Despite uncertainty surrounding the future of the 2015 Iran nuclear deal, international energy giants are competing fiercely to invest in Iran’s rich oil and natural gas sectors.

In the latest episode, Iranian media reports that the state-run National Iranian Oil Company (NIOC) on December 7 signed a preliminary agreement with Royal Dutch Shell to assess the development of Iran’s Azadegan and Yadavaran oil fields and Kish gas field.

Shell is the largest international company to return to Iran since the removal of most nuclear-related sanctions in January. On November 8, France’s Total signed a $4.8 billion deal with NIOC for the development of Phase 11 of Iran’s South Pars gas field. Total is now reportedly in talks with NIOC for potential oil projects. Both Total and Shell stopped exploration and production activities in Iran in 2010 following the imposition of a strict international sanctions regime.

According to Shana, a news agency affiliated with Iran’s Ministry of Petroleum, China National Petroleum Corporation International (CNPCI) is currently contracted to develop the initial phases of Yadavaran and North Azadegan oil fields. In 2014, Iran’s Petroleum Minister Bijan Zanganeh ended CNPCI’s South Azadegan contract due to a “lack of commitment.” And with the removal of sanctions, the government of President Hassan Rouhani appears to be favoring European companies over CNPCI.

Both Total and Shell deals are provisional and non-binding. The French and Anglo-Dutch companies run significant businesses in the United States and they are eagerly waiting to see what the Trump administration’s Iran policy will look like. But the preliminary oil and gas deals show that the two energy giants are cautiously optimistic about the future of the nuclear deal and the prospect of doing business with Iran.