“三软”煤层注水压裂增透机理及瓦斯抽采施工参数确定

Mechanism of Water-fracturing-induced Permeability Increment of “Three-Soft” Coal Seam and Construction Parameters Determination

针对豫西＂三软＂煤矿区瓦斯低渗难抽问题的特殊性,探讨了主采二1煤层生、储气层的变形特征。以ABAQUS软件为平台,依托告成煤矿建立了滑动构造带三维非线性流—固耦合水力压裂模型。应用多参数耦合模拟方法,探讨了定向注水压裂过程中目标层的流变—损伤—渗流耦合行为;同时利用T—P损伤演化准则的Cohesive单元,模拟了目标层裂隙的起裂和扩展过程。此外,探讨了煤岩体对动力荷载的响应机制和动态条件下的压裂效果。研究结果表明,定向注水新工艺条件下,当注水压力为4.5MPa,注水时间在2h左右时,水力压裂在顺层软煤中的影响半径基本可以达到80~100m这一理想数据,从而大幅度地改善了＂三软＂煤层低渗性能。实践证明,采用正确的施工方法和技术参数优化组合,可以有效提高煤层的透气性和瓦斯抽采效果,对复杂矿区瓦斯综合利用具有重要借鉴意义。

In view of the low permeability and difficult extraction of gas in ＂three soft＂ coal seam in western Henan,China,this paper studied the deformation characteristics of gas generation and storage layers in Ⅲ coal seam. Based on ABAQUS platform and Gaocheng coal mine, a three-dimensional nonlinear fluid-solid coupling hydraulic fracturing model was established. Then,the rheology-damage-seepage coupling behavior of target layer was described by multi-parameter coupling simulation method, and the initiation and propagation of crack was simulated by cohesive element of T-P damage evolution criterion. In addition, the response mechanism of rock mass against dynamic load and the fracturing effect under dynamic condition were discussed. The results show that when the injection pressure is 4.5MPa,and injection time in about 2 hours, the influence radius of hydraulic fracturing in bedding coal seam can basically reach an ideal data of 80-100m and it greatly improves the low permeability of ＂three soft＂ coal seam. Practice also proves that correct construction method and optimal combination of technical parameters can effectively improve the permeability and gas extraction of coal seam, which has important significance to comprehensive utilization of gas in complex mining area.