Numerical investigation of carbonate acidizing with gelled acid using a coupled thermal–hydrologic–chemical model

In this work, an experiment-based rheological model that accounts for the influence of polymer concentration, shear-thinning behavior, and temperature variation on the in-situ viscosity of gelled acid is developed. On the basis of the rheological model, we present a thermal–hydrologic–chemical coupled model that describes the dissolution process of carbonate acidization with gelled acid. A sensitivity analysis of the dissolution dynamic regarding the temperature variation, polymer adsorption, and non-Newtonian behavior of the injected acid is carried out. The comparison of acidization curves and dissolution patterns obtained by injecting gelled acid and HCl is conducted. It is found that the optimal dissolution regime for gelled acid has a much wider range than neat HCl. It is observed from the numerical simulations that reservoir temperature and rheological parameters of the acid are key factors that affect acidizing efficiency, while the effect of polymer adsorption can be ignored. In addition, several recommendations for optimal stimulation of carbonates with gelled acids are provided.