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Seismic data are an integrated reflection of the sedimentary interfaces and processes of paleo formations. In this study, seismic geomorphology was applied to analyze and reconstruct the paleogeomorphology of the sedimentation of the Cambrian Longwangmiao Formation in the central Sichuan area by combining three-dimensional (3D) seismic data, a large amount of drilling data, logging data, cores and thin sections. It is believed that the thickness of the Cang-2 member reflects the paleogeomorphology during the sedimentation of the Longwangmiao Formation. Forward seismic modeling was used to select the seismic physical attributes sensitive to the Cang-2 member, which were then used to reconstruct the paleogeomorphology during the sedimentation of the Longwangmiao Formation. The results of this study show that the larger the amplitude of the bottom trough of the Longwangmiao Formation, the higher the landform during the sedimentation period. Therefore, the Caledonian paleo-uplift had already taken shape before the sedimentation of the Longwangmiao Formation, creating a paleo-geomorphologic pattern containing two uplifts and one depression. The geomorphologic distribution controlled the development of the shoals and reservoirs. The geomorphic highlands not only contained shoals with large areas and thicknesses but were also susceptible to superimposed syngenetic and quasi-syngenetic exposures, which provided preferential flow channels for atmospheric fresh water in the later period and caused the reservoirs to be subjected to more intense karstification. Due to the differences in the potential energy of the topography, the quality of the reservoirs in the NW slope zone is the best, followed by that in the NW high zone and the SE sub-high zone, while the shoals and reservoirs of the sedimentary geomorphic lowlands are poorly developed. • The RMS attribute of Longwangmiao Formation bottom trough was used to reconstruct the sedimentary paleogeomorphology. • The distribution of sedimentary facies has been predicted precisely under the constraints of paleogeomorphology. • Development model of the shoals and reservoirs in the Longwangmiao Formation in the study area was established. [ABSTRACT FROM AUTHOR]

To evaluate the risk of induced seismicity due to hydraulic fracturing, a detailed stress analysis in a seismically active region, i.e., the Changning shale-gas field in the southern Sichuan Basin, was conducted utilizing sonic wave velocity logs and high-resolution electrical resistivity image logs of shale gas wells. Wells with relatively higher magnitudes of horizontal stresses are spatially located in the vicinity of thrust faults, in agreement with the stress concentration at the upper tip of the basement-involved thrust fault. The prevailing orientation of maximum horizontal principal stress (S Hmax) is N110°–120°E on the southwestern Changning anticline, which aligns with the motion of the Sichuan Basin, as driven by the continuous eastward extrusion of the Tibet plateau, which initiated at approximately 50 Ma. However, the S Hmax orientation is N30°–70°E along the northern Changning anticline, implying an inheritance of the N–S geodynamic compression during the Jurassic to Late Cretaceous. Drilling-induced tensile fractures primarily appear in compliant layers that are rich in clay or organic matter in wells located adjacent to thrust faults, suggesting that stiff layers can efficiently inhibit the hydrofracture growth height owing to more intense tectonic stress near thrust faults. A natural fault with a strike of approximately 30° to the S Hmax orientation can be more easily activated by extreme pumping pressure in wells that are weakly affected by the stress concentration along the thrust fault. Nevertheless, a cyclic injection of fracturing fluid with a gradually increasing target pressure may effectively reduce the magnitude of induced seismicity. • Detailed stress analysis of Changning shale-gas field using geophysical data. • Wells with higher horizontal stresses spatially located near thrust faults. • Drilling-induced tensile fractures appear in layers rich in clay or organic matter. • Stiff layers inhibit hydrofracture growth due to more intense tectonic stress. • Cyclic fluid injection with increasing target pressure may reduce seismicity. [ABSTRACT FROM AUTHOR]