基于细粒岩石类型对玛湖凹陷下二叠统风城组烃源岩分类评价

准噶尔盆地玛湖凹陷风城组页岩油勘探取得巨大突破，但是按照普遍认可的页岩油烃源岩评价标准，本区的烃源岩品质并不理想。为了科学评价玛湖凹陷烃源岩品质特征，本文在系统的岩心观察和有机地球化学分析的基础上，揭示烃源岩的形成环境，并按照矿物组成对烃源岩分类评价。玛湖凹陷风城组细粒岩主要沉积于正常半深湖、咸化半深湖、半咸化半深湖、含热液半深湖和滨浅湖环境中，各环境中细粒岩的有机质特征存在一定区别，其中半咸化半深湖有机质较为富集，w(TOC)均值在1%左右。进一步结合有机质类型判别图解，表明咸化半深湖和含热液半深湖有机质来源以湖泊生物为主，而其他环境中存在湖泊和陆源混合有机质来源。基于有机质生烃潜力评价和成熟度(V_re=0.74%)估算，表明目前风城组烃源岩中有机质正处于大量排烃的成熟阶段，且确定了细粒岩中的烃类为原生烃。由于不同矿物组成的烃源岩吸附能力的差异，按照陆相泥质烃源岩和碳酸盐质烃源岩开展分类评价，结果表明风城组沉积了累计厚度近250 m的的有效烃源岩，且富含以藻类体为主的有机质。

Evaluation of Hydrocarbon Source RockCharacteristics of Lower Permian Fengcheng Formation in Mahu Sag Based on Fine Grained Sedimentary RockType

 Enormousbreakthrough have been made in shale oil exploration of Fengcheng Formation inMahu sag, Junggar basin. However, according to generally accepted evaluationstandard of shale oil source rock, the quality characteristics of source rocksin this area are not ideal. In order to scientifically evaluate the quality ofsource rocks in Mahu sag, the sedimentary environment of Fengcheng Formationwas studied, and the source rocks was evaluated according to the mineralcomposition of fine-grained rocks on the basis of systematic core observationand organic geochemical analysis. Fine grained rocks of Fengcheng Formation inMahu sag were mainly deposited in normal semi deep lake, salinized semi deeplake and semi-salinized semi deep lake, hydrothermal semi deep lake and shallowlake. The organic matter characteristics of fine grained rocks in each environmentare different, and the semi-salinized semi deep lake was favored to enrichorganic matter, and the averaged TOC was nearly 1%. Further combining with thediscrimination diagram of organic matter types, it showed that the source oforganic matter in salinized semi deep lake and hydrothermal semi deep lake wasdominated by aquatic organisms, while there were mixed organic matter sourcesof lacustrine and land in other environments. Based on the hydrocarbongeneration potential evaluation and maturity estimation of organic matter (Vre=0.74%), it was revealed that thesource rocks of Fengcheng Formation were in the mature stage of hydrocarbonexpulsion, and the free hydrocarbons in fine-grained rocks were identified asprimary hydrocarbons. Finally, due to the difference of adsorption capacity ofdifferent mineral composition of source rocks, the classification evaluation iscarried out according to continental argillaceous source rocks and carbonatesource rocks. The results showed that the Fengcheng Formation depositedeffective source rocks with a cumulative thickness of nearly 250 m, withorganic matter dominated by algae.