Experimental Investigation of Acid Injection on Fracture Opening in Calcite and Dolomite Reservoirs

Acid fracturing is one of the most widely used methods in the reservoir stimulation process for higher oil production. This method in carbonate reservoirs has a crucial role in enhanced oil recovery. Acid fracturing in fractured carbonate reservoirs changes fracture opening due to the reaction between the injected acid and minerals at the surface of fracture walls. In addition, fracture opening changes affect oil movement and the amount of oil production. In this type of reservoir, parameters such as reservoir temperature, acid injection flow rate, and injection acid type are parameters that directly affect the reaction rate between acid and carbonate rock. In this study, acetic acid was injected into two types of carbonate rock, and the effect of the rock type and acid injection rate on the final fracture opening was investigated. The results showed that dolomite rocks due to their specific nature of minerals in their structure had little reactivity with acid, thus fracture opening had lower value in comparison with the calcite rock sample. Finally, by decreasing the acid injection rate, the final fracture opening was increased after the acid injection because of more reaction between acid and fracture surfaces.