North Sea’s only semi-sub performing saturation dives achieves 163 ops as rig’s decom gig approaches finish line

Aberdeen-based decommissioning services provider Well-Safe Solutions has hit a new saturation diving milestone in the UK waters with one of its rigs, which is said to be the only semi-submersible in the North Sea with saturation dive spread capability.

After buying the Ocean Guardian semi-submersible rig from Diamond Offshore in 2019 to convert it into a bespoke plug and abandonment (P&A) unit, the Aberdeen-based player changed the rig’s name to Well-Safe Guardian , modernized, refurbished, and reconfigured it exclusively for P&A scopes.

These upgrades enabled it to score a 14-well decommissioning contract with Repsol Sinopec Resources UK for the Hannay and Buchan fields in September 2021. The following month, Well-Safe won an assignment with CNR International to decommission up to 14 more wells on the Banff and Kyle fields in the UK Central North Sea.

Fitted with a D300 saturation dive system and Trendsetter Engineering ’s Trident modular intervention technology , the rig is perceived to be the right fit for well P&A activity on aging or fragile wells.

The Well-Safe Guardian rig completed the first saturation dives in Well-Safe Solutions’ history last year while working on Repsol Sinopec’s second phase of well decommissioning at the Buchan and Hannay fields in the North Sea.

According to the UK’s decommissioning services provider, diving works have been completed on the rig’s maiden project with the saturation dive system, following 163 operational dives across three drill centers and nine wells.

Well-Safe Solutions highlighted: “This fast-growing track record demonstrates the experience and tenacity of the Well-Safe Solutions team, our client, and close collaboration with RockSalt Subsea Ltd and Fugro as key partners.

“With uptime of 96% over the final three wells in this project, we saw incredible performance delivery on the final batch of legacy, dual-bore Xmas trees building on the high reliability of our diving system.”

These 163 dives enabled the completion of work scopes related to the general visual inspection of subsea dual-bore trees, removal of aged control systems and replacement with new tree control panels, installation of new hydraulic lines with pressure-testing of function and safety valves, barrier testing and remedial works to address any integrity issues, installation of tree connector override system, and removal of manual tree cap lockdown screws.

While emphasizing that this solution is “an alternative to traditional subsea well decommissioning approaches in the North Sea,” the company underlined the Well-Safe Guardian rig’s “market-leading role” in the decommissioning of fragile and aged wellheads and trees, since the rig is portrayed as the North Sea’s only semi-submersible with saturation dive capability.

“The Guardian is now latched onto the wells with Trendsetter Engineering, Inc.’s Trident intervention system, enabling safe, secure decommissioning operations to conclude later in 2024. […] Congratulations to everyone involved with the Well-Safe Guardian for this fantastic proof-of-concept of the saturation dive system,” emphasized the Aberdeen-based firm.

The Well-Safe Guardian Earl & Wright 700 series midwater semi-submersible rig is believed to be well-suited for interfacing with older wellheads and trees since it comes with the Trendsetter Trident modular intervention system, which is a single-system solution that can be configured for hydraulic intervention, riserless light well intervention, and open water intervention riser operations.

Last year, Well-Safe Solutions got a global master agreement with BP for well engineering and decommissioning support services, alongside a deal with Spirit Energy to expand the existing scope for the Well-Safe Defender semi-submersible rig with another well.

In addition, the Scottish decommissioning player decided to dip its toes into carbon capture, utilization, and storage (CCUS) projects .