Realizing efficient well abandonment safely How modular systems redefine rig-less subsea and mudline well decommissioning

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Improve your performance. Learn more at nov.com slash deepdive. Welcome to another episode of the World Oil Deep Dive Podcast.

I'm Kurt Abraham, Editor-in-Chief and Chief Forecaster, and I will be your narrator. In this episode, we're going to discuss a recent article by Richard Henderson of James Fisher Energy. The topic is Realizing Efficient Whale Abandonment Safely, How Modular Systems Redefine Rigless Subsea and Mudline Whale Decommissioning. decommissioning.

So let's get right into it. In the first section here, he talks about a new chapter for aging well stock. As offshore oil and gas basins mature, subsea well decommissioning has transitioned from a long-term liability to an immediate operational priority. In regions such as the Gulf of Mexico or Gulf of America, the UK Continental Shelf, the Gippsland Basin in Australia, and parts of Asia Pacific, operators are facing aging well inventories, tightening environmental oversight, constrained vessel availability, and escalating costs.

Now, while regulatory frameworks vary from region to region, the technical objective remains consistent to deliver permanent well integrity, to protect the environment, and to remove seabed obstructions or hazards in a safe and verifiable way. Achieving this at scale can be realized through a combination of field-proven modular technology and specialist technology support to reduce the risks presented by complex subsea decommissioning activity. So now we're going to talk about a regalist approach to permanent abandonment.

The proprietary Seabass system was designed for environmental barrier placement in subsea wells. Developed by James Fisher & Sons, the system is modular. It can be adapted for mudline well applications using Seabass MLS, which allows for anchoring and sealing inside large internal diameter conductor strings. Both versions of the system are designed for deployment from vessels via the moon pool or over the side.

Its modularity enables perforation, circulation, and cement placement for environmental barrier installation to be completed. Thus, that removes the need for a mobile offshore drilling unit, which, depending on the region, can be a significant six-figure cost per day when supporting a decommissioning campaign. So, regardless of the variant required for the particular well-type applications, CBAS has been designed with the operator and vessel provider in mind to increase project efficiency, reduce operational costs, and minimize personnel exposure to hazards.

So now we're into the section entitled Common Goals and Different Regulations. So globally, regulators share the objective of effective isolation through standards-based, evidence-driven approaches, but differ in how new technologies are evaluated and adopted thanks to key differences in the regulatory frameworks. Now, in the U.S.

, the Bureau of Safety Environmental Enforcement, BSEE, requires operators to demonstrate the new technologies provide equivalent or superior outcomes to conventional methods in terms of barrier integrity, verification, and environmental protection before they can be deployed in the field. Alternative methods such as rigless well plug and abandonment can provide additional options Their use typically depends on collaboration between operators and the supply chain to demonstrate equivalence or improvement over conventional practices, typically with a detailed technical justification supported by a safety and risk assessment.

Ongoing debate around idle iron and proposed legislation updates show a strong interest in innovation when it supports Bessie's requirements regarding long-term well integrity and the ability for the regulator to verify compliance. In comparison, the UK's North Sea Transition Authority builds on a standards-based approach with a performance-based framework that actively encourages innovative approaches to achieve reductions in cost, emissions, and offshore exposure while meeting regulatory expectations on time and in full.

The high number of late-life assets on the UKCS has accelerated the adoption of regless abandonment technologies and campaign-based decommissioning approaches designed to lower emissions and improve asset utilization, again without compromising well integrity. In the North Sea, vessel-based well decommissioning systems exist alongside rig-based options across many approved decommissioning programs. So Australia's National Offshore Petroleum Safety and Environmental Management Authority promotes a technology agnostic framework focused on outcomes.

Operators must demonstrate that risks are reduced to as low as reasonably practical and that environmental impacts are acceptable. New technologies are encouraged when they credibly achieve safe, timely, and environmentally responsible permanent well abandonment. NAPSEMA, that's that Australian group, has publicly highlighted the need for new technologies to address the growing backlog of redundant wells, as well as reducing reliance upon scarce mobile drilling rigs in the region.

So across jurisdictions, the message is clear. Innovation is welcome as a means of reducing emissions, cost, and risk, but not simply for the sake of cost reduction. Innovative technologies gain traction quickest when they are supported by robust safety cases and strengthen confidence in long-term well integrity and environmental outcomes. So now we're in a section entitled Engineering the Single Trip Solution.

So CBAS was developed to bridge the gap between lightwell intervention and conventional rig-based abandonment, combining the operational flexibility required for vessel-based deployment with the capabilities required for long-term environmental barrier placement. It combines field-proven passive ceiling technology with mechanically locking wellhead interfaces for maximum effectiveness. Modularity is fundamental to the design philosophy as no two wells are ever the same. All wells present unique challenges driven by age, integrity, damage, and even incomplete documentation after decades of ownership changes.

The system accommodates these variables through modular tooling configurations and the integration of standard industry-wide tooling, such as external wellhead connectors, maximizing compatibility across diverse global well inventories. In subsea well configuration, the CBAS system mechanically locks internally within the wellhead to provide a stable foundation for perforation, circulation, and cementing operations. An external wellhead connection provides contingency engagement capability, while dual fail-safe safety valves and a robust locking mechanism support well control throughout the operation.

