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    宣广盆地中二叠世栖霞组层序地层特征及页岩气勘探前景

    Sequence stratigraphic characteristics and shale gas exploration prospect of Middle Permian Qixia Formation in the Xuancheng-Guangde Basin

    • 摘要: 对宣广盆地中二叠世栖霞组进行层序地层学分析,结合栖霞组富有机质页(泥)岩有机地球化学特征,评价页岩气勘探前景。研究表明:区内栖霞组可分为3个三级层序;每个层序划分出海侵体系域、凝缩段和高水位体系域,代表了一次相对较大的海平面升降旋回。富有机质页(泥)岩主要分布于凝缩段、凝缩段与海侵体系域或高水位体系域的转换过渡层段。栖霞组富有机质页(泥)岩厚8~35 m,TOC值0.77%~9.49%,有机质成熟度为1.428%,脆性矿物(石英、长石)相对富集,具有良好的脆性和可压性,页岩气成藏条件良好,特别是栖霞组五段具有巨大的资源潜力。

       

      Abstract: Based on the method of sequence stratigraphy, the stratigraphic sequence of the Middle Permian Qixia Formation in the Xuancheng-Guangde Basin was analyzed. Combined with the organic geochemical characteristics of the organic-rich shale, the shale gas exploration prospect was evaluated. The results show that the Qixia Formation in the Xuancheng-Guangde Basin can be divided into three third-order sequences, which represent three relatively large cycles of sea-level rise and fall. Each sequence can be subdivided into the transgressive systems tract, the condensed section, and the highstand systems tract. The organic-rich shale mainly occurred in the condensed section and transitional sections between the condensed section and transgressive systems tract or highstand systems tract. The thickness of organic-rich shales in Qixia Formation varies from 8 to 35 m. The TOC value ranges from 0.77% to 9.49%, and the maturity of organic matter is about 1.428%. Brittle minerals (quartz, feldspar) of shales are relatively enriched, showing good brittleness and compressibility. Accordingly, shale gas accumulation conditions of Qixia Formation are good, especially for the top limestone section of Qixia Formation, which has great resource potential.

       

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