As oil and gas operators continue to seek ways to reduce their carbon footprint, carbon capture and storage (CCS) is gaining traction. With CCS, carbon dioxide (CO2) emissions are captured, transported to CO2 storage sites, and injected into geological formations deep underground, where they remain indefinitely.
GARRY STEPHEN, Oil States
Carbon capture and storage (CCS) is gaining momentum as a key tool in oil and gas decarbonization efforts, capturing carbon dioxide and permanently storing it in deep geological formations. In an offshore context, there is growing interest in using decommissioned wells as CO2 injection sites, as these existing wells provide ready-made pathways into suitable reservoirs.
Traditionally, however, end-of-life decommissioning has been an expensive process, viewed strictly as a cost center for operators—after a field’s production ceases, platforms are removed, wells are plugged and abandoned, and the seabed is restored at great expense. The prospect of repurposing mature offshore wells for CO2 storage is, therefore, very attractive: it could transform a mandatory liability into a new asset while advancing climate goals.
REIMAGING MATURE WELLS
Repurposing existing offshore wells for CCS presents a winning opportunity, turning what was once a cost center into a potential profit center. Rather than incurring the traditional costs involved with abandoning a well, operators can invest a portion of that amount to retrofit wells for CO2 injection and potentially sell storage capacity to emitters.
The scale of this opportunity is substantial. Industry projections indicate more than 20,000 offshore wells will require decommissioning globally in the next 10 to 15 years, including over 2,000 wells on the UK Continental Shelf (UKCS) alone.1 These slated abandonments not only represent a significant operating expense but also a chance to create new revenue streams by offering CO2 storage services. This enables operators to leverage a portion of aging oil and gas infrastructure that’s unusable to support emerging lower-carbon technologies, contributing to broader industry decarbonization goals while potentially creating incremental revenue.
Regulators in offshore hubs like the UK, Norway and the Netherlands are supporting this shift with clear guidance and parameters for offshore CO2 storage operations, providing certainty and oversight for repurposed well projects. By aligning business incentives with emissions-reduction imperatives, the option to reuse mature wells for carbon storage is increasingly seen as a strategic approach to meet climate goals and extend the value of existing infrastructure.
CONSIDERATIONS FOR REPURPOSING AGING WELLS
Converting an older offshore well into a safe, long-term CO2 storage site is not without challenges. Technical hurdles are significant: many wells were plugged and abandoned decades ago, using methods that were acceptable then but fall short of today’s stringent CO2 containment standards. Legacy plugs, cement and casing strings need to be modernized, to ensure a CO2-tight seal for the centuries-long storage timelines now required.
Moreover, geological factors like reservoir repressurization can threaten well integrity, as abandoned fields often build back pressure (in some cases up to ~5,000 psi), which could compromise old well barriers if not properly addressed. There’s also wide variability in well designs and conditions; older fields contain wells with many different casing sizes and configurations, meaning bespoke engineering solutions are needed for each candidate well, rather than one-size-fits-all retrofits.
A customized approach is crucial, as a converted well must meet updated standards for containment and monitoring. Despite these challenges, a systematic process can be followed to evaluate and modify a decommissioned well for CCS use.
The key steps in assessing and converting a mature well into a CO2 injection site include:
Comprehensive engineering review and planning. Careful review of all available well records—including original construction details, past production history, and prior abandonment reports—is essential. The well’s architecture and condition also must be evaluated to determine suitability for modern CCS requirements. This planning phase identifies the required upgrades and ensures compliance with current regulations. A conversion plan is then created to serve as a roadmap for repurposing the well.
Wellhead re-establishment. If the original wellhead and conductor were removed or cut off during abandonment, leaving a stub below the seabed, a new structural foundation must be installed. This typically involves using a swaging system to swage or expand a tubular inside the old casing stub to effectively create a new wellhead base that can support further equipment. This operation reestablishes a stable platform for the well, providing immediate load-bearing capacity, so that the well can once again support a wellhead, blowout preventers, and injection hardware for CO2 service. The swaged connection must form a robust metal-to-metal seal with the old casing to provide long-term structural integrity.
Restoring casing integrity and connections. Next, the well’s casing strings are reconnected or upgraded to handle injection pressures and corrosive CO2 fluids. In many cases, sections of casing need to be tied back to the new wellhead or additional casing hangers installed. Specialized high-pressure connectors are used to bridge the gap between the old well casing and the new wellhead infrastructure, creating a continuous, pressure-tight flow path from the reservoir to surface facilities.
At this stage, if a riser is required to connect the subsea well to a platform or vessel, a high-pressure riser system would be installed and tied in with suitable connectors, ensuring full well control from the seabed to the injection equipment topside. The focus is on achieving complete wellbore containment integrity—every new connection and seal must withstand the expected CO2 injection pressures and temperatures.
If required, a perforation technology like GEODynamics Connex® can reconnect and extend past damaged areas of the reservoir and existing perforations caused by lower reservoir pressures where perforation cleanup is difficult to achieve with conventional perforating technologies.
