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What is the status of geologic and terrestrial field projects? |
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In combination, the field projects are on track to develop by 2012 fossil fuel conversion systems that achieve 90% CO2 capture with 99% storage permanence at less than 10% increase in the cost of energy services. Extended field tests are characterizing potential storage sites and demonstrating the long term storage of sequestered carbon to achieve cost-effective integration with power plant systems. Carbon sequestration technologies represent critical elements in the entire energy supply picture, providing CO2 storage solutions that will enable sustained fossil fuel conversion and offer a path to greater recovery of domestic oil, natural gas, and coal bed methane. |
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What is the status of Geologic field projects? |
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The primary objective of NETL Sequestration research is to develop technologies to cost-effectively store and monitor CO2 in geologic formations with minimal environmental impacts. Accomplishing this involves improved understanding of CO2 flow and trapping within the reservoir and the development and deployment of technologies such as simulation models and monitoring systems. Experience gained from carbon sequestration field tests will facilitate the development of best practice manuals to ensure that sequestration does not impair the geologic integrity of underground reservoirs, thus assuring secured and environmentally acceptable CO2 storage. |
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NatCarb allows users to evaluate the geographic distribution, physical characteristics, and economic parameters of potential CO2 sequestration sites in the U.S. and Canada.
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Geologic formations considered for CO2 storage are layers of porous rock deep underground that are “capped” by a layer of non-porous rock above them. Sequestration practitioners drill a well down into the porous rock and inject pressurized CO2 into it. The CO2 is buoyant and flows upward until it encounters the layer of non-porous rock and becomes trapped. There are other mechanisms for CO2 trapping as well. CO2 molecules can dissolve in brine, react with minerals to form solid carbonates, or adsorb in the pores of the porous rock. The degree to which a specific underground formation is amenable to CO2 storage can be difficult to discern. Research is aimed at developing the ability to characterize a formation before CO2 injection to be able to predict its CO2 storage capacity. Another area of research is the development of CO2 injection techniques that achieve broad dispersion of CO2 throughout the formation, overcome low diffusion rates, and avoid fracturing the cap rock. These two areas, site characterization and injection techniques, are interrelated because improved formation characterization will help determine the best injection procedure. |
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Research is concentrated on five types of geologic formations, each presenting unique challenges and opportunities: oil and gas reservoirs, deep saline formations, unmineable coal seams, oil - and gas-rich organic shales, and basalts . The three priority types of geologic formations for CO2 storage R&D are depleted oil and gas reservoirs, unmineable coal seams, and deep saline formations. |
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Depleted oil and gas reservoirs are formations that held crude oil and natural gas over geologic time frames. In general, they are a layer of porous rock with a layer of non-porous rock above such that the non-porous layer forms a dome. It is the dome shape that trapped the hydrocarbons. This same dome offers great potential to trap CO2 and makes these formations excellent sequestration opportunities. The Regional Carbon Sequestration Partnerships (RCSPs) have documented the location of more than 82.4 million metric tons of sequestration potential in mature oil and gas reservoirs in the United States and Canada . As a value-added benefit, CO2 injected into a depleting oil reservoir can enable incremental oil to be recovered. The CO2 lowers the viscosity of the oil, enabling it to slip through the pores in the rock and flow with the pressure differential toward a recovery well. Typically, primary oil recovery and secondary recovery (water flooding) produce 30-40 percent of a reservoir's original oil in place. A CO2 flood enables recovery of an additional 10-15 percent or more of the original oil in place. CO2 enhanced oil recovery (EOR) is a commercial process that is in demand recently with high crude oil prices. However, commercial practitioners operate their injections with the goal of minimizing the amount of CO2 left in the ground so that the CO2 can be used for another well. NETL's research in this area is focused on CO2 EOR injection practices that maximize the amount of CO2 sequestered. |
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Unmineable coal seams are too deep or too thin to be mined economically. All coals have varying amounts of methane adsorbed onto pore surfaces, and wells can be drilled into unmineable coalbeds to recover this coalbed methane (CBM). Initial CBM recovery methods, dewatering and depressurization, leave a fair amount of CBM in the reservoir. Additional CBM recovery can be achieved by sweeping the coalbed with nitrogen. CO2 offers an alternative to nitrogen. It preferentially adsorbs onto the surface of the coal, releasing the methane. Two or three molecules of CO2 are adsorbed for each molecule of methane released, thereby providing an excellent storage sink for CO2. The RCSPs have documented the location of 156-183 billion metric tons of CO2 sequestration potential in unmineable coal seams. The maximum domestic capacity for CO2 enhanced coalbed methane (ECBM) has been estimated at 90 billion metric tons CO2, 40 billion metric tons of which are in Alaska. Like depleting oil reservoirs, unmineable coalbeds are a good early opportunity for CO2 storage. Coal swelling is a potential barrier to CO2 ECBM. It has been observed that when coal adsorbs CO2, it swells in volume. In an underground formation, swelling can cause a sharp drop in permeability, which not only restricts the flow of CO2 into the formation but also impedes the recovery of displaced CBM. NETL is pursuing angled drilling techniques and fracturing as possible means of overcoming the negative effects of swelling. |
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 Saline formations are layers of porous rock that are saturated with brine. They are much more commonplace than coal seams or oil- and gas-bearing rock, and represent an enormous potential for CO2 storage capacity. While not all saline formations in the United States have been examined, the RCSPs have documented the locations of such formations with an estimated sequestration potential ranging from 919 billion metric tons to more than 3,300 billion metric tons. However, much less is known about saline formations than is known about crude oil reservoirs and coal seams, and there is greater uncertainty associated with their amenability to CO2 storage. Saline formations tend to have a lower permeability than do hydrocarbon-bearing formations, and work is directed at hydraulic fracturing and other field practices to increase injectivity. Saline formations contain minerals that could react with injected CO2 to form solid carbonates. The carbonate reactions have the potential to be both a positive and a negative. They can increase permanence but they also may plug up the formation in the immediate vicinity of an injection well. Researchers seek injection techniques that promote advantageous mineralization reactions. |
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Basalt formations are geologic formations of solidified lava. Basalt formations have a unique chemical makeup that could potentially convert all of the injected CO2 to a solid mineral form, thus isolating it from the atmosphere permanently. Research is focused on enhancing and utilizing the mineralization reactions and increasing CO2 flow within a basalt formation. |
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NETL Sequestration Program R&D goals for the geologic storage research area are focused on reservoir characterization, storage potential, and large-scale injection, which are tied directly to the Program goal of achieving 99 percent storage permanence. The critical challenges and R&D pathways related to carbon storage are the following: |
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Research pathways |
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- Improved understanding of CO2 trapping mechanisms, leading to an ability to harness them to improve storage permanence.
