 The largest of them were combined heat and power plants, steel mills and nitrogen plants.The production and extraction of natural gas and crude oil throughout the country is handled by two main branches of the company - in Zielona Góra and in Sanok.The Zielona Góra Branch produces nitrogenous natural gas in 27 mines (17 gas and 10 oil-gas mines), while the high-methane gas is produced by the Sanok Branch and extracted in 47 mines (25 gas and 22 oil-gas mines).