U.S. crude was down $2.77 at $47.34 a barrel at around 0314 GMT. Brent crude was down $2.75 at $48.16 a barrel.

"Such huge outflows raise a question as to whether upstream business will generate enough cash, and where capex will figure in the priority order of companies," said Andrew Slaughter, executive director, Deloitte Center for Energy Solutions. "When we annualized operating cash flows of all the three company sets in 2015 for the next five years, assuming a $55/bbl average oil price, we see a total funding gap of up to $2 trillion from operations."

Global upstream development spending from 2015 to 2020 has declined 22%, or $740 billion, since fourth-quarter 2014. Including cuts to conventional exploration investment, the figure increases to just more than $1 trillion.

"We have seen a large amount of short positions being closed while long positions have been opened," Novak said in reference to speculative bets - shorts - in the market that prices will fall, and the opposite - longs - that they will rise.

"We have such low production costs that we will always be able to cut the selling price by a dollar or two when it comes to fighting off a rival," said a senior source at Gazprom.

Supply and demand for oil are coming back into balance, and the response of shale producers to rising prices will help determine how high crude can go, Christof Ruehl, the global head of research at Abu Dhabi Investment Authority, said Wednesday in an interview in Dubai. Ruehl’s view that the re-balancing will take until at least the middle of 2017 contrasts with the more optimistic outlook of some industry leaders and analysts who foresee demand nearing supply by the end of this year.

"The Kingdom's oil policies are rooted in responsibility, and Saudi Arabia is seeking to maintain that balance while also giving heed to moderate prices for producers and consumers,"

With income falling, the 13 members of the Organization of the Petroleum Exporting Countries (OPEC) posted a combined current account deficit of $99.60 billion in 2015, compared with a surplus of $238.10 billion in 2014.

Brent crude futures were up 4 cents at $50.66 a barrel, after settling down 3 cents at $50.62 on Tuesday.

"We believe that the (function of) regulation has moved to three main players, which are the United States, Saudi Arabia and Russia," he said.