Abstract: Temperature is a key factor that controls the generation and perseveration of hydrocarbon, and accurate determination of deep formation temperature is of great significance for hydrocarbon resource assessment of sedimentary basins. The Qiongdongnan Basin, located at the northern margin of the South China Sea, is the ongoing target for deepwater hydrocarbon exploration in China, so understanding the spatial pattern of the deep formation temperature for this basin is fundamental for deepwater exploration in this area.On the basis of measured borehole temperatures and estimation of deep temperature with systematic dataset of thermal properties, the distribution patterns of the deep temperatures for the T30-T70 were presented here. The results demonstrated that the dominative range of measured reservoir temperatures of the basin is 90 to 150℃ , higher than the recently proposed golden temperature zone (60 to 120℃), which is partially due to the high thermal background of the Qiongdongnan Basin. In addition, the spatial patterns of the deep temperatures for the T30-T70 formations are characterized by high in the western basin and lower in the eastern basin, and the high temperature anomaly is found in the Yanan Depression, as a result of differential burial depth, thermal conductivity and basal heat flow associated with regional crustal extension within the basin. The results would provide robust geothermal constraints on the hydrocarbon exploration and drilling safe design for this basin.

Key words: reservoir temperature, oil window, golden temperature zone, Qiongdongnan Basin, South China Sea