Date: Sept. 30, 2025 Contact: bseepublicaffairs@bsee.gov Safety Alert No. 508 Phone: (800) 200-4853

Review anchor-handling plans now: Incident damages subsea equipment, triggers gas release Incident: The Bureau of Safety and Environmental Enforcement’s Gulf of America Region (GOAR) investigated a gas-release incident involving a diver support vessel (DSV) that was marking a pipeline ahead of a jack-up rig’s subsea well recompletion. The DSV was recovering two bow anchors from the seafloor.

As the DSV approached the subsea well site, the vessel moved down current, and the No. 1 bow-anchor wire became entangled in the well. The DSV backed away, but the wire remained snagged and multiple attempts to free it failed. During the final attempt, the wire caught the annulus-valve assembly, shearing several studs and detaching the valve from the tubing spool. A strong gas plume surfaced. The DSV retreated about 1,900 feet, and an emergency response began.

During mobilization and execution, the lease operator overlooked several critical preparation steps.

Findings:

• Planning and coordination were inadequate. The operator and contractor did not conduct simultaneous operations (SIMOPS) meeting or a hazard assessment. • The Safety and Environmental Management System (SEMS) plan did not clearly specify which operations require SIMOPS planning and a hazard assessment. • Communication between the DSV and the operator was lacking. Key personnel were not notified when the job began or what work was being performed. • The absence of an anchor tug limited the vessel’s ability to hold position, increasing difficulty and risk. • Drawings were not readily available during the emergency response.

CATEGORY: Contractor Management, Gas Release, Well Operations

• The replacement valve was not configured for diver handling, delaying efforts to secure the release.

To help prevent similar incidents in the future, BSEE recommends that operators and their contractors, where appropriate, consider the following:

• Implement a pre-job checklist that verifies all preparatory steps, including pipeline marking and weather or delay considerations. • Establish a contingency-planning protocol to validate all critical steps before mobilization. If delays occur (e.g., weather), reconfirm critical steps before remobilizing. • Coordinate among internal teams and third-party contractors to ensure a shared understanding of job-readiness requirements. • Hold a formal pre-mobilization review with all stakeholders to confirm scope, readiness and safety measures. • Provide refresher training for personnel involved in offshore planning and execution to reinforce procedural compliance and communication. • Ensure anchor-handling plans account for strong currents and vessel drift. • Maintain clear communication with all stakeholders. • Confirm that critical documentation is on board and accessible before mobilization. • Include divers in preparation for subsea installation or repair activities. • Review SEMS protocols to clarify SIMOPS and hazard-assessment requirements.

– BSEE –

A Safety Alert is a tool used by BSEE to inform the offshore oil and gas industry of the circumstances surrounding a potential safety issue. It also contains recommendations that could assist avoiding potential incidents on the Outer Continental Shelf.

CATEGORY: Contractor Management, Gas Release, Well Operations