<p>The Songliao Basin in northeast China is one of the largest petroliferous basins worldwide, and features the T₂ fault system, which consists of numerous minor extensional normal faults. This study combines high-resolution 3D seismic datasets to detail the characteristics of the T₂ fault system, contributing two key findings: (1) The T₂ faults are confirmed as polygonal fault systems, characterized by closely spaced, layer-bounded faults with small throws, high dip angles, and random orientations, forming intricate polygonal networks. (2) The study reveals the influence of tectonic stresses on the fault system, showing spatial variations across different tectonic units. In depressions, T₂ faults exhibit short lengths, small throws, high density, and multiple directions. In contrast, in inverted anticline belts, they have longer lengths, bigger throws, higher density, and concordant orientations. These variations demonstrate the impact of tectonic inversion on the development of T₂ faults. The significance of this research lies in presenting a typical polygonal fault system developed in a deep lake succession and was superposed the influence by regional tectonic stress coeval with its development. The new insights facilitate a reevaluation of the T₂ fault system’s role in hydrocarbon migration and accumulation within the Songliao Basin.</p>