The Midwest Regional Carbon Initiative (MRCI) is a collaborative Regional Initiative (RI) aiming to accelerate the deployment of carbon capture, utilization, and storage (CCUS) in the Midwestern-Northeastern quadrant of the United States covering 20 states and representing multiple geologic provinces and a large fraction of CO₂ emissions in the country. The RI builds upon more than 20 years of CCUS experience in the region and combines the expertise of two Regional Carbon Sequestration Partnerships (RCSPs) – the Midwestern Regional Carbon Sequestration Partnership (MRCSP) led by Battelle and the Midwest Geologic Sequestration Consortium (MGSC) led by the Illinois State Geological Survey (ISGS).
Carbon storage has the potential to provide significant environmental, economic, and security benefits in a future where there is a price on carbon. The purpose of geologic storage of carbon dioxide is to mitigate the levels of carbon dioxide entering the atmosphere by focusing on large stationary sources of carbon dioxide emissions, such as electric power plants, cement factories, oil refineries and steel works. Carbon storage offers the most viable way to generate electricity at the current level and significantly reduce the impact on the environment. Furthermore, the use of carbon dioxide for enhanced oil recovery increases oil production while making it more economically attractive for industry to reduce carbon dioxide emissions. If geologic storage of carbon dioxide can be used on a large scale, there is potential to capture and store up to 90 percent of carbon dioxide emitted into the atmosphere from these large sources, while at the same time, when combined with oil fields, produce additional oil that would otherwise not be recovered.
Before any work is begun at a potential storage site, the rock formations and possible injection zones are carefully evaluated to ensure the presence of rocks that are suitable for storing and containing CO₂. Typically, this stage includes a seismic survey of the area and drilling and conducting tests in the well through which the CO₂ will be injected. If the area is shown to be suitable for storage and the necessary injection well permits are obtained. Before injection, the CO₂ must be captured from a point source and separated from the flue gas rather than released to the air. The captured CO₂ is compressed into a supercritical state and transported via pipelines to injection wells locations, where it is injected into rock formations that are infused with salty water. The confining zone, sometimes also called cap rock, is an impenetrable barrier that traps CO₂ in the storage reservoir. During and after injection, appropriate monitoring equipment is used both above and below ground to track the composition, pressure, and amount of injected fluids and monitor for CO₂ movement in the deep formations.
Carbon capture and storage (CCS) is one of the many methods of carbon sequestration. CCS involves first capture of the gas from its source (e.g., power plants and refineries), then purification and compression to transform it to a supercritical fluid, transport to the injection site, followed by its injection into deep geologic formations. Site characterization is conducted prior to injection to ensure the CO₂ can be permanently stored beneath overlying layers of dense rock (or caprock).
Carbon Sequestration is the term used to describe a broad class of technologies for capturing and permanently sequestering, or storing, CO₂. Ways to securely store CO₂ in biologic materials (terrestrial sequestration) or in deep underground formations (geologic storage and/or combined with enhanced oil recovery) currently are being studied in the U.S. and around the world. Terrestrial sequestration involves carbon storage in soils, including degraded soils (soils that have declined in quality), and in forests and agricultural land.
There is widespread agreement in the scientific community that, even with substantial increases in energy efficiency, conservation, and the deployment of non-CO₂-emitting renewable energy technologies, CO₂ emissions are likely to continue to grow for the foreseeable future due to an increasing global population. Affordable and environmentally safe sequestration approaches could offer a way to help stabilize atmospheric levels of CO₂ at "a level that would prevent dangerous anthropogenic interference with the climate system," a goal toward which nearly 190 nations have pledged to work. Carbon sequestration is one set of promising technologies and actions to help in the effort to reduce greenhouse gas emission. The wide-scale deployment of geologic and terrestrial sequestration technologies is key to bringing about sustained and significant reductions in CO₂ emissions at least cost.
Enhanced oil recovery (EOR) is often carried out using CO₂. Carbon dioxide is flooded into an oil field or coal bed to extract oil or methane that would otherwise be unrecoverable. Executed together, the synergy of EOR and Carbon Capture and Storage are referred to as Carbon Capture, Utilization, and Storage or CCUS.
Storing carbon dioxide indicates safe and permanent containment of injected CO₂ in deep geologic formations. Candidate storage reservoirs are located thousands of feet below the surface, beneath confining layers of dense rock (often called caprock), capable of trapping the injected carbon dioxide over thousands of years or longer. The injected CO₂ can undergo several changes over time that ensures permanent storage. It can remain in a liquid-like state, get trapped permanently within the pore spaces of the rock, dissolve into the brine, bond to the organic matter in coal and shale, and over the longer-term, react with minerals in the rock to form stable mineral compounds.
Carbon dioxide, or CO₂, is the most important greenhouse gas (GHG) in terms of its contribution to climate change. At the beginning of the Industrial Revolution concentrations of CO₂ in the atmosphere were approximately 270 parts per million (ppm). Currently, CO₂ concentrations are over 400 ppm and rising. Whether the appropriate stabilization level is as low as 450 parts per million or as high as 750 ppm, the goal of stabilization carries with it requirements to produce and sustain deep reductions in GHG emissions over the course of this century. Most importantly, stabilization will require fundamentally new and cleaner ways of generating and using the energy that drives the economies of the United States and the world.
The major geologic sequestration options being considered include sequestration of CO₂ in depleted oil and gas fields, deep saline formations, deep basalt formations, and deep unmineable coal seams. Key terrestrial sequestration technologies under investigation include the conversion of marginal lands to forests, adoption of soil conservation practices in grazing and eroded lands, adoption of low- or no-till agricultural practices, and restoration of degraded mine lands through planting cover crops and other management practices. The adoption and application of these terrestrial sequestration practices often carry with them ancillary positive benefits, such as increased agricultural productivity or reduced run-off.
When an oil field is first produced, the natural high pressure in the formation, which is a function of burial depth below the surface, helps to push the oil out of the formation and to the surface. Typically, subsurface pressure is great enough to produce roughly 10-30% of the oil in an oil field. Once the pressure is depleted during the natural or “primary” production phase, various techniques are employed to restore a pressure drive in the oil field and reduce the thickness or viscosity of the oil so that additional oil can be recovered. In addition to water flooding, the major approaches used in enhanced oil recovery (EOR) include injecting steam, polymers or surfactants, or a gas. Carbon dioxide is often injected into the oil reservoir through an injection well. The carbon dioxide mixes (becomes miscible) with the oil, swelling and decreasing the viscosity of the oil. At the same time, the injected carbon dioxide and water re-establishes high pressure in the oil field, helping to push the oil towards the production well.