Publications Database - List of storage publications

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    June, 2005

Vol 2 Chapter 29: Modeling of Near-Surface Leakage and Seepage of CO₂ for Risk Characterization

Curtis M. Oldenburg and Andre A.J. Unger

Abstract: The injection of carbon dioxide (CO₂) into deep geologic CO₂ storage sites entails risk that CO₂ will leak away from the primary storage formation and migrate upwards to the unsaturated zone from which it can seep out of the ground. We have developed a coupled modeling framework called T2CA for simulating CO₂ leakage and seepage in the subsurface and in the atmospheric surface layer. The results of model simulations can be used to calculate the two key health, safety, and environmental (HSE) risk drivers, namely CO₂ seepage flux and near-surface CO₂ concentrations. Sensitivity studies for a subsurface system with a thick unsaturated zone show limited leakage attenuation resulting in correspondingly large CO₂ concentrations in the shallow subsurface. Large CO₂ concentrations in the shallow subsurface present a risk to plant and tree roots, and to humans and other animals in subsurface structures such as basements or utility vaults. Whereas CO₂ concentrations in the subsurface can be high, surface-layer winds reduce CO₂ concentrations to low levels for the fluxes investigated. We recommend more verification and case studies be carried out with T2CA, along with the development of extensions to handle additional scenarios such as calm conditions, topographic effects, and catastrophic surface-layer discharge events.

Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from the CO₂ Capture Project Geologic Storage of Carbon Dioxide with Monitoring and Verification - Volume 2
Edited by: Sally M. Benson, Lawrence Berkeley Laboratory, Berkeley, CA, USA

(669 Kb)      View   Download

    June, 2005

Vol 2 Chapter 30: Impact of CO₂ Injections on Deep Subsurface Microbial Ecosystems and Potential Ramifications for the Surface Biosphere

T.C. Onstott

Abstract: Based upon the calculated potential microbial power for microbial redox reactions, the most readily identified impact of CO₂ injections on the subsurface microbial communities was the reduction of one pH unit for the ground water hosted in the siliclastic reservoir. The slightly lower pH is based upon the assumption, yet to be verified, that alteration of detrital feldspars to clay in equilibrium with calcite occurs on the time scale of the injection. The power levels for many of the microbial redox reactions were generally larger than in the original ground water systems but because of this reduction of one pH unit in the ground water, microbial Fe(III) reduction reactions were significantly enhanced over the expected ambient conditions. If sufficient electron donors are available for both biotic and abiotic Fe(III) reducing reactions and sufficient Fe(III) bearing oxides are present in the aquifer (as is usually the case) then these reactions will restore the aquifer’s pH to its initial, pre-injection value. CO₂ injection should cause a short-term stimulation of Fe(III) reducing communities. For long-term storage of CO₂ in siliclastic reservoirs the short-term enhancement of Fe(III) reducing microorganisms will increase the pH and most likely lead to the precipitation of various carbonates. As readily available Fe(III) is depleted it can be introduced. If this is not feasible and sulfate is not a major constituent in the ground water, then methanogenic activity will begin to dominate and the proportion of CO₂ converted to CH₄ will depend upon the H₂ and acetate fluxes. A dolomitic or carbonate aquifer may be more severely impacted by the simulated CO₂ injection because the dissolution of the carbonate failed to restore the pH to a range that is more commensurate with the pH ranges of some of the microorganisms. If mafic igneous rocks host the groundwater and contain Fe bearing clinopyroxene, then the lower pH will automatically stimulate the release of H₂ by the oxidation of this ferrous iron to Fe(OH)₃. This, in turn, would lead to stimulation of methanogenic and acetogenic communities and a reduction of the injected CO₂. Fe(III) reducing microbial reactions may also be stimulated by the appearance of Fe(OH)₃ leading to Fe(III) reduction and an eventual increase in pH. For rhizosphere and surface biosphere the most obvious impact would be due to a potential increase in crustal CH₄ flux for carbonate and mafic rock hosted aquifers and a decrease in H₂ flux in all cases. Since the fluxes of both gaseous species from fermentative communities in shallower, organic-rich aquitards are 10–100 times greater than the deep subsurface flux, this probably is not a showstopper.

Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from the CO₂ Capture Project Geologic Storage of Carbon Dioxide with Monitoring and Verification - Volume 2
Edited by: Sally M. Benson, Lawrence Berkeley Laboratory, Berkeley, CA, USA

(438 Kb)      View   Download

    June, 2005

Vol 2 Chapter 31: Framework Methodology for Long-Term Assessment of the Fate of CO₂ in the Weyburn Field

Mike Stenhouse, Wei Zhou, Dave Savage and Steve Benbow

Abstract: A key objective of the IEA Weyburn CO₂ Monitoring and Storage Project is to determine the long-term fate of CO₂ injected into the reservoir. Such a determination involves an evaluation of the potential for CO₂ to migrate away from the reservoir along both natural and artificial (wellbore) pathways to the environment, and relies on the technical input from a number of disciplines. These disciplines include geology and hydrogeology, geochemistry, geomechanics, reservoir modeling and wellbore technology. This paper describes the framework used for carrying out the long-term assessment, thus ensuring that work being carried out by other research workers is properly integrated into the CO₂ migration modeling. The discussion focuses on the various components of systems analysis, including features, events and processes and their incorporation into scenario development.

Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from the CO₂ Capture Project Geologic Storage of Carbon Dioxide with Monitoring and Verification - Volume 2
Edited by: Sally M. Benson, Lawrence Berkeley Laboratory, Berkeley, CA, USA

(599 Kb)      View   Download

    June, 2005

Vol 2 Chapter 32: CO₂ Storarge in Coalbeds: Risk Assessment of CO₂ and Methane Leakage

Shaochang Wo, Jenn-Tai Liang and Larry R. Myer

Abstract: The practice of testing seal integrity is not routinely employed in coalbed methane projects. With injection of CO₂, changes in stress caused by potential high injection pressure and rate may open previously closed fractures and faults, thus generating new leakage pathways. The research presented in this chapter focuses on assessing potential leakage pathways and developing a probabilistic risk assessment methodology. A study was performed to evaluate geomechanical factors that need to be taken into account in assessing the risk of CO₂ leakage in CO₂ storage in coalbeds. The study revealed that geomechanical processes lead to risks of developing leakage paths for CO₂ at each step in the process of CO₂ storage in coalbeds. Risk of leakage is higher for old wells that are converted to injectors. Risks of leakage are much higher for open cavity completions than for cased well completions. The processes of depressurization during dewatering and methane production, followed by repressurization during CO₂ injection, lead to risks of leakage path formation by failure of the coal and slip on discontinuities in the coal and overburden. The most likely mechanism for leakage path formation is slip on pre-existing discontinuities that cut across the coal seam. A mathematical model for probabilistic risk assessment was developed. The model consists of six functional constituents:

1. initiators,
2. processes,
3. failure modes,
4. consequences (effects),
5. indicators,
6. and inference queries.

Potential leakage pathways are usually coupled with identified failure modes. In assessing the risk of CO₂ storage in geological formations, inference rules can generally be categorized into seven different types. The inference logic of this model is based on set theory, which is superior to the traditional decision-tree based inference logic in terms of flexibility, generality, capability in dealing with uncertainties and handling large, complex problems, such as cascading phenomena. The model was designed to be implemented on a relational database.

Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from the CO₂ Capture Project Capture and Separation of Carbon Dioxide from Combustion Sources - Volume 1
Edited by: David C. Thomas, Senior Technical Advisor, Advanced Resources International Inc, USA

(746 Kb)      View   Download

    June, 2005

Vol 2 Chapter 33: Risk Assessment Methodology for CO₂ Storage: The Scenario Approach

A.F.B. Wildenborg,p, A.L. Leijnse, E. Kreft, M.N. Nepveu, A.N.M. Obdam, B. Orlic, E.L. Wipfler, B. van der Grift, W. van Kesteren, I. Gaus, I. Czernichowski-Lauriol, P. Torfs and R. Wojcik

Abstract: The ambition of the R&D work presented here was to further develop the “scenario approach” as a methodology for the long-term safety assessment of underground CO₂ storage and to demonstrate its applicability in an example of safety assessment. The developed methodology consists of three main parts:

1. scenario analysis,
2. model development and
3. consequence analysis.

