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Prediction of Scaling in Geothermal Systems

Description: One of the main objectives of the DOE Geothermal Program is to improve the efficiency and reliability of geothermal operations so that this renewable form of energy can be integrated into the nation's energy system. Scale formation and other chemical problems associated with energy extraction from high temperature brines frequently inhibit the economical utilization of geothermal resources. In some cases, these chemical problems can be so severe that development of a site must be abandoned after considerable capital investment. The goal of our research efforts is to construct an accurate computer model for describing the chemical behavior of geothermal brines under a wide range of operating conditions. This technology will provide industry a cost-effective means of identifying scaling problems in production and reinjection wells as well as in surface equipment, and also devising and testing methods for well as other uses described in table (1) can contribute significantly to meeting the objectives of the Geothermal Program. The chemical model we have developed to date can simulate calcium carbonate scale formation and gas solubilities in concentrated brines containing sodium, potassium, calcium, chloride and sulfate ions as a function of temperature to 250 C and for variable partial pressure of CO{sub 2}. It can predict the solubility of other scale-forming minerals, such as amorphous silica, gypsum-anhydrite, halite and glasserite, as a function of brine composition to 250 C. The only required input for the model is the temperature, pressure and composition of the brine. Our modeling approach is based on semi-empirical thermodynamic descriptions of aqueous solutions. The model equations are parameterized by careful comparison to a variety of laboratory data. The ability of the resulting models to accurately predict the chemical behavior of even very concentrated high temperature brines is well demonstrated. This ability is an unusual feature of our models which ...
Date: March 21, 1989
Creator: Weare, John H. & Moller, Nancy E.
Partner: UNT Libraries Government Documents Department

Calculation of the chemical behavior of highly concentrated geothermal brines

Description: In this report, the authors describe the development of a chemical equilibrium model for hydrothermal waters based on the semiempirical equations of aqueous electrolyte solutions recently introduced by Pitzer and co-workers. Accurate solubility predictions (usually within 5-10% of experimental results) can be made for ionic strengths 0-20m. Comparison with experimental data indicates that a theory parameterized by binary and ternary data can be used to accurately predict solubilities in much more complex mixtures. Mineral solubilities calculated with this model are compared with those calculated from other currently available models. Whereas the predictions are typically within 5%, the ion pairing models are substantially in error at low ionic strengths. Recent results parameterizing the H{sub 2}S and SiO{sub 2} systems will be presented.
Date: October 8, 1982
Creator: Moller-Weare, Nancy & Weare, John H.
Partner: UNT Libraries Government Documents Department

Models of Geothermal Brine Chemistry

Description: Many significant expenses encountered by the geothermal energy industry are related to chemical effects. When the composition, temperature of pressure of the fluids in the geological formation are changed, during reservoir evolution, well production, energy extraction or injection processes, the fluids that were originally at equilibrium with the formation minerals come to a new equilibrium composition, temperature and pressure. As a result, solid material can be precipitated, dissolved gases released and/or heat lost. Most geothermal energy operations experience these phenomena. For some resources, they create only minor problems. For others, they can have serious results, such as major scaling or corrosion of wells and plant equipment, reservoir permeability losses and toxic gas emission, that can significantly increase the costs of energy production and sometimes lead to site abandonment. In future operations that exploit deep heat sources and low permeability reservoirs, new chemical problems involving very high T, P rock/water interactions and unknown injection effects will arise.
Date: March 29, 2002
Creator: Weare, Nancy Moller & Weare, John H.
Partner: UNT Libraries Government Documents Department

Geothermal Brine Chemistry Modeling Program

Description: The UCSD brine chemistry program is providing highly accurate models of the behavior of high temperature brines to be used by the geothermal community to optimize production, interpret formation behavior and assist in performance assessment. Models are now available as user-oriented programs packaged for both main frame and personal computers (IBM and Macintosh). A manual describing the models and their application to various geothermal problems has been developed and made available to potential users. Tutorial sessions have been held and future sessions are planned. Present models can be used to predict the behavior of many important geothermal processes. For example, the tendency for production fluids to form carbonate, silica and sulfate scales can be predicted as a function of brine composition, temperature and CO{sub 2} partial pressure. The breakout pressure (onset of two phase flow) can be calculated as a function of temperature and brine composition. Preliminary models are available for characterizing H{sub 2}S gas/liquid distributions and the acid-base properties of the H{sub S}S-H{sub 2}O system as a function of brine composition, temperature and pressure. For the past year, a substantial part of this research has focused on the prediction of the properties of gases in the CO{sub 2}-CH{sub 4}-H{sub 2}O system. We have developed highly accurate equations of state for each of the endmembers of the system for a pressure range of 0 to 8000 bar and temperatures from 0 to 1000 C. In order to treat the mixtures of importance to geothermal applications, a mixing model based on the end-members has been developed. The resulting equation of state for mixtures can be integrated analytically to obtain the free energies and enthalpies of the mixed gases for a temperature range of 50 to 1000 C and pressures from 0 to 3000 bar. Predictions of this model are within the ...
Date: March 24, 1992
Creator: Duan, Zhenhao; Moller, Nancy; Greenberg, Jerry & Weare, John H.
Partner: UNT Libraries Government Documents Department

