June 29 (Bloomberg) -- Crude oil climbed above $71 and gasoline rose the most in six weeks after an attack by Nigerian militants shut a field operated by Royal Dutch Shell Plc, cutting output from Africa’s largest producer.

Shell said it closed the Estuary field near the Forcados export terminal after the assaults. Hostilities in the Niger River delta have cut more than 20 percent of the country’s oil exports since 2006. The International Energy Agency, an adviser to 28 developed nations, lowered its five-year forecast for global crude demand because of the economic slump.

“Nigerian militants are a crude-oil bull’s best friend,” said Tim Evans, an energy analyst with Citi Futures Perspective in New York. “The renewed militant activity has inspired additional buying of crude-oil futures.”

Crude oil for August delivery rose $2.33, or 3.4 percent, to $71.49 a barrel at 2:49 p.m. on the New York Mercantile Exchange, the highest close since June 12. Oil is poised for a quarterly gain of 44 percent, the biggest since 1990.

Gasoline for July delivery climbed 6.17 cents, or 3.3 percent, to $1.9358 a gallon in New York, the highest settlement since June 18. It was the biggest one-day increase since May 18.

Shell closed the Estuary field after attacks on production wells, Tony Okonedo, a spokesman, said by phone from Lagos today. The Movement for the Emancipation of the Niger Delta said it attacked the field. Nigeria is vying with Angola to be Africa’s largest producer.

“There are no signs that the situation in Nigeria is getting better anytime soon,” said Adam Sieminski, the chief energy economist at Deutsche Bank AG in Washington.

Rejected Amnesty

The militant group on June 25 rejected an amnesty proposal from President Umaru Yar’Adua, saying the offer failed to address key issues. Under the terms, fighters in the Niger River delta have until Oct. 4 to surrender their weapons, renounce violence and accept rehabilitation to avoid prosecution.

“The arrival of still more bad news from Nigeria has moved prices higher,” said Gene McGillian, an analyst and broker at Tradition Energy in Stamford, Connecticut. “The IEA report that came out today doesn’t bode well for demand.”

The IEA cut its oil-consumption estimates for every year through 2013 by about 3 million barrels a day, the agency said in the Medium-Term Oil Market Report today. Consumption will average 86.76 million barrels a day in 2012, the first year demand will rise above 2008’s level of 85.76 million, according to the Paris-based agency.

Supply Crunch

While the economic slump tempers global demand growth, it may also cause supply to shrink as lower exploration and production spending delays projects and reduces spare capacity, according to the agency.

“There is so much uncertainty about the economic recovery and how fast it may happen,” the IEA’s executive director, Nobuo Tanaka, said in an interview in Paris after the report’s release. “We may have a supply crunch again, just like last year, in 2014 to 2015. If the economic recovery is slower, we could have ample supply capacity.”

The Organization of Petroleum Exporting Countries is unlikely to raise output at the group’s next meeting in September, oil ministers from Algeria and Qatar said today.

“It would be very difficult to think of an increase in production at this stage” as the market is “oversupplied,” Chakib Khelil, Algeria’s oil minister, told reporters in Doha, where he and Qatari minister Abdullah bin Hamad al-Attiyah are attending the Gas Exporting Countries Forum.

Brent Futures

Brent crude oil for August settlement rose $2.07, or 3 percent, to $70.99 a barrel on London’s ICE Futures Europe exchange, the biggest gain since June 4.

New York oil futures have gained 60 percent this year, as the recent rise in world equity markets and a weaker dollar encouraged investors to buy the commodity as an alternative investment. Prices climbed to a seven-month high of $73.23 on June 11.

“Two weeks ago it looked like oil was headed straight for $85,” Sieminski said. “Trading has been range-bound recently as people have had second thoughts. There will probably have to be serious indications that demand is improving before prices jump much higher.”

A government report will probably show that U.S. crude-oil inventories dropped for the seventh time in eight weeks. Supplies slipped 1.6 million barrels in the week ended June 26, according to the median of nine estimates by analysts surveyed by Bloomberg News. The Energy Department is scheduled to release its weekly report on July 1 at 10:30 a.m. in Washington.

Crude oil volume in electronic trading on the Nymex was 325,011 contracts as of 2:56 p.m. in New York. Volume totaled 311,476 contracts June 26, the lowest since May 22 and 37 percent less than the average over the past three months. Open interest was 1.13 million contracts.

The exchange has a one-business-day delay in reporting open interest and full volume data.

To contact the reporters on this story: Mark Shenk in New York at mshenk1@bloomberg.net

Last Updated: June 29, 2009 15:49 EDT