UKCS Contribution to Delivering UK Environmental Targets

Carbon Capture and Storage (CCS) and Enhanced Oil Recovery (EOR)

Carbon Capture and Storage (CCS) is an emerging technology which has the capability to render fossil fuels carbon free. CCS captures the CO₂ from large industrial or power generation sources using a combination of physical and chemical process. The CO₂ is then transported and stored in a geological structure such as a saline aquifer or an old oil or gas field.

CO₂ storage is only currently used in the North Sea in one application at the Sleipner field in Norway. Here CO₂ is removed from the produced natural gas, to improve its quality, then reinjected in the “utsira” formation, a 200m thick sandstone aquifer located 800m below the sea bed. In the case of Sleipner, reinjection of the CO₂ was an integral part of the field’s overall development planning and economics, and the offshore production facilities were specifically designed for that purpose. Sleipner does not involve the import of CO₂ from other fields or onshore industrial processes, nor is the CO₂ used to enhance oil recovery.

Figure 47: Carbon Capture and Storage

Europe is estimated to have extensive CO₂ storage capacity, predominately located in and around the North Sea. The British Geological Society estimates potential storage capacity under the North Sea at around 20 billion tonnes of CO₂ in oil and gas fields with an additional 20 – 70 billion tonnes of CO₂ in confined aquifers. This compares with current UK CO₂ emissions of around 580 million tonnes per annum.

Re-injecting the captured CO₂ into oil reservoirs is now being used as a means of Enhanced Oil Recovery (EOR) in a limited number of applications in Canada and USA. The captured CO₂ is injected into the oil reservoir and used to drive out additional oil which might otherwise be left in place, thereby enhancing overall oil recovery.

To-date, CCS with or without EOR has not been employed in the North Sea. The use of CCS for EOR on the UKCS raises significant legal, technical, environmental and economic issues.

• CO₂ is highly corrosive. Existing platforms and processing facilities and the offshore pipelines and infrastructure are not designed to transport and to store CO₂ into the existing reservoirs. Carbon capture and storage will require very large investment in new infrastructure both onshore and offshore, including substantial retrofitting of ageing installations, where there are already severe weight and space limitations.
• The benefits of using CO₂ for EOR may not be as large as anticipated. CCS will at best provide additional tertiary oil recovery, as enhanced oil recovery techniques such as water or gas injection have already been employed on the majority of oil fields in the UKCS.
• The legality of CCS offshore is currently in question. CO₂ is officially designated a “waste” product and reinjection offshore is not allowed under current international law (OSPAR and the London Convention).
• The economic case is unproven. Current estimates for the cost of CO₂ capture, transport and storage range from €60-100 per tonne (£45-75/tonne) or even higher. CCS is shown to require fiscal incentives to be economic even in the current business environment.

Further research is required to address the costs, prevailing technologies for CO₂ capture, transport and storage and the implications of long term geological storage. The UK North Sea is a mature province, with many fields now approaching the latter stages of their economic lives. CCS may yet have a role to play in the future development of the North Sea; however viable individual field applications have yet to be identified and it may require a concerted approach by all stakeholders around the North Sea to establish whether opportunities ultimately exist.