利用稳定状态依次替换法,研究了页岩基质储集层内压力扰动的传播规律,得到动边界随时间变化的关系,考虑解吸、扩散、滑移作用及动边界的影响,建立了页岩气不稳定渗流数学模型。采用拉普拉斯变换,求解了内边界定产、外边界为动边界条件下的不稳定渗流压力特征方程。结合中国南方某海相页岩气藏储集层参数,应用MATLAB编程,计算分析了页岩气不稳定渗流压力特征及其影响因素。研究表明：页岩气开采过程中,压力传播具有动边界效应,动边界随时间延续向外传播,且传播速度逐渐减慢;动边界使压力传播速度变慢,储集层压力下降减缓;页岩气解吸使压力传播速度减慢,地层压力下降减缓;扩散系数越大,地层压力下降越慢,且扩散系数影响逐渐减小。在气藏开采过程中,扩散、滑移对产气量贡献逐渐增加,占主要地位;渗流及解吸对产气量贡献逐渐减小后趋于平稳。图9参18
Pressure disturbance propagation was investigated using the steady state replacement method, the relationship between moving boundary and time was obtained. An unstable seepage model in shale gas reservoirs was established considering the effects of desorption, diffusion, slip and moving boundary. Using Laplace transform, the pressure characteristics equation was solved for the condition of internal boundary being constant production and outer boundary being the moving boundary. Subsequently, combining the parameters of shale gas in southern China, unstable seepage pressure characteristics and its influence factors of shale gas reservoir were analyzed using MATLAB software. The results indicate that the pressure propagation is characterized by moving boundary effect during shale gas exploitation, which means that moving boundary is propagated outwards with the propagation velocity decreasing gradually. Under the effect of moving boundary or shale gas desorption, the pressure propagation velocity decreases and the reservoir pressure drop slows down. With the increasing of the diffusion coefficient, the reservoir pressure drop slows down and the effect of diffusion coefficient decreases gradually. In the process of gas reservoir exploitation, diffusion and slip contribute more and more to gas production, acting as the dominant factors, while the contribution of flow and desorption level off after decreasing.
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