An agreement that gives the U.S. control over 17 oilfields in Venezuela won't immediately boost production, but several companies look poised to benefit if the oil starts flowing.

The winners would include U.S. refiners that process Venezuelan crude oil, like Valero Energy. SLB and Halliburton, which are oil services companies with operations in Venezuela, could also win more business.

The potential losers include Canadian oil companies like Suncor and Canadian Natural Resources, which produce heavier crude that competes against Venezuelan resources.

President Donald Trump on Friday said the U.S. has inked a partnership with a private company to gain control of 65 billion barrels of oil reserves, which would exceed America's 46 billion barrels of proven reserves "at no cost to the American Taxpayer."

The Wall Street Journal reported that the acquisition will be paid for using warrants that won't cost the government money up front. The White House didn't respond to a request for more information on the financial details.

Venezuelan President Delcy Rodriguez, who was installed after the U.S. seized her predecessor Nicolás Maduro, said on state television that the agreement gives the U.S. access to 17 oilfields, with the potential to eventually boost Venezuelan production by 1.5 million barrels per day.

None of that will happen with a snap of the fingers. It will take tens of billions of dollars worth of private investment to boost production, and it's not yet clear who is willing to foot the bill. The plan will also have to be proven to be legal, enforceable and financially sound-all big questions.

In addition, many details remain unclear. Early reports said the agreement was for 100 years, but Rodriguez said it's for 25. For producers putting billions of dollars at risk, the length of the contract will matter.

Analysts are skeptical that the deal will boost overall production in the near term.

"While it could enhance US energy security and attract investment, legal and execution risks remain high, with any major production uplift likely years away," wrote Jefferies analyst Alejandro Anibal Demichelis.

But even if it doesn't move global markets, any incremental production growth from Venezuela could help well-placed companies. As of the latest U.S. figures, Venezuela produces about 1.1 million barrels per day, up only marginally from last year's average production of about 1 million barrels.

Demichelis thinks daily production could get as high as 1.5 million barrels by the end of 2027.

About one-half of Venezuela's oil ends up in the U.S., where most of it is processed into fuel by refineries on the Gulf Coast. U.S. oil imports from Venezuela have already risen this year to 544,000 barrels per day in May, from 137,000 in January. Demichelis estimates that imports reached about 700,000 barrels per day in mid-July.

Most Venezuelan oil is heavy and sulfurous, and trades at a discount to lighter and less-sulphourus U.S. oil. Gulf Coast refineries are designed to process heavier crudes, and can make large profit margins doing so, because the cost of the product they're buying is relatively cheap compared to lighter crudes. The more Venezuelan crude they can purchase, the wider those margins are likely to get.

Valero is the top refiner of Venezuelan crude, followed by Chevron and Phillips 66, according to energy research firm TPH. PBF Energy and Marathon Petroleum, which also process heavy crude, would also benefit if there's more of the heavy stuff on the market. Refiners' stocks were up on Monday, with Valero rising about 2%.

U.S. oil-services firms like SLB and Halliburton are likely to benefit too if oil-drilling picks up in Venezuela, Demichelis writes. Because they're American companies, they might get preferential treatment to operate on U.S.-controlled land, he writes.

Some Latin American companies could benefit too. One possible beneficiary that Demichelis highlights is GeoPark, a Colombian oil company. GeoPark shares were up 13% on Monday.

Venezuela's gains could pose a challenge for some other companies, however.

Canadian oil producers are among the most vulnerable. Most Canadian crude is on the heavy side, including the country's enormous reserves in Alberta's tar sands. If the market for heavy crude gets flooded with new supplies, it could weigh on profits for companies like Suncor, Cenovus, Imperial Oil and Canadian Natural Resources.

Canadian energy has been exempted from U.S. tariffs even as the U.S. and Canada have escalated their trade war, because Canadian oil is an important feedstock for U.S. refiners. But if the U.S. finds an alternative to Canadian oil, it could eventually erode the Canadian industry's protected status.

"Strategically a US-government-sponsored revival of Venezuela supports the alternative to Canadian heavy barrels to some degree (Midwest refineries remain dependent on Canadian crude), which may erode the value of that card over time for Canada even before physical production grows," writes TPH analyst Jeoffrey Lambujon.