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    鄂西黄陵隆起东缘鄂宜页2井五峰组—龙马溪组页岩气储层特征与含气性

    Reservoir characteristics and gas-bearing capacity of the Wufeng-Longmaxi Formation in the Well Eyy2, east Huangling Uplift, western Hubei Province

    • 摘要: 鄂西地区五峰组-龙马溪组已成为中国南方页岩气勘探的热点领域。为深化该区页岩储层及含气性特征认识,本文以鄂宜页2井钻井及测试分析资料为基础,以笔石带为标尺,对五峰组-龙马溪组下部黑色富有机质页岩的岩石学特征、有机地化特征、储集空间类型及结构特征进行深入研究,分析总结了页岩储层含气性特征及影响因素,并对页岩储层开展了综合评价。结果表明:鄂宜页2井五峰组-龙马溪组下部黑色岩系缺失LM5-LM6笔石带,富有机质页岩上延至LM7笔石带,总厚度约16 m;岩性以硅质页岩夹少量硅质岩、混合质页岩和黏土质页岩为主,有机质类型为Ⅰ-Ⅱ1型,Ro为1.88%~2.03%,显示黑色页岩已过大量生气阶段;页岩储集空间主要为小于100 nm的有机质纳米孔、直径大于5 μm的微米孔和构造微裂缝,其中纳米孔占比超过50%,孔隙容积、比表面积与有机碳含量存在显著正相关性;现场解析总含气量为0.068~3.33 m3/t,平均1.13 m3/t,高含气量段集中于凯迪阶WF2-WF3与鲁丹阶LM2-LM4,含气量与TOC、脆性矿物含量之间具有明显的正相关性;根据TOC、含气性、脆性矿物含量以及页岩沉积环境等参数进行综合评价,Ⅰ类储层主要对应于凯迪阶WF2-WF3笔石带以及鲁丹阶LM2-LM4笔石带以深水环境下形成的硅质页岩和硅质岩层段,总厚度约9 m,是该区五峰-龙马溪组水平钻井的最佳甜点段。

       

      Abstract: The organic-rich shale of the Wufeng-Longmaxi Formation in the western Hubei Province has become a hotspot for the shale-gas exploration in South China. In order to deepen the understanding of reservoir characteristics and gas-bearing capacity, the lithological and geochemical characteristics, types and features of reservoir space, and gas-bearing capacity were detailedly studied on the basis of the drilling and testing data of the Well Eyy2, as well as the affecting factors of shale gas and evaluation of shale reservoir. The results show that the organic-rich shale extending to LM7 graptolite zone in the Well Eyy2 is about 16m in thickness and the LM5-LM6 graptolite zone is missing, which is mainly composed of siliceous shale interbedded with silicastone, mixed shale and clay shale. Organic type is type Ⅰ and Ⅱ1, with Ro value ranging from 1.88% to 2.03% indicating that the shale is under massive gas generating stage. The main reservoir space consist of organic nanopores with diameter less than 100 nm, micropores with diameter exceed 5um and tectonic microfracture, of which the volume ratio of nanopore is more than 50%. Pore volume and specific area has closely positive relationship with total organic content (TOC). The on-site measured core gas content ranges from 0.068 to 3.33 m3/t with average of 1.13 m3/t, and the graptolite zone WF2-WF3 in the Katian and LM2-LM4 in the Rhuddanian has highest gas content. Gas content has obviously positive correlation with TOC and brittle mineral content. According to the TOC, gas content, brittle mineral content, shale sedimentary environment and other parameters, the favorable reservoir (typeⅠ) with about 9 m in thickness mainly corresponds to siliceous shale interbedded with silicastone of the graptolite zone WF2-WF3 in the Katian and LM2-LM4 in the Rhuddanian formed in the deep-water sedimentary environment, which is the best "sweet spot" for the horizontal drilling in the shale gas exploration in the Wufeng-Longmaxi Formation.

       

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