Structural characteristics and formation mechanism in Dongxin Oilfield, Jiyang Depression, Bohai Bay Basin: insights from physical simulation

The structural characteristics and formation mechanism of faults in the Dongxin Oilfield of the Jiyang Depression were systematically studied through the analyses of geometric and kinematic characteristics, genetic mechanism and structural physical simulation experiments. The structural form in the study area gradually trends toward complexity from east to west. The Xinzhen structural belt in the east is mainly composed of parallel structures, presenting a simple structural style. The transitional belt in the middle is composed of parallel and oblique structures, presenting a grid structural style. The Dongying structural belt in the west is composed of en echelon and broom-like structures, presenting a complex structural style. Vertically, there are five main fault combination styles in this region, including negative flower-like, inverse "Y" shaped, step-like, graben and horst, showing a typical "cabbage" complex fault system. Physical simulation results fit the actual geological conditions well. The experimental results further confirm that the fault structural assemblage pattern in the Dongxin area is the product of the superposition of Cenozoic extensional-strike-slip stress field and magmatic bottom rifting. Its fundamental driving force is derived from the NW-SE extensional stress field, the right strike-slip of the Tanlu fault zone and the upwelling of plastic materials such as magma.