AbstractA Pitzer ion-interaction model for concentrated aqueous solutions was added to the reactive multiphase flow and transport code TOUGHREACT. The model is described and verified against published experimental data and the geochemical code EQ3/6. The model is used to simulate water-rock-gas interactions caused by boiling and evaporation within and around nuclear waste emplacement tunnels at the proposed high-level waste repository at Yucca Mountain, Nevada. The coupled thermal, hydrological, and chemical processes considered consist of water and air/vapor flow, evaporation, boiling, condensation, solute and gas transport, formation of highly concentrated brines, precipitation of deliquescent salts, generation of acid gases, and vapor-pressure lowering caused by the high salinity of the concentrated brine.
Numerical simulations of transport and isotope fractionation provide a method to quantitatively interpret vadose zone pore water stable isotope depth profiles based on soil properties, climatic conditions, and infiltration. We incorporate the temperature‐dependent equilibration of stable isotopic species between water and water vapor, and their differing diffusive transport properties into the thermodynamic database of the reactive transport code TOUGHREACT. These simulations are used to illustrate the evolution of stable isotope profiles in semiarid regions where recharge during wet seasons disturbs the drying profile traditionally associated with vadose zone pore waters. Alternating wet and dry seasons lead to annual fluctuations in moisture content, capillary pressure, and stable isotope compositions in the vadose zone. Periodic infiltration models capture the effects of seasonal increases in precipitation and predict stable isotope profiles that are distinct from those observed under drying (zero infiltration) conditions. After infiltration, evaporation causes a shift to higher δ 18 O and δD values, which are preserved in the deeper pore waters. The magnitude of the isotopic composition shift preserved in deep vadose zone pore waters varies inversely with the rate of infiltration.
Numerical simulations of transport and isotope fractionation provide a method to quantitatively interpret vadose zone pore water stable isotope depth profiles based on soil properties, climatic conditions, and infiltration. We incorporate the temperature-dependent equilibration of stable isotopic species between water and water vapor, and their differing diffusive transport properties into the thermodynamic database of the reactive transport code TOUGHREACT. These simulations are used to illustrate the evolution of stable isotope profiles in semiarid regions where recharge during wet seasons disturbs the drying profile traditionally associated with vadose zone pore waters. Alternating wet and dry seasons lead to annual fluctuations in moisture content, capillary pressure, and stable isotope compositions in the vadose zone. Periodic infiltration models capture the effects of seasonal increases in precipitation and predict stable isotope profiles that are distinct from those observed under drying (zero infiltration) conditions. After infiltration, evaporation causes a shift to higher 18O and D values, which are preserved in the deeper pore waters. The magnitude of the isotopic composition shift preserved in deep vadose zone pore waters varies inversely with the rate of infiltration.
During the middle stages of crystallization of the Skaergaard Layered Series large numbers of blocks became detached from the Upper Border Series and settled into the mush of crystals on the floor. It has been recognized for some time that these blocks now have compositions and textures that differ markedly from those of the units from which they came. They tend to be more plagioclase rich and seem to have lost mafic components to the surrounding gabbro. Numerical simulations coupling crystallization, melting, and heat and mass transfer for a multicomponent system show how the blocks reacted with the mush in which they were emplaced. Enhanced cooling and crystallization of a compositionally stratified mush adjacent to the blocks resulted in patterns of melt compositions similar to those of layering around the blocks. Volume changes during crystallization and melting induced convection of the interstitial melt leading to changes in the bulk compositions of the blocks and the surrounding mush. Inhomogeneities such as inclusions are likely to facilitate the onset of compositional convection in a chemically stratified solidification zone.
The Snake River Plain (SRP) volcanic province overlies a thermal anomaly that extends deep into the mantle; it represents one of the highest heat flow provinces in North America. The Yellowstone hotspot continues to feed a magma system that underlies much of southern Idaho and has produced basaltic volcanism as young as 2000 years old. It has been estimated to host up to 855 MW of potential geothermal power production, most of which is associated with the Snake River Plain volcanic province in Idaho, which lies outside the area of Yellowstone National Park (Neely, K.W. and Galinato, G., 2007, Geothermal power generation in Idaho: an overview of current developments and future potential, Open File Report, Idaho Office of Energy Resources).
U.S. D EPARTMENT OF E NERGY G EOTHERMAL T ECHNOLOGIES P ROGRAM E NHANCED G EOTHERMAL S YSTEMS P EER R EVIEW Project Title: Geothermal Reservoir Dynamics - TOUGHREACT Principal Investigator: Karsten Pruess Sponsoring Organization: Lawrence Berkeley National Laboratory Other Investigators: Tianfu Xu, Chao Shan, Yingqi Zhang, Yu-Shu Wu, Eric Sonnenthal, Nicolas Spycher, Jonny Rutqvist, Guoxiang Zhang, Mack Kennedy Collaborations University of Utah, Calpine, NCPA, GeothermEx, Shell International, Electric Power Development Company (EPDC, Japan), GESAL (El Salvador), Kansas State University, U of Neuchatel (Switzerland), The University of Auckland (New Zealand), IGG (Italy) Project Purpose This project has been active for several years and has focused on developing, enhancing and applying mathematical modeling capabilities for fractured geothermal systems. The emphasis of our work has recently shifted towards enhanced geothermal systems (EGS) and hot dry rock (HDR), and FY05 is the first year that the DOE-AOP actually lists this project under Enhanced Geothermal Systems. Our overall purpose is to develop new engineering tools and a better understanding of the coupling between fluid flow, heat transfer, chemical reactions, and rock-mechanical deformation, to demonstrate new EGS technology through field applications, and to make technical information and computer programs available for field applications. Project Objective(s) Improve fundamental understanding and engineering methods for geothermal systems, primarily focusing on EGS and HDR systems and on critical issues in geothermal systems that are difficult to produce. Improve techniques for characterizing reservoir conditions and processes through new modeling and monitoring techniques based on “active” tracers and coupled processes. Improve techniques for targeting injection towards specific engineering objectives, including maintaining and controlling injectivity, controlling non-condensible and corrosive gases, avoiding scale formation, and optimizing energy recovery. Seek opportunities for field testing and applying new technologies, and work with industrial partners and other research organizations.
