A sticker reads crude oil on the side of a storage tank in the Permian Basin in Mentone, Loving County, Texas, U.S. November 22, 2019. Picture taken November 22, 2019.
A sticker reads crude oil on the side of a storage tank in the Permian Basin in Mentone, Loving County, Texas, U.S. November 22, 2019. Picture taken November 22, 2019. Reuters / Angus Mordant

Oil prices slid 2% on Wednesday as U.S. crude and gasoline stockpiles unexpectedly surged higher last week and after OPEC+ said it would raise its oil output target by only 100,000 barrels per day (bpd).

Brent crude futures were down $2.35, or 2.4%, at $98.19 a barrel by 11:09 a.m. ET (1509 GMT). West Texas Intermediate (WTI) crude futures slipped by $2.30, or 2.5%, to $92.10. Both contracts had seesawed previously.

The premium for front-month Brent futures over barrels loading in six months' time is at a three-month low, indicating concern over tight supply are abating. The premium for WTI futures for the same months touched a near four-month low.

U.S. crude oil inventories rose unexpectedly last week as exports fell and refiners lowered their runs, while gasoline stocks also posted a surprise build as demand slowed, the Energy Information Administration nL1N2ZF1LG said.

Crude stocks rose 4.5 million barrels last week, compared with an analyst forecast for a draw of 600,000 barrels, and gasoline stocks gained 200,000 barrels, versus expectations for a 1.6 million-barrel drop. [EIA/S]

"The crude oil number is well above expectations. Gasoline is a disappointment. You should never see a build in gasoline during summer. It's a very bearish report," said Bob Yawger, director of energy futures at Mizuho.

Ministers for the Organization of the Petroleum Exporting Countries (OPEC) and allies including Russia, known as OPEC+, agreed to the small increase to the group's output target, equal to about 0.1% of global oil demand.

Algerian oil production in September will rise to 1.57 million bpd, Energy Minister Mohamed Arkab told state television.

While the United States has asked the group to boost output, spare capacity is limited and Saudi Arabia may be reluctant to beef up output at the expense of Russia, hit by sanctions over the Ukraine conflict.

Ahead of the meeting, OPEC+ trimmed its forecast for the oil market surplus this year by 200,000 bpd to 800,000 bpd, three delegates told Reuters.

Also weighing on prices, top Iranian and U.S. officials said they were travelling to Vienna to resume indirect talks about Iran's nuclear programme, reviving the all but vanished hopes of a removal of sanctions hampering Iranian oil exports.