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What is monitoring, mitigation, and verification? |
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The area of monitoring, mitigation, and verification (MM&V) is aimed at providing an accurate accounting of stored CO2 and a high level of confidence that the CO2 will remain sequestered permanently. |
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MM&V research seeks to obtain:
- Instruments that can detect carbon in a storage reservoir and measure its movement and its physical and chemical state with useful precision.
- The capability to interpret and analyze the results from such instruments.
- The ability to predict how movement and/or chemical reactions of carbon in the reservoir will affect 1) the permanence of storage, 2) the environmental impacts within the reservoir, and 3) any impacts on human health.
- Best practices and procedures that can be used to respond to any detected detrimental changes in the condition of the stored carbon and thus mitigate losses of carbon and/or negative impacts on the environment and human health.
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A successful effort will enable sequestration project developers to ensure human health and safety and prevent damage to the host ecosystem and enable developers to obtain permits for sequestration projects. MM&V also seeks to enable emissions reduction credits that approach 100 percent of injected CO2, contributing to the economic viability of sequestration projects. Finally, MM&V will provide improved information and feedback to sequestration practitioners, thus accelerating technology progress. |
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MM&V efforts are divided into two sub-areas: geologic formations and terrestrial ecosystems. MM&V systems focused on below-ground CO2 storage draw upon a significant capability developed for fossil resource exploration and production. Work is centered on refining existing CO2 detection technologies and developing new ones, and developing models of subsurface systems that enable processing and analysis of information from detection devices. Measurement technologies being investigated include surface-to-borehole seismic, micro-seismic, cross-well electromagnetic, and electrical resistance tomography. This area is less mature and is focused on detecting leaks or deterioration in reservoirs and assessing ecological impacts of geologic carbon storage. |
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Traditional methods for measuring carbon in terrestrial ecosystems (e.g., measuring tree diameters and analyzing soil samples in an off-site laboratory) are labor-intensive and costly. The program is developing automated technologies that offer lower cost, more detailed, and timely information that can be used to proactively manage the sequestration site. |
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In addition, protocols for accounting for sequestration projects, both geologic and terrestrial, are currently under development by many different organizations. Monitoring and measurement systems must provide certainty to project owners, regulators and the global environmental community that sequestration projects are achieving and sustaining expected levels of CO2 permanence. A key challenge facing the carbon sequestration community, therefore, is the development of robust, equitable, and transparent accounting mechanisms with the flexibility to function within future regulatory and market regimes. |
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What is the current status of monitoring, mitigation, and verification techniques? |
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Monitoring, mitigation, and verification (MM&V) capabilities will be critical in ensuring the long-term viability of carbon capture and storage systems—satisfying both technical and regulatory requirements. Monitoring and verification encompass the ability to measure the amount of CO2 stored at a specific sequestration site, to monitor the site for leaks, to track the location of the underground CO2 plume, and to verify that the CO2 is stored in a way that is permanent and not harmful to the host ecosystem. Mitigation is the near-term ability to respond to risks such as CO2 leakage or ecological damage in the unlikely event that it should occur. |
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The MM&V goals are focused on ensuring permanence, which support the overarching NETL Sequestration Program goal of achieving 90 percent carbon capture with 99 percent storage permanence. In general, MM&V research is aimed at providing an accurate accounting of stored CO2 and a high level of confidence that the CO2 will remain sequestered permanently. A successful effort will enable sequestration project developers to obtain permits for sequestration projects while ensuring human health and safety and preventing potential damage to the host ecosystem. MM&V also seeks to set the stage for emissions reduction credits, if a domestic program is established, that approach 100 percent of injected CO2, contributing to the economic viability of sequestration projects. Finally, MM&V will provide improved information and feedback to sequestration practitioners, thus accelerating technology progress. |
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The timeline for NETL's Carbon Sequestration Program MM&V focus area R&D calls for:
- Developing MM&V protocols by 2008 that enable 95 percent of stored CO2 to be credited as a net emissions reduction.
- Developing MM&V protocols by 2012 that enable 99 percent of stored CO2 to be credited as a net emissions reduction.
