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Application of TOUGH2/EOS7R to modeling of radionuclide release from a low/intermediate level repository under two-phase conditions

Description: The generation of gas due to corrosion of repository waste packages under water-saturated conditions will give rise to pressure increases and two-phase flow conditions. We have developed a numerical simulator TOUGH2/EOS7R for modeling the two-phase flow and transport of a parent-daughter pair of radionuclides including the processes of adsorption, first-order decay, binary diffusion, and volatilization. TOUGH2/EOS7R is a descendant of EOS7, the water, brine and air module of TOUGH2. We apply TOUGH2/EOS7R to an example problem relevant to the disposal of low- and intermediate-level nuclear wastes in crystalline rock. The conceptual model and spatial discretization were provided to us by NAGRA. We demonstrate in preliminary simulations that to good approximation, the generation of hydrogen can be modeled using air as a proxy for hydrogen. Simulations of gas generation and subsequent flow and transport away from the repository demonstrate the use and flexibility of TOUGH2/EOS7R. By small modification in the code, users can printout data for calculating the fractional release curve (FR curve), which shows the instantaneous release rate from the repository.
Date: June 1, 1996
Creator: Oldenburg, C.M. & Pruess, K.
Partner: UNT Libraries Government Documents Department

Strongly coupled single-phase flow problems: Effects of density variation, hydrodynamic dispersion, and first order decay

Description: We have developed TOUGH2 modules for strongly coupled flow and transport that include full hydrodynamic dispersion. T2DM models two-dimensional flow and transport in systems with variable salinity, while T2DMR includes radionuclide transport with firstorder decay of a parent-daughter chain of radionuclide components in variable salinity systems. T2DM has been applied to a variety of coupled flow problems including the pure solutal convection problem of Elder and the mixed free and forced convection salt-dome flow problem. In the Elder and salt-dome flow problems, density changes of up to 20% caused by brine concentration variations lead to strong coupling between the velocity and brine concentration fields. T2DM efficiently calculates flow and transport for these problems. We have applied T2DMR to the dispersive transport and decay of radionuclide tracers in flow fields with permeability heterogeneities and recirculating flows. Coupling in th ese problems occurs by velocity-dependent hydrodynamic dispersion. Our results show that the maximum daughter species concentration may occur fully within a recirculating or low-velocity region. In all of the problems, we observe very efficient handling of the strongly coupled flow and transport processes.
Date: March 1, 1995
Creator: Oldenburg, C.M. & Pruess, K.
Partner: UNT Libraries Government Documents Department

Geologic carbon sequestration as a global strategy to mitigate CO2 emissions: Sustainability and environmental risk

Description: Fossil fuels are abundant, inexpensive to produce, and are easily converted to usable energy by combustion as demonstrated by mankind's dependence on fossil fuels for over 80% of its primary energy supply (13). This reliance on fossil fuels comes with the cost of carbon dioxide (CO{sub 2}) emissions that exceed the rate at which CO{sub 2} can be absorbed by terrestrial and oceanic systems worldwide resulting in increases in atmospheric CO{sub 2} concentration as recorded by direct measurements over more than five decades (14). Carbon dioxide is the main greenhouse gas linked to global warming and associated climate change, the impacts of which are currently being observed around the world, and projections of which include alarming consequences such as water and food shortages, sea level rise, and social disruptions associated with resource scarcity (15). The current situation of a world that derives the bulk of its energy from fossil fuel in a manner that directly causes climate change equates to an energy-climate crisis. Although governments around the world have only recently begun to consider policies to avoid the direst projections of climate change and its impacts, sustainable approaches to addressing the crisis are available. The common thread of feasible strategies to the energy climate crisis is the simultaneous use of multiple approaches based on available technologies (e.g., 16). Efficiency improvements (e.g., in building energy use), increased use of natural gas relative to coal, and increased development of renewables such as solar, wind, and geothermal, along with nuclear energy, are all available options that will reduce net CO{sub 2} emissions. While improvements in efficiency can be made rapidly and will pay for themselves, the slower pace of change and greater monetary costs associated with increased use of renewables and nuclear energy suggests an additional approach is needed to help bridge the ...
Date: April 1, 2011
Creator: Oldenburg, C.M.
Partner: UNT Libraries Government Documents Department

