ENERGY PRODUCERS IN EUROPE are investigating schemes for storing captured carbon-dioxide (CO2) in depleted offshore gas fields to help governments achieve emissions reduction targets. Various projects in the North Sea and Irish Sea are in the advanced planning stage, with another, Northern Lights, already under development offshore/onshore Norway.
Last October, the UK government selected two priority track 1 projects for its Carbon Capture Utilization and Storage (CCUS) cluster sequencing process. One is HyNet North West Cluster, which aims to combine production of green hydrogen with the capture and transport of CO2 from local industrial emitters in northwest England and North Wales for storage in Eni’s depleted offshore reservoirs in Liverpool Bay in the East Irish Sea.
The other Track 1 scheme is the Northern Endurance Partnership’s (NEP) East Coast Cluster, which seeks to develop infrastructure for capturing and transporting CO2 (carbon-dioxide) from carbon-emitting industries from the Teesside to north Humberside areas in northeast England for storage in a saline aquifer (named Endurance), 145 km (90 mi) offshore Teesside in the UK southern North Sea. According to NEP, a partnership between bp, Eni, Equinor, the UK’s National Grid, Shell and TotalEnergies, Endurance has the capacity to store 450 MM metric tons of CO2, while other potential sites nearby could lift the storage capacity to around 1 billion metric tons. Once operational, the development could transport and store up to 27 MM metric tons/yr (29.8 MM tons) of CO2 emissions.
Among the proposals to miss out on the government’s initial tranche of funding was Neptune Energy’s DelpHYnus in the southern UK North Sea. However, feasibility studies continue, with the company hopeful of securing government support under a future cluster sequencing program. The proposed development would combine a CO2 transport and storage solution serving companies in the South Humber industrial area close to the Lincolnshire coast with a 1.8-GW blue hydrogen production plant at the former Theddlethorpe North Sea gas reception terminal. The project would also provide the opportunity to extend the life of the production platform complex serving the Neptune-operated Cygnus gas field through partial repurposing for future CO2 storage.
Neptune has applied to Britain’s Oil & Gas Authority for a CO2 appraisal and storage license for the southern UK North Sea. Its plan involves installing new offshore facilities including renewable energy control buoys at the CO2 injection well sites, and a normally unmanned installation powered 100% by renewable energy. The company is also investigating repurposing of the 188-km (117-mi), 26-in. CMS (Caister Murdoch System) trunkline for CO2 transport: the pipeline was originally constructed in the 1990s to take gas from various fields in the southern North Sea to Theddlethorpe. If feasible, this could lower the development costs substantially, as well as reducing the environmental impact of the overall DelpHYnus transport and storage system.
Incorporating the Cygnus complex for a future CO2 storage role and the associated life extension could in turn provide the economic justification for electrification of the platforms to reduce their emissions, as well as potentially opening a path to the production of green hydrogen. In addition, DelPHYnus could be connected to Neptune’s L10 area Carbon Capture and Storage (L10-CCS) development in the Dutch sector of the North Sea via the NGT gas trunkline system. An additional area of focus is shipping, with direct injection into the wells, providing a storage solution for emitters not easily connected to stores by pipeline.
According to Pierre Girard, Director of New Energy at Neptune: “Engineering teams have assessed various aspects of the DelpHYnus project through feasibility studies, selection and early subsurface assessments. The analysis completed to date reaffirms our confidence that, with the requisite up to regulatory approvals and licenses, it could be developed at pace providing storage capacity for 570 MM t of CO2. “The assessment of the suitability of the CMS pipeline for CO2 transport is ongoing, and the analysis completed to date has been positive.” A wide variety of potential partners and emitters have expressed in the project, he added: capturing of emissions does not form part of the current business model for DelpHYnus.
In the Dutch sector of the North Sea, Neptune has been reinjecting CO2 into the gas field beneath the K12-B platform for over 14 years. The company has also completed a study into the feasibility of injecting 5-8 MM metric tons/yr of CO2 into the depleted L10 A, B, E and L offshore gas fields. “The associated platforms and pipelines remain in place,” Girard said, “offering the potential to repurpose the existing infrastructure.” If the L10-CCS project is sanctioned, it could be one of the largest carbon Capture and Storage (CCS) facilities in the Dutch North Sea, also accounting for over 50% of the CO2 reductions targeted by the Dutch industrial sector. Others participating in the program are the L-10 area partners EBN, Rosewood Exploration and XTO Netherlands, and there is growing interest from various CO2 emitters on the Dutch mainland. “However, the project remains at an early stage and we may require work with a variety of commercial and research organizations as it progresses…we are continuing to work through the process of obtaining a carbon storage license from the Dutch government.”
Girard added: “We expect to have the L10-CCS project FEED-ready by the end of 2022, with the aim of taking a final investment decision in 2023…There is a lot of work still to be done to realize our objective of first carbon injection into the reservoir in 2026 but we are committed to progressing the project and obtaining the necessary licenses and approvals.”
DNV is working on a related CCS pipeline materials study, assessing the offshore pipelines’ suitability for re-use in CO2 storage at the depleted gas fields. “Under the current first phase DNV is seeking to identify the most advanced approaches to ductile fracture assessments in dense-phase CO2 pipeline systems. It is also looking at the applicability of those assessments to both welded and seamless subsea line pipe. On completion, DNV will progress to phase two, applying those methodologies to evaluate the likely suitability of the existing pipelines for dense phase CO2 transport at up to 120 bar [1,740 psi].”
