Global miner BHP Billiton said Wednesday that its U.S. shale oil business would be one of its major cash flow generators by 2020, contributing almost 3 billion U.S. dollars a year to the company by the end of the decade.

BHP Billiton plans to invest about 4 billion U.S. dollars a year in the U.S. shale business to increase its oil and gas production.

The company expects its total onshore U.S. production to reach 500,000 barrels of oil equivalent a day by 2017.

"In this scenario, Onshore U.S. is expected to be self-funding in the 2016 financial year before generating almost 3 billion U.S. dollars of free cash flow in the 2020 financial year," BHP Billiton's head of petroleum and potash Tim Cutt said in a statement.

"As a result, Onshore U.S. is well positioned to become another major cash flow generator for BHP Billiton."

Cutt said the company had identified a focus area in the Permian Basin of Texas, where it was pursuing a 100,000 barrel of oil equivalent a day development.

He said the company's oil and gas production guidance for the 2014 financial year remained unchanged at 250 million barrels of oil equivalent.