• A nuclear deal between the U.S. and Iran could boost oil prices as it takes some uncertainty out of the market, according to Damien Courvalin of Goldman Sachs.
• Other analysts don't agree. They say a deal could mean lower prices for oil, at least in the short term.
• Tamas Varga of PVM Oil Associates said the initial reaction to a deal is likely to be a “brief sell-off.”

A nuclear deal between the U.S. and Iran could send energy prices higher — even if it means more supply in the oil markets, according to Goldman Sachs' head of energy research.

While it appears to be contradictory, a deal that brings Iranian barrels back to the market could actually see oil prices rise, said Damien Courvalin, who is also a senior commodity strategist at the bank.

Talks in Vienna are ongoing as Iran and six world powers — the U.S., China, Russia, France, U.K. and Germany — try to salvage the 2015 landmark deal. Officials say there's been progress, but it remains unclear when negotiations could conclude and oil prices have been seesawing as a result.

A deal would lift sanctions on Iran and bring Tehran and Washington back to complying with the Joint Comprehensive Plan of Action (JCPOA). The U.S. unilaterally withdrew from the nuclear deal in 2018 and reimposed crippling sanctions on Iran which dealt a blow to the Islamic Republic's oil exports.

Courvalin explained his rationale. He pointed to how oil prices rose in April after OPEC+ said they would gradually raise output from May by adding back 350,000 barrels a day.

"An increase in production … is announced that is above anyone's expectations — ours included. And yet prices rally, volatility comes down," he said.

"Why? Because we lifted an uncertainty that was weighing on the market since last year," he told CNBC's "Squawk Box Asia" last week.

Investors wondered if OPEC would end up in a price war when it tried to increase production, but the oil cartel presented a "convincing path going forward," Courvalin said.

"You could argue the same for Iran," he added. Simply knowing will likely "lift some of that uncertainty."

"If that announcement comes in the next few weeks, in our view, it actually starts that bullish repricing," he said at that time.

Opposing views

Other analysts say an agreement could mean lower prices for oil, at least in the short term.

Morgan Stanley said in a research note that an increase in Iranian exports will probably cap Brent crude at $70 per barrel, and expects the international benchmark to trade between $65 and $70 per barrel for the second half of 2021.

Brent crude was lower by 0.13% at $71.22 on Friday in Asia, while U.S. crude futures were down 0.1% at $68.75.

"Our view is that the initial reaction to a potential deal will be a brief sell-off," Tamas Varga, an analyst at PVM Oil Associates, told CNBC in an email.

Extra Iranian barrels would be a headwind if a deal materializes, according to Austin Pickle, investment strategy analyst at Wells Fargo Investment Institute.

But softer crude prices may only be temporary.

"We suspect accelerating demand and OPEC+'s disciplined supply response will support oil prices," Pickle wrote in a note, referring to OPEC and its allies.

PVM Oil Associates expects Brent prices to reach $80 per barrel by the fourth quarter of 2021, Varga said.

He also said it will take time before Iran starts to export oil again, and global demand could have improved significantly by the time additional barrels reach the market.

While the global economic recovery has been uneven — faster in the developed world, compared to the developing world — oil prices will rise more quickly when vaccine rollouts accelerate in Asia, he added.

"Extra Iranian barrels should only delay price recovery but not throw it off course," Varga said.

S&P Global Platts Analytics has the view that there is room to accommodate Iranian and OPEC+ oil supply growth in the third quarter.

Toward year-end, however, energy prices could come under pressure as Iran exports and U.S. oil production increase, said Nareeka Ahir, a geopolitical analyst at S&P Global Platts. She said Brent could fall to the mid or low $60s in late 2021 into 2022.

Supply may lag demand

Goldman Sachs sees Brent crude prices rising at a faster pace, and predicts the international benchmark could hit $80 by the third quarter of this year.

Courvalin noted that Asia's oil demand has been revised lower due to new waves of the virus, and that has been been offset by upside surprises in the U.S. and Europe.

"It really paints a picture where, once vaccination rates progress sufficiently, you really see pent-up mobility get unleashed, and a significant increase in oil demand," he said. "That's … the root of the bullish view."

He said supply will likely lag the pop in demand, and there will be "plenty of room" to absorb oil from Iran.

"In fact, if you told me Iran's not coming back, our $80 dollar forecast is way too low relative to where the oil market is heading by 2022," he added.

Concerns over an Iran deal and the pandemic may have "masked a fast-tightening oil market," Courvalin said.