"Emerging from this most vicious of all oil cycles, the need to sustain the rebalanced market in the medium- to long-term, some extra-ordinary measures could be considered by countries participating in "the Declaration of Cooperation", including expanding the membership", Barkindo said in a speech at the India Energy Forum in New Delhi.
Last year, the bloc and some others producers chose to reduce production by around 1.2 million barrels per day from January 1, 2017.
Brent crude futures LCOc1 rose 33 cents, or 0.6 percent, to settle at $56.94 per barrel.
But with strong oil demand growth, summer demand, and Brent futures flipping to backwardation, the OECD commercial stocks have started to draw down faster in the summer.
"OPEC and key non-OPEC oil producers continue to successfully drain the oil market of excess barrels".
But Mr Barkindo said he was not anxious about the rise in U.S. shale oil and gas output.
The report also cited headwinds in 2018 for an expansion of supplies in US shale, such as lower drilling efficiency and cost inflation.
It also stated that prices may fall again in the second quarter of the next year to $48 a barrel when the oil output is expected to surge again.
Increasing demand for oil will be matched by added supplies, but Opec's forecasts for the balance of supply and demand foresee a greater reliance on the cartel's output.
"A rise above that level would encourage U.S. oil producers to expand their drilling activities, otherwise the lower prices could lead to a reduction" in investments, it added.
After settlement, crude prices pared gains when the industry group the American Petroleum Institute said its data showed USA crude stocks rose unexpectedly last week, while gasoline inventories decreased and distillate stocks built.
The figures mean Opec has complied 98 per cent with the cutback pledge, according to a Reuters calculation, up from 83 per cent initially reported in August as the September rise was led by Nigeria and Libya which are exempt from the cut.
Saudi Arabia said it pumped 9.97 million barrels per day in September, up from August, but still below target.