On carbon footprints and growing energy use

Description: Could fractional reductions in the carbon footprint of a growing organization lead to a corresponding real reduction in atmospheric CO{sub 2} emissions in the next ten years? Curtis M. Oldenburg, head of the Geologic Carbon Sequestration Program of LBNL’s Earth Sciences Division, considers his own organization's carbon footprint and answers this critical question? In addressing the problem of energy-related greenhouse gas (GHG) emissions and climate change, it is essential that we understand which activities are producing GHGs and the scale of emission for each activity, so that reduction efforts can be efficiently targeted. The GHG emissions to the atmosphere of an individual or group are referred to as the ‘carbon footprint’. This terminology is entirely appropriate, because 85% of the global marketed energy supply comes from carbon-rich fossil fuel sources whose combustion produces CO{sub 2}, the main GHG causing global climate change. Furthermore, the direct relation between CO2 emissions and fossil fuels as they are used today makes energy consumption a useful proxy for carbon footprint. It would seem to be a simple matter to reduce energy consumption across the board, both individually and collectively, to help reduce our carbon footprints and therefore solve the energyclimate crisis. But just how much can we reduce carbon footprints when broader forces, such as growth in energy use, cause the total footprint to simultaneously expand? In this feature, I present a calculation of the carbon footprint of the Earth Sciences Division (ESD), the division in which I work at Lawrence Berkeley National Laboratory (LBNL), and discuss the potential for reducing this carbon footprint. It will be apparent that in terms of potential future carbon footprint reductions under projections of expected growth, ESD may be thought of as a microcosm of the situation of the world as a whole, in which alternatives to the ...
Date: June 1, 2011
Creator: Oldenburg, C.M.
Partner: UNT Libraries Government Documents Department

Health, safety, and environmental risks from energy production: A year-long reality check

Description: Large-scale carbon dioxide capture and storage (CCS) offers the benefit of reducing CO{sub 2} emissions and thereby mitigating climate change risk, but it will also bring its own health, safety, and environmental risks. Curtis M. Oldenburg, Editor-in-Chief, considers these risks in the context of the broader picture of energy production. Over the last year, there have been major acute health, safety, and environmental (HSE) consequences related to accidents involving energy production from every major primary energy source. These are, in chronological order: (i) the Upper Big Branch (coal) Mine disaster, (ii) the Gulf of Mexico Macondo (oil) well blowout, (iii) the San Bruno (natural gas) pipeline leak and explosion, and (iv) the Fukushima (nuclear) reactor radioactivity releases. Briefly, the Upper Big Branch Mine disaster occurred in West Virginia on April 5, 2010, when natural methane in the mine ignited, causing the deaths of 29 miners, the worst coal mine disaster in the USA since 1970. Fifteen days later, the Macondo oil well in the Gulf of Mexico suffered a blowout, with a gas explosion and fire on the floating drilling platform that killed 11 people. The oil and gas continued to flow out of the well at the seafloor until July 15, 2010, spilling a total of approximately 5 million barrels of oil into the sea. On September 9, 2010, a 30-inch (76-cm) buried, steel, natural gas pipeline in San Bruno, California, leaked gas and exploded in a residential neighborhood, killing 8 people in their homes and burning a total of 38 homes. Flames were up to 1000 ft (300 m) high, and the initial explosion itself reportedly measured 1.1 on the Richter scale. Finally, on March 11, 2011, a magnitude 9.0 earthquake off the coast of Japan's main island, Honshu, caused a tsunami that crippled the backup power and ...
Date: April 1, 2011
Creator: Oldenburg, C.M.
Partner: UNT Libraries Government Documents Department

Improved understanding of geologic CO{sub 2} storage processes requires risk-driven field experiments

Description: The need for risk-driven field experiments for CO{sub 2} geologic storage processes to complement ongoing pilot-scale demonstrations is discussed. These risk-driven field experiments would be aimed at understanding the circumstances under which things can go wrong with a CO{sub 2} capture and storage (CCS) project and cause it to fail, as distinguished from accomplishing this end using demonstration and industrial scale sites. Such risk-driven tests would complement risk-assessment efforts that have already been carried out by providing opportunities to validate risk models. In addition to experimenting with high-risk scenarios, these controlled field experiments could help validate monitoring approaches to improve performance assessment and guide development of mitigation strategies.
Date: June 1, 2011
Creator: Oldenburg, C.M.
Partner: UNT Libraries Government Documents Department

