基于光学显微观测的煤层裂隙发育特征、成因及其意义——以沁水盆地南部3~#煤层为例

Development characteristics, origins and significance of coal seam fractures under optical microscope： taking coal seam 3~# in southern Qinshui Basin as an example

基于光学显微观测,分析了沁水盆地南部3#煤层煤岩显微组分与内生裂隙的关系,并对外生裂隙的继承改造进行分类研究。结果表明:内生裂隙成因主要体现在显微组分的力学强度和煤化作用过程中的内张力,均质镜质体由于结构和成分均一,微孔隙发育,显微脆度高,内生裂隙最为发育;根据继承改造的方向差异,将外生裂隙继承改造类型划分为延伸型、剪切型和拓张型,外生裂隙中,张裂隙和剪裂隙发育规模大,裂隙网络发育,对储层渗透率贡献大。裂隙发育特征、类型及其成因研究,有助于认识煤储层裂隙在煤层气富集成藏和勘探开发中的作用。

Based on the optical microscope observation, correlation between macerals of 3#coal seam in southern Qinshui Basin and its endogenic fractures is analyzed. Classification on inheritance and transformation of exogenetic fractures is also studied. The result shows that the cause of endogenic fractures is manifested by the mechanical strength of maceral and internal tension during coalification. Endogenic fractures are mostly developed in telocollinite because of its homogeneous structure and composition,developed micropores and high microscopic brittleness. Types of exogenetic fractures are classified into three types： extension pattern, shearing pattern and expansion pattern according to their direction difference. Separation fractures and shear fractures have great contribution to the reservoir permeability for their large development scale and developed fracture network. The research on characteristics and origin of coal reservoir fractures can help us to recognize the significance of fractures to coalbed methane accumulation and exploration.