Geochemical Characteristics and Simulation of Hydrocarbon Generation and Expulsion of Main Hydrocarbon Source Rocks of the Mesozoic strata in Hari sag, North of Yingen- Ejinaqi Basin

Abstract In this paper, we took samples from the Mesozoic Lower Cretaceous Yingen Formation, Suhongtu Formation, Bayingebi Formation and Permian source rocks in Well YH7 and Well YH8 in Hari Sag to study the geochemical features and compared the results with early research results; Samples of the second hydrocarbon source rocks in the Yingen Formation and the Bayingebi Formation were selected for thermal simulation experiments to study the secondary hydrocarbon generation potential. By analyzing and comparing the geochemical features of the source rocks, it is found that the Mesozoic hydrocarbon source rocks in the Hari Sag are mainly deposited in a reducing environment, and some are in a weakly oxidizing-weakly reducing environment. K1y is the best II2 immature-low mature hydrocarbon source rock, K1s is the non-hydrocarbon- best II1-II2 mature hydrocarbon source rock, K1b3 is the non-hydrocarbon- good II2-III mature hydrocarbon source rock, K1b2 is the medium- best II1-III low mature- mature hydrocarbon source rock, K1b1 is the non-hydrocarbon- best Ⅱ2-Ⅲ mature- high mature hydrocarbon source rock, and P is the best III over mature hydrocarbon source rock. By the thermal simulation experiments on the secondary hydrocarbon source rock of the Yingen Formation and the Bayingebi Formation, it is found that the hydrocarbon generation and expulsion characteristics of the Mesozoic source rock samples in the Hari Sag can be roughly divided into four stages: low mature stage (0.5% < Ro < 0.7%, simulation temperature is 250 ℃ - 300 ℃), early rapid oil generation and expulsion stage (0.7% < Ro < 1.3%, simulation temperature is 300 ℃ - 400 ℃), mid-term oil cracking gas stage (1.3% < Ro < 2.0%, simulation temperature is 400 ℃ - 500 ℃), and late major gas generation stage (Ro ＞ 2.0%), simulation temperature is 500 ℃ - 550 ℃). The K1b2 hydrocarbon source rock in the late first stage and early second stage has much larger exploration potential than K1y in the first stage.