| 摘要: |
| 从各向同性线弹fe材料应力应变关系出发，考虑气体解吸引起的基质收缩效应和孔隙压力对储层应力的影 响，建立了包含基质压缩系数、裂隙体积压缩系数和流体压力项的渗透率动态变化方程，分析了储层力学参数对渗 透率变化的影响。结果表明:排水降压初期，有效应力处于主导地位，裂隙发生压缩变形，渗透率降低;气体解吸后 基质收缩占主导地位,裂隙张开幅度增大,渗透率升高;弹性模量、泊松比越大,基质变形程度越大，渗透率呈先降低 后升高的回归趋势越明显，弹性模量较泊松比对回归趋势的影响更大;当孔隙压力较高时，低孔低渗煤层渗透率随 孔隙压力降低变化的幅度不大;裂隙体积压缩系数变化的起始压力点可以根据不同起变压力下渗透率与储层压力 的关系确定。 |
| 关键词: 煤层气藏 渗透率 应力 |
| DOI： |
| 分类号: |
| 基金项目:教育部创新团队项目(IRT0411) |
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| Effects of coal bed stress on fracture permeability |
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ZHANG Jian, WANG Zhi-ming
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(Faculty of Petroleum Engineering in China University of Petroleum, Beijing 102249，China)
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| Abstract: |
| Based on the relationship of stress and strain for isotropic linear elastic material, a permeability model including matrix compressibility coefficient，crack coefficient of bulk compressibility and fluid pressure was established, in which shrinkage caused by desorption and effect of pore pressure on stress were concerned. The influences of mechanical parameters on permeability were analyzed. The results show that the permeability decreases as a result of cracks compression caused by effective stress as the pore pressure decreasing. As a result of matrix shrinkage caused by desorption, the crack width was expanded and the permeability increases. The reversion trend of permeability is much more obvious with elastic modulus and Poisson's ratio increasing, which lead to greater deformation. The elastic modulus has a greater influence on the trend than Poisson^ ratio. When the pore pressure is relatively high, the change of permeability is not great for low-porosity and low-permeability formation with pore pressure decreasing. According to the relationship of permeability and pressure with different given pressures, the start point pressure of coefficient of crack bulk compressibility changing can be determined. |
| Key words: coal bed gas reservoir permeability stress |
