France’s Total has signed a deal with Iran to further develop its part of the world’s largest gas field, becoming the first western energy company to sign a major deal with Tehran since the lifting of international sanctions earlier this year.

Total confirmed on Tuesday it had signed a heads of agreement with National Iranian Oil Company (NIOC) for the Phase 11 development of South Pars in the Gulf, which extends into Qatari waters where it is known as the North field, Reuters reports.

The SP11 project will progress in two stages, the first costing an estimated $2 billion, Total said. The produced gas will be fed into Iran’s gas network.

The French company has already played a key role in Iran’s energy industry, including the development of phases 2 and 3 of South Pars in the 2000s, before pulling out of the country after international sanctions were imposed in 2010.

Foreign companies keen to tap into Iran’s vast oil and gas reserves have so far made little inroads into the country despite the lifting of many sanctions earlier this year following a landmark agreement on Iran’s nuclear program.

Tehran has pledged to open up its oil industry but foreign companies, including BP and Italy’s Eni recently said they still have little information about Iranian oil fields and contract terms, hindering investment decisions.