| Popis: |
Anthropogenic sources have caused the rise of CO2 in the atmosphere, necessitating the reduction of the release of this gas from major point sources. An important mitigation technique is the injection of CO2 into deep saline reservoirs as part of CO2 capture and storage (CCS). However, there are gaps in the understanding of the medium- to long-term processes for the safe and efficient storage of CO2. Solubility trapping involves the dissolution of CO2 into brine, causing the formation of carbonic acid, which increases brine density. Additional waste gases from fossil fuel production, such as SO2, can also be injected and increases density further. As CO2 migrates away from the injection site, more CO2 is able to dissolve and interact with the formation. The dissolution of minerals within the formation changes the porosity and permeability of the rock and provides ions to ultimately precipitate CO2 as part of the mineral trapping process.Solubility and mineral trapping are both important processes for retaining CO2 in saline reservoirs. Solubility of CO2 in multi-salt brines is poorly understood, especially at conditions relevant to CCS. In addition, it may be more feasible to inject SO2 with CO2 because of the cost benefit. There is little data on how co-dissolved SO2 will affect CO2 solubility. CO2 solubility was measured in brines containing NaCl, KCl, CaCl2 and MgCl2 as well as co-dissolved with 2% SO2 in DI and 1 mole/kg NaCl at 297 K and pressures up to 14 MPa. CO2 solubility is affected by the concentration and composition of multi-salt brines but not by the presence of the limited amount of SO2.Although potential injection horizons contain mostly the nonreactive mineral quartz, silicates provide ions for the eventual precipitation of new minerals. Experiments were conducted using crushed and sieved albite in a 0.7 mole/kg KCl brine at room temperature, 35ºC, 75ºC and 100ºC at pressures up to 9.3 MPa for up to 546 days. The concentration of Na, Al, Si and Fe were measured. Dissolution rates were calculated based on release of Si and were found to vary depending on temperature and pH of the solution. |
