Sand Production Analysis for Depleted Reservoir

Abstract

For most oilfields, the later development stage will be after long time production, and pore pressure is seriously depleted. The in situ stress of reservoir will be affected, and the stress state will be changed, so that to cause sand production. Based on Hooke’s law, the theoretical formula of two horizontal stress changes is obtained, and the stress distribution is established. The model of critical down-hole pressure for sand production in depleted reservoir is established. Based on the model, the influence of pressure depletion on critical drawdown pressure is analyzed for sand production. The results show that: with the pore pressure decreasing, the horizontal in situ stress and critical drawdown pressure decrease; Dynamic stress distribution is obtained with the pressure depletion in the development process, but the critical drawdown pressure decreasing rate with reservoir pressure depletion is less than the pore pressure. The critical drawdown pressure based on Mogi-Coulomb criterion is the most accurate, but that based on Mohr-Coulomb criterion is the most safety.
Key words: Pressure depletion; Sand production; Critical drawdown pressure