THE RESEARCH ON ACCUMULATION CONDITION FOR SECONDARY GAS POOL IN PENGLAIZHEN FORMATION, THE SUMATOU STRUCTURE OF WEST SICHUAN

The shallow gas pool of Penglaizhen Formation,Upper Jurassic located in the Sumatou structure of West Sichuan is a typical subnormal-normal secondary gas pool far from source rock.Based on analysis of its characteristic,the pool-forming conditions can be study.The effective source rock which is thick,of abundant organic matter,of long period and high intension to generate hydrocarbon can supply with a plenty of gas for the shallow gas pool in Penglaizhen Formation.The paleostructure is useful for gas accumulation in the early time and succeed to develop,superposed with now-day good trapping condition.The high quality sand body controlled by sedimentary facies serve as a storage for nature gas accumulation.The preservation conditions show big discrepancy,which is the deeper,the batter.The rules for gas pool accumulation are the early accumulation,middle local destruction,and late adjustment and finalization.The enrichment and high producing of gas are controlled both by structure and sand body,especially the distribution and quality of reservoir are most important.