London - Violence, unrest and investment hurdles are making African producers in OPEC its weakest supply link, helping prop up oil prices to the benefit of the group's strongmen led by Saudi Arabia.
Oil supply in Nigeria, Africa's biggest producer, Algeria and Libya - which pump 15% of Opec's 30 million barrels per day (bpd)- has been underperforming for some time and little if any growth is expected in the medium term.
And rising Islamist violence since the Arab Spring of 2011 and unappealing commercial terms for foreign investors are making it even more difficult for some African Opec nations to boost production capacity.
"The Arab Spring is a bigger deal than we expected," said Antoine Halff of the International Energy Agency, introducing an IEA report earlier in May which lowered output forecasts for African Opec members.
Shrinking oil output and rising social spending have already pushed Algeria to join the ranks of Iran and Venezuela in the Organization of the Petroleum Exporting Countries as a hawk on oil prices.
Those countries are among those with the highest budget breakeven oil prices in Opec and have the most to fear from the growth of shale oil in the United States, where homegrown production means imports are declining.
The 12-member Opec is widely expected to keep its official target unchanged when it meets on Friday, although Algeria could call for Saudi Arabia to lead a supply cut to support prices.
Nigeria and Libya are still likely to fall in line with Saudi Arabia, which favours an oil price of $100 a barrel and tweaks its supply depending on demand.
Unable to expand supplies in the good times, the African OPEC members would be reluctant to contribute to any cut in Opec output. But unintended curbs will make Riyadh's task in supporting the market easier if needed.
"If we enter a bumpy period for demand over the next several months, it makes it much easier for Opec to control the price with many members not expanding production," said Paul Tossetti, analyst at PFC Energy.
No African growth
Nigeria, Libya and Algeria have been posting falling or stagnant output in the last few years.
According to the IEA's report launched earlier this month, Nigeria, Angola, Libya and Algeria will collectively post zero growth in production capacity during 2012-2018, when Opec's overall capacity is forecast to rise by 1.75 million bpd to 36.75 million bpd.
Nigerian crude exports are running at a four-year low below 2 million bpd, suffering from oil theft and increased sectarian violence.
It has also felt the heat from the rise of shale oil in the United States, losing ground in its most lucrative export market and diverting sales to Asia. Exports of Nigeria's crude to the United States dropped to zero for a week in March.
Opec does not hold a common position on the benefits or otherwise of US shale.
While Saudi Oil Minister Ali al-Naimi says he welcomes the US shale boom, his Nigerian counterpart Diezani Alison-Madueke has said it will have a "major impact."
Nigeria should add a small net 85 000 bpd of capacity to 2.66 million bpd by 2018, the IEA forecasts.
Although Libya swiftly restored output after the 2011 uprising that ended Muammar Gaddafi's rule, a new wave of unrest has kept flows at around 1.4 million bpd, less than it pumped before the conflict.
Algerian output has fallen below 1.2 million bpd from a peak of 1.37 million bpd in 2007. Even before the deadly attack at the In Amenas gas plant, oil firms saw Algerian production terms as unattractive at a time of rising global competition.
The governments are trying to boost output. Algeria has said it plans to review fiscal terms and a test will come later this year when the government relaunches a licensing round. Libya announced a new bidding round will be held at end-2013.