Integrated Analysis of Tectonic Evolution and Hydrocarbon Potential in the Aonan Sag, Northern Songliao Basin: Insights from Rift-Phase Structural Controls

In the northern part of the Songliao Basin, the Aonan Depression is a significant structural feature. It plays a crucial role in the relationship between tectonic evolution and deep natural gas accumulation mechanisms. While previous studies have revealed faulting and sedimentary characteristics in the region, the precise connection between tectonic evolution and hydrocarbon accumulation, particularly for deep natural gas, has not been systematically studied. This research uses structural modeling and stratigraphic restoration to reconstruct the tectonic evolution of the third section of the Shahezi Formation and develops a 3D geological model of the study area. The results show that the tectonic evolution of the Aonan Depression can be divided into three stages: rifting, sagging, and inversion. Each stage significantly controls hydrocarbon distribution. A self-sourced, self-storage gas system formed in the Shahezi Formation, while the Denglouku and Yingcheng formations exhibit a source–reservoir combination. The study reveals how tectonic evolution influences hydrocarbon accumulation and distribution on a regional scale. Based on these findings, a “rift-controlled source, sag-controlled storage, and structure-controlled trapping” accumulation model is proposed, providing new insights into tectonic evolution and hydrocarbon accumulation mechanisms, with important implications for similar basins’ exploration and structural studies.