Thermal conductivity column of rocks and distribution characteristics of paleo-geothermal field in the Songliao Basin

The paleo-geothermal field of a basin is closely related to the formation and evolution of geothermal, oil, and gas resources. To ascertain the characteristics of the paleo-geothermal field in the Songliao Basin during some critical periods, this study established the thermal conductivity column of rocks in the basin using measurements from 269 samples and compiled previous data. Then, it simulated the burial and thermal histories of multiple wells under the constraint of vitrinite reflectance (R_ran). The results indicate that the thermal conductivity of the Songliao Basin increases with the depth, with increasing rates higher in the upper strata than in the lower strata and an average of 1.79 W/(m·K). Furthermore, the thermal conductivity also increases with the age of strata. The R_ran of the northern Songliao Basin primarily ranges from 0.8% to 1.6%, peaking in the Qijiagulong sag. The burial and thermal histories reveal that the paleo-geotemperature of the Cretaceous Qingshankou Formation peaked in the late stage of the Mingshui Formation deposition, followed by a gradual decrease until the present. The planar distribution of the paleo-geothermal field indicates that the Qingshankou Formation in the northern Songliao Basin exhibited a maximum paleo-geotemperature of above 120°C in most areas, which is significantly higher than the present level. The basin entered the thermal subsidence stage after the deposition of the Qingshankou Formation, and its paleo-geotemperature gradually peaked with an increase in the paleo-burial depth. In this stage, the high paleo-geotemperature was favorable for the maturation of shale oil and gas. In the late stage of the Mingshui Formation, the Songliao Basin underwent a notable uplifting and cooling event under the influence of the movement of the Paleo-Pacific Plate. In the cooling process, areas with a small decreasing amplitude of the geothermal gradient became favorable areas of geothermal conditions. The results of this study will provide a theoretical reference for research on the formation mechanisms of geothermal, oil, and gas resources in the Songliao Basin.