1. TOUGHREACT: A Reactive Transport Simulator
for CO2 Geological Sequestration
Tianfu Xu, Eric Sonnenthal, Nicolas Spycher, Liange Zheng, and Karsten Pruess
Earth Sciences Division, Lawrence Berkeley National Laboratory
ABSTRACT
EXAMPLES
TOUGHREACT is a numerical simulation program for chemically reactive non-isothermal flows of multiphase fluids in porous and fractured media. The program is written in Fortran 77 and was developed by introducing reactive chemistry into the multiphase flow code TOUGH2 V2. Interactions between mineral assemblages and fluids can occur under local equilibrium or kinetic rates. The gas phase can be chemically active. Precipitation and dissolution reactions can change formation porosity and permeability.
The TOUGHREACT program is distributed to the public through the US Department of Energy's Energy Science and Technology Software Center ( It is among the most frequently requested codes in the library of the ESTSC. It is widely used internationally for CO2 geological sequestration, geothermal energy development, nuclear waste isolation, environmental remediation, and increasingly for petroleum applications. Additional information is available on the TOUGHREACT homepage (
1-D radial model for changes in water chemistry in the observation well induced by CO2 Injection at Frio Pilot test site. Use physical and chemical conditions and parameters encountered in US Gulf coast sandstone formations. .
2-D radial model for long-term CO2 storage. Use physical and chemical conditions and parameters as in the previous 1-D radial example:
INTRODUCTION
One possible means of reducing atmospheric CO2 emissions is to inject it into deep saline formations.
Mineral trapping is potentially attractive because it could immobilize CO2 for long time scales.
Alteration of the predominant host rock aluminosilicate minerals is very slow and is not experimentally accessible under ambient deep conditions.
Numerical modeling is a necessary tool for addressing and answering the following issues and questions:
Changes in groundwater quality induced by CO2 injection (storage formation and shallow aquifers),
What is the long-term fate of injected CO2?
What fraction of CO2 is stored as a free phase, dissolved in the aqueous phase, or sequestered in solid minerals?
How do the proportions in these different? storage modes change over time?
Is co-injection with H2S feasible?
PROCESSES AND FEATURES
CONCLUSIONS
Multiphase fluid and heat flow: TOUGH2 V2 (Pruess, et al., 1999).
A new EOS (ECO2N) is connected (Pruess and Spycher, 2007)
Transport: advection and diffusion in both liquid and gas phases.
Chemical reactions: aqueous complexation, acid-base, redox, mineral dissolution and precipitation (equilibrium and/or kinetics), gas dissolution and exsolution, cation exchange, and surface complexation.
Changes in porosity and permeability, and unsaturated zone properties due to mineral dissolution and precipitation.
General: Porous and fractured media; five porosity-permeability models; general reaction rate laws; any number of chemical species.
Physical and chemical heterogeneity.
Wide range of conditions: P, T, pH, Eh, and salinity.
A comprehensive general-purpose reactive transport simulation tool TOUGHREACT has been developed for CO2 geological sequestration (CGS), which incorporates aqueous reactions, mineral dissolution and precipitation under equilibrium and kinetic conditions, CO2 dissolution and exsolution, and coupled to multi-phase CO2-water flow.
The program has been validated using data from laboratory experiments, observations from field demonstration projects, and from natural CO2 reservoirs.
The tool can solve problems and answer questions related to CGS, such as fate and transport of injected CO2, amount of CO2 dissolved in groundwater, trapped by carbonate minerals, variations of these storage forms over time.
It’s also an important tool to study storage security, caprock integrity, and degradation of wellbore cements.
Leakage from CO2 storage formations into potable aquifers and its impact on groundwater quality is a potential concern, which can be best studied through reactive transport modeling.
Improvements continue to meet challenges and community needs such as multi-scale coupled processes in space and time, thermodynamic and kinetic data, and reactivity of SC CO2 with rock and organic matter.
NUMERICAL METHODS
REFERENCES
Sequential iteration for flow, transport and reaction.
Transport equations: component by component.
Reaction equations: grid block by grid block.
Newton-Raphson iteration.
Preconditioned conjugate gradient solvers.
Integral finite difference.
Implicit time weighting.
1-D, 2-D, or 3-D.
Pruess, K., Oldenburg, C., Moridis, G., TOUGH2 user’s guide, Version Lawrence Berkeley Laboratory Report LBL-43134, Berkeley, California.
Pruess, K., Spycher, N., 2007. ECO2N – A fluid property module for the TOUGH2 code for studies of CO2 storage in saline aquifers. Energy Conversion and Management 48(6),
Xu, T., E.L. Sonnenthal, N. Spycher, and K. Pruess, TOURGHREACT: A simulation program for non-isothermal multiphase reactive geochemical transport in variably saturated geologic media. Computer & Geosciences 32,
ACKNOWLEDGMENTS
The development of TOUGHREACT was supported by various Program Offices of the U.S. Department of Energy. Recent application to CO2 geological sequestration was supported by the Zero Emission Research and Technology project (ZERT) of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 with Lawrence Berkeley National Laboratory.
Authors thank to Guoxiang Zhang, John Apps, Curt Oldenburg, Yousif Kharaka, Christine Doughty, Barry Freifeld, and Thomas M. Daley for help on the code development and applications.