Abstract: A gas-generator is disclosed to intensify output of oil, gas, including gas from coal formations, or metals extracted by underground leaching by breakage and thermo gas chemical treatment of the critical formation zone with gaseous combustion products from a solid propellant. The rate of increase of gas pressure is raised and the effect on the formation is enhanced by assembling the gas generator using coated and bare charges in a selected ratio. The charges burn radially, so the coated charges, which burn only from the center outwards, burn for longer and with a rising output. A two-peaked pressure characteristic is thus obtained. A high-velocity igniter may also be used to give a third, early pressure peak.