bitumen heavy oil or another oil and extracting them from a reservoir 110 fig1 illustrates a configuration of the preferred embodiment of the system that generates a syngas with a rather high temperature and pressure that is injected into an injection well while it may not be practical to inject syngas with such high temperatures and pressures this figure is useful for understanding some of the novelty of the invention after fig1 is discussed other figures that implement more detailed and more practical systems and methods such as those which reduce the temperature of the syngas before it is injected into a well are discussed further in fig1 fuel is input to a high pressure gasifier 102 through a feed line 101 along with oxygen from line 120 and steam from line 121 the fuel is partially burned in the gasifier with the oxygen and steam to generate a high temperature high pressure syngas the high temperature and high pressure syngas includes primarily hydrogen and carbon monoxide in this configuration of preferred embodiment the ratio of hydrogen to carbon monoxide in the syngas is in the range of 2 to 3 1 the high pressure gasifier 102 that generates the syngas can be a market available high pressure gasifier such as the zeep zero emissions energy plant gasifier developed by pratt and whitney rocketdyne u s pat no 7 547 423 describes other aspects of a high pressure gasifier the contents of which are incorporated herein by reference the system 100 injects the syngas at a controlled temperature into the reservoir 110 to heat crack hydrogenate and upgrade heavy oil insitu cracking the heavy oil in the presence of hydrogen can.