Abstract

The non-Darcy flow called various term such as turbulent flow or inertial flow, etc. is often occurred through reservoir formation in near well region during injection or production. An occurrence criterion and characterization for predicting non-Darcy flow is needed because of the impact as a critical factor in reducing well productivity and reserve recovery. The Forchheimer equation which describes the fluid flow considering an inertial effect can be adopted for analyzing the non-Darcy flow. Especially, the non-Darcy coefficient in the equation represents the inertial resistance in porous medium and is an empirical value depending on the pore geometry and fluid properties. In this study, as part of the research on CO2 geological storage, we conducted non-Darcy flow tests with a high flow rate and examined the non-Darcy coefficient by using supercritical CO2 and various sandstones that have different properties like pore diameter and permeability. Variation of the coefficient depending on the properties of the supercritical CO2 was also assessed by a series of non-Darcy tests under different pore pressure. It was identified that the coefficient could be different depending on the properties of the supercritical CO2 and sandstones. As the permeability of sandstone was higher, the non-Darcy coefficient decreased nonlinearly and converged on a value within a specific range. Also, the results would indicate that the coefficient have the lower value with decreasing the ratio of density to viscosity of supercritical CO2.

1.
Introduction

Accurate prediction of fluid flow behavior in porous media is an important issue for successful design and operation in petroleum and reservoir engineering. In general cases in the injection or recovery process, the Darcy's law describes fluid flow behavior in porous media. Darcy's Law is a constitutive model that is valid under limited range of low velocities and describes laminar flow in a linearly proportional relation between pressure gradient and flow velocity (Zeng and Grigg, 2006; Ye et al., 2014; Balhoff and Wheeler, 2016). However, deviations from linear Darcy's flow called various term such as non-Darcy flow, high velocity flow or inertial flow, etc. are often occurred through reservoir formation in near well region during injection or production. An occurrence criterion and characterization for predicting non-Darcy flow is needed because of the impact as a critical factor in reducing well productivity and reserve recovery (Huang and Ayoub, 2008). It is generally agreed that the influence of the inertia effect on nonlinearity between the pressure gradient and the flow velocity is greater than the turbulence in porous media (Bear, 1972; Geertsma, 1974; Ruth and Ma, 1993).

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