波斯湾盆地主力烃源岩特征及成因主控因素

Characteristics and Dominating Genesis Factors of Main Source Rocks in Persian Gulf Basin

波斯湾盆地优质烃源岩发育,其发育特征可为我国油气公司战略选区提供决策参考,其成因主控因素对有机质富集机理研究具有借鉴意义。通过文献调研发现,波斯湾盆地发育前寒武-寒武系、志留系和侏罗-白垩系三套主力烃源岩。随时代渐新,烃源岩分布自西向东迁移,有机质类型由腐泥型向腐殖型转变。三套主力烃源岩的TOC(总有机碳)普遍大于2%,总体进入成熟(R_(o)>0.7%)阶段。对烃源岩成因分析认为,各套烃源岩发育时期存在的局限洼地阻断了中深层海水循环,导致洼地内部底水缺氧;而同时发生的海侵事件不仅促进了洼地内海水分层和深部缺氧,更保证了这种缺氧现象得以长期维持。二者耦合形成的良好保存条件使有机质得以富集,是波斯湾盆地主力烃源岩形成的主控因素。

The development characteristics of high-quality source rocks in the Persian Gulf Basin can provide the reference of strategic decision-making for Chinese oil companies,and the main genetic controlling factors are extremely valuable for the study of organic matter enrichment mechanism.Through research in literature,it is found that there are three main source rocks of Persian Gulf Basin which are in Precambrian-Cambrian,Silurian and Jurassic-Cretaceous.As time goes by,the distribution of source rocks migrated from west to east and the organic matter changed from sapropel to humic.TOC(Total Organic Carbon)of three main source rocks is greater than 2%,and generally enters the mature stage(R_(o)>0.7%).It is considered that the limited depressions existing in the development period of each set of source rocks block the circulation of seawater in the middle and deep layers,resulting in anoxic bottom water.The simultaneous transgression not only promoted the stratification of seawater and deep hypoxia,but also ensured the long-term maintenance of this hypoxia.The preservation conditions formed by the coupling of the limited depression and transgressions make the organic matter enriched,which is the main dominating genesis factors of the main source rocks in Persian Gulf Basin.