Testing and verification. Once the new wellhead, casing connections and seals are in place, rigorous testing is conducted to verify the well’s readiness for CO2 storage. Each new connection or packer is pressure-tested to its design limits, to confirm the absence of leaks. Verification protocols often include inflow/outflow tests, pressure hold tests and even thermally cycled pressure tests to simulate the conditions during CO2 injection and long-term storage.
The well may also undergo integrity logging or monitoring to establish a baseline. Only when all components demonstrate a gas-tight seal can the well be certified for CO2 injection operations. This thorough verification ensures the converted well meets stringent containment standards and gives regulators and operators confidence in the well’s long-term storage integrity.
By carefully executing each of these steps, operators can overcome the technical challenges and safely transform an abandoned well into a functional CO2 storage well. The process demands meticulous planning, specialized tooling, and strict quality assurance at every stage to create a pathway to extend the useful life of old wells in service of emissions reduction.
CCS WELL CONVERSION BEST PRACTICE
Field-proven oil and gas technology is helping operators give old wells new life, Fig. 1. In a recent Netherlands pilot project, Oil States enabled an operator to repurpose multiple mature offshore wells for CO2 storage, demonstrating a successful technology transfer from traditional oilfield applications to a lower-carbon context. Oil States’ Hydra-Lok™ (Fig. 2) and formConnect™ systems (Fig. 3), which were originally developed for offshore drilling and infrastructure, were instrumental to the project to ensure structural integrity and containment for CCS.
Originally designed to make structural connections in offshore platforms, such as securing platform jacket legs to seabed piles, Hydra-Lok is a hydraulic swaging tool that creates a strong metal-to-metal bond between tubulars. It can be deployed diverlessly and provides immediate, full structural strength upon installation, which significantly reduces offshore work time and risk.
In CCS well repurposing, Hydra-Lok is used to swage new casing into existing well stubs, effectively forming a new wellhead base in previously abandoned wells. This gives the old well a robust, load-bearing foundation, ready to support new wellheads and injection equipment. The fast, one-trip installation and instant integrity that this technology delivers proves critical when modifying offshore wells for CO2 service.
The formConnect technology then tackles the challenge of casing string reconnection for CO2 injection. As many abandoned wells have sections of casing removed or lacking a modern completion, formConnect is used to install new casing tie-backs and high-capacity connections that meet today’s CO2 storage requirements. The system creates pressure-tight, high-strength joints between old and new piping, enabling the attachment of new wellhead components and casing hangers, even when the original infrastructure is absent.
This effectively bridges the gap between the legacy well architecture and the needs of a CO2 injection well, ensuring the upgraded well can safely contain and deliver CO2 at high pressure. By using formConnect to restore full casing integrity, operators can equip an old well with a modern completion and monitoring system as if it were a new injection well—but at a fraction of the cost and without drilling a new hole.
These technologies, along with others like specialized wellbore cleanout tools, sealing packers and high-pressure riser systems, form a comprehensive toolkit for CCS well conversion. The Netherlands pilot project demonstrates that applying proven deepwater oilfield technologies can dramatically simplify the conversion of aging wells for carbon storage.
THE FUTURE IMPACT: REDUCING COSTS AND ACCELERATING DEPLOYMENT
Repurposing mature offshore wells for CCS could significantly boost the scale and cost-effectiveness of CCS as a global decarbonization pathway. By converting what would have been decommissioning liabilities into productive CO2 storage assets, operators can offset abandonment costs, create new revenue from carbon services, and help meet climate targets in tandem. This strategy leverages the oil and gas sector’s unique strengths—its extensive infrastructure and deep technical expertise—to promote greater sustainability. The industry is uniquely positioned to lead large-scale carbon storage efforts, as it possesses the engineering skill to manage wells and reservoirs, as well as offering an existing supply chain for deploying equipment offshore.
By deploying field-proven technologies like advanced swaging connectors, high-pressure seals, and monitoring systems, the industry can help create reliable CO2 storage at a manageable cost. The result is a more viable and scalable CCS industry, where trusted oil and gas solutions make carbon storage projects more feasible. As demand for CCS grows, the ability to reuse and reinvent offshore wells as carbon sinks could transform the decommissioning process from a pure cost center into a key enabler of CCS operations. WO
REFERENCE
Offshore Energies UK. (2024, November 11). Forecast number of oil wells to be dismantled on the United Kingdom Continental Shelf (UKCS) between 2024 and 2033, by well type and region [Graph]. Statista. https://www.statista.com/statistics/749371/forecast-ukcs-oil-well-decommission/
GARRY STEPHEN is group vice president, UK and Asia, at Oil States, a role he has held since 2019. He has more than 20 years of expertise in global oil and gas offshore drilling, and he previously served as Oil States’ managing director from January 2012 to March 2019. Prior to his time with Oil States, he worked with other industry companies, such as Cameron, Expro and Aker Solutions. Mr. Stephen is based in Aberdeen, UK.