Modelling of Thermal Effects of Igneous Intrusions on the Temperature Field and Organic Maturity in the Changchang Sag, Qiongdongnan Basin, South China Sea

AbstractThe latest seismic interpretation suggests the presence of several igneous intrusions in the Changchang sag, Qiongdongnan basin, South China Sea. A 2D geothermal modeling based on the finite element method (FEM) is performed to analyze the thermal effects of three intrusions of different scales distributed in the same seismic line. A quantitative evaluation is made on the organic maturity change for the Yacheng Formation caused by intrusions in artificial wells 2 km and 5 km away from each igneous body in combination with the acquired paleo‐geothermal field and the Easy%Ro model. The results indicate that the temperatures of igneous bodies dropped down rapidly during the first 1 Ma after the intrusion and lowered to the nearly same values as that of the wall rock after 10 Ma. The biggest intrusion caused a theoretical vitrinite reflectance (Ro) 1.6% higher than normal for the Yacheng Formation at the place 2 km away and only 0.4% higher for that 5 km distant.