NIOC has added Russia's Gazprom Neft, Rosneft, Tatneft and Zarubezhneft and Azerbaijan's state-owned Socar, taking its list of prequalified companies to a total of 34.
Russia now has six companies with Gazprom and Lukoil in the list, the single largest number of prequalified companies for Iran's upstream projects, followed by five companies from Japan.
Officials at Russian companies have said they are potentially interested in projects in Iran but the companies are waiting for a final contract to evaluate the economics and decide whether they are to take part in them and in which form, individually or via consortia.
NIOC's updated prequalified list of companies comes as Tehran is gearing up for the biggest test of interest in the country's oil sector in years, as major international oil companies prepare to bid for the right to develop the Azadegan oil field, one of its most prized assets.
The prequalified oil companies have been asked to provide details of their planned consortium partners by Monday, as part of NIOC's planned tender to develop the giant onshore Azadegan oil field.
NIOC has also asked prequalified companies to seek its approval if they are selecting partners that have not been prequalified for Iran's upstream bidding rounds.
It plans to distribute detailed tender documents to the companies in July.
The tender will be Iran's first bidding round for a major oil field, having previously relied on bilateral negotiations to award development contracts. It is also the first to be launched under Iran's new model contract, the Iran Petroleum Contract, which is yet to be published.
This replaces the buyback contract, which was not successful enough to attract sufficient investor interest due to its tough terms.
The delay in launching the new contract has held up Iran's ambitious plans to bring in new international oil companies and restore its oil production to pre-sanctions levels of around 4 million barrel per day.
"Azadegan is the core of Iran's upstream development plans, and accounts for most of Iran's target for oil production capacity increase. Hence, the upcoming tender is perhaps the most important event the government has been looking forward to for a while.
The tender covers the development of the entire Azadegan field.
Azadegan currently produces around 125,000 b/d, with 75,000 b/d from the northern portion and 50,000 b/d from the south. NIOC plans to raise production to 150,000 b/d in the north and as much as 600,000 b/d in two phases from South Azadegan.
At the start of June, Gazprom Neft and Austria's OMV, which is also a prequalified company, signed an agreement on cooperation on projects in Iran.
Gazprom Neft was "studying the possibility of participating in the development of two blocks in Iran" and given OMV's experience in Iran and the Middle East, "joint geological assessment of blocks will be most effective."
Gazprom Neft earlier said it was looking at the Changouleh and Cheshmeh Khosh oil fields.
Iran has already invited OMV to participate in an imminent tender to develop the Azadegan oil field.
Malaysia's state-owned Petronas and Royal Dutch Shell have handed over their technical studies report on the Azadegan oil field to NIOC.
France's Total and Japan's Inpex Corp. have also offered their surveys on Iran's largest crude reserves, Noureddin Shahnazizadeh, the managing director of Iran's Petroleum Engineering and Development Company said.
Total, Shell, Inpex and Petronas are among the prequalified companies to bid for the Azadegan field.