Thermal evolution modeling of Neopaleozoic source rocks in Hangjinqi region, Ordos Basin

Taking the measured R_o values which reflected the characteristics of thermal evolution degree of source rocks as calibration, the thermal evolution history of source rocks of the Taiyuan Formation and members 1 and 2 of the Shanxi Formation in Neopaleozoic was modeled through erosion thickness restoration and the selection of ancient heat flow. We analyzed well logging data of different strata from more than 70 wells, and established a corresponding geological model. Source rocks reached the threshold of hydrocarbon generation (R_o>0.65%) during the mid-late stage of Late Triassic in Xinzhao, Shilijiahan, Azhen and Haoraozhao areas in the western and southern Hangjinqi region and during the early stage of Early Jurassic in Gongkahan and Shiguhao areas in the northern Hangjinqi region. The thermal evolution degree of source rocks decreases from southwest to northeast in the study area. The maximum R_o values in Xinzhao and southern Shilijiahan are 1.43% and 1.46% respectively, reaching the over-mature stage of evolution. However, the R_o values in Shiguhao and Azhen areas in the northern and eastern Hangjinqi region range from 0.85%-1.0%, showing that the source rocks are still in the early stage of hydrocarbon generation peak.