Carbon Capture and Storage in Geologic Formations

Abstract

Carbon dioxide (CO2) emissions, the most important anthropogenic greenhouse gas (GHG), can be reduced by CO2 capture and storage (CCS). This strategy is applicable to many large stationary sources including power generation plants, oil and gas refinery, cement production and other industrial sectors generating large point source of CO2. While the technology for CCS is currently available, significant improvements are needed to enhance confidence in storage security. In 1996, the first CCS project established for the purpose of mitigation of CO2 emission began injecting CO2 into deep geological formation in offshore aquifer in the North Sea, Norway. Since that time, science has advanced in areas such as geophysics, chemical engineering, monitoring and verification, and other areas, while also governments have funded demonstration projects at various sizes ranging from small-scale proof of concept to industrial-scale demonstration projects. Five industrial-scale CCS projects are currently operational globally with more than 0.035 Pg of CO2 captured and stored since 1996. Observations from these industrial scale projects and commercial CO2 enhanced oil recovery (CO2-EOR), engineered natural analogues as well as theoretical consideration, models and laboratory studies have suggested that appropriately selected and well managed CCS sites are likely to retain almost all of injected CO2 for long time and provide the benefits for the intended purpose of CCS. However, CCS is still struggling to gain foothold as one of the main options for mitigating climate change due to high costs, advances in other options including renewable energy, as well as discovery of shale natural gas and the associated hydrological fracturing extraction techniques, absence of international action by governments and private sectors on climate change, economic crisis-induced low carbon (C) prices, and public skepticism. The estimated costs for CCS varies widely depending on the application—such as gas clean-up versus electricity generation, type of fuel, capture technology , and assumptions about the baseline technology. Generally, for current technology, CCS would increase cost of generating electricity by 50–100%, and parasitic energy requirement of 15–30%. In this case, capital costs and energy requirements are the major cost drivers. In addition, significant scale-up compared to existing CCS activities will be needed to achieve intended large reductions of CO2 emissions. For example, a 5- to 10-fold scale-up in the size of individual projects is needed to capture and store emissions from a typical coal-fired power plant of 500–1000 MW, while a thousand-fold scale-up in size of current CCS enterprise would be needed to reduce emissions by 1 Pg C yr−1. The estimated global oil and gas reservoirs are 1000 Pg CO2, saline aquifers global potential capacity ranges from 4000 to 23,000 Pg CO2. However, there is considerable debate about how much storage capacity actually exists and is available for CCS, particularly in saline aquifers. Research, improved geological assessments and commercial scale demonstration projects will be needed to verify the estimated capacity and improve confidence in storage capacity estimates.