A method for fracturing an oil or gas formation. The method includes introducing a gas impulse device into a wellbore followed by pumping a pressurized liquid into a wellbore at a pressure equal to or lower than the estimated fracture pressure of the formation. Finally, the method includes firing the gas impulse device periodically so that the device releases high pressure compressed gas impulses. The impulses when expanding through the pumped pressurized liquid substantially instantaneously increases the fracturing liquid flow rate into the oil or gas formation. It causes the total pressure to exceed the actual fracturing pressure of the formation thereby initiating or extending fractures in the formation stimulating the flow of the oil or gas therefrom into the wellbore.