Carbon Capture Utilization & Storage
Following the Paris Agreement of 2015, several countries have committed to reaching carbon neutrality achieving net-zero emissions within a few decades. However, reaching this goal will not only require renewable sources of energy, but also negative emission technologies.
Carbon capture and storage or carbon capture and sequestration (CCS) is the process of capturing carbon dioxide (CO2) from large point sources before it enters the atmosphere, transporting it, and storing it in underground geological formations (geosequestration) for centuries or millennia. The aim is to prevent the release of CO2 from heavy industry, such as the oil- and gas industry, process industries and others with the intent of mitigating the effects of climate change.
Carbon capture and utilization (CCU) means using captured CO2 directly – or converting captured CO2 to be recycled into useful industrial products. CCS is a relatively expensive process yielding a product with an intrinsic low value (i.e. CO2). Hence, carbon capture makes economically more sense when being combined with a utilization process where the cheap CO2 can be used to produce high-value chemicals to offset the high costs of capture operations. Some of these chemicals can on their turn be transferred back into electricity, making CO2 not only a feedstock, but also an ideal energy carrier! CCS and CCU are usually discussed collectively as carbon capture, utilization, and sequestration (CCUS). Unlike CCS, CCU does not aim for permanent geological storage. See diagram:
Comparison between sequestration and utilization of captured carbon dioxide (source Wikipedia)
Cost is a significant factor affecting CCS. The cost of CCS, plus any subsidies, must be less than the expected cost of emitting CO2 for a project to be considered economically favorable.
Capturing CO2 is most cost-effective at its origin, such as large carbon-based energy facilities, industries with major CO2 emissions and natural gas processing plants, synthetic fuel plants and fossil fuel-based hydrogen production plants. After capture, the CO2 must be transported to suitable storage sites (such as injection in old produced fields!). Pipelines are principally the cheapest form of transport, and are, e.g., considered the main transport in the UK. Impurities in CO2 streams, like sulfurs and water, could pose a significant threat of increased pipeline and well corrosion. This is one of the risks associated with CCUS developments and needs to be properly managed.
As of 2020, about one thousandth of global CO2 emissions are captured by CCS. Most projects are industrial. This demonstrates there is still immense room for enhancement.
CO2 has been injected into geological formations for several decades for various purposes, including enhanced oil recovery. This is not carbon neutral, as that CO2 is released when the oil is burned. However, the long-term storage of CO2 is a relatively new concept. This is where the global E&P industry will play a major role in the years and decades to come. It is, as yet, uncertain to predict the long term security of submarine or underground storage, due to the lack of experience. However, it is believed that CO2 could be trapped for millions of years, and although some leakage may occur, appropriate storage sites are likely to retain over 99% for over 1000 years. The best example is Norway's Sleipner gas field, the oldest industrial scale retention project. An environmental assessment conducted after ten years of operation concluded that geosequestration was the most definite form of permanent geological storage method. A major condition is that the geological environment is tectonically stable and a site suitable for CO2 storage. Physical (e.g., highly impermeable caprock) and geochemical trapping (e.g. carbonate precipitation) prevent the CO2 from escaping to the surface. Equally important is the proper management of the injection of CO2, as escape of the gas from the injection pipe is considered a potentially greater risk. This requires expert knowledge!
Monitoring allows leak detection with enough warning to minimize the amount lost, and to quantify the leak size. Monitoring can be done at subsurface levels:
A direct method of subsurface monitoring involves drilling deep enough to collect a sample.
An indirect method is with sound or electromagnetic waves
Seismic monitoring can identify migration pathways of the CO2 plume
Organic chemical tracers can be used during injection of CO2 into an existing oil or gas field, either for EOR, pressure support or storage. Regular sampling at producing wells will detect if injected CO2 has migrated from the injection point to the producer
Or at surface levels:
Eddy covariance, measuring the flux of CO2 from the ground’s surface, either from towers or accumulation chambers, which are sealed to the ground
Satellite measurements (InSAR); in areas of stored CO2, the ground surface often rises due to high pressures, resulting in measurable change in distance from the satellite
Despite carbon capture increasingly appearing in policymakers' proposals to address climate change, the major challenge is that to date, CCS processes are usually less economical than renewable sources of energy.
Social acceptance is another important issue in the CCUS discussion. Since 2014, the public’s reaction was not supportive, rather passive or unwilling, due to the lack of knowledge, experience with industrial activity (positive or negative) and the controversies surrounding CCUS. Risk and benefit/cost perception are the most essential components of social acceptance. Risk perception is mostly related to the concerns on its safety issues in terms of hazards from its operations and the possibility of CO2 leakage which may endanger communities, commodities, and the environment in the vicinity of the infrastructure. Obviously, people are also very much concerned on the cost impact on their lives. However, mitigating climate change plays an increasing role in political discussions and populations are getting more and more aware of the potential threats of global warming and the need to change. Therefore, a global increase of CCUS is anticipated.
Upon requests from our clients, OPS OES Thailand will provide CCUS specialists who not only have the technical know-how and expertise of secure leak-proof way of CO2 transportation and how to inject it into deep geological formations (e.g. depleted oil- and gas fields). They also have knowledge on climate, energy (policy) targets and have the social skills and ability to overcome public and stakeholder opposition to necessary change. Given the immense financing needs and accepting challenges of CCUS, he/she will always consider the economic and political feasibility.
The whole process of CCUS is summarized in the figure below.
Source: International Energy Agency.