Carbonate Acidizing: Effect of Additives on Reactivity and Wormhole Development.

The reduction in productivity in carbonate reservoirs is often associated with near-wellbore formation damage, making matrix acidizing an essential strategy to restore permeability. In this context, treatment efficiency depends on the balance between reaction kinetics and mass transport, which governs the formation of dominant wormholes. Although additives such as corrosion inhibitors and emulsion preventers are widely used for operational purposes, their effects on the reactive behavior of acid systems remain poorly understood. This study investigates the influence of commercial additives on HCl-based acid systems, using an additive-free system (NA) as a reference. An emulsion preventer (EP), a corrosion inhibitor (CI), and a formulation containing both additives (BA) were evaluated. The EP and CI were used at concentrations of 0.2 and 0.5 vol %, respectively, and the BA formulation contained both additives at the same concentrations. The formulations were evaluated through physicochemical characterization, carbonate dissolution kinetics, and reactive-flow experiments performed on Indiana Limestone samples (18.4% average porosity and 123 mD average permeability) during the injection of 15 wt % HCl until breakthrough. The presence of additives led to a significant reduction in surface tension, suggesting changes in interfacial conditions. Batch reactor experiments showed a pronounced retardation in dissolution kinetics, with reaction times increasing by approximately 4.5-fold, 30.6-fold, and 18.2-fold for the EP, CI, and BA systems, respectively, compared with NA. In reactive-flow experiments, the minimum pore volume to breakthrough (PV