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Monitoring and verification activities for geologic sequestration encompass three components: modeling , plume tracking , and leak detection . |
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Modeling involves simulating the underground conditions that influence the behavior of CO2 injected into geologic formations and characterizing any resulting geomechanical changes to the reservoir. Comprehensive CO2 storage reservoir modeling will enable researchers to predict how CO2 plumes will flow and become hydrodynamically trapped in the short term and to understand the effects of chemical reactions (and other mechanisms) that will immobilize CO2 over the longer term. These models will help operators reduce the risks associated with inducing fractures in caprock and reactivating faults during injection. Such modeling capabilities engender confidence that injected CO2 will remain securely stored before injection commences. Comprehensive CO2 storage modeling does not just examine the target reservoir but also the potential pathways that fugitive CO2 may follow. The ability to model fluid transport and chemical reactions within geologic reservoirs already exists. Models are currently in use to manage secondary and tertiary oil recovery and to examine the long-term fate of industrial hazardous wastes disposed underground. Activities are underway to adapt these models to geologic CO2 storage. The Program seeks to acquire the detailed data needed to support reliable operation of these models (i.e., chemical reaction kinetics and two- and three-phase vapor/liquid equilibrium data at supercritical conditions) and to develop integrated models that support early small-scale pilot field tests. |
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Underground plume tracking provides the ability to “map” the injected CO2 and track its movement and fate through a reservoir. The ability to verify the location of injected CO2 over time is necessary to assure storage permanence. Seismic surveys (e.g., 4-D seismic, time-lapse vertical seismic profiling) and sampling from wells ( borehole logging ) are key technologies used for plume tracking. Because supercritical CO2 is less dense and more compressible than saline water, seismic waves travel through it at a different velocity. As a result of the velocity contrast, the presence of free CO2 in a saline formation leaves a distinct seismic signature, as seen at the Weyburn (Canada) and Frio (Texas) field sites. Observation wells instrumented to monitor reservoir conditions such as pressure, temperature, and other properties are another important source of information for plume tracking. Much can be learned from the monitoring efforts used by CO2 EOR projects and particularly by the gas storage industry. Work in this area is focused on adapting these technologies for use in CO2 sequestration applications, where knowledge gained from field tests will help optimize CO2 storage and identify the least-cost approach to effective MM&V. |
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Beyond serving as backstops for modeling and plume tracking, CO2 leak detection systems provide critical measures of whether CO2 is escaping from the storage reservoir. One challenge for leak detection is the need to cover large areas cost-effectively at the required resolution. The CO2 plume from an injection of 1 million tons of CO2 per year in a deep saline formation for 20 years could be spread over a horizontal area of 15 square miles or more. |
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There are important interconnections among these three areas. Data from plume tracking enable validation of reservoir models; robust reservoir models enable operators to design and better interpret data from plume tracking; and models and plume tracking help focus leak detection efforts on high-risk areas. Such information provides a basis for addressing public and regulatory concerns and ensures that no adverse events are likely to occur in the storage formation. |
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Mitigation
The science and technology of remediating CO2 leakage is still emerging. Storing CO2 in rigorously selected geological formations such as at Weyburn (Canada), Sleipner (Norway), and In Salah ( Algeria ) suggests that the inherent risks and potential quantities of CO2 leakage will be minimal. In the unlikely event that CO2 leakage occurs, steps can be taken to arrest the flow of CO2 and mitigate the impacts. For example, lowering the pressure within the CO2 storage reservoir by stopping injection could reduce the driving force for CO2 flow and close a leaking fault or fracture. Other options include forming a “pressure barrier” by increasing the pressure in the reservoir into which CO2 is leaking or by intercepting the CO2 leakage paths. Another strategy is plugging the region where leakage is occurring with low-permeability materials. Additional research in this area is needed, especially on quantifying the costs associated with different remedial actions. |
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Terrestrial MM&V |
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MM&V activities focused on terrestrial ecosystems encompass three components: organic matter measurement, soil carbon measurement, and modeling. Traditional methods for measuring carbon in terrestrial ecosystems (e.g., measuring tree diameters and analyzing soil samples in an off-site laboratory) are labor-intensive and costly. NETL research is developing automated technologies that provide more detailed and timely information at lower cost for use in managing a sequestration site. |
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Soil carbon offers the potential for long-term CO2 storage. The Program is developing automated technologies for measuring soil carbon. Detailed models are used to extrapolate the results of carbon uptake activities from random samples to an entire plot and to estimate the net increase in carbon storage relative to a case without enhanced carbon uptake. Economic models show accumulations of emissions credits and revenues versus an initial investment. |
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These three components have a vital role in proving the permanence of CO2 storage in terrestrial ecosystems. Continued research is needed, particularly since quantifying CO2 leakage rates from terrestrial ecosystems using current technology is more challenging than identifying leaks in geologic storage formations. In addition, the development of robust and flexible accounting protocols that function within future regulatory and market regimes is critical to the verification of long-term storage in terrestrial ecosystems. |
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