Signs that oil markets are weighted on the supply side and lingering uncertainty about price trajectories send crude oil prices lower in Wednesday trading.

Crude oil prices have drifted lower for most of July in part because of dual strains imposed by concerns about Greek government debt and the eventual return of Iranian crude oil that would come as a result of the lifting of sanctions after last week's breakthrough nuclear agreement.

While lower crude oil prices means less spending on exploration and production, data from industry group the American Petroleum Institute show a 2.3 million barrel increase in stockpiles in the United States. That data could be trumped by late afternoon reports from the U.S. Energy Information Administration, though markets reacted early to the API release.

West Texas Intermediate, the U.S. benchmark, fell 1.3 percent in early Wednesday trading to $50.19 per barrel. Brent crude oil prices declined eight tenths of a percent to $56.54 per barrel.

In April, Jamie Webster, a research director at IHS Energy, warned crude oil prices should remain unsettled for most of the year. Martin Craighead, chairman and chief executive officer at oil services company Baker Hughes, said Tuesday he expects "unfavorable market dynamics to persist."

That followed a string of reports from leading investments banks, which said downside risks remain for crude oil prices moving through the latter half of 2015.