Abstract: The shale gas reservoirs of the Wufeng-Longmaxi Formations in the Fuling shale gas play,the eastern Sichuan Basin have been put into commercial production.In the first-phase development block,the single well productivities show a great difference and the gas storage varies laterally,but the causes are still poorly understood.The previous geological evaluation indicated that the lateral distributions of the primary reservoir qualities like shale thickness,mineral composition,and organic carbon content are stable,thus could not be the key factors affecting gas storage.Instead,the variation of gas storage may be closely related to structural deformation.Starting with the characterization of regional structural deformation,this paper presents a systematical research on the structural features,tectonic framework and structural styles in the study area.The study area experienced multi-stage tectonic movements,resulting in multi-level decollement structures,which can be vertically divided into 3 structural deformation layers and 7 structural styles,with an obvious difference in structural deformation intensity.A preliminary quantitative characterization of the structural deformation intensity shows that the fault throw,formation thickening ratio,curvature and fault density are the key parameters for characterizing the structural deformation intensity of the study area.Based on the quantitative characterization,four structural deformation areas are recognized in the study area,and they have significantly different gas storage,indicating that the structural deformation intensity is the key factor causing the variation of gas storage in the study area.

Key words: detachment structure, structural style, structural deformation intensity, gas storage, shale gas play, eastern Sichuan Basin