A two-dimensional dispersion module for the TOUGH2 simulator

Description: A standard model for hydrodynamic dispersion has been added to TOUGH2- The dispersion model, intended for use with the EOS7 fluid properties module, accounts for the effects of hydrodynamic dispersion and molecular diffusion in two-dimensional rectangular domains. Because the model.requires Darcy velocity and species concentration gradient vectors at all connections, known vector components (perpendicular to the grid block interfaces) from neighboring connections are interpolated to form the unknown components (parallel to the grid block interfaces) at each connection. Thus the dispersive fluxes depend not only on the primary variables of the two connected grid blocks but on all p variables of the six neighbor grid blocks of each interface. This gives rise to added terms in the Jacobian matrix relative to standard TOUGH2 where fluxes depend only on primary variables in the two connected grid blocks. For flexibility in implementing boundary conditions, the model allows the user to define a flow domain that is a subset of the calculation domain. The PARAM and SELEC blocks of the TOUGH2 input file are used to specify parameters and boundary condition options for the dispersion module. The dispersion module has been verified by comparing computed results to analytical solutions. As an introduction to applications, we demonstrate the solution of a difficult twodimensional flow problem with variable salinity and strong coupling between dispersive and advective flow.
Date: September 1, 1993
Creator: Oldenburg, C. M. & Pruess, K.
Partner: UNT Libraries Government Documents Department

Numerical simulation of coupled flow and transport with TOUGH2: A verification study

Description: We have tested T2DM, the dispersion module of TOUGH2, on two classic flow problems: (1) the seawater intrusion problem of Henry (1964); and (2) the pure solutal free convection problem of Elder (1967). T2DM produces results in agreement with prior work for similar spatial discretizations. In the Henry problem, finer spatial discretization allows the seawater tongue to penetrate slightly farther without affecting the overall flow dynamics. In the strongly coupled pure solutal free convection problem of Elder, results produced by T2DM using high-resolution grids differ markedly from lower-resolution results. These high-resolution simulations agree closely with laboratory experiments.
Date: October 1, 1994
Creator: Oldenburg, C. M. & Pruess, K.
Partner: UNT Libraries Government Documents Department

Carbon sequestration with enhanced gas recovery: Identifying candidate sites for pilot study

Description: Depleted natural gas reservoirs are promising targets for carbon dioxide sequestration. Although depleted, these reservoirs are not devoid of methane, and carbon dioxide injection may allow enhanced production of methane by reservoir repressurization or pressure maintenance. Based on the favorable results of numerous simulation studies, we propose a field test of the Carbon Sequestration with Enhanced Gas Recovery (CSEGR) process. The objective of the field test is to evaluate the feasibility of CSEGR in terms of reservoir processes such as injectivity, repressurization, flow and transport of carbon dioxide, and enhanced production of methane. The main criteria for the field site include small reservoir volume and high permeability so that increases in pressure and enhanced recovery will occur over a reasonably short time period. The Rio Vista Gas Field in the delta of California's Central Valley offers potential as a test site, although we are currently looking broadly for other potential sites of opportunity.
Date: March 1, 2001
Creator: Oldenburg, C.M. & Benson, S.M.
Partner: UNT Libraries Government Documents Department

EOS7R: Radionuclide transport for TOUGH2

Description: EOS7R provides radionuclide transport capability for TOUGH2. EOS7R extends the EOS7 module (water, brine, and optional air) to model water, brine, parent component, daughter component, and optional air and heat. The radionuclide components follow a first-order decay law, and may adsorb onto the solid grains. Volatilization of the decaying components is modeled by Henry`s Law. The decaying components are normally referred to as radionuclides, but they may in fact by any trace components that decay, adsorb, and volatilize. The decay process need not be radioactive decay, but could be any process that follows a first-order decay law, such as biodegradation. EOS7R includes molecular diffusion for all components in gaseous and aqueous phases using a simplified binary diffusion model. When EOS7R is used with standard TOUGH2, transport occurs by advection and molecular diffusion in all phases. When EOS7R is coupled with the dispersion module T2DM, one obtains T2DMR, the radionuclide transport version of T2DM. T2DMR models advection, diffusion, and hydrodynamic dispersion in rectangular two-dimensional regions. Modeling of radionuclide transport requires input parameters specifying the half-life for first-order decay, distribution coefficients for each rock type for adsorption, and inverse Henry`s constants for volatilization. Options can be specified in the input file to model decay in inactive grid blocks and to read from standard EOS7 INCON files. The authors present a number of example problems to demonstrate application and accuracy of TOUGH2/EOS7R. One-dimensional simulation results agree well with analytical solutions. For a two-dimensional salt-dome flow problem, the final distribution of daughter radionuclide component is complicated by the presence of weak recirculation caused by density effects due to salinity.
Date: November 1, 1995
Creator: Oldenburg, C.M. & Pruess, K.
Partner: UNT Libraries Government Documents Department

