Study on the Characteristics and Sealing Capacity of Major Controlling Faults in the Mesozoic of the Chengdao-Zhuanghai Area, Jiyang Depression: A Proposed Method for Sealing Capacity Identification

Since the Mesozoic, the Chengdao-Zhuanghai area of the Jiyang Depression in eastern China has undergone multiple tectonic movements, leading to extensive fault development in Mesozoic strata. This study analyzes fault features and evolution using seismic, well logging, and mud logging data to clarify the major characteristics of Mesozoic faults and the impact of their sealing capacity on hydrocarbon migration and accumulation. It quantitatively evaluates sealing capacity using a fuzzy evaluation method based on fault plane effective normal stress, shale gouge ratio, and tightness factor, and discusses hydrocarbon-related impacts using well testing and production data. The results showed that the major faults are secondary and tertiary normal faults, predominantly ramp-flat or listric in cross section, with NW, NNW, NNE (NE), and nearly EW strikes and dips of 50–70°; the Chengbei Fault has the largest throw (2–3.2 km) and the longest extension (45.94 km). These faults transition from reverse to normal during Fangzi Formation deposition. The Chengbei 30 North and 304 Faults exhibit poor sealing capacity (hydrocarbon migration), whereas the Chengbei, Chengbei 20, Chengbei 30 South, and Zhuanghai 104 South Faults exhibit good sealing capacity (trap formation and hydrocarbon entrapment). This study provides guidance for the exploration of hydrocarbon-enriched fault block reservoirs near major faults.