With an expertise in geopolitics, RBC Capital Markets' Helima Croft says Rex Tillerson's exit could create "very big implications" for the global oil markets.

Croft, who has held positions at the Council on Foreign Relations and the CIA, sees President Donald Trump's decision to tap Mike Pompeo as secretary of State as a bullish catalyst for oil prices.

According to Croft, Pompeo's appointment will likely be the "nail in the coffin" for the Iran nuclear deal and spur additional sanctions on Venezuela.

"Rex Tillerson had been a moderating influence in the Trump administration. He had argued for maintaining the Iran nuclear agreement. He argued against very tough economic sanctions on Venezuela," RBC's global head of commodity strategy said Tuesday on CNBC's "Futures Now." "With Pompeo, a known hawk taking the top diplomat job, I could see Trump easily making the decision to not renew sanctions waivers on May 12 effectively ending U.S. participation in the Iran nuclear deal."

Yet, the oil markets didn't react to the news with a run higher. WTI crude fell 1.06 percent to $60.71 a barrel, and Brent crude dipped 0.48 percent to $64.64. Both saw their fourth negative sessions in five.

"The oil market is still very fixated on the U.S. supply story. We constantly have data revisions," she said. "There's a perception in the market that U.S. production is going to cause the market to become oversupplied again. Not in our focus, I would argue on the robust demand picture."

Her bullish case for rising oil prices is supported by Venezuela's ongoing battle against debt and keeping its state oil company afloat. The country, one of the world's top oil producers, has been facing U.S. sanctions over political turmoil.

"Venezuela really is the fundamental story to watch," she said. "Venezuela is a clear and present danger to get worse and have more barrels of oil removed from the market."

Croft acknowledges new Trump tariffs on steel and aluminum imports could spark a trade war in Asia and negatively affect oil demand. But she believes it's premature to worry.

"There's nothing to indicate that we're going to have a soft demand story this year unless we do have a trade war," Croft said. "We're really going to have to get to May for the market to really believe that these risks may materialize. I think that's when it could become pretty monumental for the oil market."