Prof. Jefferson W Tester

Recovery of energy and mineral sources from the crust of the earth involves the application of virtually every chemical engineering discipline. For example, in order to gain access to the resource, drilling is commonly used. This is a risky and painfully expensive process involving comminution of rock and the use of jet and fluid hydraulics to efficiently remove rock chips produced by the drill bit. The extraction of natural gas, hydrocarbon liquids or geothermal heat from underground reservoirs couples fluid flow and heat transfer in porous, fractured rock. In the specific case of a low-permeability, fractured geothermal reservoir, predicting the production temperature history involves combining the effects of forced and buoyantly-driven convection of fluids contained in fractures to the transient thermal conduction of heat in the surrounding rock. For permafrost and marine sediments containing natural gas trapped in solid hydrates, the transfer of heat and pressure to specific regions will critically influence rates of gas production.

Environmental issues also often appear. These frequently involve the application of similar phenomena found in the recovery of the energy or minerals themselves. Relevant topics include the migration of chemicals into rock surrounding a land-based waste repository, the sequestration of carbon dioxide in geologic formations and in deep ocean environments, and the chemical treatment of liquid and gaseous effluents to remove toxic contaminants that may be present in groundwater and soils.

Motivated by these environmental goals, we are examining chemical and physical interactions in supercritical fluids utilized as solvent media for destroying organic wastes by oxidation in supercritical water (T>374†C, P>220 bar), for improved emission performance in the combustion of fossil and biomass fuels and for the synthesis of a variety of chemicals in supercritical carbon dioxide. Experimental measurements and molecular simulations are being used to understand solvent-solute interactions in concentrated aqueous salt solutions from ambient to supercritical conditions. Important molecular-level effects, including ion pairing, solvent-solute clustering, and degree of hydrogen bonding, are correlated to changes in dielectric constant, dissociation constant, salt solubility, and phase partitioning in general.

Current research activities also include studies of molecular modeling of methane and carbon dioxide hydrate properties and of salt-water interactions in supercritical water using statistical mechanics and quantum chemistry methods, fundamental kinetic measurements and multiscale modeling of hydrolysis and oxidation of model hydrocarbons (e.g., methylene chloride, methyl phosponic acid, and methyl tert-butyl ether), system modeling of geothermal heat mining, experimental and theoretical studies of rock drilling by thermally-induced rock spallation using combustion flame jets, and dissolution and deposition kinetics of solids in hydrothermal environments.