The Simulation Of The Cenozoic Tectonic Stress Field In Jizhong Depression

Jizhong depression is located in the northwest of Bohai Gulf basin and composed of many uplifts and sags. Among these sags Langgu sag, Ba Xian sag and Rao Yang sag are rich of oil and gas resources and known as oil-rich sags where a number of various types of oil and gas fields have been found. The research area has undergone multiphase complex tectonic movements where the formation and transformation process of reservoirs is complex, and has a huge potential for exploration.Some research results and practice has indicated that structural stress is closely linked with the oil and gas distribution. Development and evolution of tectonic stress field not only controls the formation of oil and gas basins and the formation & distribution of related structures within the basin, but also affects the development of source rocks, reservoirs and seals and the processes of the hydrocarbon generation, migration and accumulation. Therefore, taking the tectonic stress field simulation and analyzing the relationship between the distribution of the regional faults and stress field will be very efficient and helpful in further oil and gas exploration.Based on former research results, this paper summarizes the regional geology of Jizhong depression and clarifies the tectonic setting of Jizhong depression. The tectonic evolution history of Jizhong depression can be divided into four stages: the SEE-direction extension stage in Ek & Es4, the SE-direction extension stage in Es3 & Es2, the SSE-direction extension & strike-slip stage in Es1 & Ed and the depression stage in Neogene.On the base of these analysis above and the finite element method, this paper simulates the tectonic stress field of the Jizhong depression by using ANSYS systematic simulation software, then analyzes the relationship between tectonic stress field and fault distribution bycombining the simulation results and fault distribution. The result suggests that in those 4 stages mentioned before, the minimum principal stress in Jinzhong depression was always tensile stress while the shear stress was always dextral. With such tectonic stress field acting on, Jizhong depression was easy to derive NNE-NE secondary normal faults, which are more intensive near the main faults.Oil and gas always moves from higher potential area of stress field to lower potential area. In this depression, the high value areas of absolute value of minimum tensile stress should be the advantage gathering area of oil and gas. Comparing simulation results and distribution of proved reserves can prove the conclusion above. Furthermore, the intense transtension in Neogene made the faults open, turning them into favorable migration pathways of oil and gas and structural traps.