黔西地区煤层埋深与地应力对其渗透性控制机制

基于黔西六盘水煤田和织纳煤田16口井36层次的试井资料, 采用地质统计分析等方法, 探讨了黔西地区煤储层渗透性的展布规律与地应力特征, 论证了煤层埋深与地应力对其渗透性的控制机制.研究表明, 研究区煤储层以特低渗-低渗透率储层(＜0.1×10-9m2)为主, 中渗透率储层(0.1×10-9~1.0×10-9m2)也占有相当大比例; 应力场类型在浅部表现为大地动力场型, 一定深度可能转化为准静水压力状态.煤储层渗透率及其埋深的负幂指数关系较为离散, 但在不同深度渗透率转折点与地应力场类型转变一致; 单井煤储层试井渗透率差异较大, 随地应力增大和埋深增加而降低, 平面展布受地应力强度控制由SW-NE具"低-高-低"发育规律.埋深对渗透率的控制实质是地应力的控制, 区域构造位置及其所处高应力场作用下的煤体形变与破碎致使孔裂隙压缩或闭合是该区渗透性差异的主要控制机制. 

Control Mecganism of Buried Deptg and In-Situ Stress for Coal Reservoir Permeability in Western Guizgou

Based on geological analysis of data of 16 testing wells in the Liupanshui and Zhina coalfields, the spatial distribution of coal reservoir permeability and characteristics of in-situ stress in the western Guizhou are discussed, and the control mechanism of buried depth and in-situ stress for coal reservoir permeability is obtained in this study. It is shown that the coal reservoirs have the characteristic of ultra-low and low permeability (< 0.1×10-9m2), and the permeability of coal reservoir with 0.1×10-9-1.0×10-9m2 has considerably large proportion. The type of in-situ stress field is gradually undergoing a possible change from dynamic field in shallow layer to hydrostatic pressure field in deep layer. It has a negative power exponent relationship of coal reservoir permeability and buried depth, but the change of permeability is in accordance with in-situ stress field changed. The permeability of coal reservoir varies in different testing wells, decreasing with the increased in-situ stress and depth, and its spatial distribution has a law of "low-high-low" from SW to NE for the intensity of the stress controlled. The role of coal depth to permeability is supposed to be the in-situ stress in action essentially. The main control mechanism of coal permeability difference is that the pore and fracture tend to compress or close caused by the deformation and fragmentation of coal reservoirs under the influence of high in-situ stress in regional tectonic location of study area.