Long-term estimates of trapping(CO2) Containment or immobilisation of CO2, there are four main trapping mechanisms: structural or stratigraphic trapping; residual CO2 trapping (capillary trapping) by capillary forces; solubility trapping by dissolution of CO2 in resident formation fluids forming a non-buoyant fluid; and mineral trapping where CO2 is absorbed by solid minerals present in the storage volume mechanisms introduced in the previous chapters, i.e., structural, solubility and kineral trapping(CO2) Containment or immobilisation of CO2, there are four main trapping mechanisms: structural or stratigraphic trapping; residual CO2 trapping (capillary trapping) by capillary forces; solubility trapping by dissolution of CO2 in resident formation fluids forming a non-buoyant fluid; and mineral trapping where CO2 is absorbed by solid minerals present in the storage volume, require the development of a reactive transport model able to accurately describe hydrodynamic and geochemical processes (Audigane, et al., 20072007 - P. Audigane, I. Gaus, I. Czernichowski-Lauriol, K. Pruess and T. XuTwo dimensional reactive transport modelling of CO2 injection in a saline aquifer at the Sleipner site, North Seasee more). The potential geochemical feedback on physical properties through highly coupled processes has been recognised as being of great importance for CCSCarbon dioxide Capture and Storage (e.g. Czernichowski-Lauriol et al., 19961996 - I. Czernichowski-Lauriol, C. Rochelle, E. Lindeberg, L. Bateman and B. SanjuanAnalysis of the geochemical aspects of the underground disposal of CO2see more). During recent years, chemical and solute transport modelling for CCSCarbon dioxide Capture and Storage has made significant progress, building upon the earlier coupled flow models developed for both geothermalConcerning heat flowing from deep in the earth systems and radioactive waste disposal. Reactive modelling has evolved from simple, chemical, batch models assuming only interactions between CO2Carbon dioxide dissolved in brine and host rocks, without taking into account any flow aspects, to complex three-dimensional fully coupled chemical and flow models accountingActivities aiming to document and report avoided CO2 emissions for a project for the geological complexity of the storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids and caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir(s) (Gaus et al., 20082008 - I. Gaus, P. Audigane, L. André, J. Lions, N. Jacquemet, P. Durst, I. Czernichowski-Lauriol and M. AzaroualGeochemical and solute transport modelling for CO2 storage, what to expect from it?see more).
Current solute transport model codes consider either two components (e.g. CO2Carbon dioxide, fluid) or three components (CO2Carbon dioxide, oil, fluid) as wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids as density dependent flow, dissolution of CO2Carbon dioxide, chemical speciationThe determination of the number of species into which a single species may evolve over time, dissolution of minerals of the host rock(geology) The rock formation that contains a foreign material and precipitation of new secondary phases, and porosityMeasure for the amount of pore space in a rock changes in the host rock(geology) The rock formation that contains a foreign material as a consequence of these processes. To address these processes the equations of conservation of energy, momentum, mass and solute mass, together with constitutive laws are coupled in either an implicit or an explicit manner (Gaus et al., 20082008 - I. Gaus, P. Audigane, L. André, J. Lions, N. Jacquemet, P. Durst, I. Czernichowski-Lauriol and M. AzaroualGeochemical and solute transport modelling for CO2 storage, what to expect from it?see more).
