The Regional Carbon Sequestration Partnerships' (RCSP) validation phase focuses on validating the most promising regional opportunities to deploy carbon capture and storage (CCS) technologies by building upon the accomplishments of the characterization phase. Efforts are being conducted to:
* Data current as of June 2010.
- Validate and refine current reservoir simulations for CO2 storage projects.
- Collect physical data to confirm CO2 storage potential and injectivity estimates.
- Demonstrate the effectiveness of monitoring, verification, and accounting (MVA) technologies.
- Develop guidelines for well completion, operations, and abandonment.
- Develop strategies to optimize the CO2 storage potential of various geologic formations.
* Data current as of November 2010.
Geologic field tests were conducted on the most promising storage formations in rock types representative of the varying depositional environments present both in North America and around the world. These tests targeted four geologic storage types: saline formations, oil and gas reservoirs, unmineable coal seams, and basalt formations. These first field injection projects were akin to exploration projects in the petroleum industry and involved small-scale CO2 injections (less than 500,000 metric tons total). The projects were designed to test areas where regional mapping and depositional models indicated that storage resources would be present, but additional subsurface information was needed to verify CO2 storage resources and injectivity. The geologic data acquired through these studies have been instrumental in further refining of regional CO2 storage resource calculations within each RCSP. The completed tests have provided valuable information to better understand each region's geologic CO2 storage potential and determine specific areas within each RCSP that are in need of future research.
The terrestrial validation phase tests focus on the uptake of atmospheric CO2 into soils and vegetation through activities such as tree-plantings, no-till farming, wetlands restoration, land management (grasslands, grazing lands), fire management, forest preservation, employing effective monitoring, verification, and accounting (MVA) technologies, and implementing and understanding accounting protocols for trading markets.
Other activities include refining regional characterizations, public outreach and education, and regulatory compliance issues for the respective field projects. The knowledge gained from these validation procedures and tests can be used to develop commercially viable technologies that will be integral to a carbon management strategy. The results of the field tests will prove that the regional capacity and injectivity exists for commercialization. Lessons learned from these validation phase projects are being integrated into the larger-scale projects in the development phase, which includes more detailed characterization, injection, and monitoring of larger volumes of CO2 in subsurface formations. DOE is compiling the lessons learned from the RCSPs in a series of best practices manuals.
Small-Scale Tests in Clastic and Carbonate Formations Containing Saline Waters
A total of six validation phase field tests were performed in saline formations across multiple depositional environments. Saline formations targeted for geologic storage are porous sedimentary deposits saturated with brine having salinity greater than 10,000 mg/l total dissolved solids (TDS). Such formations are widely distributed globally and the 2010 Carbon Sequestration Atlas of the United States and Canada – Third Edition estimates 1,653 to 20,213 billion metric tons of prospective CO2 storage resource in saline formations throughout the United States and parts of Canada. Saline formations are much more extensive than coal seams or oil- and gas-bearing rock and possess enormous potential for CO2 geologic storage. However, much less is known about saline formations because they lack the characterization data that industry has acquired through their resource recovery efforts from oil and gas reservoirs and coal seams. Therefore, a greater amount of uncertainty still exists regarding the suitability of saline formations for CO2 storage. The six field tests injected a total of more than 63,000 metric tons of CO2 with test results indicating that these formations can accept and safely store CO2.
Small-Scale Tests in Clastic and Carbonate Formations Containing Oil and Gas
The RCSPs have conducted eight small-scale validation phase tests in oil and gas reservoirs across multiple types of depositional environments. Oil and gas reservoirs offer significant near-term potential for CO2 storage as they have held crude oil and natural gas for millions of years and are typically well studied due to oil and gas exploration. An added benefit of CO2 injection in oil and gas reservoirs is the potential for enhanced oil recovery (EOR) in which CO2 injection may recover an additional 10-15 percent of the oil in place. The RCSPs have documented the locations of approximately 143 to 155 billion metric tons of prospective storage in oil and gas reservoirs distributed over 27 states and three Canadian provinces. Although all these tests have been successful, further investigation is still needed to understand the CO2 plume migration in these types of reservoirs. Initial indications from the Southeast Regional Carbon Sequestration Partnership's (SECARB) Cranfield test show that plume migration is highly influenced by the stratigraphy within a depositional environment (i.e. fluvial channel). Because oil and gas formations typically have large amounts of existing data, including well logs, core, production history, and seismic, sufficient subsurface information supports simulations and further research to predict, monitor, and understand plume migration and control. A total of more than 1.4 million metric tons of CO2 were safely injected during these validation tests and the production of oil increased as a result, demonstrating the ability of the reservoirs to accept and safely store injected CO2 while increasing hydrocarbon production.
