Pore-scale simulation of carbonate dissolution and acid transport based on Darcy–Brinkman–Stokes method

The study of acid-rock reactive dissolution processes is crucial for many engineering applications, such as acidizing processes during oilfield development and geological storage of CO2. The aim of this study is to investigate the acid-rock reactive dissolution process and the influencing factors under the real pore space of carbonate reservoirs at the pore scale. A single-connected pore space model was established by reconstructing real micrometer computed tomography scan images of carbonate rocks. A micro-continuum volume method based on the Darcy–Brinkman–Stokes equation was used on the OpenFOAM platform to simulate the acid-rock reactive dissolution process in carbonate reservoirs at the pore scale. The accuracy of the model was verified by comparing it with the previous experimental results. Different injection rates, reaction constants, and injected acid concentrations were considered in the model. The results show that during the dissolution process, different injection rates affect the dissolution pattern, which is face dissolution at low flow rates, wormhole dissolution when the injection rate is increased, and uniform dissolution when the injection rate is further increased. In addition, the study also shows that the reaction constant has a limited effect on accelerating the reaction rate, and if the dissolution rate needs to be increased further, either the injection rate or the acidic fluid concentration needs to be increased to ensure that enough acid is available for the reaction to occur.