Abstract: The Wanjinta area is located in the step fault system at the western edge of the Dehui fault Depression. The structural features and deformation mechanism of the area are closely related with hydrocarbon accumulation. The structure, fault system features, periods of fault activity, and the stress fields of the WanJinta area were analyzed by employing information from regional geology, drilling, and three-dimensional seismic resolution data. Two geological sections that cross the study area were selected for analysis, and 3D move-balanced sectional-structure recovery technology was used to recover and remodel the tectonic evolution history. Based on the fracture reservoir-control function, the average-weighted algorithm was used to establish the corresponding mathematical evaluation model. The "three-parameter evaluation method" was proposed to evaluate quantitatively the activity level of the deep fracture. Research shows that the WanJinta area has been subject to transformation adjustment following polycyclic tectonic movement. The area has a complex superimposed structure and forms two fracture systems, with deep rift-basement faults and a shallow reverse-fault system. The deep fault indicates deep formation change characteristics along segments of the deep part, and the shallow part shows the characteristics of section change. The level of fault activity in the reverse-fault slip region is relatively high, controlling the enrichment of the CO₂ gas reservoir in the plane. However, there could be reservoirs enriched in organic hydrocarbon gas in areas that are located far away from the deep faults subject to high-level activity, with little impact from a second fold structure superimposed fracture adjacent to the Shahezi Formation hydrocarbon source rocks.

Key words: Dehui fault depression, Wanjinta, tectonic deformation, positive flower strike slip, tectonic superposition