HSE: Thistle issues ‘appear specific to platform’ – Upstream Online

The UK offshore safety regulator has said its initial inquiries into the structural problems at the Thistle platform that led to the sudden evacuation of all 115 workers on board on Monday appear to be specific to that facility.

The Health & Safety Executive (HSE) said on Wednesday that EnQuest is helping its inspectors with its inquiries.

Lines of inquiry are being identified, an HSE spokesperson said on Wednesday.

The spokesperson added that while HSE does not comment about ongoing investigations: We will encourage EnQuest to provide information if any important safety matters arise that should to be shared, but at present the issues appear to be specific to the Thistle platform.

Yesterday an official with the RMT union called on EnQuest and the North Sea industry to be as open as possible in sharing details about what has happened.

We keep hearing from the industry about the need for learnings, sharing and openness," said Jake Molloy, RMT regional organiser in Aberdeen.

"Well, there are a number of jacket-based platforms in the North Sea are of this advanced age.

If there are learnings to be gained from what happened on Monday, lets hear about them and share them with the operators who have those older platforms."

EnQuest "proactively downmanned" Thistle, in Block 211/18, in what it called a "precautionary move" on Monday.

This followed an inspection of a support element on a redundant subsea storage tank.

Direct oil export was installed on Thistle in 2008 and the crude oil storage tank system, known as COST, was taken out of service.

The platform has been known to workers for years by its nickname "The Black Pig".

Located 200 kilometres north-east of Sumburgh, in the Shetlands, the development was the farthest north the offshore oil and gas industry had ventured by the time it started production in 1978.

Production hit a peak of 125,000 barrels per day in 1982.

When Thistle and the Deveron field were acquired by DNO 20 years later, production averaged 5500 barrels per day, and was declining.

Output is now understood to be less than 4000 barrels of oil equivalent per day.

EnQuest said in its 2019 half-year results that Thistle has seen high levels of production and water injection efficiency, without giving specific production numbers.

The 60-slot platform was installed in 160-metre water depths then a record for fixed platforms. The then record-setting 30,600-tonne jacket with four main legs supports 36 modules arranged on three deck levels.

Five years ago, EnQuest launched a 300 million ($470 million) rejuvenation effort, dubbed Thistle LLX (late life extension).

The project was aimed at recovering an additional 35 million barrels of oil from the Thistle and Deveron fields.

Thistle changed hands again in 2004, to Lundin Petroleum, and then, following the demerging of the Swedish independents UK assets in 2010, EnQuest took over as operator.

Some 28 of the 36 modules comprise the production, utilities, drilling systems and facilities. The remaining eight, situated on the south-east end of the installation, contain living quarters, offices, the central control room, the helideck and workshops.

Fluids from the Thistle and Deveron reservoirs exported to the Brent Pipeline System.

Oil is also imported from the Dons field via an eight pipeline and the combined oil production is exported from Thistle platform via 16-inch export pipeline through the Brent Pipeline System to the EnQuest-operated Sullom Voe Terminal in Shetland.

The original gas compression system has been decommissioned and gas separated from the oil is now flared.

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HSE: Thistle issues 'appear specific to platform' - Upstream Online