## 2 Simulation  
### Scenarios  
In this study, twenty scenarios were numerically simulated to analyze the effects of lithology, pore size, pore-structure type, and CO\({}_{2}\) injection rate on the process of carbonate rock dissolution. These four parameters are studied because the lithology, pore-structure type, and pore size are the most important geophysical features, and the injection rate is one of the most important operating parameters. The numerically constructed geological models used in the scenarios have the same dimensions of 10 m in length, 10 m in width, and 1 m in height. The porosity of the geological model used in each scenario is also the same and set at 10%. The lithology, pore space type, pore size, and CO\({}_{2}\) injection rate in each scenario are listed in Table 1. The lithologies in Scenarios #1-10 and #11-20 are limestone and dolostone, respectively. Scenarios #1-3, #6-8, #11-13, and #16-18 are simulated to investigate the CO\({}_{2}\) injection rate effect on carbonate matrix dissolution in different reservoirs with different lithologies and pore space types. Scenarios #1-3 have limestone lithology, pore-dominant space type, 5 um pore size, and varying CO\({}_{2}\) injection rates of 0.1, 0.5, and 1.0 mol/min to examine carbonate matrix dissolution in limestone pore-dominant reservoirs. Similarly, scenarios #6-8, #11-13, and #16-18 are simulated to understand the effects of CO\({}_{2}\) injection rate on carbonate matrix dissolutions in limestone fracture-dominant, dolomite pore-dominant, and dolomite fracture-dominant reservoirs, respectively.  
Scenarios #3-5, #8-10, #13-15, and #18-20 are simulated to investigate the effect of pore/fracture size on the carbonate matrix dissolution process in different carbonate reservoirs with different lithologies and pore space types. For example, the pore size effect on limestone pore-dominant reservoirs can be found in Scenarios #3-5. Similarly, the other three groups of scenarios, i.e., Scenarios #8-10, #13-15, and #18-20, are simulated to investigate the pore space size effect on limestone fracture-dominant reservoirs, dolomite pore-dominant reservoirs, and dolomite fracture-dominant reservoirs, respectively. It is worth noting that the residual water saturations in the reservoirs with different pore sizes are different. The residual water saturations are 76.5%, 55.0%, and 18.4% for pore-dominant reservoirs with pore sizes of 5 um, 10 um, and 50 um, respectively. For the fracture-dominant reservoirs, the residual water saturations are 68.2%, 44.1%, and 8.7% for the reservoirs with fracture diameters of 5 um, 10 um, and 50 um, respectively. The calculation of the residual water saturation will be presented in Section 2.3.  
Two groups of scenarios, i.e., #3 and #6, as well as #13 and #16, are compared to analyze the CO\({}_{2}\)-brine-rock interactions in pore-dominant and fracture-dominant reservoirs. Scenarios #3 and #6 are simulated to compare the dissolution process in limestones. Scenarios #3 and #6 have the same lithology, pore/throat size, and CO\({}_{2}\) injection rate, which are limestone, 5 um, and 10 mol/min, respectively. The difference between these two scenarios is that the geological model used in Scenario #3 is pore-dominant type, whereas the other is fracture-dominant in Scenario #6. Scenarios #13 and #16 are similar to Scenarios #3 and #6. The difference between these two series is that scenarios #13 and #16 are used to compare the dissolution processes in different pore-throat types in dolomite reservoirs instead of limestone reservoirs.