Fault-Fold System

The formation of bed folding along weakened zones often leads to the emergence of subsidiary faults, thereby creating intricate fault-fold systems with fractures. These systems are of paramount importance for the exploration of methane. While existing literature on fault-fold systems predominantly relies on field observations, there has been scant research focusing on their subsurface structures. Utilizing three-dimensional seismic data, this study endeavors to identify and quantify the principal fault-fold systems within the No. 3 coal seam of the Shanxi Formation and the No. 15 coal seam of the Taiyuan Formation, situated in the Zhengzhuang block of the southern Qinshui Basin, China. The findings reveal: (1) The presence of five principal fault-fold systems, with four exhibiting a North–South orientation and one aligning East–West; (2) The establishment of an asymmetric model for the fault-fold system through a quantitative analysis of seismic attributes, particularly focusing on the high-angle normal faults along the folds’ limbs; (3) The identification of a normal fault on the left side of the No. 3 fault-fold system, with an estimated fault damage zone width of about 200 m, contrasting with the right side, where the fault damage zone width ranges from 50 to 500 m. These initial assessments propose a geological model based on seismic attributes, aiming to enhance the exploration and exploitation of deep methane and petroleum within fractured reservoirs.