Automatic Transformation of MPI Programs to Asynchronous, Graph-Driven Form

Description: The goals of this project are to develop new, scalable, high-fidelity algorithms for atomic-level simulations and program transformations that automatically restructure existing applications, enabling them to scale forward to Petascale systems and beyond. The techniques enable legacy MPI application code to exploit greater parallelism though increased latency hiding and improved workload assignment. The techniques were successfully demonstrated on high-end scalable systems located at DOE laboratories. Besides the automatic MPI program transformations efforts, the project also developed several new scalable algorithms for ab-initio molecular dynamics, including new massively parallel algorithms for hybrid DFT and new parallel in time algorithms for molecular dynamics and ab-initio molecular dynamics. These algorithms were shown to scale to very large number of cores, and they were designed to work in the latency hiding framework developed in this project. The effectiveness of the developments was enhanced by the direct application to real grand challenge simulation problems covering a wide range of technologically important applications, time scales and accuracies. These included the simulation of the electronic structure of mineral/fluid interfaces, the very accurate simulation of chemical reactions in microsolvated environments, and the simulation of chemical behavior in very large enzyme reactions.
Date: April 30, 2013
Creator: Baden, Scott B.; Weare, John H. & Bylaska, Eric J.
Partner: UNT Libraries Government Documents Department

Computational Studies in Molecular Geochemistry and Biogeochemistry

Description: The ability to predict the transport and transformations of contaminants within the subsurface is critical for decisions on virtually every waste disposal option facing the Department of Energy (DOE), from remediation technologies such as in situ bioremediation to evaluations of the safety of nuclear waste repositories. With this fact in mind, the DOE has recently sponsored a series of workshops on the development of a Strategic Simulation Plan on applications of high perform-ance computing to national problems of significance to the DOE. One of the areas selected for application was in the area of subsurface transport and environmental chemistry. Within the SSP on subsurface transport and environmental chemistry several areas were identified where applications of high performance computing could potentially significantly advance our knowledge of contaminant fate and transport. Within each of these areas molecular level simulations were specifically identified as a key capability necessary for the development of a fundamental mechanistic understanding of complex biogeochemical processes. This effort consists of a series of specific molecular level simulations and program development in four key areas of geochemistry/biogeochemistry (i.e., aqueous hydrolysis, redox chemistry, mineral surface interactions, and microbial surface properties). By addressing these four differ-ent, but computationally related, areas it becomes possible to assemble a team of investigators with the necessary expertise in high performance computing, molecular simulation, and geochemistry/biogeochemistry to make significant progress in each area. The specific targeted geochemical/biogeochemical issues include: Microbial surface mediated processes: the effects of lipopolysacchardies present on gram-negative bacteria. Environmental redox chemistry: Dechlorination pathways of carbon tetrachloride and other polychlorinated compounds in the subsurface. Mineral surface interactions: Describing surfaces at multiple scales with realistic surface functional groups Aqueous Hydrolysis Reactions and Solvation of Highly Charged Species: Understanding the formation of polymerized species and ore formation under extreme (Hanford Vadose Zone and geothermo) conditions. By understanding ...
Date: April 18, 2006
Creator: Felmy, Andrew R.; Bylaska, Eric J.; Dixon, David A.; Dupuis, Michel; Halley, James W.; Kawai, R. et al.
Partner: UNT Libraries Government Documents Department

Session: Energy Conversion

Description: This session at the Geothermal Energy Program Review X: Geothermal Energy and the Utility Market consisted of five presentations: ''Hydrothermal Energy Conversion Technology'' by David Robertson and Raymond J. LaSala; ''Materials for Geothermal Production'' by Lawrence E. Kukacka; ''Supersaturated Turbine Expansions for Binary Geothermal Power Plants'' by Carl J. Bliem; ''Geothermal Waster Treatment Biotechnology: Progress and Advantages to the Utilities'' by Eugen T. Premuzic; and ''Geothermal Brine Chemistry Modeling Program'' by John H. Weare.
Date: January 1, 1992
Creator: Robertson, David; LaSala, Raymond J.; Kukacka, Lawrence E.; Bliem, Carl J.; Premuzic, Eugene T. & Weare, John H.
Partner: UNT Libraries Government Documents Department