there is dynamic force equilibrium within the system equation of motion the inclusion of inertia by way of the force equilibrium condition in the process is thus an improvement over the conventional methods of evaluating porous formations e g as disclosed in u s pat nos 4 328 705 and 4 779 200 in which inertia is ignored an element of the process in accordance with the invention is the application of mathematical expressions for inertial flow in porous formations these expressions include the governing differential equations for flow in a porous formation and a new boundary condition at the junction between a well and a porous formation the preferred embodiment of the invention uses these expressions to couple flow in a formation to oscillatory flow in a formation these novel features are explained as follows a completely saturated elastic porous medium is modeled in the well 50 by a cylinder 52 of radius r and constant thickness b fig4 it is assumed that the porous medium 52 is homogeneous isotropic and confined between two impermeable beds not shown under these conditions flow of a homogeneous compressible liquid away from the well is governed by the following partial differential equations equ3 where f is the radial distance from the center of the well 50 t is time g is the acceleration due to gravity u03c6 is.