The scenario analysis focuses on a comprehensive inventory of risk factors (Features, Events and Processes, FEPs) and subsequent selection of the most critical factors that will be grouped into discrete CO₂ leakage scenarios. Quantitative physico-mathematical models need to be developed to enable a quantitative safety assessment of the scenarios in the consequence analysis. The developed method was successfully applied to two virtual settings in the southern part of the North Sea. In these examples, two leakage scenarios were considered, leakage up a fault and through a failed well. Modeling showed that CO₂ concentrations and fluxes in the biosphere were largest in the case of a leaking well, compared to the leaking fault. However, the duration of release of CO₂ to the biosphere was longer in case of the leaking fault. The assessed scenarios did not include any monitoring or mitigation measures and thus represent worst-case situations in this respect. The outcome of the assessment enables the development of a monitoring system and mitigation plan so that the safety risks can be adequately managed.

Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from the CO₂ Capture Project Geologic Storage of Carbon Dioxide with Monitoring and Verification - Volume 2
Edited by: Sally M. Benson, Lawrence Berkeley Laboratory, Berkeley, CA, USA

(782 Kb)      View   Download

    June, 2005

Vol 2 Chapter 34: Key Findings, Technology Gaps and the Path Forward

Scott Imbus and Charles Christopher

Abstract: Options for large-scale geological storage of CO₂ emissions have proceeded from concept development and capacity inventories in the 1990s to systematic site characterization and strategies for injection, long-term monitoring and risk assessment in recent years. To date, the only purpose-built CO₂ storage facility is the 1 million tonne/year Sleipner–Utsira project in the Norwegian North Sea. Although the project is deemed successful, it is doubtful that numerous projects of the scale or considerably larger such projects will be permitted without extensive technical due diligence. In the constellation of industry, academic and government programs addressing geological CO₂ storage, the role assumed by the CCP Storage Monitoring and Verification (SMV) program over 2000–2004 is unique. The risk-based approach adopted entailed identifying technical gaps and addressing them by leveraging the existing natural and industrial analog knowledge base and developing new R&D avenues. Whereas some projects were based on a specific asset or storage venue type, the applications developed are universally applicable. The present chapter outlines the key findings of the SMV program and identifies needs for further R&D needed to support pilots, demonstration and commercial projects. The SMV program was comprised of some 30 projects organized along four technical areas.

1. “Integrity”—assessing the competence of natural and engineered systems to retain CO₂ over extended periods.
2. “Optimization”—strategies for improving the efficiency and economics of CO₂ transportation and storage.
3. “Monitoring”—identification of techniques suitable for tracking CO₂ movement within (performance) and outside (leakage or seepage) the injection target.
4. “Risk Assessment”—development of concepts, protocols and methodologies to quantify probability and impact of CO₂ leakage from storage sites.

Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from the CO₂ Capture Project Geologic Storage of Carbon Dioxide with Monitoring and Verification - Volume 2
Edited by: Sally M. Benson, Lawrence Berkeley Laboratory, Berkeley, CA, USA

(101 Kb)      View   Download

    June, 2004

CCP PHASE 1 - Storage Monitoring and Verification Results Workshop

Vito Caruso, Eni E&P, in co-operation with Scott W. Imbus, ChevronTexaco, and Charles A. Christopher, BP Americas

An overview of the results of the CCP work program on storage, monitoring and verification (SMV) presented in Brussels June 2004. Covers: Integrity and Competence of Natural and Engineered Systems, Optimization and Economic Offsets, Efficiency, Transportation; Monitoring and Performance and Leak Detection; Risk Assessment and Probability x Consequences, FEPs, Methodologies, Modeling, Mitigation / Remediation.

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    October, 2003

The Sleipner & SACS experience

Bjorn Berger, Trude Sundset, Tore Torp

Geological Storage Case History. A report on the Sleipner experience with geological storage of CO₂ in the Utsira formation (saline aquifer) offshore Norway. The report summarizes the Sleipner Aquifer CO₂ Storage (SACS) project, which studies the impact of CO₂ injection and tracks the disposition of the CO₂ after injection.

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    October, 2003

Long-Term Sealing Integrity of Wells

Ider Akervoll, Erik Lindeberg, Sjur Moe, SINTEF Petroleum Research

Geological Storage. A study by SINTEF of the long-term sealing capacity of wells drilled into geological storage systems. Two files are available, the presentation and a long-term computer simulation.

(1.45 Mb)      View   Download

    October, 2003

Long-Term Sealing Integrity of Wells - computer simulation

Idar Akervoll, Erik Lindeberg, Sjur Moe, SINTEF Petroleum Research

Geological Storage. A study by SINTEF of the long-term sealing capacity of wells drilled into geological storage systems. Two files are available, the presentation and a long-term computer simulation.

(721 kb)      View   Download

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