Transport and Thermodynamics

Scope:

This research area has a dual scope.  The first involves the study of the basic concepts, phenomena and processes involved in the transport of solutes and/or colloids in the subsurface.  Investigations on the subject include conceptual models and mathematical representations of diffusion, mechanical dispersion, sorption (for solutes) and filtration (for colloids) in both porous and fractured systems, and are based on theoretical, laboratory, and field studies.  Understanding of these processes is vital to environmental protection and remediation applications, particularly to nuclear waste disposal and radionuclide transport investigations.

The second part focuses on the complex interaction of flow and transport of fluids and heat with the thermodynamic processes associated with the physical and chemical changes exhibited by the geological system under study.  Gaining an insight in this area is necessary to accurately describe fluid behavior, phase changes, and chemical reactions in the subsurface, and is important to applications such as hydrocarbon recovery, carbon sequestration, and geochemistry.

This research area covers transport and thermodynamics, and encourages the integration of existing data with new theoretical, experimental, and modeling approaches, and including development of new conceptualizations for dynamic and non-equilibrium processes.  

ESD Activities:

The current activities within the Transport and Thermodynamics Research Area are in two areas reflecting the dual scope discussed above.

The first is developing a deeper understanding of the concepts, phenomena and processes involved in the transport of solutes and colloids, with particular emphasis on the transport of radioactive substances.  The impetus for this study is ESDÕs work on the proposed High Level Radioactive Waste Repository in Yucca Mountain, Nevada.  The effort addresses all components of transport, including advection, diffusion, hydrodynamic dispersion, radioactive decay, solute sorption, colloid filtration (both physical-chemical attachment and mechanical straining), and colloid-facilitated solute transport.  Emphasis is given to the subject of diffusion in unsaturated media, and particular attention is paid to the issue of diffusion from fractures into the matrix of variably-saturated fractured media.  To describe the problem, new concepts (such as the Active Fracture Model with Matrix diffusion) and the corresponding quantitative models have been developed, and are being experimentally investigated.  The colloid transport behavior is a relatively unexplored area, and constitutes a very active component of our research activities.  Work on the subject focuses on describing both diffusion and filtration (a kinetic process) in porous and fractured media, areas on which there is practically no information.  Results of these studies, along with recent advances reported in the literature, are incorporated in semianalytical and numerical codes used for transport studies. 

The second area focuses on incorporating the most recent advances in our understanding of thermodynamic processes into existing models of flow, transport, and reactive geochemistry in the subsurface.  Such processes include phase changes of compounds of interest (e.g., water, methane hydrates, etc.), thermophysical properties of liquids and gases, liquid and gas dissolution into water under conditions that cover the entire pressure and temperature range expected in subsurface applications.  The quantitative models derived from these studies are incorporated into the TOUGH2 family of codes, and are used in studies on environmental applications, conventional hydrocarbon recovery, CO₂ sequestration and resource recovery from unconventional sources (e.g., methane hydrates and coal-bed methane), as well as in the exploration of more exotic issues such as fluid flow in the shallow subsurface of planets in the solar system.

Contact:

George Moridis
ph: 510.486.4746
email: gjmoridis@lbl.gov