On the development of MP-TOUGH2

Description: The authors are developing MP-TOUGH2 for exploiting massively parallel computers. The goals of this effort are to (1) create a data-parallel subsurface transport code for solving larger problems than currently practical on workstations, (2) write portable code that can take advantage of scalability to run on machines with more processors, and (3) minimize the necessity for additional validation and verification of the resulting code. The initial strategy they have followed is to focus on optimizing the generic and time-consuming task of linear equation solution while leaving the bulk of TOUGH2 unmodified. In so doing, they have implemented a massively parallel direct solver (MPDS) that takes advantage of the banded structure of TOUGH2 Jacobian matrices. The authors have compared timings of the iterative conjugate gradient solvers DSLUBC, DSLUCS, and DSLUGM written in Fortran77 for the front end with the MPDS which uses the data parallel unit. The MPDS shows good performance relative to the iterative conjugate gradient solvers on the free-convection test problem. The robust direct solution provided by MPDS can be used to (1) check on the veracity of a given iterative conjugate gradient solution, or (2) be used on certain problems where iterative solvers fail to converge. The test problem used in this study is the Elder pure thermal convection problem. For generality, the authors use the TOUGH2 equation of state module EOS3 for water, air, and heat, although this particular problem is a single-phase flow problem.
Date: February 1, 1995
Creator: Oldenburg, C.M.; Hinkins, R.L.; Moridis, G.J. & Pruess, K.
Partner: UNT Libraries Government Documents Department

Site S-7 Representative Model and Application for the Vadose Zone Monitoring System (VZMS) McClellan AFB - 1998 Semi-Annual Report

Description: Vadose zone data collection and enhanced data analysis are continuing for the Vadose Zone Monitoring System (VZMS) installed at site S-7 in IC 34 at McClellan MB. Data from core samples from boreholes drilled in 1998 and from VZMS continuous monitoring are evaluated and compared to previously collected data and analyses. The suite of data collected to date is used to develop and constrain a spatially averaged, one-dimensional site S-7 representative model that is implemented into T2VOC. Testing of the conceptual model under conditions of recharge of 100 mm/yr produces plausible moisture contents relative to data from several sources. Further scoping calculations involving gas-phase TCE transport in the representative model were undertaken. We investigate the role of recharge on TCE transport as well as the role of ion- and gas-phase flow driven by density and barometric pumping effects. This report provides the first example of the application of the site S-7 representative model in th e investigation of subsurface VOC movement.
Date: December 1, 1998
Creator: James, A.L. & Oldenburg, C.M.
Partner: UNT Libraries Government Documents Department

Economic Feasibility of Carbon Sequestration with Enhanced Gas Recovery (CSEGR)

Description: Prior reservoir simulation and laboratory studies have suggested that injecting carbon dioxide into mature natural gas reservoirs for carbon sequestration with enhanced gas recovery (CSEGR) is technically feasible. Reservoir simulations show that the high density of carbon dioxide can be exploited to favor displacement of methane with limited gas mixing by injecting carbon dioxide in low regions of a reservoir while producing from higher regions in the reservoir. Economic sensitivity analysis of a prototypical CSEGR application at a large depleting gas field in California shows that the largest expense will be for carbon dioxide capture, purification, compression, and transport to the field. Other incremental costs for CSEGR include: (1) new or reconditioned wells for carbon dioxide injection, methane production, and monitoring; (2) carbon dioxide distribution within the field; and, (3) separation facilities to handle eventual carbon dioxide contamination of the methane. Economic feasibility is most sensitive to wellhead methane price, carbon dioxide supply costs, and the ratio of carbon dioxide injected to incremental methane produced. Our analysis suggests that CSEGR may be economically feasible at carbon dioxide supply costs of up to $4 to $12/t ($0.20 to $0.63/Mcf). Although this analysis is based on a particular gas field, the approach is general and can be applied to other gas fields. This economic analysis, along with reservoir simulation and laboratory studies that suggest the technical feasibility of CSEGR, demonstrates that CSEGR can be feasible and that a field pilot study of the process should be undertaken to test the concept further.
Date: February 26, 2003
Creator: Oldenburg, C. M.; Stevens, S. H. & Benson, S. M.
Partner: UNT Libraries Government Documents Department

