This comes just as OPEC’s biggest production gain occurred in Nigeria, where Total’s Egina field has helped boost output, Reuters reported.
Libya, another producer exempted from making voluntary curbs, also boosted output.
A survey attributed this to further involuntary declines in sanctions-hit Iran and Venezuela and output restraint by top exporter Saudi Arabia.
The 30.23 mbd was down by 90,000 bpd from March and the lowest OPEC total since 2015.
The survey suggests that Saudi Arabia and its Persian Gulf allies are maintaining even larger supply cuts than called for by OPEC’s latest deal, shrugging off pressure from US President, Donald Trump.
Last week, Trump said he had called OPEC to tell the group to bring down prices.
Crude oil is trading above $73 a barrel and hit a six-month high above $75 last week, boosted by Saudi supply restraint and curbs in Venezuela and Iran.