准噶尔盆地侏罗系层序地层格架中的烃源岩评价

对准噶尔盆地侏罗系层序地层格架中的烃源岩进行了详细的评价。侏罗系大多数属差-中等的烃源岩,八道湾组比三工河组的生烃条件要好些。在一个层序中,凝缩段的有机碳丰度明显高于湖进体系域段和高位体系域段,即凝缩段有利于烃类的生成。侏罗系的干酪根类型主要为Ⅲ和Ⅱ2,少数为Ⅱ1。侏罗纪并非是典型的成煤沼泽环境,而主要是淡水的滨浅湖-半深湖-深湖环境,主要形成于弱还原-强氧化的地球化学环境中,具有明显的姥鲛烷优势。侏罗系成熟度很低,且不同地区也有所差异,大多数样品处于低成熟阶段 (R_o=0.5 0 %～ 0.80 % ),意味着盆地的侏罗系没有大量生成常规的液态烃类,寻找由侏罗系生成的未熟-低熟油和天然气可能更为现实

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 detailin thispa -per. 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 lacus-trine -semi-deep lacustrine -deep lacustrine ones, with weakly reducing -strongly oxidizing geochemical conditions and evident pristane pre -dominance.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.