A coupled geochemical and fluid flow model to simulate permeability decline resulting from scale formation in porous media

Abstract

Scale precipitation due to the mixing of incompatible injected water with formation brine and its subsequent deposition in porous media is an unpleasant phenomenon in water injection projects that can lead to severe injectivity and productivity decline. As a result of the complexity of geochemical reactions, modelling scale precipitation and deposition is a challenge. This paper presents a coupled geochemical and fluid flow model to simulate reactive flow in porous media which models pressure difference increase resulting from scale formation during water injection into porous media. To simulate chemical reactions during scale formation and subsequent rock permeability decline, PHREEQC software was coupled with a fluid transport model. The pressure difference and outlet ion concentration from three laboratory data were successfully matched. The coupled model that is proposed considers injected and formation water compositions and their associated chemical reactions. The formation damage coefficient is the single optimisation parameter of the proposed model. With matching parameters from experimental data, the proposed model can be used for predicting well injectivity decline and sensitivity analysis.