An improvement in Nigeria’s oil earnings is on course as prices held firm on Friday near three-year highs reached earlier this week as ongoing OPEC-led supply cuts, as well as strong demand, gradually draw down excess supplies.

Brent crude oil futures were up at 73.79 dollars per barrel at 0440 GMT.U.S. West Texas Intermediate (WTI) crude futures down 2 cents at 68.40 dollars a barrel.

Both Brent, which Nigeria produces, and WTI hit their highest levels since November 2014 on Thursday, at 74.75 and 69.56 dollars per barrel respectively.

WTI is set for its second weekly gain. Oil prices have been pushed up by a gradually tightening market.

Led by top exporter Saudi Arabia, the Organization of Petroleum Exporting Countries (OPEC), has been withholding production since 2017 to draw down a global supply overhang.

The tighter oil market is feeding into refined products.

Oil supply tightness is also a result of healthy oil demand.

Beyond OPEC’s supply management, crude prices have also been supported by an expectation that the United States will re-introduce sanctions on OPEC-member Iran.