Unmineable Coal Seam Tests
Unmineable coal seams are too deep or too thin to be economically recovered. However, these formations can be developed for their ability to both produce methane and store CO2. Current estimates for CO2 storage in unmineable coal areas in the United States and Canada ranges from 60-117 billion metric tons. Five RCSP validation phase tests injected a combined volume of more than 18,000 metric tons of CO2 into coal seams to study their storage capability. These tests were conducted at various injection volumes, seam thicknesses, and coal types. Test results showed adequate CO2 containment capabilities for the geologic sealing layers located above the injected formations. Coal swelling, due to adsorption of CO2, is a potential barrier to CO2 injection into coal seams. In an underground formation, swelling can cause a drop in permeability, which not only restricts the flow of CO2 into the formation, but also impedes the recovery of displaced coalbed methane. The RCSP validation phase tests focus on addressing challenges to CO2storage in unmineable coal seams to move toward commercialization of this technology.
Basalt Formation Tests
Basalt is a volcanic rock with a unique chemical makeup that could potentially convert the injected CO2 to a solid mineral form, isolating it from the atmosphere permanently. This, combined with basalt's tendency to be porous and fractured, makes these formations potential candidates for CO2 storage. However, little is known about whether these characteristics can be utilized because basalt formations have not received much attention to date with respect to their potential for CO2 storage. The Big Sky Carbon Sequestration Partnership is the only RCSP investigating basalts by conducting a pilot-scale injection of approximately 1,000 metric tons of supercritical CO2 into a deep basalt formation (Grande Ronde Basalt) in western Walla Walla County in eastern Washington. The test is assessing the mineralogical, geochemical, and hydrologic impact of injected CO2 within a basalt formation and conducting MVA. Because this is the only basalt injection, additional research is still needed regarding CO2 reactions in basalts, fundamental basalt geology (for example, distribution of breccias), and determining the effectiveness of confining layers.
The distribution of the different depositional environments that NETL is investigating across the RCSP small-scale, RCSP large-scale, and ARRA site characterization testing is presented below. The field activities are in various stages of investigation with some completed and others just underway. Additional investigations, including small- and large-scale injection tests, must be completed on all the depositional environments. This will provide information on the behavior and flow of CO2 in the different reservoirs.
Click image to enlarge.
The RCSPs conducted 11 terrestrial storage field tests as part of the validation phase to reduce the amount of CO2 in the atmosphere by enhancing the storage capability of soils, grazing and crop lands, and trees through changes in management practices. Through photosynthesis, vegetation removes CO2 from the atmosphere and converts it to carbohydrates, so with improved management practices, the amount of carbon stored in soils and plants (called "terrstrial storage") can be increased. The terrestrial storage projects have recently been completed and no additional projects in this area are anticipated.
The RCSP validation phase terrestrial field tests were designed to test multiple terrestrial storage options across varying regional settings and reduce the amount of CO2 in the atmosphere by enhancing the storage capability of soils, grazing and crop lands, and trees through changes in management practices. A variety of options for terrestrial storage are available, including restoring mined lands, aforestation, reforestation, rangeland improvement, improved tillage practices, and wetlands restoration. Results from the RCSP validation phase tests were used to develop a Best Practices Manual for Terrestrial Carbon Storage, in which Chapter 6 specifically highlights the RCSP terrestrial field test results and accomplishments. Many of these projects will help develop MVA protocols to allow the carbon stored in these terrestrial ecosystems to be credited as greenhouse gas emissions reductions.
Terrestrial Carbon Storage Potential in the United States
*Million metric tons per year
||Carbon Storage Potential, Mt/y*