川南自贡地区海相页岩沉积环境及有机质富集主控因素研究

Study on the Sedimentary Environment and Main Controlling Factors of Organic Matter Enrichment of Marine Shale in Zigong Area of the Southern Sichuan Basin

为深化对川南自贡地区五峰组-龙马溪组海相页岩沉积环境特征及有机质富集机理认识,通过开展有机地球化学和元素地球化学等实验,对Z303井沉积环境特征进行综合研究。结果表明:研究区海相页岩有机质丰度高,TOC平均为2.15%,矿物组成以石英和黏土矿物为主,氧化还原环境是自贡地区有机质富集的主控因素;五峰组和下龙马溪组沉积时期有机质富集条件相比中龙马溪组和上龙马溪组沉积时期更加优越,形成了一套富含有机质且脆性矿物含量高的优质页岩,是研究区页岩气勘探开发的首选目标。

To deepen the understanding of the sedimentary environmental characteristics and organic matter enrich-ment mechanism of the marine shale of the Wufeng Formation-Longmaxi Formation in the Zigong area of the south-ern Sichuan Basin,a comprehensive study was carried out on the sedimentary environmental characteristics of the Well Z303 by conducting experiments on organic geochemistry and elemental geochemistry.The results of the study show that:The organic matter abundance of marine shales in the target area is high,with an average TOC content of 2.15%;the mineral composition is dominated by quartz and clay minerals,and the redox environment is the main controlling factor for organic matter enrichment in the Zigong Area;the organic matter enrichment conditions during the deposition period of the Wufeng Formation and Lower Longmaxi Formation are more superior than those during the deposition period of the Middle and Upper Longmaxi Formations,formning favorable shales rich in organic matter and high in britle minerals.It is the prefered target for shale gas exploration and development in the study area.