To increase a yield of a hydrocarbon such as oil from a subsurface reserv, the reservoir is stimulated by pumping liquid gun propellant (LP) into the reservoir and igniting the LP. The LP is pumped into a packed-off region in a cased well; the depth of the packed-off region is selected to lie within the reservoir. The ignition of the LP causes a pressurization of the reservoir, thus fracturing the reservoir. The fracture increases a surface area through which the hydrocarbon can be extracted, and the heat from the ignition reduces the viscosity of the hydrocarbon.