Sequestration of CO2 in geological media in response to climate change: capacity of deep saline aquifers to sequester CO2 in solution

Sedimentary basins are suitable to different degrees for CO2 geological sequestration as a result of various intrinsic and extrinsic characteristics, of which the geothermal regime is one of the most important. Warm basins are less favorable for CO2 sequestration than cold basins because of reduced capacity in terms of CO2 mass, and because of higher CO2 buoyancy, which drives the upward CO2 migration. A set of 15 criteria, with several classes each, has been developed for the assessment and ranking of sedimentary basins in terms of their suitability for CO2 sequestration. Using a parametric normalization procedure, a basin's individual scores are summed to a total score using weights that express the relative importance of different criteria. The total score is ranked to determine the most suitable basin or region thereof for the geological sequestration of CO2. The method is extremely flexible in that it allows changes in the functions that express the importance of various classes for any given criterion, and in the weights that express the relative importance of various criteria. Examples of application are given for Canada's case and for the Alberta basin in Canada.

Screening and ranking of sedimentary basins for sequestration of CO2 in geological media in response to climate change

The deep sea, the largest ecosystem on Earth and one of the least studied, harbours high biodiversity and provides a wealth of resources. Although humans have used the oceans for millennia, technological developments now allow exploitation of fisheries resources, hydrocarbons and minerals below 2000 m depth. The remoteness of the deep seafloor has promoted the disposal of residues and litter. Ocean acidification and climate change now bring a new dimension of global effects. Thus the challenges facing the deep sea are large and accelerating, providing a new imperative for the science community, industry and national and international organizations to work together to develop successful exploitation management and conservation of the deep-sea ecosystem. This paper provides scientific expert judgement and a semi-quantitative analysis of past, present and future impacts of human-related activities on global deep-sea habitats within three categories: disposal, exploitation and climate change. The analysis is the result of a Census of Marine Life – SYNDEEP workshop (September 2008). A detailed review of known impacts and their effects is provided. The analysis shows how, in recent decades, the most significant anthropogenic activities that affect the deep sea have evolved from mainly disposal (past) to exploitation (present). We predict that from now and into the future, increases in atmospheric CO2 and facets and consequences of climate change will have the most impact on deep-sea habitats and their fauna. Synergies between different anthropogenic pressures and associated effects are discussed, indicating that most synergies are related to increased atmospheric CO2 and climate change effects. We identify deep-sea ecosystems we believe are at higher risk from human impacts in the near future: benthic communities on sedimentary upper slopes, cold-water corals, canyon benthic communities and seamount pelagic and benthic communities. We finalise this review with a short discussion on protection and management methods.

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Man and the last great wilderness: human impact on the deep sea.

A review of developments in carbon dioxide storage

Demonstrating storage of CO2 in geological reservoirs: The Sleipner and SACS projects

The member countries of the European Union plan to reduce their CO2 emissions in accordance with the international protocol agreed in Kyoto in 1997. The accepted options for doing this include fuel switching, improving energy efficiency, and the introduction of renewable energy sources. Geological storage of CO2 from fossil fuel use is also an option to reduce CO2 emissions, which does not require major changes in the energy infrastructure. Two projects are now under way in the European Union to study the potential for geological CO2 storage. The first project, known as GESTCO, will assess the potential CO2 storage capacity of the main sedimentary basins within Europe. GESTCO will examine in detail the geological storage potential and coincidence of CO2 emission sources to storage sites. In the North Sea the world’s first commercial geological storage project has now been in operation for 3 years. The natural gas from the Sleipner West field contains about 9% CO2, which must be reduced to 2.5% before sale. The CO2 is stripped by an amine scrubbing plant and then injected into a deep saline reservoir about 800 m below the seabed. To date, about 3 million tonnes of CO2 have been injected. To monitor the storage of CO2 in the reservoir, a project entitled Saline Aquifer CO2 Storage commenced in April 1998.

Annette Cutler

Papers

Demonstrating the Potential for Geological Storage of CO2: The Sleipner and GESTCO Projects