The success of CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere and its worldwide deployment might largely depend on the understanding of the interaction of CO2Carbon dioxide with fluids and minerals within the reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids for thousands of years. Saline reservoirs in sedimentary basins constitute one of the best targets for the CCSCarbon dioxide Capture and Storage projects due to their massive storage capacityThe accumulated mass of CO2 that can be stored environmentally safely, i.e., without causing leakage of CO2 or native reservoir fluids or triggering geologic activity that has a negative impact on human health or the environment. The formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it waters in these reservoirs are characterised by salinities ranging from 5,000 to > 350,000 mg/L dissolved solids. They cannot be considered as water resource because they usually contain dissolved species e.g. metals and organic components (Kharaka and Hanor, 20072007 - Y. K. Kharaka and J. S. HanorDeep fluids in the continents: I. Sedimentary basinssee more). The chemistry of these waters is the result of various different hydrogeochemical processes. Hence, the injectionThe process of using pressure to force fluids down wells of CO2Carbon dioxide into such reservoirs constitutes an additional process that influences the chemistry of these waters and increases the chemical reactivity of the system. Although dry CO2Carbon dioxide does not react, wet CO2reacts and forms a weak acid (H2COCarbon monoxide3) that almost immediately dissociates. This makes the pH of the brine to decrease.
CO2Carbon dioxide(g) +H2O CO2Carbon dioxide(aq) +H2O H2COCarbon monoxide3° HCO3-+H+ COCarbon monoxide32-+2H+
The above series of linked reversible reactions is controlled by in-situ temperature, pressure and salinity. As stated in Gaus et al., 20082008 - I. Gaus, P. Audigane, L. André, J. Lions, N. Jacquemet, P. Durst, I. Czernichowski-Lauriol and M. AzaroualGeochemical and solute transport modelling for CO2 storage, what to expect from it?see more, there is evidence that dissolved CO2Carbon dioxide may have an important impact during CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere operations and, may influence the success or failure of a carbon storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere project. Once injected, CO2Carbon dioxide dissolves into the fluids present in the formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it and might induce geochemical reactions in the reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids, the wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids infrastructure and the reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir that need to be fully evaluated. From enhanced oil recoveryThe recovery of oil additional to that produced naturally, achieved by fluid injection or other means (EOREnhanced Oil Recovery: the recovery of oil additional to that produced naturally, achieved by fluid injection or other means) operations, there is indirect evidence of geochemical reactions in the near-wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids environment causing injectivityA measure of the rate at which a quantity of fluid can be injected into a well difficulties (Czernichowski-Lauriol et al., 19961996 - I. Czernichowski-Lauriol, C. Rochelle, E. Lindeberg, L. Bateman and B. SanjuanAnalysis of the geochemical aspects of the underground disposal of CO2see more). Generally, injectivityA measure of the rate at which a quantity of fluid can be injected into a well changes are poorly explained and have been tentatively attributed to multiphase flow, CO2Carbon dioxide/oil interactions and/or CO2Carbon dioxide/mineral interactions (Cailly et al., 20052005 - B. Cailly, P. Le Thiez, P. Egermann, A. Audibert, S. Vidal-Gilbert and X. LongaygueGeological storage of CO2: a state of the art of injection processes and technologiessee more). Only occasionally, increased injectivityA measure of the rate at which a quantity of fluid can be injected into a well is observed. Evidence of geochemical interactions caused by the presence of CO2Carbon dioxide in geological sequences where CO2Carbon dioxide occurs naturally (e.g. natural CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere analogues) is particularly valuable since it illustrates the long-term impact of CO2Carbon dioxide on natural rocks that cannot easily be reproduced during experiments or short-term field tests. In some natural analogues, chemical equilibrium is not reached, even over very long (geological) contact times (Haszeldine et al., 20052005 - S. R. Haszeldine, O. Quinn, E. G., W. M., Z. K. Shipton, J. P. Evans, J. Heath, L. Crossey, C. J. Ballentine and C. M. GrahamNatural geochemical analogues for carbon dioxide storage and sequestration in deep geological porous reservoirssee more). This suggests that chemical equilibrium might not be attained during the expected lifetime of a CCSCarbon dioxide Capture and Storage storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere site, i.e., thousands to hundreds of thousands of years (Gaus et al., 20082008 - I. Gaus, P. Audigane, L. André, J. Lions, N. Jacquemet, P. Durst, I. Czernichowski-Lauriol and M. AzaroualGeochemical and solute transport modelling for CO2 storage, what to expect from it?see more).