A notable feature is its emergency disconnect and reconnect capability In the event of vessel drive or deteriorating weather conditions SEBAS and SEBAS MLS can be rapidly disconnected and reconnected while safely maintaining pressure and fluids in the wellbore This capability is particularly valuable in regions such as Southeast Asia, where local weather systems can cause extensive and repeated disruption to offshore operations leading to nonproductive time. In addition, the system has no water depth limitations while its modular capabilities enable ROVs to interface with the system in deepwater environments, giving a broader use profile with a wider array of well stock.

The system is delivered, fully assembled and tested, reducing offshore integration time and deck complexity relative to multi-section alternatives. So as we talk now in the topic of efficiency, drivers, and cost performance, we can tell you the continual development of the sea bass system for both subsea and mudline well applications has been made possible by specialists with considerable operational and engineering experience in both rig and vessel-based abandonment, including the challenges and opportunities enabled by both methodologies.

So this experience includes practical knowledge of traditional well P&A solutions, some of which have previously involved a technical specialist now within the decommissioning team at James Fisher. Based on internal analysis, James Fisher estimates that the system can reduce operational time by up to 25% compared with other vessel-based well P&A systems. Several engineering features underpin this efficiency. The system uses passive sealing elements rather than inflatable packers, significantly reducing the time required for sending and unsending operations.

Given the typical abandonment scopes involve either single annulus or dual annulus operations, this benefit alone can contribute to a reduction of 12 to 16% in scheduled time. As with any new technology, operational reliability is paramount to a project's success. During the decommissioning operations, inflatable packers can become damaged through regular use and take considerable time to replace. When sealing elements require replacement, this can typically be completed in around 30 minutes, compared with more complex sealing arrangements that can take hours to replace.

In addition to physically shorter system length, enables it to be supplied to the vessel fully built and tested, avoiding multi-part offshore assembly and delivering an estimated additional 4% vessel time saving. Premobilization onshore testing can also further reduce deck testing requirements. When taken together, these design features further enhance reliability and optimize handling time contributing to improved project uptime. Now, in this section, managing uncertainty through experience, we note that some see wells marked for abandonment are often poorly documented and may suffer from degraded integrity after decades of operation in harsh marine environments.

An all-too-common challenge is finding out that the reality of the well schematics deviates from what's been documented often decades after drilling and when multiple well interventions have taken place. The system has been developed with this challenging industry reality in mind. The system supports multi-barrier placement of environmental plugs, and its modular architecture suits both subsea and mudline well applications. The approach is supported by James Fisher's technical decommissioning team, which brings extensive experience in de-risking such scenarios.

These specialists operate globally and support customers with contingencies for a wide range of scenarios, enabled by a decommissioning toolbox. This encompasses everything from cutting and severance technologies to structure removal and recovery including supporting systems such as control flow excavation tooling But it not just the technical capabilities that make such a difference Collectively, team members have designed well-abandoned methodologies and project-managed and executed global projects in harsh environments worldwide.

James Fisher also carries forward this extensive decommissioning project management and delivery experience into the renewable energy sector, having completed the world's largest and first ever abrasive cut on a 10-meter diameter offshore wind monopile during 2025. So, under the regulatory acceptance section, as we have seen in our regulatory comparison, of BESI, NSTA in the UK, and NAPSEMA in Australia, regulators require varying standards approved to encourage the uptake of new technologies.

Across regions, our analysis has shown that without credible new technologies, the industry will struggle to meet decommissioning timelines safely and economically. So in the latter part of this article, We have a case study about UKCS subsea well abandonment. In this case, with the North Sea operators seeking a safe and cost-effective decommissioning approach for two wells, sea bass was first deployed commercially on the UKCS in late 2022. James Fisher developed and safely executed a single-trip abandonment program supporting permanent well abandonment.

This allowed for the surface well structure to be removed without environmental contamination from well fluids. Operations included the drifting and scraping of the well with the system pressure tested before perforation of the 13 3⁄8 inch casing. Oil-based mud was flushed and fluid returns were managed on the vessel enabling a 300-foot environmental cement barrier to be placed. During this project, approximately 200 barrels of OBM were recovered from the 13 3⁄8-inch by 20-inch annulus.

Back deck filtration allowed contaminated fluids to be managed offshore, avoiding costly port calls and benefiting productive time. Both wells were abandoned safely and within the operational schedule. So, looking beyond the North Sea, the feedback from this inaugural project has been vital in supporting continuous development. Operator concerns regarding the availability of a compact spread suitable for vessels with reduced deck space, for example, make both variants well-suited to highly regulated legacy basins such as Australia and Asia Pacific, or smaller vessels are often preferred.

The system is being considered for deployment in multiple regions as operators seek scalable, field-proven, and modular abandonment solutions, with the added reassurance of an internationally experienced decommissioning team. So looking ahead and supporting mature wells through RICLIS P&A, CBAS and CBAS MLS represent an evolving approach to well decommissioning, combining modular design and single trip efficiency to enhance operating safety, reduce project expenditure, and support more efficient decommissioning of aging wells.

So as well inventories continue to age and the decommissioning burden grows, such technologies backed by highly experienced decommissioning specialists will be critical in enabling safe, timely, and economically suitable well abandonment worldwide.