Transport in Porous Media, Vol.110, No.1, 127-140, 2015
Importance of Gas Acceleration Near the Wellbore in Radial Compressible Porous Media Flows for a Vertical Gas Well
The importance of gas acceleration near a wellbore in radial compressible porous media flows is quantified in terms of a dimensionless parameter, and conditions are identified under which gas acceleration is mainly responsible for the change in the pore pressure distribution and mass flux. Gas acceleration and Forchheimer drag both steepen the pressure profile and have significant impact on the pressure curve near the wellbore for a given wellbore pressure. For unchoked flows, the properties of a compressible accelerating gas flow can be modeled by a Darcy-Forchheimer flow with an upward adjusted Forchheimer drag coefficient. For choked flows, the Darcy-Forchheimer equation cannot be used to mimic the accelerating flow no matter how large the Forchheimer drag coefficient is. It is demonstrated that the value of the Forchheimer drag coefficient in some previous studies was inflated due to omission of the gas acceleration in the momentum equation.
Keywords:Compressible flow;Gas acceleration;Near a wellbore;Forchheimer drag coefficient;Choked flow