Exclusive: Oil & gas industry fears more deep-sea leaks linked to drill fluid

Thu Sep 5, 2013 11:32am EDT
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By Stephen Eisenhammer, Oleg Vukmanovic and Muriel Boselli

LONDON/PARIS (Reuters) - A corrosive drilling fluid that triggered the North Sea's worst gas leak in 20 years could threaten similar deep-sea wells across the world, and operator Total has already warned Shell that its nearby Shearwater field may be at risk.

The corrosive fluids implicated in the leak at Total's Elgin field, such as calcium bromide, are commonly used in such deep-sea wells, and experts fear a recurrence as operators, under pressure to offset declining output from conventional reservoirs, turn to deeper, hotter and higher pressure fields.

"Bromide brines have been used in thousands of wells since their introduction in the 1980's," John Downs, a chemical engineer who runs his own consultancy group, told Reuters. "An extensive well repair program may be needed if the stress corrosion cracking caused by bromide brine in Elgin is also happening elsewhere."

So worried is Total about recurrence in the Elgin field itself, it has plans to kill at least 10 other wells in the complex as well as the one that leaked, which could cost more than 1.5 billion pounds ($2.34 billion) to replace.

The North Sea is host to the highest number of high-pressure, high-temperature (HPHT) reservoirs of any mature oil and gas producing basin.

Total UK chairman Patrice de Vivies told Reuters he had cooperated particularly closely with Royal Dutch/Shell when sharing information on the causes of the leak.

"With Shell we have shared even more as they have a neighboring field, Shearwater, meaning they potentially have, perhaps, not identical, but similar problems," de Vivies said.

Like Elgin, Shell's Shearwater field is fed by a HPHT reservoir where temperatures can reach 140 degrees Celsius.   Continued...

The Elgin platform in the North Sea is seen in this undated photograph received in London on March 30, 2012. Total said the photograph was taken on March 29, 2012. REUTERS/Total E&P/Handout/Files