LONDON (Reuters) – OPEC oil supply fell to a four-year low in February, a Reuters survey found, as top exporter Saudi Arabia and its Gulf allies over-delivered on the group’s supply pact while Venezuelan output registered a further involuntary drop.

The 14-member Organization of the Petroleum Exporting Countries pumped 30.68 million barrels per day (bpd) last month, the survey showed on Friday, down 300,000 bpd from January and the lowest OPEC total since 2015, according to Reuters surveys.

The survey suggests that Saudi Arabia and its Gulf allies over-delivered on pledged supply curbs to avert the possibility of a new glut building up this year. A formal accord by OPEC and its allies to cut supply in 2019 took effect on Jan. 1.

Crude oil has risen to $66 a barrel after a dip below $50 in December, boosted by the Saudi move, involuntary curbs in other OPEC countries and the prospect of lower supply from Venezuela after U.S. President Donald Trump imposed sanctions on its oil industry.

OPEC, Russia and other non-members — an alliance known as OPEC+ — agreed in December to reduce supply by 1.2 million bpd from Jan. 1. OPEC’s share of the cut is 800,000 bpd, to be delivered by 11 members — all except Iran, Libya and Venezuela.

In February, the 11 OPEC members bound by the new agreement achieved 101 percent of pledged cuts, the survey found. Among exempt producers, Venezuelan supply fell while Iran, which is also subject to U.S. sanctions, managed to boost exports.

The latest OPEC+ deal came just months after the group agreed to pump more oil, which in turn partially unwound their original supply-limiting accord that took effect in 2017.

February’s output is the lowest by OPEC as a group since February 2015, excluding membership changes that have taken place since then, according to Reuters surveys.

The Reuters survey aims to track supply to the market and is based on shipping data provided by external sources, Refinitiv Eikon flows data and information provided by sources at oil companies, OPEC and consulting firms.