Determining the Appropriate Rate of Acid Injection in Carbonate Formations to Increase Permeability

Rate production and final recycling rates are heavily influenced by permeability as a dynamic parameter, but this parameter is low in some carbonate reservoirs and requires an appropriate solution to increase it. The purpose of this study was to investigate the effect of injection and confining pressure in a laboratory study of the permeability of reservoir rocks during acid-bed corrosive operations. Considering this approach, 6 samples of carbonate reservoir rock from one of Iran’s oil fields have been prepared. After determining the physical and mechanical properties of the samples, the effect of the confining pressure and the injection pressure on permeability variations and optimal flow rates were studied. Examination of the results of the experiments as well as the CT scans of the samples after acidizing operation showed that permeability increased to an acceptable level in all samples. In lower injection rates, the acid has enough time to react with the rock, wormholes are well-formed, and the rest of the sample space retains its density to a large extent, but by increasing acid injection rates, there are wormholes changing themselves with the complete destruction of the primary core section, and the remaining density has been reduced. This is accompanied by a combination of the two above-mentioned behaviors, by increasing the rate to a maximum. This has led to an increase in over 530 times permeability over the initial value of the sample. However, there is a slight difference between the formation time of the formation of wormholes in the injected sample with maximum discharge and the sample injected with a minimum. However, there is a slight difference between the formation time of wormholes in the injected sample with maximum rate and the sample injected with a minimum.