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TOUGH: Suite of Simulators for Nonisothermal Multiphase Flow and Transport in Fractured Porous Media

Seepage into TunnelThe TOUGH ("Transport Of Unsaturated Groundwater and Heat") suite of software codes are multi-dimensional numerical models for simulating the coupled transport of water, vapor, non-condensible gas, and heat in porous and fractured media. Developed at the Lawrence Berkeley National Laboratory (LBNL) in the early 1980s primarily for geothermal reservoir engineering, the suite of simulators is now widely used at universities, government organizations, and private industry for applications to nuclear waste disposal, environmental remediation problems, energy production from geothermal, oil and gas reservoirs as well as gas hydrate deposits, geological carbon sequestration, vadose zone hydrology, and other uses that involve coupled thermal, hydrological, geochemical, and mechanical processes in permeable media. The TOUGH suite of simulators is continually updated, with new equation-of-state (EOS) modules being developed, and refined process descriptions implemented into the TOUGH framework (see the overview of the TOUGH development history). Notably, EOS property modules for mixtures of water, NaCl, and CO2 has been developed and is widely used for the analysis of geologic carbon sequestration processes.

TOUGH and its application have been the subject of more than 500 peer-reviewed journal articles, conference proceedings, and project reports. TOUGH and its various modules are documented in a series of manuals.

Karsten Pruess was presented a Lifetime Achievement Award for Development of the TOUGH Codes on Tuesday, September 18th at the 2012 TOUGH Symposium in Berkeley, CA.

TOUGH questions, comments, and suggestions as well as replies can be posted in the User Forum.

Below you will find a quick summary of the suite, with links to more detailed information on each module:

Tracer transport through heterogeneous columnTOUGH2 is the basic simulator for nonisothermal multiphase flow in fractured porous media. Although primarily designed for geothermal reservoir studies and high-level nuclear waste isolation, TOUGH2 can be applied to a wider range of problems in heat and moisture transfer, and in the drying of porous materials. The TOUGH2 simulator was developed for problems involving strongly heat-driven flow. To describe these phenomena a multi-phase approach to fluid and heat flow is used, which fully accounts for the movement of gaseous and liquid phases, their transport of latent and sensible heat, and phase transitions between liquid and vapor. TOUGH2 takes account of fluid flow in both liquid and gaseous phases occurring under pressure, viscous, and gravity forces according to Darcy's law. Interference between the phases is represented by means of relative permeability functions. The code includes Klinkenberg effects and binary diffusion in the gas phase, and capillary and phase adsorption effects for the liquid phase. Heat transport occurs by means of conduction (with thermal conductivity dependent on water saturation), convection, and binary diffusion, which includes both sensible and latent heat.

Steam EORT2VOC is a TOUGH module for three-phase flow of water, air, and a volatile organic compound (VOC). T2VOC was designed to simulate processes such as the migration of hazardous non-aqueous phase liquids (NAPLs) in variably saturated media, forced vacuum extraction of organic chemical vapors from the unsaturated zone (soil vapor extraction), evaporation and diffusion of chemical vapors in the unsaturated zone, air injection into the saturated zone for removal of volatile organics (air sparging), direct pumping of contaminated water and free product, and steam injection for the removal of NAPLs from contaminated soils and aquifers.

Steam EORTMVOC is a numerical simulator for three-phase non-isothermal flow of water, soil gas, and a multicomponent mixture of volatile organic chemicals (VOCs) in multidimensional heterogeneous porous media. TMVOC is designed for applications to contamination problems that involve hydrocarbon fuel or organic solvent spills in saturated and unsaturated zones. It can model contaminant behavior under "natural" environmental conditions, as well as for engineered systems, such as soil vapor extraction, groundwater pumping, or steam-assisted source remediation. TMVOC is backwards compatible with T2VOC and can be initialized from T2VOC-style initial conditions.

TOUGHREACTTOUGHREACT is a numerical simulation program for chemically reactive non-isothermal flows of multiphase fluids in porous and fractured media, developed by introducing reactive chemistry into the multiphase flow code TOUGH2. 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, and can also modify the unsaturated flow properties of the rock.

TOUGH+ is the result of a re-engineering effort in which the capabilities of TOUGH2 have been recast in a modular design that adheres to the tenets of object-oriented programming as implemented in Fortran 95. New capabilities have been added. I particular, the range of thermodynamic properties of water has been extended to include ice for the modeling of freezing and thawing in permafrost regions, and - specifically - for the simulation of processes in hydrate-bearing sediments, which involve. formation and dissociation of ice-like hydrates with associated changes in porosity, permeability, and two-phase flow characteristics. The first module released in the new framework is TOUGH+Hydrate for the simulation of these processes in hydrate-bearing formations. TOUGH+ maintains backwards compatibility with TOUGH2 input files.

iTOUGH2 LogoiTOUGH2 (inverse TOUGH2) is a computer program that provides inverse modeling capabilities for the TOUGH codes. iTOUGH2 solves the inverse problem by automatically calibrating a TOUGH2 model (or any other model) against observed data. Any TOUGH2 input parameter can be estimated based on any observation for which a corresponding TOUGH2 output can be calculated. An objective function measures the difference between the model calculation and the observed data, and a minimization algorithm proposes new parameter sets that iteratively improve the match. Once the best estimate parameter set is identified, iTOUGH2 performs an extensive error analysis, which provides statistical information about residuals, estimation uncertainties, and the ability to discriminate among model alternatives. Furthermore, an uncertainty propagation analysis allows one to quantify prediction errors.

Additional Information