余吾矿煤/岩层组合类型划分及压裂措施

    Classification of coal/rock formation combination types and fracturing measures in Yuwu Mine

    • 摘要: 为了划分煤/岩层水力压裂组合类型,以潞安矿区余吾矿3#煤层为研究对象,通过测井解释及力学测试得出顶板岩性及力学特征;采用取心井与测井相结合识别出煤层段的煤体结构;根据水力压裂计算地应力方法结合密度测井得出了地应力状态;由此划分出水力压裂煤/岩层组合类型,并提出了不同组合类型下的水力压裂措施建议。结果表明:研究区水力压裂煤/岩层组合类型可以划分为硬岩硬煤、软岩硬煤、硬岩软煤、软岩软煤组合的过渡型和拉张型等7种类型;硬岩硬煤组合类型时,采用大排量、多液量、低/中砂比、逐级加砂方式能营造出较长裂缝并能有效支撑;软岩硬煤组合时,应避射部分煤层,防止水力压裂裂缝进入煤层与软岩交界面,影响压裂效果;硬岩软煤拉张组合时,建议采用顶板水力压裂;进行硬岩软煤过渡型水力压裂时,根据水平应力与垂直应力的差值优化压裂参数;软岩软煤组合时,不建议采用水力压裂方式进行改造。

       

      Abstract: In order to classify the types of hydraulically fractured coal and rock seam combinations, the No.3 coal seam in Yuwu wellfield of Lu’an Mining area are taken as the research object in this paper, and the lithology and mechanical characteristics of the roof was obtained by logging interpretation and mechanical testing. The coal structure of coal seam section is identified by the combination of core well and logging. The stress state was obtained according to the method of calculated stress of hydraulic fracturing stress and density logging. On this basis, types of hydraulically fractured coal and rock seam combinations were classified, and the hydraulic fracturing measures for different combination types are proposed. The results show that the types of hydraulically fractured coal and rock combinations in the study area can be classified into seven types: hard rock and hard coal, soft rock and hard coal, hard rock and soft coal, soft rock and soft coal combination of transitional type and tensile type. When hard rock and hard coal was combined, long fractures and effectively supported fractures can be created by adopting large displacement, multiple fluid volume, low or medium sand ratio and step by step sand addition. When soft rock and hard coal was combined, avoid shooting part of the coal seam to prevent fracturing fluid entering the interface between coal seams and soft rocks, which can ensure the fracturing effect. Roof hydraulic fracturing is recommended for the stretching combination of hard rock and soft coal. In the transitional hydraulic fracturing of hard rock and soft coal, the fracturing parameters are optimized according to the difference between horizontal stress and vertical stress. When soft rock and soft coal are combined, hydraulic fracturing is not recommended for reconstruction.

       

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