OPEC is facing a series of challenges as it tries to shore up a deal to cut the global oil output. But analysts say oil prices are likely to be stuck within a range of 40-60 US dollars per barrel for the next year or more.

OPEC leader Saudi Arabia said on Monday the group would quickly address weak compliance on output cuts by some OPEC members, and would monitor rising production from Nigeria and Libya.

OPEC had agreed with several non-OPEC producers led by Russia to cut oil output by a combined 1.8 million barrels per day from January 2017 until the end of March 2018.

The deal to curb output propelled crude prices above 58 US dollars a barrel in January, but they have since slipped back to a 45-50 US dollars range.

Analysts say that weaker compliance with cuts by some OPEC members were helping soften prices. Saudi Arabia and Kuwait have cut more than they pledged, but others, such as the United Arab Emirates and Iraq, have shown relatively weak adherence to the limits. 

“Although conformity with the production agreement remains strong at the aggregate level, some countries continue to lag, which is a concern we must address head on,” said Saudi Energy Minister Khalid Al-Falih.

Rising output from US shale producers has also offset the impact of the output curbs, as has climbing production from Libya and Nigeria.

“The other major issue that markets are focused on is the expansion of supplies from Nigeria and Libya, both of which have been exempted from our agreement. And of course, we remain supportive of our brothers and partners and both of those nations as they work on the recovery of their oil industries, their economies. The committee however should monitor the impact of such growth on global supply and demand balances,” Falih said.  

Falih added that demand was expected to grow by about 1.4 million to 1.6 million barrels per day next year, similar to 2017. That could significantly lessen the pressure on oil producers.