Multi-scale Fractures and Their Influence on Shale Gas Deliverability in the Longmaxi Formation of the Changning Block, Southern Sichuan Basin, China

The capacity and deliverability of shale gas are closelylinkedto the presence of multi-scale fractures, including fractures andfaults, within organic-rich shales. This study aims to investigatethe fracture system of the Longmaxi Formation shale in the ChangningBlock of the southern Sichuan Basin and quantify the influence ofmulti-scale fractures on shale gas capacity and deliverability. Thefracture system was analyzed through outcrop, core observations, and3D seismic interpretation. Criteria for fault classification wereestablished based on the horizon, throw, azimuth (phase), extension,and dip angle. The Longmaxi Formation shale mainly comprises shearfractures that form under multi-phase tectonic stress, characterizedby large dip angles, small extensions, small apertures, and high density.The high content of organic matter and brittle minerals in the Long1-1 Member facilitates the occurrence of natural fractures, whichsomewhat enhance shale gas capacity. Reverse faults with a dip angleof 45-70 degrees exist vertically, while laterally, there areearly-stage nearly E-W faults, middle-stage NE faults, and late-stageNW faults. Based on the established criteria, faults that cut upwardthrough the strata in and above the Permian with a throw greater than200 m and a dip angle greater than 60 degrees have the greatest influenceon shale gas preservation and deliverability. These results provideimportant guidance for shale gas exploration and development in theChangning Block and contribute to our understanding of the relationshipbetween multi-scale fractures and shale gas capacity and deliverability.