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    黔南地区下寒武统牛蹄塘组页岩气顶底板特征研究

    Effects of bottom and top layers of Niutitang Formation on preservation of shale gas in southern Guizhou

    • 摘要: 下寒武统牛蹄塘组顶底板条件是评价区域页岩气保存条件的重要因素之一。本研究在对黔南地区地表剖面和钻井资料分析的基础上,将该区域牛蹄塘组底板按岩性分为溶孔白云岩区、硅质岩-白云岩混合区和硅质岩区三个岩性组合类型区。硅质岩区具有超低孔、超低渗、高突破压力的特征,对页岩气的封存效果好,底板条件好;硅质岩-白云岩混合区由于白云岩具有溶蚀孔洞且低突破压力的特征,对上部页岩气封堵效果较差,底板条件较差;溶孔白云岩之上存在的暴露不整合面是页岩气散失重要通道,底板条件差。顶板按岩性分为泥岩区和灰岩区,其中泥岩区具有低孔、低渗、高突破压力的特征,顶板条件好,灰岩区次之。以底板为主控因素,综合顶板条件,综合研究结果认为岑巩-三都以东地区顶底板条件好,瓮安-福泉以西顶底板条件较差。黔南地区经历多期次构造运动,泥岩、硅质岩、灰岩在构造抬升改造后易产生裂缝,使得其对页岩气封盖能力变差,提出瓮安-福泉以东构造稳定区是牛蹄塘组页岩气顶底板条件较有利区。

       

      Abstract: Lithology of the bottom and top layers of the Lower Cambrian Niutitang Formation plays an important role in evaluating the preservation conditions of shale gas in southern Guizhou. Based on outcrops and drilling data of the bottom layers of the Niutitang Formation, the studied area can be divided into the dolomitic rock zones, the mixed siliceous-dolomitic rock zones and the siliceous rock zones. Due to its ultra-low porosity, ultra-low permeability and high breakthrough pressure, siliceous rock is the best bottom layers for the preservation of shale gas. According to outcrops and drilling data of the top layers of the Niutitang Formation, the studied area can be divided into mudstone zones and limestone zones. The mudstone zones with low porosity, low permeability and high breakthrough pressure, so they are better than the limestone zones in the preservation of shale gas. Eastern Cengong-Sandu region is the most favorable area for exploring shale gas because of its siliceous rock bottom layers and mudstone top layers.

       

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