Petroleo Brasileiro SA, a Brazilian oil company that plans to spend $112 billion over five years to expand operations, and Mitsui & Co. signed an agreement to study the extraction of oil from shale deposits in Utah.

Petrobras, as the company is known, Mitsui and the Oil Shale Exploration Co., based in Vernal, will study the development of more than 30,000 acres of leases containing an estimated 3 billion to 4 billion barrels of shale oil, according to statements Monday from the companies.

In exchange, Petrobras and Mitsui may each take interests of as much as 20 percent in Oil Shale Exploration, the largest non-government holder of oil-shale reserves in Utah.

Petrobras, which has been producing oil from shale commercially for 30 years in Brazil's Parana state, is seeking to expand oil output in the United States and other fuel-hungry markets and to use its patented Petrosix processing technology to diversify the sources of oil, according to the statement.