The Main Factors Of Shale Gas Enrichment And High Yield Of The Silurian Longmaxi Formation In The Southeast Of Sichuan Basin

The practice of exploration and development of shale gas by former people shows that shale gas has great potential as an unconventional resource.The shale gas revolution has changed the world's energy landscape.Shale gas in China has a good development prospect,in 2010,commercial gas flow was drilled in the Silurian shale formation in the Weiyuan block of the Sichuan Basin.It is proved that the Silurian Longmaxi Formation shale in the Sichuan Basin is a very effective exploration stratum.It is of great significance to analyze the main controlling factors of shale gas enrichment for searching for favorable areas of shale gas and its efficient development.The study used the Longmaxi Formation shale in the Nanchuan-Pengshui area of the Sichuan Basin interval as an example.We report the exploration for marine shale gas in the Nanchuan-Pengshui shale gas field including Wells SY-1,NY-1,LY-1 and PY-1.Shale samples with different degrees deformation carried out total organic carbon content(TOC),rock pyrolysis,X-ray diffraction(XRD),elemental analysis,scanning electron microscopy(SEM),low-temperature nitrogen adsorption(LTNA),mercury intrusion porosimetry(MIP).The physical basis,the enrichment mechanism,and the main development stratum of the marine shale in the Longmaxi Formation are analyzed and discussed from the perspective of shale reservoir physical properties,organic geochemical characteristics,and gas content.We reveal the main influencing factors of shale gas enrichment and the prediction of favorable areas.Enrichment and high yield of shale gas in the southeastern Sichuan is mainly controlled by organic carbon content,siliceous content,micropore development,pressure,and cap rock conditions.The following results were obtained:(1)High TOC and high bio-siliceous shale are the material basis;exploration practice shows that there is a very positive correlation between organic carbon content and quartz content and shale gas volume in the southern area.Higher organic carbon and siliceous contents result in better enrichment conditions for the shale gas.(2)A large number of organic matter pore and micropore development guarantees enrichment.This study shows that a large number of micro-nanoscale pores are developed in the shale,and the micropores below 50 nm are the main spaces containing shale gas.This plays a key role in the enrichment of shale gas.(3)Good preservation conditions are key factors in its enrichment: a dense top plate is an important factor for shale gas enrichment and preservation.In addition,micro cracks due to tectonism and denudation play an important role in the enrichment and preservation of shale gas.This paper mainly studies marine shale gas exploration practices in the Nanchuan-Pengshui area of the Sichuan Basin,especially for the collection and analysis of the information on Wells SY-1,NY-1,LY-1 and PY-1.This focuses on the main factors of shale enrichment and its high yield in the Longmaxi Formation in southeastern Sichuan.This determines the favorable development area and provides necessary help for the future exploration and development of marine shale gas in the Sichuan Basin.