Geothermal Characteristics and Hydrocarbon Accumulation of the Northern Marginal Basins, South China Sea

Abstract

A total of 65 new heat flow data were obtained based on newly determined thermal conductivity and collected temperature logging data. Using these data together with those from previous studies, we constructed a geothermal gradient map as well as a heat flow map for the northern marginal basins of the South China Sea. Furthermore, geothermal characteristics of these basins and their relationship with oil and gas field distribution were analyzed. The results show that the four sub-basins located in the northern South China Sea, namely the Pearl River Mouth Basin, Qiongdongnan Basin, Beibuwan Basin and Yinggehai Basin, are typical “hot basins” with average heat flow of 68.7±11 mW/m2, 71.1±13 mW/m2, 65.7±8.9 mW/m2, and 74.7±10 mW/m2, respectively. The overall heat flow distribution pattern in the study area, which gradually increases from the shelf to the slope corresponding with crust thinning trend, are generally controlled by regional tectonic setting. Meanwhile some high local heat flow anomalies are likely to be attributed to the fault and magmatic activities. The geothermal field may control and restrict oil and gas accumulation in the study area. In light of exploration results of these basins, we find that the gas fields are mostly located in the high heat flow basins (depressions) while the oil fields more likely lie in relatively lower heat flow basins (depressions).