Sand production from weak, but competent, rock as a result of high production rates is a growing concern. In unconsolidated sand, the decision to gravel pack is usually clear; however, the decision is harder in weak rock because the need for sand control often depends on the desired drawdown or production rate. Also, wells that do not initially require sand control may later become sand producers. The ability to predict at what point sand problems will occur is useful. This paper presents a method for predicting sand production in gas wells and the results of applying that method to 13 fields in the U.S. gulf coast area. The method has since been applied extensively worldwide by Arco. In the fields addressed in this paper, rock strength was determined in one or more ways: core testing, log correlations by use of direct shear velocity measurements with the dipole sonic log, or log correlations with traditional sonic logs and calculated shear velocities. Rock strengths determined by core tests and log correlations are compared. The prediction method was incorporated into a simple log analysis program that facilitates quick identification and analysis of potential sand-producing zones, and this program is discussed. Field production data are presented and compared with theoretical predictions as well as with predictions based on traditional shear failure theories. The method presented differs from commonly used log-based sand-prediction models in two important ways. It models pressure gradients in the reservoir instead of assuming that ah the pressure drop occurs at the perforation face. In addition, it allows for higher drawdowns than those permitted by the shear failure criteria, up to the drawdown that would produce tensile stresses at the perforation face. The method also addresses how allowable drawdown changes with reservoir depletion, which existing models do not consider.
