Evaluation on Source Rocks in the Jurassic Sequence Stratigraphic Frameworks of the Junggar Basin, China

The source rocks in the Jurassic sequence stratigraphic frameworks of the Junggar basin were evaluated in detail in this paper. The results showed that the most Jurassic samples belong to poor medium source rocks, and the hydrocarbon generation conditions of Badaowan Formation are better than those of Sangonghe Formation. In a sequence, the organic carbon abundance of condensed section is obviously higher than those of lacustrine transgressive system tract interval and high stand system tract interval, i.e., the condensed section is more favorable for hydrocarbon generation. The kerogen of Jurassic is mainly of type Ⅲ and Ⅱ 2, with small amount of Ⅱ 1. The Jurassic was not deposited in a typical coal forming marsh environment, but mainly in fresh water lacustrine shore shallow lacustrine semi deep lacustrine deep lacustrine ones, with weakly reducing strongly oxidizing geochemical conditions and evident pristane predominance. The thermal maturity of the Jurassic is low and a little different in different areas, and most samples are at lower mature stage presently ( R o=0.50%～0.80%), indicating that there is no large amount of normal liquid hydrocarbon generated from the Jurassic in the Basin. It is more realistic to seek for immature to lower mature oil and gas generated from the Jurassic in the Basin.