Limits...
Reactive Transport Modeling of the Enhancement of Density-Driven CO2 Convective Mixing in Carbonate Aquifers and its Potential Implication on Geological Carbon Sequestration.

Islam A, Sun AY, Yang C - Sci Rep (2016)

Bottom Line: We study the convection and mixing of CO2 in a brine aquifer, where the spread of dissolved CO2 is enhanced because of geochemical reactions with the host formations (calcite and dolomite), in addition to the extensively studied, buoyancy-driven mixing.The nonlinear convection is investigated under the assumptions of instantaneous chemical equilibrium, and that the dissipation of carbonate rocks solely depends on flow and transport and chemical speciation depends only on the equilibrium thermodynamics of the chemical system.Early saturation of the reservoir can have negative impact on CO2 sequestration.

View Article: PubMed Central - PubMed

Affiliation: Bureau of Economic Geology, The University of Texas at Austin, TX, USA.

ABSTRACT
We study the convection and mixing of CO2 in a brine aquifer, where the spread of dissolved CO2 is enhanced because of geochemical reactions with the host formations (calcite and dolomite), in addition to the extensively studied, buoyancy-driven mixing. The nonlinear convection is investigated under the assumptions of instantaneous chemical equilibrium, and that the dissipation of carbonate rocks solely depends on flow and transport and chemical speciation depends only on the equilibrium thermodynamics of the chemical system. The extent of convection is quantified in term of the CO2 saturation volume of the storage formation. Our results suggest that the density increase of resident species causes significant enhancement in CO2 dissolution, although no significant porosity and permeability alterations are observed. Early saturation of the reservoir can have negative impact on CO2 sequestration.

No MeSH data available.


Equilibrium concentrations after breakthrough.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4837360&req=5

f1: Equilibrium concentrations after breakthrough.

Mentions: We first have conducted sanity test of chemical speciation. CO2 leak problem is solved considering chemical reactions of Eqs 3, 4, 5, 6, 7, 8 by following the semianalytical approach in Yang et al.28. It is noteworthy that coupled reactive transport calculations strongly depend on accuracy of geochemical database. Different geochemical databases and uncertainty of thermodynamics data can severely affect the results. For the transport part analytical solution for the scenario with leaky well was used. Figure 1 shows that CO2 stream in host carbonates after equilibrium dissolution can be increased by more than 1.5 folds. In our simulation the maximum equilibrium dissolved CO2 concentration of 0.97 mol/l is used in saturated CO2-brine interface at the top. In order to quantify saturation area of the aquifer, average concentration formulation, , is used. The direct numerical simulations have been carried out for Ra numbers of 1000 and 10,000, where the associated mean permeability values are 10 and 100 mD, respectively.


Reactive Transport Modeling of the Enhancement of Density-Driven CO2 Convective Mixing in Carbonate Aquifers and its Potential Implication on Geological Carbon Sequestration.

Islam A, Sun AY, Yang C - Sci Rep (2016)

Equilibrium concentrations after breakthrough.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837360&req=5

f1: Equilibrium concentrations after breakthrough.
Mentions: We first have conducted sanity test of chemical speciation. CO2 leak problem is solved considering chemical reactions of Eqs 3, 4, 5, 6, 7, 8 by following the semianalytical approach in Yang et al.28. It is noteworthy that coupled reactive transport calculations strongly depend on accuracy of geochemical database. Different geochemical databases and uncertainty of thermodynamics data can severely affect the results. For the transport part analytical solution for the scenario with leaky well was used. Figure 1 shows that CO2 stream in host carbonates after equilibrium dissolution can be increased by more than 1.5 folds. In our simulation the maximum equilibrium dissolved CO2 concentration of 0.97 mol/l is used in saturated CO2-brine interface at the top. In order to quantify saturation area of the aquifer, average concentration formulation, , is used. The direct numerical simulations have been carried out for Ra numbers of 1000 and 10,000, where the associated mean permeability values are 10 and 100 mD, respectively.

Bottom Line: We study the convection and mixing of CO2 in a brine aquifer, where the spread of dissolved CO2 is enhanced because of geochemical reactions with the host formations (calcite and dolomite), in addition to the extensively studied, buoyancy-driven mixing.The nonlinear convection is investigated under the assumptions of instantaneous chemical equilibrium, and that the dissipation of carbonate rocks solely depends on flow and transport and chemical speciation depends only on the equilibrium thermodynamics of the chemical system.Early saturation of the reservoir can have negative impact on CO2 sequestration.

View Article: PubMed Central - PubMed

Affiliation: Bureau of Economic Geology, The University of Texas at Austin, TX, USA.

ABSTRACT
We study the convection and mixing of CO2 in a brine aquifer, where the spread of dissolved CO2 is enhanced because of geochemical reactions with the host formations (calcite and dolomite), in addition to the extensively studied, buoyancy-driven mixing. The nonlinear convection is investigated under the assumptions of instantaneous chemical equilibrium, and that the dissipation of carbonate rocks solely depends on flow and transport and chemical speciation depends only on the equilibrium thermodynamics of the chemical system. The extent of convection is quantified in term of the CO2 saturation volume of the storage formation. Our results suggest that the density increase of resident species causes significant enhancement in CO2 dissolution, although no significant porosity and permeability alterations are observed. Early saturation of the reservoir can have negative impact on CO2 sequestration.

No MeSH data available.