Iran will offer three gas fields to foreign investors at a conference in London later this year, an Iranian official said on Aug. 26.

Development of North Pars, Golshan and Ferdowsi gas fields will be offered to investors at the upcoming London conference where Iran is due to unveil its new contract model, managing director of Pars Oil and Gas Company (POGC) said, according to Shana, the oil ministry's news agency.

North Pars off-shore gas field covers an area of 25 square km and holds 57.1 trillion cubic metres of sour gas, while Golshan gas field is located south of Iran and is expected to produce 2 billion cubic feet of gas once it is fully developed, Shana said. Ferdowsi is also off-shore gas field.

Iran had defined a new model contract which it calls its integrated petroleum contract (IPC) - offering longer terms and more liberal conditions. It plans to unveil the details of the contracts in London in December.

Iran and six world powers agreed a deal in July to curb Tehran's nuclear programme, but sanctions imposed in 2012 are unlikely to be removed until next year, as the deal requires approval by the U.S. Congress. Nuclear inspectors must also confirm that Iran is complying with the deal.

Many foreign energy companies have already shown interest in reestablishing business in Iran, with delegations of leading business figures from European and Asian countries have been visiting Tehran over the past weeks.

Iranian officials had said Tehran had identified nearly 50 oil and gas projects worth $185 billion that it hoped to sign by 2020. OPEC-member Iran has the world's largest gas reserves and is fourth on the global list of top oil reserves holders.

Iran has huge gas reserves. It exports small quantities to Turkey but has been unable to increase production quickly enough to meet its own demand and northern Iran relies heavily on gas imports from Turkmenistan, especially for heating in winter.