Abstract:

At present,injecting CO₂ into the subsurface oil and gas reservoirs,deep saline aquifers and disused coal-beds to store CO₂ in subsurface is the most valid and economic choice in reducing the CO₂ emission into the atmosphere.Several factors should be considered during the operation of CO₂ geological storage in the reservoirs as mentioned above.Once injecting CO₂ as a compressed liquid into the subsurface reservoirs,partial CO₂ will be retained due to physical and geochemical trapping.The most effective storage sites are those where CO₂ is trapped permanently under a thick,low-permeability caprock,or is adsorbed on the surface of coal micropores,or is converted to solid minerals through interactions of physical and chemical processes.No matter what reservoirs will be chosen to the subsurface geological storage of CO₂,some criteria should be met,including adequate storage capacity,regionally stable caprock,confined hydrologic system,stable compartment without risks of leakage and well-established industry and infrastructure and societal issues (i.e.,level of development,economy,environmental concerns,public education and attitudes).However,due to difference of physical and chemical properties of storage media,different strategies should be adopted during operation of subsurface CO₂storage.

Key words: CO₂, oil and gas reservoirs, coalbeds, saline aquifers, theory of geological storage, conditions of geological storage