Curtis M. Oldenburg

TOUGH2 User's Guide Version 2

TOUGH2 is a numerical simulator for nonisothermal flows of multicomponent, multiphase fluids in one, two, and three-dimensional porous and fractured media. The chief applications for which TOUGH2 is designed are in geothermal reservoir engineering, nuclear waste disposal, environmental assessment and remediation, and unsaturated and saturated zone hydrology. TOUGH2 was first released to the public in 1991; the 1991 code was updated in 1994 when a set of preconditioned conjugate gradient solvers was added to allow a more efficient solution of large problems. The current Version 2.0 features several new fluid property modules and offers enhanced process modeling capabilities, such as coupled reservoir-wellbore flow, precipitation and dissolution effects, and multiphase diffusion. Numerous improvements in previously released modules have been made and new user features have been added, such as enhanced linear equation solvers, and writing of graphics files. The T2VOC module for three-phase flows of water, air and a volatile organic chemical (VOC), and the T2DM module for hydrodynamic dispersion in 2-D flow systems have been integrated into the overall structure of the code and are included in the Version 2.0 package. Data inputs are upwardly compatible with the previous version. Coding changes were generally kept to a minimum, and were only made as needed to achieve the additional functionalities desired. TOUGH2 is written in standard FORTRAN77 and can be run on any platform, such as workstations, PCs, Macintosh, mainframe and supercomputers, for which appropriate FORTRAN compilers are available. This report is a self-contained guide to application of TOUGH2 to subsurface flow problems. It gives a technical description of the TOUGH2 code, including a discussion of the physical processes modeled, and the mathematical and numerical methods used. Illustrative sample problems are presented along with detailed instructions for preparing input data.

Dispersive Transport Dynamics in a Strongly Coupled Groundwater‐Brine Flow System

Many problems in subsurface hydrology involve the flow and transport of solutes that affect liquid density. When density variations are large (>5%), the flow and transport are strongly coupled. Density variations in excess of 20% occur in salt dome and bedded-salt formations which are currently being considered for radioactive waste repositories. The widely varying results of prior numerical simulation efforts of salt dome groundwater-brine flow problems have underscored the difficulty of solving strongly coupled flow and transport equations. We have implemented a standard model for hydrodynamic dispersion in our general purpose integral finite difference simulator, TOUGH2. The residual formulation used in TOUGH2 is efficient for the strongly coupled flow problem and allows the simulation to reach a verifiable steady state. We use the model to solve two classic coupled flow problems as verification. We then apply the model to a salt dome flow problem patterned after the conditions present at the Gorleben salt dome, Germany, a potential site for high-level nuclear waste disposal. Our transient simulations reveal the presence of two flow regimes: (1) recirculating and (2) swept forward. The flow dynamics are highly sensitive to the strength of molecular diffusion, with recirculating flows arising for large values of molecular diffusivity. For pure hydrodynamic dispersion with parameters approximating those at Gorleben, we find a swept-forward flow field at steady state rather than the recirculating flows found in previous investigations. The time to steady state is very sensitive to the initial conditions, with long time periods required to sweep out an initial brine pool in the lower region of the domain. Dimensional analysis is used to demonstrate the tendency toward brine recirculation. An analysis based on a dispersion timescale explains the observed long time to steady state when the initial condition has a brine pool in the lower part of the system. The nonlinearity of the equations and the competing effects of dispersion and gravity make this variable-density problem a challenge for any numerical simulation method.

Biologically Enhanced Carbon Sequestration: Research Needs and Opportunities

Biologically Enhanced Carbon Sequestration: Research Needs and Opportunities Lead Authors: Curtis M. Oldenburg (LBNL) and Margaret S. Torn (LBNL) Contributing Authors: Terrestrial Carbon Sequestration Kristen DeAngelis (LBNL), Ron Amundson (UCB), Carl Bernacchi (UIUC), Eoin Brodie (LBNL), Martin Carerra (BP), Atul Jain (UIUC), Markus Kleber (Oregon State), Kevin O’Hara (UCB), Bill Parton (Colorado State), Whendee Silver (UCB), Johan Six (UCD), Tetsu Tokunaga (LBNL), David Zilberman (UCB). Geologic Carbon Sequestration Jonathan Ajo-Franklin, Gillian Bond (NMT), John Christensen (LBNL), Al Cunningham (MSU), Bruce Fouke (UIUC), Terry Hazen (LBNL), Kevin Knauss (LBNL), Seiji Nakagawa (LBNL), Will Stringfellow (LBNL), Tianfu Xu (LBNL) Suggested citation: Oldenburg, C.M., M.S. Torn, K.M. DeAngelis, J.B. Ajo-Franklin, R.G. Amundson, C.J. Bernacchi, G.M. Bond, E.L. Brodie, M. Carerra, J.N. Christensen, A.B. Cunningham, B. Fouke, T.C. Hazen, A.K. Jain, M. Kleber, K.G. Knauss, S. Nakagawa, K.L. O’Hara, W.J. Parton, W.L. Silver, J.W. Six, W.I. Stringfellow, T.K. Tokunaga, T. Xu, and D. Zilberman (2008). Biologically Enhanced Carbon Sequestration: Research Needs and Opportunities. Report on the Energy Biosciences Institute Workshop on Biologically Enhanced Carbon Sequestration, October 29, 2007, Berkeley, CA. March 21, 2008 Rev. 8.1