Analytical solution for Joule-Thomson cooling during CO2 geo-sequestration in depleted oil and gas reservoirs

Description: Mathematical tools are needed to screen out sites where Joule-Thomson cooling is a prohibitive factor for CO{sub 2} geo-sequestration and to design approaches to mitigate the effect. In this paper, a simple analytical solution is developed by invoking steady-state flow and constant thermophysical properties. The analytical solution allows fast evaluation of spatiotemporal temperature fields, resulting from constant-rate CO{sub 2} injection. The applicability of the analytical solution is demonstrated by comparison with non-isothermal simulation results from the reservoir simulator TOUGH2. Analysis confirms that for an injection rate of 3 kg s{sup -1} (0.1 MT yr{sup -1}) into moderately warm (>40 C) and permeable formations (>10{sup -14} m{sup 2} (10 mD)), JTC is unlikely to be a problem for initial reservoir pressures as low as 2 MPa (290 psi).
Date: May 21, 2010
Creator: Mathias, S.A.; Gluyas, J.G.; Oldenburg, C.M. & Tsang, C.-F.
Partner: UNT Libraries Government Documents Department

Origin of the patchy emission pattern at the ZERT CO2 Release Test

Description: A numerical experiment was carried out to test whether the patchy CO{sub 2} emission patterns observed at the ZERT release facility are caused by the presence of packers that divide the horizontal injection well into six CO2-injection zones. A three-dimensional model of the horizontal well and cobble-soil system was developed and simulations using TOUGH2/EOS7CA were carried out. Simulation results show patchy emissions for the seven-packer (six-injection-zone) configuration of the field test. Numerical experiments were then conducted for the cases of 24 packers (23 injection zones) and an effectively infinite number of packers. The time to surface breakthrough and the number of patches increased as the number of packers increased suggesting that packers and associated along pipe flow are the origin of the patchy emissions. In addition, it was observed that early breakthrough occurs at locations where the horizontal well pipe is shallow and installed mostly in soil rather than the deeper cobble. In the cases where the pipe is installed at shallow depths and directly in the soil, higher pipe gas saturations occur than where the pipe is installed slightly deeper in the cobble. It is believed this is an effect mostly relevant to the model rather than the field system and arises through the influence of capillarity, permeability, and pipe elevation of the soil compared to the cobble adjacent to the pipe.
Date: October 15, 2009
Creator: Lewicki, J.L.; Pan, L.; Dobeck, L.; Spangler, L. & Oldenburg, C.M.
Partner: UNT Libraries Government Documents Department

Time-windows-based filtering method for near-surface detection of leakage from geologic carbon sequestration sites

Description: We use process-based modeling techniques to characterize the temporal features of natural biologically controlled surface CO{sub 2} fluxes and the relationships between the assimilation and respiration fluxes. Based on these analyses, we develop a signal-enhancing technique that combines a novel time-window splitting scheme, a simple median filtering, and an appropriate scaling method to detect potential signals of leakage of CO{sub 2} from geologic carbon sequestration sites from within datasets of net near-surface CO{sub 2} flux measurements. The technique can be directly applied to measured data and does not require subjective gap filling or data-smoothing preprocessing. Preliminary application of the new method to flux measurements from a CO{sub 2} shallow-release experiment appears promising for detecting a leakage signal relative to background variability. The leakage index of ?2 was found to span the range of biological variability for various ecosystems as determined by observing CO{sub 2} flux data at various control sites for a number of years.
Date: February 28, 2010
Creator: Pan, L.; Lewicki, J.L.; Oldenburg, C.M. & Fischer, M.L.
Partner: UNT Libraries Government Documents Department

Pressure perturbations from geologic carbon sequestration: Area-of-review boundaries and borehole leakage driving forces

