Modeling and simulation of the carbonate reactive-dissolution process by viscoelastic-surfactant-based acid

In carbonate reservoir treatment, uneven distribution of acid may occur due to strong heterogeneity. To avoid the selective flow of fluid into the high permeability zones, viscoelastic surfactant-based self-diverting acids are commonly used in stimulation operations. To better comprehend this phenomenon, this work proposes a mathematical model to describe the dissolution process associated with this problem. The rheology of the acid solution was experimentally obtained for some degrees of neutralization and the flow curves were fitted by a Carreau model with neutralization dependent coefficients. In addition to the usual governing equations of this problem that include mass conservation, momentum balance, and acid concentration conservation, we considered a transport equation for the reaction products. The solid–liquid interaction term at the porous scale is determined by the fractions of acid and products, that in addition to brine compose the total fluid phase. Simulations in plug geometry were performed to validate this model against experimental results in different samples, where good agreement was found. •A new model to capture the acidizing process in carbonate porous media is developed.•A Carreau-type self-diverting non-Newtonian model is used for the acid rheology.•The parameters of the model are written as functions of the neutralization degree.•An additional transport equation for the products of the reaction is considered.•Characteristic shear rate is calibrated from experimental results in plug samples.