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By Rania El Gamal, Reem Shamseddine and Alex Lawler
DUBAI/KHOBAR, Saudi Arabia/LONDON, Jan 26 (Reuters) - Stateoil giant Saudi Aramco has tasked two U.S.industry leaders in oil reserves auditing to review the contentof its deposits as it pushes ahead with a share listing nextyear, industry sources said on Thursday.
Aramco, whose fields are estimated to contain 15 percent ofthe world's oil, has asked a unit of oil services firm BakerHughes - Gaffney, Cline and Associates - to carry outthe review, three sources familiar with the move told Reuters.
Two separate sources said Aramco had also asked Dallas-basedDeGolyer and MacNaughton, one of the world's oldest names inreserves auditing, to perform some work.
Baker Hughes and Aramco declined to comment. DeGolyer didnot immediately respond to a request for comment.
The listing, expected to be the world's biggest initialpublic offering (IPO), is a centrepiece of a Saudi Arabiangovernment plan to transform the kingdom by enticing investmentand diversifying the economy away from a reliance on oil.
Aramco, once U.S.-based and run by Americans, has long beena Saudi state corporation. It dwarfs all others in the industryby production and reserves, with crude reserves of 265 billionbarrels.
The plan to list Aramco, the kingdom's crown jewel, is beingchampioned by Deputy Crown Prince Mohammed bin Salman, whooversees energy and economic policy in the world's topoil-exporting nation.
He is leading a reform drive, called Vision 2030, to addressfalling oil revenue and fiscal deficits by boosting the privatesector, ending government waste and diversifying the economy.
Last year, Prince Mohammed said he expected the IPO wouldvalue Aramco at a minimum of $2 trillion, but that he thoughtthe figure might end up higher.
Any valuation would account for oil price expectations andthe size of Saudi Arabia's proven crude reserves.
Industry sources say the right to own the reserves is asovereign issue retained by the Saudi government, while Aramcois most likely to keep its concession, meaning it would havedirect access to those reserves with sole rights of explorationand production.
The main question is how much of the oil reserves would bereflected in Aramco's financial books after an independent auditas a result of the concession, the sources say.
"Aramco is in talks with a company to audit its reserves andanother one to audit its finances," another Saudi-based industrysource said.
"Whether (all) the oil reserves would be IPO-ed or not,that's still being discussed."
The Wall Street Journal was first to report that Aramco hadhired Gaffney, Cline & Associates to assess its oil reserves,citing sources.
MILESTONES
Saudi officials and their advisers are aiming for two keymilestones in 2017 as they push ahead with the flotation.
Saudi-based industry sources say 2018 remains the planneddate and up to 5 percent is the stake size being considered forthe offer, though this could be raised depending on oil pricesand market reaction to the listing.
"There are two key milestones this year. Choosing banks forthe IPO and choosing an exchange," said a senior industry sourcefamiliar with the IPO plans.
"Aramco is looking at all options - ranging from NorthAmerica, Europe and Asia. In terms of deadlines, 2018 is stillthe plan to list the company."
Aramco had said it was considering several options for theflotation, including a single domestic stock exchange listingand a dual listing with a foreign market.
Officials from the oil firm plan "discovery trips" toforeign exchanges in the next few months and have invited banksto pitch for an advisory position in the IPO, the sources said.
Morgan Stanley and HSBC are among the banksthat have received a request for proposals. The invitation wasto evaluate Aramco's business and help it with measuressurrounding the share sale. (Additional reporting by Dmitry Zhdannikov in London; Editingby Dale Hudson)
