Well injectivity decline for nonlinear filtration of injected suspension: Semi-analytical model

Abstract

Injectivity decline due to injection of water with particles is a widespread phenomenon in waterflood projects. It happens due to particle capture by rocks and consequent permeability decline and also due to external cake formation on the sandface. Since offshore production environments become ever more complex, particularly in deep water fields, the risk associated with injectivity impairment due to injection of seawater or re-injection of produced water may increase to the point that production by conventional waterflood may cease to be viable. Therefore, it is becoming increasingly important to predict injectivity evolution under such circumstances. The work develops a semi-analytical model for injectivity impairment during a suspension injection for the case of filtration and formation damage coefficients being linear functions of retained particle concentration. The model exhibits limited retained particle accumulation, while the traditional model with a constant filtration coefficient predicts unlimited growth of retained particle concentration. The developed model also predicts the well index stabilization after the decline period.