裂缝宽度对页岩气开发的影响研究

Fracture width effect on shale gas development based on DFM

长水平井体积压裂作为页岩气藏开发的主要技术手段,裂缝网络的有效性影响着开发效果。文中基于离散裂缝模型(DFM),综合考虑页岩气藏多尺度渗流机理,利用有限元分析方法进行数值求解,通过典型模型研究裂缝宽度对近井地带压力分布和生产井动态响应特征的影响。结果表明:对于特定页岩气藏,压裂裂缝宽度和天然裂缝宽度只有满足一定条件才能高效开发,当压裂裂缝超过一定限度时,由于裂缝的高导流能力使得压力波迅速传播到边界,不利于赋存在微纳尺度孔隙中页岩气的渗流,从而降低了页岩气的开发效果;在控制压力波传播到边界时间的同时,适当改善天然裂缝宽度,可以有效增加基质-裂缝接触面积,提高页岩气产量。针对不同页岩气藏天然裂缝实际发育状况和地质特征,利用数值模拟结果可以指导压裂施工,实现页岩气藏的高效开发。

Being the major production means of shale gas by segmented multi-cluster fractured horizontal well, the fracture network effect directly decides whether the shale gas can be efficiently developed. In this paper, based on the discrete fracture network（DFN） model, the shale gas multi-scale percolation mechanism and the nonlinear equation by finite element analysis, the fracture width effect on the pressure distribution and the dynamic response characteristics of the production well is studied. Results show that only fracturing fracture width and natural fracture width meet certain conditions, the specific shale gas reservoir can be effectively developed; if fracturing fracture width exceed certain limit, fracture high flow conductivity will make the pressure wave spread to the border fast, which is bad for the shale gas in matrix system to flow, thereby reduce the shale gas development effect;controlling the time of pressure wave propagation to the boundaries, improving the natural fracture width appropriately and increasing the matrix-fracture contact area can enhance the shale gas production. According to the natural fracture growing conditions and actual geological features, the numerical simulation results can be used to guide fracturing construction to develop shale gas reservoirs effectively.