In Norway, the Northern Lights joint venture between Equinor, Shell and TotalEnergies is developing the transportation and offshore storage facilities for Longship, the Norwegian government’s carbon and capture and storage project. Phase one of Northern Lights is due to be completed in mid-2024, with an initial capacity of up to 1.65 MM metric tons/yr (1.82 MM tons) of CO2. This will be transported by specially designed ships from capture facilities in liquid form to a terminal in the Naturgassparken industrial area in Oygarden, western Norway. From there, the CO2 will be pumped through pipelines for injection and permanent storage 2,600 m (8,530 ft) beneath the seabed in the Aurora storage complex in Exploitation License EL001 in the Norwegian North Sea. Here the Eos appraisal well, drilled and completed in March 2020, confirmed the reservoir characteristics and storage capacity. The reception terminal, offshore pipeline and umbilical to the offshore template are all being sized to allow for expansion of capacity to 5 MM metric tons/yr (5.5 MM tons) of CO2 in a later phase. Eventually, the intention is to extend the facilities to other CO2 emitters outside Norway.
Earlier this year Northern Lights signed a non-exclusive Memorandum of Understanding with Aker Carbon Capture to collaborate on CCS projects in Norway and throughout Europe, covering the full chain from carbon capture through transport and storage. Goals include optimizing logistics and standardize ship-shore interfaces and developing source-to-storage carbonization on a pay-per-metric ton of captured CO2 model.
Among the other schemes progressing in the North Sea is Denmark’s Project Greensand backed by 23 companies and organizations, including Danish North Sea operators INEOS (the project’s leader) and Wintershall Dea, Maersk Drilling, Magseis and Welltec. The CO2 would be stored in depleted oil fields in the Siri area, with potential to store further volumes in a saline aquifer. The initial plan is to store up to 1 MM metric tons (1,1 MM tons) of CO2 annually from 2025 rising to 4-8 MM metric tons/yr (4.4-8.8 Mm tons) by 2030.
Subsidiaries of Aker Solutions recently entered an agreement to co-operate on subsea injection systems for CCUS. Dril-Quip will provide Aker Solutions with the CO2 injection Xmas trees and wellheads for integration into a larger subsea injection purpose-designed for CO2 injection and storage. Aker Solutions would manage any projects as an integrated provider of CCUS systems and associated controls/electronic components. The companies also agreed to jointly target the Northern Endurance project in northeast England using where possible equipment services from their local organizations. Elsewhere, Aker Solutions has been working on the carbon capture FEED for the Net Zero Teesside development associated with Northern Endurance, under a consortium with Siemens Energy and Doosan Babcock.
Aker Carbon Capture (ACC), the subcontractor for this program, is collaborating with Dan-Unity CO2 of Denmark on another development, flexible CO2 transport solutions by sea which would offer multiple sourcing points to deliver economics of scale for CCS projects. Dan-Unity CO2 is a CCS-specific shipping entity formed by Danish shipping groups Evergas and Navigator Gas. The two co-venturers are examining the technical and commercial risks associated with capture/liquefaction technology, loading/offloading operations, offshore offloading, intermediate storage and permanent subsurface storage. In addition, ACC is collaborating on another CCUS full-value chain development with maritime/infrastructure specialists Altera Infrastructure and Höegh LNG: their Stella Maris CCS project involves developing large-scale transport with shuttling of CO2 to an offshore location for injection and permanent storage into a subsea reservoir.
Last month, the Net Zero Technology Centre (NZTC) in Aberdeen launched its latest funding competition for new technologies to address issues associated with CCUS. The focus areas are transportation and storage, the geological behavior of CO2, and site monitoring and containment. According to NZTC, while there is good technical understanding of CO2 transportation, new pipelines are costly. Existing oil and gas pipelines can potentially be repurposed, but more work is needed on the cost and methodology associated with retrofits. New characterization/coating/material solutions will likely be needed to prevent corrosion caused by impurities in the CO2. The NZTC is also seeking predictive maintenance solutions to protect against crack propagation, and low-cost control valves to maintain pressure, especially in longer pipelines. Other issues highlighted include the need for software to model CO2 migration and interactions in different rock structures to improve understanding of CO2 behavior to inform injection and sealing strategies, particularly critical around existing wells, where there could be a higher risk of leakage.
Classification societies will have a major role to play in certifying these and other new solutions proposed for CCUS in offshore locations. At present, Lloyd’s Register (LR) is investigating the associated issues under the remit of its offshore technical committee, said Global Power to X Director Mark Tipping. “LR will look at what it means for the engineering ecosystem in terms of offshore and marine ships capturing and transporting CO2, and for injection of CO2 or strengthening subsea pipelines.”
Tipping added: “CO2 is a hazard, there is a risk of an inadvertent release during transportation. But it is also an inert gas, with fewer risks than LNG. And when stored cryogenically, the temperature is not as extreme as with LNG and hydrogen when transported in bulk. The quality of the CO2 is important: the associated containment system must be designed accordingly, for instance, if there were high levels of impurities. The same issues apply to the pipelines.” As for offshore loading/unloading of CO2 from a vessel, “You couldn’t simply adapt a system used for LNG or LPG, without understanding the metallurgy and existing infrastructure in detail,” Tipping explained. “It would have to be designed or validated specifically for handling CO2 in a gaseous, or liquid form.”
While current developments in CO2 transport and loading offshore have focused on newbuild vessels, “it is highly likely that at some point the industry will consider repurposing existing vessels or even convert floating storage units close to the offshore injection/storage site. Because the development of CO2 containment for bulk transport does not present the same challenges as, say, hydrogen. Typically, with new developments in this industry, people start with newbuilds and then progress to conversions. It is achievable from the mid-2020s onwards.”