Abstract:

The hydrocarbon resources from Jurassic source rocks account for more than 30% and the natural gas resources account for 28% of the total amount in the Junggar Basin according to the third resource evaluation in 2000. According to the evaluation result，about 30.7% of the oil and 45.7% of the natural gas of the Jurassic resource are from the southern margin of the Junggar Basin(SMJB).Thus，it is critical to keep on studying the characteristics and the hydrocarbon generating potentials of the Jurassic source rocks. Data compiled during the hydrocarbon exploration in the last ten years are helpful for a better characterization of the source rocks in the SMJB. Three sets of source rocks were recognized. The Badaowan Formation of the Lower Jurassic was high quality source rocks. Source rocks from the Sangonghe Formation in the Lower Jurassic and the Xishanvao Fomation in the Middle Jurassic are characterized by medium quality. The above three sets of source rocks are characterized by humic organic types which fall within type II₂ and type III source rocks. All the source rocks are mature-overmature source rocks. The source rocks were buried to the peak of oil generation at the end of Cretaceous. Neocene is the period when the source rocks were buried to the peak of gas generation.  The perfeet match between the key period of hydrocarbon generation and the initiation and formation of the trap facilitate large-scale hydrocarbon migration and accumulation. The research is significant in guiding the hydrocarbon exploration in SMJB.

Key words: source rock, resource evaluation, Jurassic, southern margin of the Junggar Basin