基于启动压力梯度的火山岩气藏多重介质试井模型

火山岩储层发育气孔、粒间孔、溶蚀孔和炸裂缝、构造缝等，基质物性差，渗透率低，束缚水饱和度较高。物理模型实验结果表明气体流动过程中存在启动压力梯度，常规试井模型解释存在较大误差。为此，在物理模型实验的基础上，建立了基于启动压力梯度的火山岩气藏多重介质不稳定试井模型，采用拉普拉斯变换、格林函数等方法对该模型进行求解，推导了无限大边界和圆形边界两种条件下的Laplace空间解析解，获得了试井分析典型图版，并分析了启动压力梯度对典型版图的影响。研究结果表明：启动压力梯度越大，流体流动阻力越大，导致基质孔隙向裂缝的供给能力越弱，使得基质与裂缝发生窜流的时间向后推迟，无因次拟压力及其导数曲线上翘更加明显；如果忽略启动压力梯度的影响，试井解释渗透率、探测范围、弹性储能比等参数值偏小，窜流系数则偏大。

A dual porosity model for transient well tests in volcanic gas reservoirs considering threshold pressure gradient

Stomas,intergranular pores,vugs,cracks,and tectonic fractures are abundant in volcanic gas reservoirs,characterized by inferior property,low permeability,and high constrained water saturation.The experimental results of physical modeling show that there is the threshold pressure gradient(TPG) in the gas flow,showing a large difference from the regular transient well test model.Therefore,on this basis,a dual porosity model for transient well tests in volcanic gas reservoirs is built considering the TPG.First...