关键词: 大地热流, 地温梯度, 岩石热物性, 热体制, 库车前陆盆地

Abstract: Geothermal regime of the sedimentary basins is key for understanding the formation and evolution of the basins and assessing hydrocarbon and geothermal energy, and has attracted much attention from the academia and industrial circles. Kuqa Foreland Basin, located between the Tarim Basin and Southern Tianshan Mountain, is one of major hydrocarbon exploration targets in China, and accurate knowledge of geothermal regime of this basin is beneficial for hydrocarbon potential assessment. Here we integrate updated steady-state temperature logs and oil testing temperature, with thermal properties data, to decipher the thermal characterization of the Kuqa Foreland Basin. The geothermal gradient of the basin ranges from 17.3 to 25.7 ℃ /km, with an average of 21.5±2.6 ℃ /km; while the heat flow varies from 27.4 to 57.9 mW/m2, with a mean of 40.9±7.2 mW/m2. The range and average of estimated formation temperatures at 1000-6000 m in the basin are 26-49 ℃ (36±4.6 ℃ ), 42-82 ℃ (59±7.5 ℃ ), 64-113 ℃ (82±10.3 ℃ ), 85-127 ℃ (102±11.6 ℃ ), 98-140 ℃ (119±12.8 ℃ ) and 110-155 ℃ (133±13.9 ℃ ), respectively. Generally, the present-day thermal state of the Kuqa Foreland Basin is relatively low and the thermal pattern is characterized by hot in the north and east, cold in the south and west, which is attributed to the east-west differences in the thickness of the Cenozoic sediments and the lateral variations in the intensity of active deformation associated with the far field effects of the Indo-Asian continental collision. The large thickness of the sediments in the western part of the basin, which forms the thermal blanketing effects owing to their low thermal conductivities, preventing the transport of heat from the deep to the surface. In addition, the active deformation in the eastern part of the basin is more intense, and the friction heating effect of fault movements is obvious. These two factors are combined to account for the observed present-day geothermal field pattern of Kuqa Foreland Basin.

Key words: Heat flow, geothermal gradient, thermal properties, thermal regime, Kuqa Foreland Basin