineral content and oil-gas geological condition. It shows that in this area， the shale of Longmaxi formationexperiences a complex tectonic movement， but it also has oil-gas preservation unit withclosure. Moreover， its brittle content is large， and this benefits to shale gas exploration.According to the comprehensive evaluation， the preservation condition of west Xiang-E isgeneral， and west E-east Yu is better. It is beneficial to the preservation of shale gas and is thefavorable aera of exploration and development.