Numerical predictions on critical pressure drawdown and sand production for wells in weak formations
Sand production is an important issue affecting oil production; it can cause serious problems in oil flow within a sand reservoir as well as to the proper functioning of the oil production equipment. Furthermore, for wells with openhole completion, sand production can cause cavity enlargement and further collapse of the borehole. The major cause of sand production is the material instability in poorly consolidated and unconsolidated formations. As a kind of material instability, it was proved that material plasticity plays an important role in the process of sand production (Papamichos and Stavropoulou 1998; Papamichos and Malmange 2001; van den Hoek et al., 1996). In the last twenty years, the investigation and application of plasticity-based methods for the prediction of sand production have been reported by various researchers. Wang and Lu (2001) introduced their work on the relationship between the onset of sand production and equivalent plastic strain by using a coupled reservoir-geomechanics model. Yi et al. (2004) proposed their sanding onset-prediction model, which can analytically calculate the critical pressure drawdown by using a set of material-flow parameters. Oluyemi and Oyeneyin (2010) presented their analytical model for the prediction of critical pressure drawdown that is based on the Hoek-Brown failure criterion, rather than on the Mohr-Columb criterion.