Description: We investigate the possibility that brine could be displaced upward into potable water through wells. Because of the large volumes of CO2 to be injected, the influence of the zone of elevated pressure on potential conduits such as well boreholes could extend many kilometers from the injection site-farther than the CO2 plume itself. The traditional approach to address potential brine leakage related to fluid injection is to set an area of fixed radius around the injection well/zone and to examine wells and other potentially open pathways located in the ''Area-of-Review'' (AoR). This suggests that the AoR eeds to be defined in terms of the potential for a given pressure perturbation to drive upward fluid flow in any given system rather than on some arbitrary pressure rise. We present an analysis that focuses on the changes in density/salinity of the fluids in the potentially leaking wellbore.
Date: July 1, 2009
Creator: Nicot, J.-P.; Oldenburg, C.M.; Bryant, S.L. & Hovorka, S.D.
Partner: UNT Libraries Government Documents Department

Predicting the spatial extent of injection-induced zones of enhanced permeability at the Northwest Geysers EGS Demonstration Project

Description: We present the results of coupled thermal, hydraulic, and mechanical (THM) modeling of a proposed stimulation injection associated with an Enhanced Geothermal System (EGS) demonstration project at the northwest part of The Geysers geothermal field, California. The project aims at creating an EGS by directly and systematically injecting cool water at relatively low pressure into a known High Temperature (about 280 to 350 C) Zone (HTZ) located under the conventional (240 C) steam reservoir at depths below 3 km. Accurate micro-earthquake monitoring from the start of the injection will be used as a tool for tracking the development of the EGS. We first analyzed historic injection and micro-earthquake data from an injection well (Aidlin 11), located about 3 miles to the west of the new EGS demonstration area. Thereafter, we used the same modeling approach to predict the likely extent of the zone of enhanced permeability for a proposed initial injection in two wells (Prati State 31 and Prati 32) at the new EGS demonstration area. Our modeling indicates that the proposed injection scheme will provide additional steam production in the area by creating a zone of permeability enhancement extending about 0.5 km from each injection well which will connect to the overlying conventional steam reservoir.
Date: February 1, 2010
Creator: Rutqvist, J.; Oldenburg, C.M. & Dobson, P.F.
Partner: UNT Libraries Government Documents Department

Measuring and Modeling Fault Density for Plume-Fault Encounter Probability Estimation

Description: Emission of carbon dioxide from fossil-fueled power generation stations contributes to global climate change. Storage of this carbon dioxide within the pores of geologic strata (geologic carbon storage) is one approach to mitigating the climate change that would otherwise occur. The large storage volume needed for this mitigation requires injection into brine-filled pore space in reservoir strata overlain by cap rocks. One of the main concerns of storage in such rocks is leakage via faults. In the early stages of site selection, site-specific fault coverages are often not available. This necessitates a method for using available fault data to develop an estimate of the likelihood of injected carbon dioxide encountering and migrating up a fault, primarily due to buoyancy. Fault population statistics provide one of the main inputs to calculate the encounter probability. Previous fault population statistics work is shown to be applicable to areal fault density statistics. This result is applied to a case study in the southern portion of the San Joaquin Basin with the result that the probability of a carbon dioxide plume from a previously planned injection had a 3% chance of encountering a fully seal offsetting fault.
Date: May 15, 2011
Creator: Jordan, P.D.; Oldenburg, C.M. & Nicot, J.-P.
Partner: UNT Libraries Government Documents Department

Percolation-theory and fuzzy rule-based probability estimation of fault leakage at geologic carbon sequestration sites

Description: Leakage of CO{sub 2} and displaced brine from geologic carbon sequestration (GCS) sites into potable groundwater or to the near-surface environment is a primary concern for safety and effectiveness of GCS. The focus of this study is on the estimation of the probability of CO{sub 2} leakage along conduits such as faults and fractures. This probability is controlled by (1) the probability that the CO{sub 2} plume encounters a conductive fault that could serve as a conduit for CO{sub 2} to leak through the sealing formation, and (2) the probability that the conductive fault(s) intersected by the CO{sub 2} plume are connected to other conductive faults in such a way that a connected flow path is formed to allow CO{sub 2} to leak to environmental resources that may be impacted by leakage. This work is designed to fit into the certification framework for geological CO{sub 2} storage, which represents vulnerable resources such as potable groundwater, health and safety, and the near-surface environment as discrete 'compartments'. The method we propose for calculating the probability of the network of conduits intersecting the CO{sub 2} plume and one or more compartments includes four steps: (1) assuming that a random network of conduits follows a power-law distribution, a critical conduit density is calculated based on percolation theory; for densities sufficiently smaller than this critical density, the leakage probability is zero; (2) for systems with a conduit density around or above the critical density, we perform a Monte Carlo simulation, generating realizations of conduit networks to determine the leakage probability of the CO{sub 2} plume (P{sub leak}) for different conduit length distributions, densities and CO{sub 2} plume sizes; (3) from the results of Step 2, we construct fuzzy rules to relate P{sub leak} to system characteristics such as system size, CO{sub 2} plume size, and ...
Date: May 1, 2009
Creator: Zhang, Y.; Oldenburg, C.M. & Finsterle, S.
Partner: UNT Libraries Government Documents Department

