Task 1. Performance prediction for underground fate and transport of CO₂

 

Contact:	Karsten Pruess
Key Personnel:	Tianfu Xu Christine Doughty

 

Goal: To develop reliable techniques to predict CO₂ migration and trapping mechanisms.

 The computer simulators TOUGH2 and TOUGHREACT will be further developed to accurately simulate the fate and transport of CO₂ in the subsurface. The codes will be made available to the public through the Department of Energy’s National Energy Software Center. TOUGH2 is a new and improved version of the TOUGH simulator ("transport of unsaturated groundwater and heat"). It is a multi-dimensional numerical model for simulating the coupled transport of water, vapor, non-condensible gas, and heat in porous and fractured media. TOUGH2 offers added capabilities and user features, including the flexibility to handle different fluid mixtures (water, water with tracer; water, CO₂; water, air; water, air, with vapor pressure lowering, and water, hydrogen). TOUGH2 also has facilities for generating computational grids, and an internal version control system to ensure referenceability of code applications. TOUGH2 uses an integral finite difference method for space discretization, and first-order fully implicit time differencing. A choice of a sparse direct solver or various preconditioned conjugate gradient algorithms are available for linear equation solution. Thermophysical properties of water are represented, within experimental accuracy, by steam table equations provided by the International Formulation Committee. The program provides options for specifying injection or withdrawal of heat and fluids. Double-porosity, dual-permeability, and multiple interacting continua (MINC) methods are available for modeling flow in fractured porous media. 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.

Sub Tasks 1a – 1c:

Task 1a. Leakage scenarios
Task 1b. TOUGHREACT
Task 1c. Hysteresis