页岩气藏压裂井产能评价及分析

页岩气储存在自生自储的纳米级孔隙中，压裂成为页岩气开发的重要技术。在考虑了多尺度非达西渗流机理的基础上，建立了多种流态多尺度渗流模型，求出考虑有限裂缝流动的页岩气藏压裂井稳态产能方程，在该模型中充分考虑了孔隙尺寸对Knudsen扩散系数的影响，并探索了滑脱现象、Knudsen扩散系数D_K、渗透率K、裂缝半长L_f、裂缝穿透比L_f/R_e与裂缝流动能力K_f·W_f对压裂井产能的影响规律。研究结果表明，渗透率修正因子ξ对产能的影响较大，以多尺度渗流模型确定的页岩气压裂井产能与实际生产数据非常稳合。当井底流压<15 MPa时，滑脱效应对压裂井产能的影响开始增强，并且随着滑脱因子增加，压裂井的产能随之增加；岩芯渗透率越低，Knudsen扩散系数D_K和滑脱效应对产能影响越大。

Productivity Evaluation of Fractured Wells in Shale Gas Reservoirs

Shale reservoir has nano-pores structure with self-generation and self-storage, so fracturing has become an important technology for shale gas exploitation. Based on the multi-scale non Darcy flow model, a multi-scale flow model is established to simulate various flow states including continuous flow, transition flow, slippage flow and free molecular flow. The steady-state production equation of fractured well with finite conductivity fracture is obtained. In this model, the influence of pore size on Knudsen coefficient is fully considered. The IPR curve of fractured well is obtained, and the effects of fracture half length, Knudsen diffusion coefficient, shale permeability, slippage factor, fracture penetration ratio and fracture conductivity on the production of fractured well are explored. The results show that the permeability correction coefficient has a great influence on productivity, and the productivity of fracturing well determined by multi-scale seepage model is very consistent with the actual production data. When the flow pressure in the bottom hole is less than 15 MPa, the slippage effect on production begins to increase in the fracturing well, and with the increase of slippage factor, the fracturing well production increases. The lower the permeability of shale gas reservoir, the greater Knudsen diffusion coefficient D_K and slippage effect on production.