Invited Paper IPF-TuM11
Carbon Sequestration to Mitigate Climate Change - A Geological Perspective

Tuesday, October 16, 2007, 11:20 am, Room 602/603

The fraction of global carbon emissions that must be eliminated to impact climate change is huge, about 70% of present emissions over many years (100's to 1000's of gigatonnes of CO₂) to stabilize atmospheric CO₂ at about 500 ppm. Such reductions require all means of carbon management, including geological and biological sequestration; shift from fossil fuel to renewable biomass; electricity from solar, wind, and nuclear power; and improved efficiency of generation and use. The IPCC Special Report on Carbon Capture and Storage (2005) estimates that storage of CO₂ in geological formations (geological sequestration) could eliminate about 50% of emissions. The potential role of enhanced carbon storage in biomass and soils (biological sequestration) is difficult to evaluate due to the complex dynamics of greenhouse gases in the global biosphere. Geological sequestration involves injection of supercritical CO₂ into porous and permeable rock formations at depths of 1 to 3 km beneath low permeability seals. Storage formations include oil and gas reservoirs, saline aquifers, coal beds, and organic-rich shale. Over 30 years of experience with CO₂ injection in oil fields for enhanced oil recovery demonstrate that injection and storage of CO₂ is possible with existing technology. Geological sequestration projects currently deployed in Norway, Canada, and Algeria, collectively store 3 megatonnes (MT) CO₂/year. For perspective, a 1000 MW coal-fired power plant emits about 4 MT CO₂/yr and the largest CO₂ separation plant captures 4 MT CO₂/yr. Clearly, CO₂ capture and storage to eliminate a significant fraction of atmospheric emissions will require deployment of new energy systems at an enormous scale. Although the basic principles of geological sequestration are well known and reservoir engineering for CO₂ injection is understood, significant research remains. A particular concern is identification of storage sites with adequate capacity for commercial projects (CO₂ storage from a 1000 MW power plant for 50 years requires a volume equivalent to a 2-3 billion barrel oil field). Other concerns include detailed knowledge of the integrity of sealing formations, and the rates of reaction of CO₂ with dissolved components in formation water, host rocks, and organic matter. This information is needed to assess the permanence of CO₂ storage and the potential environmental impacts of leakage.