A NUMERICAL MODELING STUDY OF THE MECHANISMS OF GELATION IN POROUS-MEDIA

Polymer gel treatments are sometimes proposed to alleviate high watercuts in North Sea producer wells. Numerical simulations are required to design such treatments, and these require models of the behaviour of the gelling system in the rock matrix. This paper describes a numerical modelling study of the xanthan-Cr(III) gelling system in porous media. Models of the adsorption of both species and of the gelation process are tested, by comparison with data from core-flooding experiments. The xanthan data are consistent with reversible kinetic Langmuir adsorption. The Cr(III) data require a two-site adsorption model, comprising fast reversible and slow irreversible components. The gelation reaction is modelled as the successive build-up of layers of polymer and cross-linker, the initial layer being polymer which is adsorbed on the pore surfaces. The stoichiometry of the cross-linking reaction suggests that most of the adsorbed chromium is inaccessible to xanthan.