Relations between the thermal history and petroleum generation in the Huh Lake depression, Hailar basin

Abstract：The present geothermal gradient of the Huh Lake depression is 3.54℃/100 m, so it is a middle-temperature geothermal field. The paleogeothermal gradient reconstructed by the vitrinite reflectance, microthermometric measurements of fluid inclusions and fission-track path method was 3.7-6.5℃ /100 m, which is higher than the present geothermal gradient, and the ancient subsurface temperatures are higher than the present subsurface temperatures. The reconstruction of the paleogeothermal gradient and modeling of the thermal history indicate that the maximum paleogeothermal values were reached in the Late Cretaceous and that the paleogeothermal field controlled the maturity of Lower Cretaceous hydrocarbon source rocks. Study of the relation between the thermal history and hydrocarbon shows that the formation of hydrocarbon in the Huh Lake depression mainly progressed through two stages: the late Early Cretaceous stage and stage since the Paleogene, with the late Early Cretaceous being the main stage of hydrocarbon accumulation. The intensity of hydrocarbon generation has become weak since the Paleogene with decreasing temperatures in the target strata.