Classification of shale gas enrichment patterns based on structural styles:a case study of the Wufeng Formation and Longmaxi Formation in Sichuan Basin,China
This paper is the result of shale gas.[Objective]The shale of Wufeng-Longmaxi formation in Sichuan Basin and its surrounding areas has experienced complex tectonic activities and strong reworking.The degree of reworking has a direct impact on the accumulation of shale gas,it is of great significance to classify shale gas enrichment models according to structural styles.[Methods]Mainly based on the structural zoning and the changing trend of reconstruction intensity,in this paper the structural division of Shale series of the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in Sichuan Basin and its surrounding areas,the difference of the time of tectonic uplift in different blocks,and the enrichment patterns of shale gas in different structural areas are summarized.[Results]By studying the differences in the intensity of structural transformation,structural morphology,burial depth and burial uplift time of Wufeng-longmaxi formation in different areas,the main marine shales of the lower Paleozoic in Sichuan Basin and its surrounding areas are divided into 9 first-class structural areas and 20 second-class structural areas.The structural burial history and hydrocarbon generation history of typical wells in different structural areas are further studied.There are 9 structural styles and enrichment patterns of shale gas in and around the Sichuan Basin:large slope type(Type Weiyuan),low-steep and broad-gentle syncline type(Type Luzhou),basin-marginal syncline type(Type Changning),basin-margin complex structure type(Type Zhaotong),basin-margin broad gentle fault anticline type(Type Jiaoshiba),basin-margin slope reverse fault sealing type(Type Dingshan),basin-outside complex anticline type(Type Wuxi),residual syncline type(Type Pengshui),the residual synclinal reverse fault outside the basin is sealing type(Type Zhengan).The enrichment and preservation conditions of shale gas are getting worse and worse.[Concluslions]The nine shale gas enrichment models,which provide an overview of the overall tectonic evolution and accumulation patterns of shale gas from the inner Sichuan Basin to the outer edge of the basin,can provide scope and targets for further optimization of shale gas favorable areas,better guide shale gas exploration in and around Sichuan Basin.
Sichuan Basin and its peripheryWufeng-Longmaxi formationstructural transformation of shalestructural stylesenrichment model of shale gas
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