(London) Oil prices faltered slightly on Wednesday, with mixed first weekly data on US commercial reserves ending a series of bullish sessions.

Around 5:30 a.m. (Eastern time) (11:30 a.m. Paris), the price of a barrel of North Sea Brent, for delivery in August, lost 0.25% to $85.12.

Its American equivalent, a barrel of West Texas Intermediate (WTI), for delivery in July, lost 0.49% to 81.17 dollars.

The API, the American federation of professionals in the sector, reported on Tuesday an increase in commercial crude reserves of approximately 2.3 million barrels per day for the week ended June 14, and a decrease of nearly 1.1 million barrels per day for gasoline.

For DNB analysts, these figures are “mixed due to a modest, but stronger than expected, increase in crude oil production, which is partially offset by reductions in gasoline stocks.”

The data “calls for caution,” also notes Tamas Varga, an analyst at PVM Energy, saying that in the “absence of palpable signs of decline in U.S. commercial inventories,” any price increases would be corrected.

Investors are now awaiting the publication of the weekly report from the US Energy Information Administration (EIA) on the state of oil stocks.

DNB also underlines that “the oil market should be rather tight this summer, because OPEC “(the Organization of the Petroleum Exporting Countries and their allies, Editor’s note) has extended its production cuts until the end of the third quarter “.

But as early as October, with the group increasing production, analysts say the market could experience “oversupply” which could push prices back down.

The first figures on American stocks interrupted the rise in crude prices the day before after new Russian and Ukrainian attacks targeting their energy infrastructures.

Ukraine on Tuesday claimed responsibility for a “successful” attack on a Russian oil refinery in a nighttime drone attack in Azov, in the southern Rostov region, which caused a large fire, according to local authorities.

At the same time, a nighttime attack by Russian drones damaged electrical installations in central and western Ukraine, leading to new power outages, the Ukrainian Energy Ministry said on Wednesday.

In addition to these events which “contributed to the recovery of prices”, American economic data had “also contributed to maintaining optimism in the oil market” on Tuesday, underlines Tamas Varga.