Experimental Investigations of Acid Fracturing in Layered Carbonate Rocks Utilizing Chelating Agents

One of the methods to improve carbonate formation productivity is acid fracturing. The acid injection creates dissolution along the fracture, which improves fracture conductivity. This study investigated chelating agents such as glutamic diacetic acid and ethylene diamine triacetic acid on acid fracturing treatments to sustain the conductivity of layered minerals of carbonate formations. Chelating agents are less reactive than HCl and do not need large quantities of corrosion inhibitors, especially in high-temperature environments. Three cylindrical samples of 1.5 in. × 6 in. were cored from casted layered calcite and dolomite. The roughness and hardness of the fracture surface before and after the stimulation have been examined. The fracture conductivity was also evaluated before and after acid etching using a core flooding setup at different flow rates under four closure stress values. Inductively coupled plasma analysis has been carried out to estimate rock dissolution based on quantifying calcium and magnesium ions. Results showed that chelating agents have improved fracture conductivity and resulted in a sufficiently rougher fracture surface compared to HCl. The rock samples’ surface hardness has been reduced relatively post-treatment, with chelating agents being gentler on the rock. The novelty of this study is that for the first time, chelating agents have been tested as acid fracturing fluids on carbonate reservoirs for generating sustainable conductivity.