Non-Darcy-Flow Studies in Anisotropie Porous Media

Abstract

Summary The velocity-pressure drop relationship in the near-wellbore region of high capacity gas and condensate reservoirs often deviates from Darcy's law. Furthermore, many naturally occurring porous media are anisotropic and often layered. This study is directed at combining these facts in developing a mechanistic understanding of non-Darcy gas flow in anisotropic porous media. Non-Darcy flow coefficients, permeabilities, and electrical tortuosities are measured in cores with layers both in the parallel and perpendicular directions to flow and in nonlayered, anisotropic cores. The presence of a connate water saturation decreases permeability in all cores but increases the non-Darcy coefficient significantly only in the perpendicular core. Both a macroscopic and a pore-scale network (microscopic) model of anisotropy are proposed. The product of permeability and non-Darcy coefficient is shown to be less anisotropic than either the permeability or the non-Darcy coefficient tensors in both experiments and simulations. In the microscopic model, the non-Darcy term has been found to be tensorial and proportional to the square of the superficial velocity at the macroscopic scale. As the pore-scale anisotropic parameter increases, the non-Darcy coefficient and tortuosity increase, but permeability decreases. Models show order of magnitude agreement with experimental data.