Abstract:

Basing on the empirical equation of pressure stress-sensitive effect and the basic theory of fluid flowing mechanics in porous medium,a mathematical model for well testing analysis in homogeneous gas reservoirs is established with considerations of permeability sensitivity to stress,effect of wellbore storage,and skin effect.The perturbation technique and Laplace transform method are employed in the calculation of the model to study the features of percolation in stress-sensitive gas reservoirs and the influence of different stress sensitivities on bottom hole pressure behaviors during well opening and shut-in.The results show that along with the stress sensitivity of permeability increases,derivative curve may upturning higher during drawdown test,while the derivative curve may drop down during pressure build-up test.If the damage to permeability caused by stress sensitivity during drawdown/build-up test is irreversible,the permeability can not be fully recovered through pressure boosting and the degree of pressure buildup is still lower.

Key words: perturbation method, Laplace transform, percolation feature, pressure derivative, stress sensitivity, well test model