The thermal history in sedimentary basins: A case study of the central Tarim Basin, Western China

Abstract

• Heat flow of the Shunbei area decreased since the Ordovician with a Permian peak. • The middle-lower Ordovician reservoirs experienced three stages of heating process. • Hydrocarbon charging periods of No.1, 5, and 7 strike-slip fault zones are different. The reconstruction of thermal history is essential for the superdeep (>6,000 m) hydrocarbon exploration and development in the Central Tarim Basin, Western China. This study first recovered the burial histories of five typical wells in the Shunbei area (the Central Tarim Basin) based on the drilling data and calculated the erosional thicknesses using the well-tie profiles. The thermal histories and hydrocarbon charging periods of the Shunbei area were studied with the measured equivalent vitrinite reflectance ( R equ ) and fluid inclusion assemblage homogenization temperature data, respectively. Except for some abnormal values, most R equ data with 0.45%–1.48% gradually increase with depth. The thermal modeling revealed that the heat flow in the Shunbei area gradually decreased since the Early Ordovician, with an abrupt peak of ∼45–47 mW/m 2 during the Early Permian. The temperature histories of the Ordovician Yijianfang and Yingshan Formation reservoirs in the Shunbei area could be divided into three stages of rapid heating (1.27–1.36 °C/Ma), slow heating (0.07–0.09 °C/Ma) and rapid heating (1.20–1.28 °C/Ma). We recognized three hydrocarbon charging periods in the No. 1 strike-slip fault zone, which occurred at ∼435–420 Ma, ∼263–220 Ma, and 18–3 Ma, respectively, while the No. 5 and 7 strike-slip fault zones only experienced the first two periods. This study provides new insights into the thermal history and hydrocarbon accumulation in the Shunbei area, which would be very useful for further superdeep oil and gas exploration and resource evaluation in the Central Tarim Basin.