Tectonic-sedimentary features of the Shahejie Formation in Chengbei Sag and its implications for oil and gas exploration

Based on three-dimensional seismic, core, logging, and logging data, guided by the "source-valley-sink" concept, the evolution of the structural fault system in the Shahejie Formation and its sedimentary response characteristics in the Chengbei Sag were analyzed. The development types and spatiotemporal distribution of sedimentary systems in different stages of structural evolution were clarified. Results show that the sedimentation of the Shahejie Formation was controlled by the Chengbei Fault and Chengzikou Fault, reflecting typical episodic structural evolution characteristics. The sedimentation period of the third member of the Shahejie Formation is characterized by strong faulting and subsidence, during which the activity of the Chengbei Fault was strong. A fan delta sedimentary system was developed in steep slope zone along a large ancient valley, while a delta sedimentary system was developed in the western slope along a fault-trough-typed valley. The sedimentary period from the first to second members developed a strike-slip-fault depression, during which the activity of the Chengbei Fault was significantly weakened, and that of the Chengzikou Fault remained relatively strong. The steep slope zone and the western slope both inherited the development of the delta sedimentary system along material supply route. The exploration practice has verified that the sand-body development area was resulted from the structural sedimentary response, indicating the direction for oil and gas exploration in the study area.