Page 44: of Offshore Engineer Magazine (Jan/Feb 2015)

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Starting up a high-pressure, high-temperature ? eld

EPIC prone to hydrate formation can be a daunting task,

Restarting not least when it has been shut-in and isolated, with the amount of safety critical maintenance limited by international sanctions for nearly four years.

Rhum

That was the task facing BP engineers in 2014 on the North Sea Rhum ? eld. Elaine Maslin reports. hen Rhum ? rst came online, on any related Rhum topside facilities, senior well integrity engineer at BP. A in December 2005, it was on the host Bruce CR platform. third Rhum production well, which had

W described as a world ? rst, By 2013, there were concerns that if failed before starting production, had a due to the high-temperatures and pres- Rhum was left shut-in it could become downhole pressure gauge. “Throughout sures in the reservoir, as well as its stranded, should Bruce reach a point in the four years we knew what the pres- 44km-long tieback distance. The largest its life where its production dropped to sures were down there, so we always had undeveloped gas discovery in the North a certain level. Also, there was a concern eyes on it,” Labroo says.

Sea at the time, it was expected to access about the risk to the environment in the In some shut-in ? elds, pressure build some 800 Bcf of natural gas. event of a leak from the HPHT ? eld, if up can be expected, if there is pressure

Rhum had been discovered in 1977, left unmaintained. support from water, for example. Rhum, some 240mi northeast of Aberdeen Last year [2014], amid moves to ease however, stayed relatively stable, at just in 109m water depth, by BP and its sanctions on Iran, the UK government under 8000 psi, close to the level it had partner Iranian Oil Company (IOC). The took steps to enable BP to restart produc- been when it was shut-in, Labroo says. ? eld experienced temperatures around tion, including temporarily taking over “The fascinating thing was challenges 150°C and pressures around 12,700psi. management of IOC’s share in Rhum, around the hardware, proving it all

Production started nearly three decades with IOC’s shares of Rhum gas sales rev- worked,” says Scott Forrester, project later from two wells. enues being placed in a frozen account. manager, Rhum restart, BP. “Up until that

In 2010, just under four years after The ? eld came back on stream mid-late point, we had been restricted on what ? rst production, the ? eld was shut-in October 2014. level of maintenance we could do on the and the system depressurized. Rhum How do you restart an HPHT ? eld system, meaning that no preservation operations were subject to EU and US that has been shut-in for nearly four on the equipment could be carried out. sanctions, due to IOC’s 50% stake, years with no maintenance, apart from We used our maintenance management which also meant BP was unable to minimal EX inspections on the topsides system and took time to understand all perform any work on the ? eld, including equipment? of the work we should have been doing (but couldn’t) over the past four years. While maintenance was limited, BP existed prior to shut in, but where, for

We also took time to understand where did have an idea of what was happen- the same reasons, we had been unable

The ? eld’s infrastructure comprises equipment reliability challenges had ing in the reservoir, says Manish Labroo, to take advantage of the four-year shut- two producing wells, connected via a two producing wells, connected via a in period to work on removing these manifold, containing a HIPPS, set to issues.” trip at 190 bar g, as well as a control

Safety critical, environmental criti- umbilical, an industrial methanol spir- cal and production critical work scopes its (IMS) line and a 44km-long pipe-in- were prioritized with the aim to bring pipe pipeline system back to the Rhum back the facilities to the “status quo.” In production riser. The 44km pipeline addition, the entire system topsides and includes a forti? ed section 300m subsea system was assessed by a multi- from the Bruce facilities, designed to discipline team of engineers, including protect the platform from any possible the manifold and high-integrity pressure rupture.

protection systems, to return the whole

Topside, there is an inlet separator, system from its unpreserved state, in with o