准噶尔盆地腹部及西南缘侏罗系烃源岩分子地球化学特征及形成环境剖析

The Sedimentary Environment and Molecular Geochemical Characteristics of Jurassic Source Rock in Central and Southern Junggar Basin

准噶尔盆地腹部及西南缘侏罗系烃源岩厚度大,分布广,部分层段烃源岩较好,并已发现油源贡献,勘探前景较好。本文在前人基础之上,依据有机地球化学及有机岩石学的实验室分析测试手段,系统研究了侏罗系烃源岩分布特征、生烃潜力、分子地球化学特征及沉积环境。结果表明,盆1井西凹陷整体上侏罗系烃源岩生烃潜力较差,沙湾凹陷侏罗系八道湾组与西山窑组部分层段生烃潜力较好,三工河组烃源岩较差,四棵树凹陷侏罗系八道湾组分布较好的烃源岩,而三工河组与西山窑组烃源岩较差。此外,八道湾组沉积早期,主要发育三角洲前缘亚相与滨浅湖相,沙湾凹陷发育滨浅湖相、湖沼相,其南部发育半深湖相,有机质发育,烃源岩主要形成于以陆源高等植物输入为主的弱氧化—强氧化的沉积环境。三工河组沉积期,研究区大部分地区发育滨浅湖相,沙湾凹陷及东部地区局部发育半深湖相,烃源岩形成于强氧化的沉积环境,有机生源主要为陆源高等植物碎屑。西山窑组沉积期间,玛湖凹陷、陆梁隆起带及盆1井西凹陷发育三角洲平原与前缘亚相,沉积中心向沙湾凹陷的东部和南缘迁移,主要发育半深湖相沉积,烃源岩主要形成于弱氧化—强氧化的湖沼环境,生源输入以陆源高等植物为主。

In central and southern Junggar basin,Jurassic source rock is characterized by the large thickness,widespread,whose partial interval have well potential hydrocarbon and exploration.Based on the former study,according to the organic geochemistry and organic petrology experiment analysis method,the distribution characteristics,hydrocarbon potential,biomarker geochemistry and sedimentary environment have been investigated.The results indicate that in western Well Pen 1 depression,the Jurassic formation source rock has worse hydrocarbon potential,in Shawan depression,the Badaowan Formation and Xishanyao Formation have better hydrocarbon potential,but Sangonghe Formation source rock is worse.In Sikeshu depression,Badaowan Formation source rock has better hydrocarbon potential.Additionally,in earlier sedimentary period of Badaowan Formation,the research area developed delta front sub-facies and shore shallow lake facies.In Shawan depression,the formation developed shore shallow facies and limnetic facies with much organic matter input.The source rock is formed in weak oxidation-strong weak sedimentary environment with high plant input.In Sangonghe Formation sedimentary period,the study area distributed shore shallow lake faices,whose source rock is formed in strong oxidation environment with lacustrine high plant input.In Xishanyao Formation sedimentary period,in Mahu depression,Luliang uplift,and Western Well Pen 1 depression distributed delta plain facies and front plain facies.The sedimentary centre moved to eastern and southern depression with sub-deep lake facies,whose source rock is formed in weak oxidation-strong oxidation environment with high lacustrine plant input.