Sand-production prediction in high-rate perforated and openhole gas wells

An analytical model has been developed to predict the onset of sand production, or critical drawdown pressure (CDP), in high-rate gas wells. The model describes the perforation- and openhole-cavity stability by use of both rock and fluid mechanics. The pore-pressure gradient is calculated with the non-Darcy-gas-flow equation, then coupled with the stress state for a perfect Mohr-Coulomb material. Sand production is assumed to initiate when the drawdown-pressure condition (i.e., at CDP) induces tensile stresses across the cavity face. The spherical model is suitable for cased-and-perforated applications, while a cylindrical model is used for horizontal-openhole completions.