Effect of Additives on the Dissolution Rate of Different Carbonate Rocks by Hydrochloric Acid

Matrix acidizing is a widely applied technique for stimulating carbonate reservoirs by promoting mineral dissolution and restoring well productivity. In this context, this study aimed to investigate the effect of commercial additives, a corrosion inhibitor and an emulsion preventer, both containing surfactants in their formulations, on the dissolution rate of different carbonate rocks by hydrochloric acid (HCl), comparing the performance of systems with and without additives. Samples of Indiana Limestone, Mount Gambier Limestone, Wisconsin Dolomite, and Bonneterre Dolomite, which exhibit distinct mineralogical compositions and structural characteristics, were analyzed. The samples were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), nuclear magnetic resonance (NMR), and porosity measurements. Dissolution experiments were conducted in a batch reactor, allowing the acquisition of kinetic curves for the acid-rock reaction. The results showed that, in the absence of additives, predominantly calcitic rocks exhibited the highest dissolution rates (exceeding 1 g min^-1), with dissolution kinetics primarily controlled by mass-transfer limitations. In contrast, dolomitic rocks displayed lower reactivity, with rates below 0.1 g min^-1. The presence of additives significantly retarded the reaction in all rock types, with the most pronounced effect observed for calcitic samples, where the dissolution time increased by more than 18-fold. This behavior can be attributed to foam formation and the reduction of H⁺ availability at the acid-rock interface caused by the surfactants contained in the additives.