Iran would seem like a shaky bet for oil companies: The U.S. president-elect has threatened to withdraw from a deal reached last year that lifted international sanctions on the Persian Gulf nation in exchange for Tehran limiting its nuclear program. During his election campaign, Trump called dismantling the deal "my No. 1 priority."
But Shell's move toward developing oil and gas fields in Iran suggests at least some of the big, integrated oil companies expect the agreement between Iran and several world powers — including the United States — to stay in place.
France's Total last month announced it would develop a massive natural gas field in Iran, and other European energy companies are actively exploring their options in the oil- and gas-rich country. Among the six powers that signed the Iran deal last year were European countries France, Germany, Great Britain and Russia.
American oil companies are prohibited from doing business with Iran due to separate, unilateral U.S. sanctions that remain.
Shell declined to comment on Trump's statements, but confirmed that it has signed a deal with the National Iranian Oil Co. "to further explore areas of potential cooperation."
Total did not immediately return requests for comment.
To be sure, the deals announced so far only lay groundwork for potential oil and gas development in Iran.
While the companies likely expect the nuclear deal to hold, the provisional nature of the deals allow Shell and Total to explore their options without making huge financial commitments, said Scott Modell, managing director at the Rapidan Group and a former Central Intelligence Agency officer.
"They have realized we better not get too far down this road until we figure out exactly what Trump is going to do, and I think that's why they bought six to 12 months with this sort of thing," he said.
If Trump decides to pull out of the deal unilaterally, the accord gives him a path forward. It begins with the United States alleging that Iran is not complying with the terms of the deal, and ends with the country using its veto power as a permanent member of the U.N. Security Council to kill any continued sanctions relief.
But that course of action could have serious ramifications for the United States.
When the United States first tried to isolate Iran in 1996 by threatening sanctions on any foreign company that developed Tehran's oil and gas industry, the European Union forbade companies from complying with the U.S. sanctions. Ultimately, the U.S. backed down and declined to enforce the sanctions.
The EU finally got on board a decade later after Iran's covert nuclear program came to light.
But now, Europe — as well as Russia and China — would not be pleased if the United States sabotaged a hard-won deal that it helped negotiate. The agreement limits Iran's nuclear program and gives international inspectors access to its atomic facilities.
High-ranking U.S. officials including CIA Director John Brennan have said that tearing up the Iran deal would be "disastrous," undermining America's credibility and possibly setting off a nuclear arms race in the Middle East.
If Trump tries to scrap the deal anyway, he could blow much of his diplomatic capital with America's closest European allies, putting his larger foreign policy agenda in peril, said Matthew Bey, energy analyst at strategic intelligence firm Stratfor.
"Is this the one that he really wants to burn his bridges for? I think that's going to constrain him at least initially," Bey told CNBC.
In a worst-case scenario, the Trump administration renews so-called secondary sanctions, which take advantage of U.S. influence on the international banking system to block countries from doing business with Iran. But that could force the Europeans to respond by putting pressure on American companies on the Continent, Bey said.
It is far more likely that the Trump administration and congressional Republicans will seek to pressure Iran by increasing the existing U.S.-only sanctions, Modell said. The GOP can revisit 10 acts on that front that don't have the support of the Obama White House, according to Rapidan Group.
"In the meantime, the transition team is going to ramp up pressure on Iran, but it's not deal-killing pressure," he said.
"The Iranians, as long as they can keep the U.S. isolated in the corner, barking really loud against Iran, but continue to do business with the Europeans and everybody else, they're fine," Modell said.