Baiyun Sag has become the primary focus of deepwater exploration in the Pearl River Mouth Basin. However, its complex and high-variate geothermal characteristics have severely constrained further oil and gas exploration and resource evaluation. In this study, the present-day geothermal field and tectono-thermal evolution histories of Baiyun Sag were systematically studied based on measured rock thermal conductivity and heat generation data, borehole temperatures, low-temperature thermochronometer analyses, and geodynamic methodologies. The thermal conductivity of 251 core samples ranges from 1.131 to 4.478 W/(m·K), with an average of 2.258 W/(m·K), while the heat generation rate of 106 samples ranges from 0.868 to 1.735 μW/m³, averaging 1.499 μW/m³. The thermal conductivity in Baiyun Sag exhibits a gradual decrease from the Wenchang Formation to the Hanjiang Formation, whereas the heat generation rate decreases with depth. The present-day heat flow in Baiyun Sag ranges from 66.6 to 139.1 mW/m2, with an average of 89.7 ± 14.7 mW/m2, showing a gradual increasing trend from northwest to southeast. Formation temperature at depths of 1–5 km increases proportionally with depth. Thermal inversion, as inferred from low-temperature thermochronological data of six basement samples, reveals distinct temperature paths for each tectonic unit in Baiyun Sag. These paths are primarily linked to regional tectonic uplift-subsidence and basement heat flow variation. Geodynamic simulations further indicate two extensional events in Baiyun Sag during the Eocene and Middle Miocene, leading to a rapid increase in basement heat flow. This study systematically elucidates the present-day geothermal field characteristics and tectono-thermal evolution history of Baiyun Sag, bearing significant implications for regional tectonic evolution and future deepwater oil and gas explorations.
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