Approximate solutions for diffusive fracture‐matrix transfer: Application to storage of dissolved CO2 in fractured rocks

Author(s): Zhou, Q; Oldenburg, CM; Spangler, LH; Birkholzer, JT | Abstract:

Leakage and Seepage in the Near-Surface Environment: An Integrated Approach to Monitoring and Detection

LEAKAGE AND SEEPAGE IN THE NEAR-SURFACE ENVIRONMENT: AN INTEGRATED APPROACH TO MONITORING AND DETECTION Curtis M. Oldenburg and Jennifer L. Lewicki Earth Sciences Division 90-1116, LBNL, Berkeley CA 94720 Abstract Monitoring and detection of leakage and seepage of carbon dioxide (CO 2 ) in the near-surface environment is needed to ensure the safety and effectiveness of geologic carbon sequestration. Large leakage fluxes, e.g., through leaking wells, will be easier to detect and monitor than slow and diffuse leakage and seepage. The challenge of detecting slow leakage and seepage is discerning a leakage or seepage signal from within the natural background variations in CO 2 concentration and flux that are controlled by a variety of coupled processes in soil. Although there are no direct examples of leaking geologic carbon sequestration sites on which to base a proposed verification approach, we have been guided by our prior simulation studies of CO 2 leakage and seepage, which showed that large CO 2 concentrations can develop in the shallow subsurface even for relatively small CO 2 leakage fluxes. A variety of monitoring technologies exists for measuring CO 2 concentration and flux, but there is a gap between instrument performance and the detection of a leakage or seepage signal from within large natural background variability. We propose an integrated approach to monitoring and verification. The first part of our proposed approach is to characterize and understand the natural ecosystem before CO 2 injection occurs so that future anomalies can be recognized. Measurements of natural CO 2 fluxes using accumulation chamber (AC) and eddy correlation (EC) approaches, soil CO 2 concentration profiles with depth, and carbon isotope compositions of CO 2 are needed to characterize the natural state of the system prior to CO 2 injection. From this information, modeling needs to be carried out to enhance understanding of carbon sources and sinks so that anomalies can be recognized and subject to closer scrutiny as potential leakage or seepage signals. Long-term monitoring using AC, EC, and soil-gas analyses along with ecosystem and flow and transport modeling should continue after CO 2 injection. The integrated use of multiple measurements and modeling offers a promising approach to discerning and quantifying a small CO 2 leakage or seepage signal from within the expected background variability. Introduction One of the outstanding challenges of geologic carbon sequestration is verification, that is, ensuring that carbon dioxide (CO 2 ) is not leaking from the intended sequestration formation and seeping out of the ground. The most straightforward way of verifying CO 2 sequestration would seem to be direct monitoring and detection of anomalous CO 2 in the near-surface environment. While catastrophic releases to the atmosphere, such as through well blowouts, will be obvious failures and therefore present no challenge for detection, slow or diffuse leakage and seepage of CO 2 will be much more difficult to detect, monitor, and quantify. The difficulty of observing and quantifying diffuse CO 2 leakage and seepage arises because there are large spatial and temporal changes in CO 2 concentration and flux in natural ecosystems, making the main challenge the detection of a CO 2 leakage or seepage signal from within the natural background variation. We have developed an approach for monitoring and verification that involves a variety of integrated measurements and modeling that could be used to discern a CO 2 leakage or seepage signal. In this brief paper, we summarize our proposed approach for geologic carbon sequestration verification. This approach is guided by results of numerical simulations of CO 2 leakage and seepage that we have carried out over the last few years, and by our experience in monitoring natural systems. Next we review controls on natural CO 2 in the shallow subsurface, and the technologies used for detecting and monitoring CO 2 in the near-surface environment. Finally, we present our ideas for an integrated approach to CO 2 verification. Corresponding author: Tel. (510) 486-7419, Fax. (510) 486-5686, Email: cmoldenburg@lbl.gov