鄂西地区震旦系—寒武系页岩气成藏模式

Accumulation model of the Sinian-Cambrian shale gas in western Hubei Province,China

通过对鄂西震旦系陡山沱组和寒武系牛蹄塘组页岩气勘查大量实际资料总结研究,创新性地提出了针对鄂西地区震旦系和寒武系"岩相控炭、成岩控烃、构造控藏"的页岩气成藏理论认识。震旦系陡山沱组和寒武系牛蹄塘组富有机质页岩沉积受控于鄂西裂陷海槽,富有机质页岩甜点层段主要形成于海侵体系域和早期高水位体系域。黄陵古隆起周缘震旦纪—三叠纪长期浅埋,为生油提供了充足时间,三叠纪短暂快速深埋,为页岩气生成的主峰期。古隆起刚性基底、区域性泥页岩盖层以及后期逆冲推覆构造,为页岩气保存提供了良好的条件。从而建立了鄂西震旦—寒武系"深水海槽控炭、古隆起浅埋控烃、古隆起+逆冲断裂控藏"的页岩气成藏模式。

Based on the study of a large number of real data of shale gas exploration in the Sinian Doushantuo Formation and the Cambrian Niutitang Formation in western Hubei Province,the theoretical understanding of shale gas accumulation in the Sinian and Cambrian that lithofacies controls carbon,diagenesis controls hydrocarbon and structure controls reservoir is put forward innovatively.The deposition of organic-rich shales in the Sinian Doushantuo Formation and the Cambrian Niutitang Formation were controlled by the rift trough in western Hubei.Sweet spots of organic-rich shales were mainly formed in the transgressive system tract and the early high water-level system tract.The long-term shallow burial in the Sinian and Triassic around the Huangling paleo-uplift provided sufficient time for the oil generation.The Triassic is a short-term and rapid burial period,which is the main peak period of shale gas generation.The rigid basement of paleo-uplift,regional shale cap rock and later thrust nappe structure provided good conditions for the shale gas preservation.Thus,the shale gas accumulation model of the Sinian and Cambrian in western Hubei Province is established,which includes carbon control by deep-water trough,hydrocarbon control by shallow burial of paleo-uplift,reservoir control by paleo-uplift and thrust fault.