致密油藏体积压裂水平井不稳定压力分析

水平井结合体积压裂改造成为目前开发致密油藏的关键技术。考虑到致密油藏多尺度渗流(基质、天然裂缝和水力裂缝)及多种流动机理(启动压力梯度和应力敏感)相互耦合的复杂渗流过程,该文建立了综合考虑致密油藏启动压力梯度和应力敏感的体积压裂水平井不稳定压力分析模型。通过Laplace变换和摄动变换等求解得到了拉氏空间中的井底压力,应用Stehfest数值反演绘制了相应的压力动态响应曲线。研究结果表明:压力响应曲线可以划分为6个流动阶段,模型的退化结果与Ozkan模型一致,验证了该文模型的正确性,并在此基础上进行了影响因素分析。该文研究结果可为致密油藏体积压裂水平井的不稳定压力分析提供一定的理论依据。

Pressure transient analysis for volume-fractured horizontal well in tight oil reservoirs

Volume-fractured horizontal well has been proved to be an effective method to develop tight oil reservoirs.Considering the multi-scaled flows (matrix,natural fractures,hydraulic fractures) and complex seepage mechanisms (threshold pressure gradient,stress sensitivity) in tight reservoirs,this paper presents a mathematical model for pressure transient analysis of volume-fractured horizontal well in tight oil reservoirs,in which the effects of threshold pressure gradient and stress sensitivity are both taken into consideration.Laplace transformation and perturbation technique are employed to solve the model and the type curves of pressure response are plotted through Stehfest numerical inversion.The results show that the type curves can be divided into six flow periods.On the basis of model validation,some influential parameters are analyzed.The results summarized in this paper can provide theoretical basis for pressure transient analysis of volume-fractured horizontal well in tight oil reservoirs.