Chevron is expected to be the next oil supermajor to break into Kurdistan, the semi-autonomous region of northern Iraq.
On Friday, ahead of today's major oil conference in the Kurdistan capital of Erbil, it emerged that ExxonMobil is the first supermajor to have signed exploration contracts in the region.
Kurdistan regional government adviser Michael Howard claimed there had been talks with several of the world's biggest oil companies. According to sources, Chevron has "run the slide rule" over the Shaikan onshore block, which is majority owned by London-listed group Gulf Keystone Petroleum.
However, it is believed that the Shaikan field, which is estimated to hold an extraordinary 10.5 billion barrels of oil, is actually the subject of one of the six licences that Exxon has taken.
The details of the six licences did not emerge on Friday. But, sources suggest that Dr Ashti Hawrami, Kurdistan's Minister for Natural Resources, plans to open today's conference by revealing the specifics of the deal.
It seems likely that Exxon has taken a 20 per cent stake in Shaikan. The Kurdistan government had an option of taking this stake once the field was proven to be commercially viable, and it is this that has been sold on rather than a portion of Gulf Keystone's undiluted 75 per cent holding.
Gulf Keystone owns other interests in Kurdistan, and sources close to the company believe that at least another two of Exxon's six interests relate to these fields. However, this could not be confirmed yesterday.
The news will be a huge boost to Gulf Keystone's large investor base, which includes a vast number of highly active private investors. The company is one of the biggest on the junior Aim market and its share price has been held back by doubts over the validity of oil contracts in Kurdistan and, arguably, court cases involving boss Todd Kozel.
Baghdad has long argued that contracts signed with Kurdistan are invalid, as the government based in the Iraqi capital takes precedence. There have even been suggestions from Baghdad officials that Exxon has jeopardised its contract on the massive West Qurna-1 field in southern Iraq as a result of the Kurdistan news.
However, Exxon is considered to be a conservative company and oil experts feel that it would not have taken the leap of investing in Kurdistan unless Erbil and Baghdad were close to an agreement on how contracts are to be carved up. Chevron would not face Exxon's potential problems as it does not have any contracts in Baghdad-run southern Iraq.
A spokesman said: "Chevron continues to be interested in pursuing opportunities that help the Iraq government achieve its objectives for the oil and gas industry, while meeting our criteria for investment. We do not discuss specific business opportunities."
Gulf Keystone shares soared on Friday, up 25 per cent to 177.25p. Should the Exxon news prove correct, the group's value should grow higher, provoking feverish chatter that Exxon might attempt to buy Gulf Keystone ahead of its promotion to the main London Stock Exchange next April.
Gulf Keystone's investors are generally loyal and their faith could soon be rewarded. They have been defensive over press stories detailing two ongoing legal cases . One involves Excalibur Ventures, which claims that it is owed about 30 per cent of Gulf Keystone for introducing the company to opportunities in Kurdistan. Excalibur's claims have been fiercely contested, though it is believed that the mysterious US company has heavyweight financial backing.
The other is the estimated $100m divorce of Mr Kozel and his wife, Ashley. This has revealed details of Mr Kozel's share ownership of Gulf Keystone and how he entertained clients.
Another potential entrant to Kurdistan is BP. Former chief executive Tony Hayward recently went into the region through his Vallares investment vehicle, though at the end of last week BP dismissed speculation that it could soon follow. It is more concerned with its difficulties in Russia. On Friday, the group was celebrating a Siberian court victory, when a judge dismissed claims of $16bn against BP.
A minority shareholder in BP's Russian joint venture, TNK-BP, had claimed that the British group had denied the partnership billions of dollars, when, earlier this year, it agreed a complicated share swap arrangement with state-owned Rosneft that involved exploring the Arctic. This collapsed after AAR, the Russian partner in TNK-BP, argued that it defied the terms of their joint venture contract.
Minority shareholder Andrey Prokhorov argued that BP cost the partnership by not putting TNK-BP forward as Rosneft's partner. Eventually, Rosneft agreed to explore the Arctic with Exxon, leaving BP and TNK-BP out of the potentially lucrative deal.