构造煤裂隙及渗流孔隙分形特征研究

    Study on Fracture and Seepage Pore Fractal Characteristics of Tectonic Coal

    • 摘要: 构造煤的孔裂隙系统对煤层气吸附、运移以及瓦斯突出均具有控制作用,选取淮北朱仙庄矿12块不同变形类型构造煤进行显微镜观测和压汞测试,并利用分形方法对样品裂隙系统、渗流孔孔隙系统及二者的关联性进行研究,结果表明:样品显微裂隙信息维数分布于1.2~1.9,孔隙分形维数分布于2.6~3.0;随着煤体变形程度增强,显微裂隙分形维数Dl线性增大,渗流孔隙分形维数Dk在脆性变形阶段变化不大,脆-韧性和韧性变形阶段呈线性减小。Dl增大,样品渗流孔孔容和比表面积呈指数增大,平均渗流孔孔隙直径减小,渗流孔发育程度提高,渗透性增强。孔隙分形维数随裂隙分形维数增大呈抛物线形式减小,以Dl=1.6为界,可根据Dl值将变形环境分为小于1.6的脆性变形环境以及大于1.6的脆-韧性/韧性变形环境。

       

      Abstract: The pore-fracture system of tectonic coal has control function on coalbed methane adsorption, migration and gas outburst. Based on microscopy and mercury testing of 12 different types of tectonic coal from Zhuxianzhuang Coal Mine in Huaibei Coalfield, pore system and fracture system and the relevance of both were studied by fractal method. Results showed that micro fracture information dimension of samples in study area distributed from 1.2 to 1.9, fractal dimension of pore system distributed from 2.6 to 3.0; with the increase of coal deformation degree, micro fractures fractal dimension Dl increases linearly, seepage pore fractal dimension Dk has little change in the brittle deformation stage and decreases linearly in brittle-ductile and ductile deformation stage. When Dl increases, pore volume and specific surface area increased exponentially, and average pore diameter of seepage pore reduced; seepage holes develop rapidly, and permeability increases. With the increasing of fractured fractal dimension, pore fractal dimension decreases in parabolic form; taking Dl=1.6 as the boundary point, deformation environment can be divided into brittle deformation environment (Dl<1.6) and brittle-ductile/ductile deformation environment (Dl>1.6) according to microscopic fractal dimension.

       

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