Geologic formations suited for CO2 storage are porous to provide large capacities for the CO2, are deep underground (nominally 3,000 feet or more), and there must be a caprock of non-porous material to seal the CO2 in the formation. After the CO2 is injected, it flows upward to the non-porous caprock and becomes trapped. Depending on the formation, CO2 molecules can dissolve in brine, react with minerals to form solid carbonates, or adsorb in the pores of the porous rock.
There are three primary geologic formations of interest for storing CO2:
- Depleted Oil and Gas Reservoirs: These formations have a high potential for meeting CO2 storage criteria because they held crude oil and natural gas in them over geologic time frames. In some cases of depleted or declining oil/gas fields, the CO2 can produce incremental oil. CO2 enhanced oil recovery (EOR) is a commercial process in demand recently due to high crude oil prices. Commercial EOR operations minimize the amount of CO2 left in the ground so that the CO2 can be recovered and reused.
- Unmineable Deep Coal Seams: Coal seams that are too deep or too thin to be mined economically can be used to store CO2. There is a potential for enhanced coal-bed methane (CBM) recovery from some coal seams. CBM is a large commercial operation, especially in the Western US. Current enhanced recovery techniques use nitrogen, but CO2 may be an alternative. Two or three molecules of CO2 are adsorbed for each molecule of methane released, thereby providing an excellent storage for CO2.
- Deep Saline Formations: Saline formations contain porous rock layers that are saturated with brine. They are very widely distributed in North America and globally and represent by far the largest potential for CO2 storage capacity. Saline formations tend to have a lower permeability than do hydrocarbon-bearing formations, and research is required with hydraulic fracturing and other field practices to increase injectivity.
Nexant has been involved in studies and research programs that incorporate the use of carbon sequestration. Major work includes:
- Regional Sequestration Partnerships: Nexant is a member of both the West Coast Regional Carbon Sequestration Partnership (WESTCARB) and the Plains CO2 Reduction Partnership (PCOR), two programs that are part of the DOE's Carbon Sequestration Regional Partnerships. Nexant has engaged in work identifying and quantifying major carbon dioxide emissions sources for each partnership, as well as providing additional technical expertise.
CO2 Separation, Capture, and Transport Issues for the West Coast Regional Carbon Sequestration Partnership
Partnership Information
- Canadian CO2 Enhanced Oil Recovery Project: Nexant is working with a private client to determine the availability, properties and capture requirements for up-to 20,000 tones per day of CO2 for EOR operations in Western Canada. CO2 sources in the area include gas processing plants, petroleum upgrading/refining facilities, chemical and fertilizer plants and power generation. Working with a CO2 separation technology provider and local engineering firm, Nexant has estimated performance and costs for recovering the CO2, gathering it in a system of pipelines, and compressing it for overland pipeline transport to the oil fields. Work continues to resolve economic issues and expand the choice of CO2 sources.
- Presentations at the US DOE Carbon Sequestration Conference: Nexant's technical and policy expertise has been presented at a number of conferences, including the annual US DOE Conference on Carbon Capture and Sequestration. Recent work has focused on the IGCC vs. PC cost tradeoff when the cost of carbon capture and sequestration is included, and the impact of greenhouse gas control policies on the development of future coal to liquids plants.
2006 Conference Presentation
Will Maturing GHG Markets Make IGCC the Coal Technology of Choice?
2007 Conference Paper
Impacts of Future US GHG Regulatory
Policies on Large-Scale Coal to Liquids Plants
CO
|
Tan-Ping Chen
Senior Vice President, Energy Technology
Tel: +1 415 369 1077
Email: tpchen@nexant.com
|
