泸州古隆起下三叠统嘉陵江组成藏地球化学特征

泸州古隆起划分为核部、斜坡及外围3个部分。古隆起核部以嘉陵江组一段气藏为主;北缘斜坡以嘉陵江组二段气藏为主;南缘斜坡为以嘉陵江组三段气藏为主的多产层气藏分布区。泸州古隆起嘉陵江组天然气性质复杂,既有分布于古隆起核部产凝析油的湿气,又有分布于古隆起斜坡区不含凝析油的干气。利用天然气组成与生物标志化合物等全烃地球化学方法分析,古隆起核部以志留系烃源为主,并有上二叠统龙潭组煤系烃源的混入,斜坡区则以下二叠统碳酸盐岩烃源为主,同时存在上二叠统龙潭组煤系烃源的注入。泸州古隆起嘉陵江组油气藏的形成经历了印支期古隆起核部古油藏的形成与破坏;燕山早中期古隆起核部含油气藏的形成;燕山末期斜坡区干气藏的形成及喜马拉雅期天然气进一步富集、调整4个成藏阶段。嘉陵江组油气成藏的主控因素是泸州古隆起的发展演化控制了嘉陵江组油气藏的分布格局;充足的多期多源油气注入是油气成藏的物质基础;“烃源断层”控制了油气的富集程度;晚期溶蚀孔和扩溶孔发育决定了气藏的储集能力;古隆起核部固体沥青和沥青质提供了油气封堵条件,是油气富集的保障。

Geochemical research of hydrocarbon reservoiring in Lower Triassic Jialingjiang Formation in Luzhou palaeohigh

Luzhou palaeohigh can be divided into 3 parts,including core,slope and periphery.The core of the palaeohigh is dominated by gas reservoirs in the first member of Jialingjiang Formation,the slope on the northern edge is dominated by gas reservoirs in the second member of Jialingjiang Formation,and the slope on the sou-(thern) edge is dominated by multilayered gas reservoirs in the third member of Jialingjiang Formation.The pro-(perties) of gas in Jialingjiang Formation in Luzhou palaeohigh are complex,i.e.there are both the wet gas with condensate oil as that in the core of the palaeohigh and the dry gas without condensate oil as that in the slope zones of the palaeohigh. Based on geochemical analysis of total hydrocarbon by using gas composition and biomarkers,gas in the core of the palaeohigh has mainly been sourced from the Jurassic source rocks with some from the Upper Permian Longtan Fm coal-measure source rocks,while that in the slope zone has mainly been sourced from the Lower Permian carbonate source rocks with some from the Upper Permian Longtan Fm coal-measure source rocks.Oil and gas reservoirs in Jialingjiang Fm in Luzhou palaeohigh have been formed in 4 stages: formation and destruction of fossil oil reservoirs in the core of the palaeohigh during Indo-Chinese epoch;formation of gas reservoirs with some oil in the core of the palaeohigh during Early-Middle Yanshanian epoch;formation of dry gas reservoirs in the slope zone at the end of Yanshanian epoch;and further enrichment and adjustment of gas reservoirs during Himalayan epoch.The evolution of Luzhou palaeohigh controlled the distribution of the oil and gas reservoirs in Jialingjiang Fm;plenty of multistage and multi-source oil and gas charging was the material base of oil and gas reservoiring;"faults connecting the source rocks" controlled the level of oil and gas enrichment;later development and enlargement of dissolution pores determined the reservoiring capabi-(lity) of gas reservoirs;the solid bitumen and asphaltene in the core of the palaeohigh provided the sealing conditions,as well as ensured oil and gas enrichement.