沁水盆地南部煤储层显微裂隙发育的影响因素

为研究沁水盆地南部3号和15号煤储层显微裂隙的发育情况，借助扫描电镜显微裂隙分析、荧光显微镜显微裂隙统计、X射线衍射分析等手段，总结了地应力、煤岩显微组分、煤变质程度、煤中矿物质与显微裂隙发育的关系，探讨了影响煤储层显微裂隙发育主要因素。结果表明，该区煤储层显微裂隙较为发育，显微裂隙密度一般为7~59条/9 cm²，以C型和D型裂隙为主，扫描电镜下常见张性裂隙、剪性裂隙，对煤储层渗透性贡献较大，内生裂隙较少见。显微裂隙通常发育于镜质组中，裂隙密度随变质程度的升高表现出降低的趋势，煤中矿物的充填作用对于显微裂隙的发育影响较大，对煤样渗透性造成了直接破坏作用，地应力场的方向和大小控制着外生显微裂隙的开合程度，进而对煤储层的渗透性产生影响。因此认为，地应力和煤中矿物是影响该区煤储层显微裂隙发育的主要因素。

Study on the influencing factors of the microfracture development in coal reservoir in southern Qinshui basin

The developmental characteristics of microfractures in No.3 and No.15 coal seams in southern Qinshui basin were studied by means of scanning electron microscope, fluorescence microscope, X ray diffraction and so on. The relationship between microfracture and influencing factors including crustal stress, micropetrological unit, metamorphic grade and mineral were summarized. The main factors affecting the development of microfractures in coal reservoir were discussed. The results show that the microfractures in coal reservoir of this area are relatively developed and the density is generally 7~59 strips per 9 cm2. Microfractures of type D and type C dominate. Tensile fractures and shear fractures that make relatively larger contribution to the permeability are common in scanning electron microscope, whereas endogenetic fractures are rare. Microfractures are generally developed in vitrinite component. Microfracture density decreases with the increase of metamorphic grade. The mineral filling effect in coal has great influence on the development of microfracture and destroys the permeability of coal directly. The magnitude and direction of crustal stress field control the opening degree of exogenous microfracture and then affect coal permeability. Therefore, crustal stress and mineral in coal are the main factors that influence the development of microfractures in coal reservoir of this area.