Chevron Corp. (NYSE: CVX) is abandoning natural gas exploration in Poland’s shale formations, joining at least four other international energy producers who quit the nation because of disappointing results, Bloomberg reported Jan. 30.

Chevron, which began drilling Polish shale wells in 2012, dropped any plans for additional exploration after finding the gas-bearing rocks were unsuitable for commercial extraction, Kurt Glaubitz, a spokesman for the San Ramon, Calif.-based company, said in an interview on Jan. 30.

The departure of the second-largest U.S. energy company by market value deals another blow to Poland’s ambition to tap vast shale formations and help itself and its central and eastern European neighbors shake loose of Russian gas supplies.

“The company has decided to discontinue shale gas operations in Poland as the opportunities here no longer compete favorably with other opportunities in Chevron’s global portfolio,” Chevron said in a statement e-mailed Jan. 30.

ExxonMobil Corp. (NYSE: XOM) abandoned Polish shale in 2012 after drilling unsuccessful wells. Talisman Energy Inc. (NYSE: TLM) and Marathon Oil Corp. (NYSE: MRO) quit in May 2013 and Eni SpA (NYSE: E) left in early 2014.