THE INFLUENCE OF PRE-EXISTING STRUCTURES ON FRACTURE SYSTEMS IN THE JURASSIC SURAT BASIN, QUEENSLAND, AUSTRALIA

Abstract

Pre-existing structures can influence the spatial distribution and geometry of subsequent fractures in sedimentary basins. In Queensland, Australia, contractional structures in the Permian-Triassic Bowen Basin control fracture development in the overlying Jurassic Surat Basin, where the Precipice sandstone is targeted for geological storage of carbon dioxide (CO₂). Understanding the influence of pre-existing structures in the Bowen Basin on fracture systems in the Surat Basin is vital for the site selection process of CO₂ geological storage projects in Queensland. This study focuses on the NW-SE trending Miles Thrust Fault (MTF) and its associated fault-propagation folds in the Bowen Basin, aiming to understand their influence on fracture systems in the overlying Jurassic succession of the Surat Basin. Results from 3D seismic interpretation and structural reconstruction reveal that the Surat Basin is characterized by localized extensional faults. These faults crest above the fault-propagation folds of the MTF and strike parallel to the NW-SE trending fold axis. An overlapping relay zone of the extensional faults occurs above the bend of the fold axis, suggesting that structural deformation follows the pre-existing structural trend. Strain distribution in the Jurassic succession increases toward the fold hinge, resulting in the highest fracture intensity. Utilizing the Discrete Fracture Networks (DFNs) model, the N-S trending joint (tension) fracture set follows reginal stress associated with the Surat Basin subsidence. Other fractures are strongly controlled by localized stress influenced by the pre-existing MTF.