Preservation condition for shale gas of Wufeng-Longmaxi Formations in Xichang Basin

In this paper, based on data of drilling wells and geological survey, the main factors affecting the preservation of shale gas such as the lithological conditions of roof and floor rocks, strucure conditions, pressure conditions, and gas components of the Wufeng-Longmaxi Formations in Xichang Basin are detailedly studied from both macro and micro aspects. The results show that the depressions in Xichang Basin are separated by strike-slip belts or thrust belts. Strata within depressions are gently dipping, usually developing broad, slow and open folds. Due to activities of thrust faults in basin margins, folds usually appear as tight folds and strata are often nearly upright or even overturned in basin margins. Within Xichang Basin, tectonic deformation is weak. Shale rocks of Longmaxi Formation in Butuo, which is located in the southern Xichang Basin, have formed the typical pressure sealing box-type geological structure which is propitious to shale gas. Based on an overall consideration of structural deformation conditions of fault, fracture, uplifting and the erosion of Xichang Basin, it is suggested that Zhaojue and Butuo are two favorable areas for shale gas in the eastern edge of Xichang Basin.