[competentone]

This is not "speculation":

BP closed the Forties Pipeline System, carrying 40 percent of the U.K.'s oil output, after a strike at the Grangemouth refinery cut power supplies to the network that delivers 700,000 barrels daily. Five police were killed and guns and ammunition seized in yesterday's attack in the Niger Delta where output has already been halved by strikes and attacks on pipelines....
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Nigeria is losing about 50 percent of its output after staff at Exxon Mobil Corp.'s operations went on strike April 24 and militants attacked a Royal Dutch Shell Plc pipeline later the same day.

Nigeria pumped 1.96 million barrels a day in March, according to Bloomberg estimates. Recent attacks on Shell-run pipelines, including the latest one, are cutting oil flows by about 140,000 barrels a day, the country's oil minister H. Odein Ajumogobia said April 25. The Exxon Mobil strike is halting about 765,000 barrels a day, according to union estimates.

http://www.bloomberg.com/apps/news?pid=20601087&sid=aPx0VvNedgHs&refer=worldwide