A Simplified 1-D Model for Calculating CO2 Leakage through Conduits

Description: In geological CO{sub 2} storage projects, a cap rock is generally needed to prevent CO{sub 2} from leaking out of the storage formation. However, the injected CO{sub 2} may still encounter some discrete flow paths such as a conductive well or fault (here referred to as conduits) through the cap rock allowing escape of CO{sub 2} from the storage formation. As CO{sub 2} migrates upward, it may migrate into the surrounding formations. The amount of mass that is lost to the formation is called attenuation. This report describes a simplified model to calculate the CO{sub 2} mass flux at different locations of the conduit and the amount of attenuation to the surrounding formations. From the comparison among the three model results, we can conclude that the steady-state conduit model (SSCM) provides a more accurate solution than the PMC at a given discretization. When there is not a large difference between the permeability of the surrounding formation and the permeability of the conduits, and there is leak-off at the bottom formation (the formation immediately above the CO{sub 2} plume), a fine discretization is needed for an accurate solution. Based on this comparison, we propose to use the SSCM in the rapid prototype for now given it does not produce spurious oscillations, and is already in FORTRAN and therefore can be easily made into a dll for use in GoldSim.
Date: February 15, 2011
Creator: Zhang, Y. & Oldenburg, C.M.
Partner: UNT Libraries Government Documents Department

Injection, flow, and mixing of CO2 in porous media with residual gas.

Description: Geologic structures associated with depleted natural gas reservoirs are desirable targets for geologic carbon sequestration (GCS) as evidenced by numerous pilot and industrial-scale GCS projects in these environments world-wide. One feature of these GCS targets that may affect injection is the presence of residual CH{sub 4}. It is well known that CH{sub 4} drastically alters supercritical CO{sub 2} density and viscosity. Furthermore, residual gas of any kind affects the relative permeability of the liquid and gas phases, with relative permeability of the gas phase strongly dependent on the time-history of imbibition or drainage, i.e., dependent on hysteretic relative permeability. In this study, the effects of residual CH{sub 4} on supercritical CO{sub 2} injection were investigated by numerical simulation in an idealized one-dimensional system under three scenarios: (1) with no residual gas; (2) with residual supercritical CO{sub 2}; and (3) with residual CH{sub 4}. We further compare results of simulations that use non-hysteretic and hysteretic relative permeability functions. The primary effect of residual gas is to decrease injectivity by decreasing liquid-phase relative permeability. Secondary effects arise from injected gas effectively incorporating residual gas and thereby extending the mobile gas plume relative to cases with no residual gas. Third-order effects arise from gas mixing and associated compositional effects on density that effectively create a larger plume per unit mass. Non-hysteretic models of relative permeability can be used to approximate some parts of the behavior of the system, but fully hysteretic formulations are needed to accurately model the entire system.
Date: September 1, 2010
Creator: Oldenburg, C.M. & Doughty, C.A.
Partner: UNT Libraries Government Documents Department

Welcome to Greenhouse Gases: Science and Technology: Editorial

Description: This editorial introduces readers and contributors to a new online journal. Through the publication of articles ranging from peer-reviewed research papers and short communications, to editorials and interviews on greenhouse gas emissions science and technology, this journal will disseminate research results and information that address the global crisis of anthropogenic climate change. The scope of the journal includes the full spectrum of research areas from capture and separation of greenhouse gases from flue gases and ambient air, to beneficial utilization, and to sequestration in deep geologic formations and terrestrial (plant and soil) systems, as well as policy and technoeconomic analyses of these approaches.
Date: February 1, 2011
Creator: Oldenburg, C. M. & Maroto-Valer, M. M.
Partner: UNT Libraries Government Documents Department