A study on maturity evolution of Lower Silurian marine hydrocarbon source rocks and thermal history in the southern Jianghan basin

The data from typical boreholes in the southern Jianghan basin were modeled using the geothermal history simulation system of hydrocarbon-bearing basin, and the thermal history and burial history were reconstructed. Based on the thermal history, maturity evolution of the Lower Silurian source rocks was modeled. The results show that the basin was in a stable stage before Indosinian movement, the paleo-heat flow was between 50 mW/m(2) and 55 mW/m(2). After Indosinian period, the heat flow was elevated in the whole basin. In Yanshan period (155 Ma or so), The heat flow reached their maximum values of 72 mW/m2 at 155 Ma in the north of the Qianbei Fault, The heat flows reached their maximum values of similar to 76 mW/m(2) at 40 Ma in the south of the Qianbei Fault. Since the late Himalayan epoch, the Jianghan basin was subjected to a deposition withering period accompanied by a cooling episode. In early Triassic, the maturity of source rocks in Zhijiang, Dangyang and Mianyang depression area first reached oil generation threshold, the maturity of source rocks increased rapidly during early Jurassic to early Cretaceous. The maturity was higher in the north of the Qianbei Fault than in the south of the Qianbei Fault. Based on this, in Late Cretaceous, the maturity of source rocks in the east area was higher than in the west area. The thermal evolution of source rocks terminated in the later Neogene. The heat flow history and Lower Silurian source rocks maturity evolution was calculated, which provides the basic data for source rocks evolution, hydrocarbon generation and expulsion prediction.