江汉平原白垩-下第三系泥岩盖层影响因素

江汉平原南部中、古生界地层具有多旋回残余改造盆地的特征,油气成藏表现为"多期多源成烃、晚期次生成藏",而对晚期成藏整体封闭保存具有关键性作用的因素是白垩系-下第三系盖层封闭能力和对油气保存的有效性。利用常规测试方法、气体吸附法与压汞法,对白垩系-下第三系泥岩盖层的孔隙度、渗透率、粘土矿物及微孔隙结构特征进行分析,指出沉积环境和成岩作用是泥岩盖层封闭性的主要影响因素,埋藏深度1400m为本区盖层封烃门限深度,预测了白垩系-下第三系泥岩盖层有利分布区,结合中、古生界烃源岩演化和构造演化评价,论述了盖层对油气保存的有效性。

Affecting factors of Cretaceous-Paleogene shale cap in Jianghan Plain

Mesozoic-Palaeozoic strata of Southern Jianghan Plain represents a residual basin characteristics developed frommulti-cycle transformation. Hydrocarbon generated from multi-periodical, multi-source rocks and accumulates in late period secondarily. The key factors for sealing and preservation of the hydrocarbon are the sealing ability and effectiveness of the Cretaceous-Paleogene system shale cap. Analyzing on porosity, permeability, clay mineral content and micropore texture of Cretaceous-Paleogene shale cap have been conducted by using conventional tests method,gas adsorption method and mercury intrusion method, which indicates that the sedimentary environment and diagenesis are key factors influencing the sealing property of the shale cap, with a threshold sealing depth about 1400m in the studying region, and the favorable distributive province of Cretaceous-Paleogene shale cap is forecasted. By combining with the evolution of hydrocarbon source rocks of Mesozoic-Palaeozoic and the appraisal of tectonic evolution, the effectiveness of the shale cap for hydrocarbon preservation is here discussed.