The return of oil from Iran following the landmark nuclear energy deal with world powers could create fresh tensions within Opec but may reinforce the group’s output strategy.
Tehran and major powers - Britain, China, France, Germany, Russia and the US - clinched a historic nuclear agreement in Vienna on Tuesday,  paving the way for the removal of sanctions and the gradual return of Iranian oil to the global market next year.
The Vienna accord puts strict limits on Iran’s nuclear activities for at least a decade. In return, sanctions that have slashed the oil exports of Iran, Opec’s fifth-largest producer, will be lifted and billions of dollars in frozen assets unblocked.
Iran’s exports could reach a potential 2.4mn barrels per day (bpd) in 2016, from 1.6mn bpd in 2014, according to an estimate.
The Organisation of the Petroleum Exporting Countries - whose 12 members  pump one third of global oil - is mindful that increased Iranian oil exports could worsen a global supply glut and depress energy prices further.
Opec decided at its last meeting in Vienna in June to maintain output levels, extending its Saudi-backed strategy to preserve market share and fend off competition from booming US shale.
Oil prices sank last week, hit by the Iran nuclear deal and the strong dollar, raising jitters among some Opec members who next meet on December 4.
London Brent oil slid to about $56 per barrel and New York’s West Texas Intermediate dropped to around $52 a barrel.
Poorer Opec  members Angola, Algeria and Venezuela - whose budgets are heavily reliant on oil revenues - may again argue for less output to support prices.
But richer Gulf producers remain eager for the organisation to preserve valuable market share and force out high-cost US shale producers with lower oil price levels.
Faced with stubbornly low prices, Algeria’s energy minister Salah Khabri indicated to state news agency APS last week that an emergency Opec meet could be needed.
“The real problem starts when Opec  members begin to fight for quotas amid oversupply and market share disputes,” says Jassem al-Saadun, head of Kuwait’s Al-Shall Economic Consultants.
In June, Opec ’s collective output ceiling was left at 30mn bpd - where it has stood for three and a half years - despite an oil price collapse between June 2014 and January that slashed precious revenues.
The organisation appeared to shrug off calls from some members, including Iran, for a “reasonable” oil price of between $75 and $80 per barrel.
Oil is forecast to languish at an average of just above $62 per barrel next year, according to French bank Natixis.
But there is a strong possibility that low price levels could slow down US shale energy production and make room for returning supplies from Iran - provided that global energy demand does not falter.