Experimental study of the dissolution of carbonate samples with acid solutions

In this paper, we study the interaction of eight carbonate core samples (the same size, almost entirely composed of calcite) with hydrochloric acid solutions with concentrations of 12% and 18% at solution flow rates of 1, 2, 4, and 8 ml/min, respectively. During flooding experiments, the flow rate of acid solutions unevenly affected the final permeability and breakthrough pore volumes. In the case of injection of a 12% HCl solution, an average of almost 20% more acid solution was required for a breakthrough comparing to the injection of a 18% HCl solution, although in both cases the injection was carried out at the same rates. It was found that the largest increases in permeability are achieved mainly at high flow rates of the solution. Speaking of the 18% HCl solution during flooding experiments, almost identical pore volumes of solution were required to breakthrough for all flow rates; also, with an increase in the injection rate, a progressive increase in permeability was observed. The results of laboratory studies can be useful in the treatment of near wellbore zones and CO2 sequestration on a large scale for an approximate assessment of the final permeability of the treated zone and the required volumes of acid solutions.