Abstract: A system for containing well pressure including a well, a well casing, a blowout preventer (BOP), and a fuel container fluidly connected to the BOP that contains a fuel composition. The fuel composition auto ignites at a temperature between 150° F. and 1100° F. The fuel container of the system is configured to transfer heat from outside the fuel container to inside. A method for containing well pressure including heating a fuel container fluidly connected to a BOP and containing a fuel composition, autoigniting the fuel composition, producing a pressurized gas from a reaction activated by the autoignited fuel composition, directing the pressurized gas from the fuel container to a first volume of a ram casing of the BOP, expanding the pressurized gas in the first volume, driving the ram piston into a second volume of the ram casing, and driving a ram head or annular ram thereby sealing the well.