Iran’s expected re-entry to the global oil market might have turned thoughts to the impact on U.S. and large OPEC producers, but another set of oil-producing countries have far more to lose.

Already reeling from lost business from the U.S. amid other challenges, including OPEC’s November 2014 decision not to cut production, Angola, Nigeria and Venezuela are likely to further suffer when Iran ramps up production and puts its flagship light and heavy crudes in front of buyers worldwide again, according to a recently released Thomson Reuters report.

Iraq and Russia could also find themselves competing to keep market share, particularly for heavy crudes, after world leaders agreed to lift sanctions against Iran. Although the agreement still requires approval from the governments of countries involved, Iran is making plans to boost oil production and exports to regain market share.

Growing Production: Within six months of the removal of sanctions, Thomson Reuters said Iran is capable of producing 500,000 additional barrels of day of oil from its main three oil fields—the Ahwz-Asmari, Gachsaran and Maroon. OPEC reported Aug. 11 that Iranian crude oil output has increased slightly in recent months, going from about 3.11 million barrels per day (bbl/d) in June to 3.13 MMbbl/d in July. Crude oil production averaged about 3.12 MMbbl/d in 2014.

But if the country secures private investment and needed technology, production could grow more. Iran has already been working on making its contracts more attractive to investors with revised terms set to be unveiled during a London roadshow later this year. Iran produced about 6 MMbbl/d in the mid-1970s, but a combination of sanctions, war, limited investment and declining fields caused the fall, data from the U.S. Energy Information Administration (EIA) show.

However, “The geological challenges presented by these fields can be easily surmounted if there is expertise present, both domestically and through foreign investment,” the Thomson Reuters report said. Fields in the Western Karoon area could add about 1 MMbbl/d to production. “If all goes to plan with the easing of sanctions and injection of foreign investment to revive these fields, Iran could reach its pre-sanction production level by early 2017.”

Losing End: If that happens and Iran grows its market share, Nigeria, Angola and Venezuela could suffer—given today’s saturated market.

“The internal rivalry between Saudi Arabia, Iran and Iraq will have a knock on effect on the less economically stable OPEC members who are already suffering from the group’s decision to maintain output,” the report said. Instead of lowering production as supplies—mainly from the U.S.—grew faster than demand worldwide, OPEC decided to maintain its 30 MMbbl/d production target to keep market share, sending oil prices down.

But the latest OPEC oil market report shows its members have upped output. Citing secondary sources, OPEC said it produced 30.51 MMbbl/d in July.

“Venezuela is perhaps the worst affected by OPEC’s decision to maintain output,” the report said. Its relationship with the U.S., which has grown its own light tight oil, is a major problem. Despite some demand from the U.S. for Venezuela’s heavy crudes for blending with shale oil, Thomson Reuters said “exports to the U.S. have steadily declined.” Exports fell by 600,000 bbls between May and June.

Finding Solutions: In response Venezuela has turned to China as a buyer to help fill the void.

The story is similar for Angola and Nigeria, which has turned to India.

EIA data show Nigerian exports to the U.S. have plummeted from about 50% in 2007 to only 3% in 2014.

“Due to Saudi dominance, it appears unlikely that OPEC policy will change at the December meeting unless regional unrest affects supply elsewhere within OPEC,” the report said. “Whatever the next six months hold for the oil market, OPEC’s smaller members must continue in the short term to diversify their economies or they will face further hardships.”

Venezuela appears to be doing just that with crude blending. Thomson Reuters said Venezuela could fetch better prices for a new medium-grade crude blend, alleviating some pressure, especially if Algeria, Angola and Nigeria are on board.

The report noted that Venezuela piloted the crude blending option in 2014, but logistical and other disagreements caused PDVSA to stop importing Algerian Saharan Blend crude for the mix in January 2015. However, Nigeria brought its crude to the venture in July.

“If the creases in this scheme can be ironed out, crude blending could provide means for oil-dependent OPEC members to diversify their crude offerings and find new, buoyant markets for their grades,” the report said.

Velda Addison can be reached at vaddison@hartenergy.com or via Twitter @veldaaddison.