Characteristics of Multi-Phase Fracture Development in Cretaceous Granite from Coastal Region of South China and Its Implications for Buried-Hill Exploration
Characteristics of fracture distribution are vital for research of granitic reservoirs. Here,unmanned aerial vehicle (UAV)-based photogrammetric data were used to identify and quantitatively analyze the structural fractures developed in the outcrops of Cretaceous granites from coastal region of South China. Fracture density and connectivity were described in detail to gain a better insight into the nature of fracture distribution developed in multi-phase tectonic events. The results show that the study areas predominantly exhibit two sets of fractures of NE20°-40° and SE100°-140°. The NE-trending fractures developed earlier than SE-trending fractures. Multiphase tectonic deformation significantly enhances the connectivity and density of fracture network. Areas of elevated density are concentrated within the extensive intrusion zone of diabase dikes and the interior of fault zones. The linear density,surface density,and connectivity of the structural fracture network are positively correlated with the size of the fault zone. This study allows us to build a structural model to elucidate the development of multi-phase structural fractures in coastal region of South China. It underscores that fracture intersections such as fault zones and intrusions by diabase dikes are areas of high fault network connectivity and density,and thus optimal reservoir conditions. This research provides a guideline for understanding fracture network distribution in granitic reservoirs and for reservoir evaluation in crystalline basement during petroleum exploration.
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