考虑吸附效应的非达西流压裂水平井试井分析

页岩气藏渗透率较低,流动过程中存在边界层影响和吸附解吸现象。在建立页岩气藏压裂水平井试井模型过程中,非压裂区域考虑为存在吸附效应的非达西流动,压裂区域考虑为双重孔隙介质达西流动,水力压裂裂缝区为达西流动。基于油气渗流理论和数学物理方法,建立了考虑吸附效应的非达西流压裂水平井试井模型,求解得到了考虑井筒存储和表皮效应的压裂水平井井底压力响应,并进行了压力响应参数敏感性分析。结果表明:启动压力梯度主要影响特征曲线后期上翘程度;窜流系数主要影响"凹槽"的位置,当同时考虑启动压力梯度和吸附解吸时,窜流系数还影响着解吸时间的长短;解吸系数主要反映解吸扩散程度,随着压力降低,页岩气解吸效果越明显,特征曲线中的"凹槽"宽度和下凹程度越大。研究对于页岩气藏压裂水平井的开发与动态监测具有一定的指导意义。

Well Test Analysis of Fractured Horizontal Well Considering Non-Darcy Flow and Adsorption Effect

The permeability of shale gas reservoir is low. Therefore, the effect of boundary layer and absorption-desorption occurs in the fluid flow process. To create the well test model of fractured horizontal well in shale gas reservoir, it is assumed that the flow in non-fractured area is non-Darcy flow considering absorption effect, the flow in fractured area is considered as Darcy flow of dual-porosity reservoir, and the flow in hydraulic fracture obeys Darcy flow. Based on the oil and gas seepage theory and method of mathematical physics, we get the well test model of fractured horizontal well considering non-Darcy flow and adsorption effect. By solving the model, the bottom-hole pressure of fractured horizontal well considering wellbore storage and skin effect is obtained. Sensitivity analysis of the pressure response was analyzed. The results show that the threshold pressure gradient affects mainly the upward degree of the typical curve in late stage. The inter-porosity flow coefficient has an effect on the location of the groove. When the threshold pressure gradient and desorption coefficient is considered at the same time, inter-porosity flow coefficient also influence the time of desorption. The desorption coefficient mainly reflect the degree of desorption and diffusion. The effect of desorption becomes more obvious and the concave degree of the curve becomes larger as the pressure decreases. It can provide guidance to the development and dynamic monitoring of fractured horizontal well in shale gas reservoir.