NEW YORK/SINGAPORE, (Reuters) – Top oil exporter Saudi Arabia has unexpectedly called on oilfield service firms to expand the kingdom’s oil rig count by nearly 30 percent, according to Simmons & Co, to ensure spare production capacity remains ample as supply uncertainty grows.

Saudi state-run oil giant Saudi Aramco met with leading oil service companies including Halliburton over the weekend, unveiling plans to boost the country’s rig count this year and next to 118, from around 92 now, Simmons & Co analyst Bill Herbert said on Monday.

“Saudi Arabia has been expected to tread water on its production capacity, so this is unexpected,” Herbert said from Houston in a phone interview.

“The risk premium in the Middle East has risen. Also, with Libyan production falling, Saudi Arabia may feel it has to be ready for higher production capacity.”

Plans to boost the rig count constitute the most overt evidence that Saudi Arabia, holder of the world’s biggest oil reserves, is stepping up investment in the face of crude prices of over $100 a barrel, though it is unclear whether this will expand the kingdom’s spare capacity beyond the current total of as much as 3.5 million bpd, or merely prevent it from falling.

“It’s definitely not for expanding capacity,” said Siamak Adibi, senior consultant at FACTS Global Energy in Singapore.

“For this year, the majority of new wells to be drilled is just for maintaining existing capacity” of 12.5 million barrels per day, Adibi added, including the neutral zone.

Saudi oil-minister Ali al-Naimi has outlined plans to boost the kingdom’s crude oil production capacity to 15 million bpd, including mention of specific fields, saying such an expansion would only proceed if warranted by demand.

But Simmons & Co founder Matthew R. Simmons, until his death in August 2010, repeatedly questioned the kingdom’s ability to boost and sustain production at high levels in the long term, citing geological constraints.

‘IMPORTANCE IN THE WORLD’

More than any other country, Saudi Arabia defines its international role by the ability to rapidly increase oil production to meet growing demand or cover disruptions elsewhere, such as the recent collapse in shipments from war-torn Libya. The kingdom has responded by pumping 500,000 to 750,000 barrels a day more in recent weeks, analysts said.

“This is Saudi Arabia’s raison d’etre. It must ensure that spare capacity is sufficient or else its importance in the world will be diminished,” said oil analyst Peter Beutel of Cameron Hanover in Connecticut.

Analysts said a recent Saudi output boost to around 9 million barrels a day may have made Aramco apprehensive about its ability to prime the pumps further if the world calls for much greater volumes.

“At the start of the year they were producing around 8.5 mln bpd of oil and were sitting on around 3.5 mln bpd of spare capacity. They’ve had to increase production by between 500,000 and 750,000 bpd after Libya went out of the market so their spare capacity is already way down,” said Roger Read, managing director at Morgan Keegan in Houston.

A New York-based oil analyst, who tracks Saudi production and requested anonymity, said: “You could see this in one of two ways. Either they realize that 3 million barrels of spare capacity isn’t enough, or they realize their capacity isn’t actually that high.”

Saudi Arabia hasn’t publicly discussed plans to expand its overall crude capacity since completing a $100 billion project to raise it by 3 million bpd to a “sustainable” 12 million bpd last year, excluding the neutral zone, leading some analysts to conclude that the increase in rig counts responds to decline at older fields.

“The decline rate in some large OPEC producers like Iran and Saudi Arabia is not new. It’s a challenging issue for these countries, so they just want to drill more wells to keep the same production capacity,” Adibi said.

SOARING RIG COUNT

Saudi Arabia wants the rig count to rise quickly in the second half of 2011 and the first half of next year, and may use some of them for a $16 billion Moneefa project, Herbert said.

Aramco is undertaking the Moneefa project to compensate for declines at other fields rather than to boost capacity, with a planned start-up by June 2013 at 500,000 bpd and a ramp-up to 900,000 bpd by 2024.

“There will be some new rigs for Moneefa, but they won’t go ahead to drill all wells in one year,” Adibi from FACTS said.

“It will gradually increase production over ten years and it will be offsetting decline from other fields. It’s not additional capacity.”

Halliburton said late on Monday that it would accelerate activity at Moneefa, a project to tap massive offshore heavy crude reserves, following recent discussions with Saudi Arabia. In 2008, the company was awarded a contract to provide drilling and associated work at 93 Moneefa wells off northeast Saudi Arabia.

The plans are “manifestly positive” for oil service companies, Herbert said. Their shares soared on Monday.

Halliburton rose 4 percent to $47.90 on the New York Stock Exchange after touching a 52-week high. Shares in Schlumberger also rose more than 4 percent, while Baker Hughes rose 3.8 percent.

Schlumberger Chief Executive Andrew Gould privately told analysts on Monday he was encouraged by Saudi Arabia’s commitment to expand spare capacity regardless of any pullback in oil prices, an analyst at the Howard Weil oil conference in New Orleans told Reuters. Crimped oil activity elsewhere in the Middle East and Africa is likely to hit Schlumberger’s first-quarter earnings, Gould said separately.

U.S. oil futures CLc1 fell 14 cents to $103.84 a barrel early on Tuesday, down from a 30-month high near $107 last week.

Since January, political unrest in North Africa and the Middle East has helped to lift prices. So far, the kingdom has avoided major domestic unrest, although the upheaval has been threatening the regimes of neighboring Yemen and Bahrain.

“If we did see a significant oil supply shock and Saudi Arabia came out to produce more, that would be the telling factor that they are willing to supply the market in difficult times,” said Ben Westmore, a commodities analyst at National Australia Bank, adding that “more exploration goes somewhere at communicating that sort of sentiment.”

Saudi Arabia is OPEC’s top producer and controls more than a fifth of world oil reserves.