Description of Formations Fault Activity Characteristics and Genesis Mechanism Using of Paleogeomorphic Restoration Techniques

The Xujiaweizi Fault Depression has experienced multiple stages of tectonic activity and its geological conditions are complex. Palaeogeomorphic restoration can provide a new idea for efficient exploration of oil and gas. At present, there is no systematic study on paleo-geomorphology restoration in the Anda Sag of the northern Xujiaweizi Fault Depression. In this paper, a large number of drilling and seismic data have been used to study the fault activity characteristics and genesis mechanism of the Anda Sag based on the structural analysis theory. Furthermore, the paleogeomorphology of the Anda Sag was restored. The study shows that the NE and NW trending preexisting boundary normal faults and the near E-W trending extensional activities controlled the formation and development of the Xujiaweizi Fault Depression. The Shahezi Formation had low extensional intensity in the early stage and was dominated by NE and NW trending fault activities. In the late period, it was dominated by S-N trending fault activities with high extensional intensity. The mechanism of formation denudation in the Anda Sag includes regional uplift and reverse extrusion deformation. The distribution of fault depression structures and main troughs of the Shahezi Formation in the Anda Depression have good inheritance characteristics. The denudation of the edge strata and the inner extrusion reversed zone is relatively serious, and most of the residual strata are in the delta front and lacustrine sedimentary development areas. Therefore, effective source rocks are developed in the residual formation areas, which are conducive to the formation of deep self-source gas reservoirs.