准噶尔盆地南缘侏罗系烃源岩生烃特征

中—下侏罗统烃源岩是准噶尔盆地南缘主力烃源岩,为进一步加深对其生烃特征与分布的认识,梳理了准噶尔盆地南缘9口井和9条露头剖面的沉积学和地球化学分析结果,开展了泥岩、碳质泥岩和煤3类岩性的生烃热模拟实验,并结合油源对比,开展3种岩性生烃演化特征的研究。结果表明,准噶尔盆地南缘下侏罗统八道湾组发育中等—好烃源岩,中侏罗统西山窑组和下侏罗统三工河组发育中等烃源岩,煤是重要的气源岩。侏罗系来源的原油主要来自暗色泥岩的贡献,而八道湾组泥岩在3套烃源岩中有机质类型最优,规模最大,是主力生油层。侏罗系烃源岩镜质体反射率达到0.9%~1.8%时,进入快速生气和排气阶段,是形成大规模天然气藏的关键时期,霍玛吐背斜带位于南缘侏罗系烃源岩生烃中心,镜质体反射率普遍大于2.0%,是寻找大型天然气田的有利区域。

Hydrocarbon Generation of Jurassic Source Rocks in the Southern Margin of Junggar Basin

The source rocks in the Lower and Middle Jurassic strata are generally considered as the major source rocks in the southern mar gin of Junggar basin. In order to deepen the understandings on the hydrocarbon generation features and distribution of the source rocks, the paper teases out the results of sedimentary and geochemical analysis on 9 outcrop sections and the data from 9 wells in the southern margin of Junggar basin, carries out thermal simulation experiments on hydrocarbon generation for mudstone, carbonaceous mudstone and coal, and studies the hydrocarbon generating evolutions of the 3 types of source rocks by combining with oil source correlation. The study results show that in the southern margin of Junggar basin, medium-good source rocks are developed in the Lower Jurassic Badaowan formation, medium quality source rocks are mainly distributed in the Middle Jurassic Xishanyao formation and the Lower Jurassic Sangonghe forma tion and coal acts as the important source rocks of gas. The oil mainly comes from the Jurassic dark mudstone and the mudstone in the Bad aowan formation is the best source rock and widely distributed, which should be considered as the major hydrocarbon generation zone. The key gas generation and expulsion period of the Jurassic source rocks was the phase when the vitrinite reflectance reached 0.9%-1.8%, and the Huo-Ma-Tu anticline belt is located in the Jurassic hydrocarbon generating center in the southern margin of Junggar basin, where the vitrinite reflectance is generally higher than 2.0%. Therefore, the Huo-Ma-Tu-Hu anticline belt is the most favorable area for natural gas exploration.