A method for predicting the on-set of sand production or critical drawdown
pressure (CDP) in high flow rate gas wells. The method describes the
perforation and open-hole cavity stability incorporating both rock and
fluid mechanics fundamentals. The pore pressure gradient is calculated
using the non-Darcy gas flow equation and coupled with the stress-state
for a perfectly Mohr-Coulomb material. Sand production is assumed to
initiate when the drawdown pressure condition induces tensile stresses
across the cavity face. Both spherical and cylindrical models are
presented. The spherical model is suitable for cased and perforated
applications while the cylindrical model is used for a horizontal
open-hole completion.