Oil Minister Bijan Zanganeh opened a two-day conference in the capital attended by BP, Shell, Total of France, ENI of Italy, Repsol of Spain, OMV from Austria and other majors.
All are weighing a return if, as expected, sanctions related to Iran's nuclear programme are lifted in early 2016 in line with a July 14 deal between Tehran and six world powers led by the United States.
The new Iran Petroleum Contract will replace "buy-back" agreements in which foreign companies were paid a set price for all oil and gas it helped Iran exploit. Iran at that point took over production.
The Iranian partner in a joint venture must have a majority stake of at least 51 per cent.
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Zanganeh said consultations with international companies led to the new contracts, which would initially be four years in length, extendible for a further two years.
Iran will have between five and seven years to pay back initial sums invested by the foreign companies but production cooperation could go on as long as 25 years, officials said.
"Like any other human creation it may need amendment and development," he said of the new contract.
Iran has the world's fourth largest oil and second-largest proven gas reserves and its energy industry has been under-developed since the Islamic revolution in 1979.
Asked why no US companies were at Saturday's event, Zanganeh said there was no bar on them considering Iran's energy market but American firms were put off because sanctions are still in place.
An oil embargo imposed in 2012 by the US and European Union as punishment for Iran's disputed nuclear programme -- it denies ever seeking to develop a bomb -- decimated Tehran's energy industry.
Iran produces about 2.8 million barrels per day, compared to 4.0 million bpd in 2011, following US and other Western pressure on buyers to steer clear of the country.
The nuclear deal, however, has paved the way for new tie-ups and 152 international companies were at the event, organisers said.