The United States’ record oil production is driving down prices and may threaten future output from the shale formations responsible for the current increase in domestic supplies, according to Bloomberg.com.

U.S. oil formations will add “an unprecedented” 1.1 million barrels of production a day in 2014 and add nearly 1 million barrels more in 2015, according to the U.S. Energy Information Administration. U.S. oil output will reach levels not seen since 1970. Meanwhile, oil consumption is expected to drop 0.2 percent to 18.9 million barrels a day this year, the lowest level since 2012.

The increase in supply and the dip in demand helped drop the price of West Texas intermediate crude, the U.S. benchmark, by more than 20 percent in the last four months. West Texas intermediate slipped below $90 a barrel on Oct. 2.

Shale wells are expensive and only profitable if oil prices remain high enough, Ed Morse, Citigroup Inc.’s head of global commodities, told Bloomberg.

It costs $50 to $100 a barrel to produce shale oil, compared to between $10 and $25 a barrel in the Middle East and North Africa.

There is some concern that “the chickens” of declining demand and increasing supply will come home to roost, according to Bobby Tudor, chief executive officer of Tudor Pickering Holt & Co., a Houston investment bank that focuses on the energy industry.