Present‐Day Geothermal Regime in Tarim Basin, Northwest China

Abstract

AbstractGeothermal gradient and surface heat flow are key parameters that describe the thermal regime of sedimentary basin, and are so vital for understanding the tectono‐thermal evolution and associated hydrocarbon potential assessment of oil and gas bearing basin. Here we presented the distribution pattern of the updated present‐day geothermal gradient and determined 38 surface heat flow values in the Tarim basin, the biggest sedimentary basins in China, on the basis of formation temperature data from approximately 470 wells and 941 measured thermal conductivities of rocks within this basin. Our results showed that the present‐day geothermal gradient of Tarim basin varied between 17~32°C/km and with a mean of 22.6±3.0°C/km, and the surface heat flow ranged from 26.2 to 65.4 mW/m2 with a mean of 43.0±8.5 mW/m2, suggesting its thermal regime as a cold basin of low temperature and heat flow, compared with other large‐middle scale sedimentary basins in China. Accordingly, this low thermal regime also makes Tarim basin to share the similar thermal regime of other typical craton basins in the world. It is obvious that the geothermal gradient and surface heat flow in uplift areas are usually larger than those in the depressions, indicating the influence of configuration of basement on geothermal field pattern. We also found that the discovered oil and gas fields in Tarim are usually with relatively large geothermal gradient, the cause for this coincidence is not clear but the upward movement and accumulation of hot fluid below is speculated to account for this positive geothermal anomaly. Finally, we summarized the factors that influence the geothermal distribution of basin as deep structure, tectonic evolution and basement configuration of basin, thermal physical properties of rocks and hydrocarbon accumulation as well.