- Improved predictive modeling capability for CO2 injection in porous rock.
- Improved understanding of coal properties and their changes with CO2 sorption under reservoir conditions.
- Improved predictive modeling capability for CO2 injection in coals.
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Cross-cutting R&D issues
- New CO2 injection well design and operational techniques.
- Existing well management.
- Injection well cements and drilling materials resistant to carbonic acid.
- Technologies for treating and managing produced water.
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NETL's CO2 Storage program focus area timeline calls for the following goals:
- By 2011, initiate at least one large-scale demonstration of CO2 storage (=1 million tons per year of CO2) in a geologic formation.
- By 2016, begin at least one demonstration in which CO2 is sequestered in a saline formation and brine water from the saline formation is recovered for beneficial use.
- By 2020, initiate a field demonstration of at least one technology for enhancing the rate of CO2 mineralization in-situ.
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The RCSPs are conducting a variety of geologic field tests as part of the Validation Phase. Additionally, a variety of worldwide projects related to carbon dioxide capture and geologic storage are contributing to understanding of these options. |
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What is the status of Terrestrial field projects? |
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Responsibility for terrestrial sequestration research is shared by many Federal agencies, and the NETL CO2 Sequestration Program coordinates activities in the area of terrestrial sequestration with the DOE Office of Science, U.S. Department of Agriculture, U.S. Environmental Protection Agency, and U.S. Department of Interior Office of Surface Mining. The scope of terrestrial sequestration options addressed in NETL's core R&D is limited to the integration of energy production, conversion, and use with land reclamation-with a focus on increasing carbon uptake on mined lands. Specifically, this involves the reforestation and amendment of minelands and other damaged soils, when possible, using solid residuals from coal combustion. |
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Alkaline fly-ash experiment conducted at the Santee Experimental Forest in South Carolina.
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Afforestation on minelands provides more carbon sequestration per acre of land compared with grass planting. Tilling and soil amendment approaches provide a layer of loose earth that enables trees to take root. In some cases, the tilled mineland is amended with coal combustion by-products to reduce its acidity. A layer of compacted earth is maintained under the loose earth to prevent rainwater from draining through the mine slag. These approaches can be applied both to closure practices at currently operating mines and to reclamation of the nearly 6,070 square kilometers of lands in the United States damaged by past mining practices. |
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Reclamation of degraded and disturbed lands, such as mine spoil materials, highway rights-of-way, and poorly managed lands, through the addition of beneficiating amendments has a long history of research, but there are new factors to consider, since the need for carbon sequestration may change the economics. In the United States , about 1 percent of the surface area consists of mined lands or highway rights-of-way. Poorly managed lands account for another 15 percent. Over the next 50 years, an increase of 1 percent by weight in stored-carbon content on these lands could remove on the order of 12 billion tons of carbon, a significant fraction of the total needed to stabilize atmospheric CO2 levels. |
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NETL's Sequestration Program has been a leader in efforts to enhance terrestrial ecosystems as carbon sequestration sites and to calibrate models for quantifying the amount of carbon stored. Each of the seven Regional Carbon Sequestration Partnerships (RCSPs) have identified significant terrestrial sequestration opportunities within their respective regions and are participating in terrestrial field tests. Program efforts in the area of terrestrial sequestration are focused on increasing carbon uptake on mined lands and supporting efforts by the RCSPs to evaluate no-till agriculture, reforestation, rangeland improvement, wetlands recovery, and riparian restoration. |
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Another important area of research in terrestrial sequestration is the development of technologies for quantifying carbon stored in a given ecosystem. Should the United States and other nations one day adopt a carbon emissions trading program, measuring techniques with high precision and reliability will be necessary. The critical research pathways for the Program's terrestrial sequestration focus area include the following: |
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Research pathways |
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- Tree planting instead of grass on mine land.
- Soil reclamation using coal combustion by-products or other solid residuals.
- No-till farming, afforestation, and other activities applied to a wide range of geographies to increase carbon uptake.
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Cross-cutting pathways
- Enhanced carbon transfer from plant to soil.
- Technologies for quantifying carbon storage.
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The timeline for the Program's terrestrial sequestration focus area R&D goals calls for developing terrestrial sequestration technologies to the point of commercialization at a cost not exceeding $5 per metric ton of carbon sequestered. |
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