is injected into boreholes 24 in order to permeate the resource heated within resource formation 20 thereby causing the resource to become less viscous and to gravity flow with the displacing means to the bottom of borehole 24 the resource may consist of any formation deposit having a low initial relative permeability to a displacing means if introduction of heat will act upon the resource in such a manner so as to increase the relative permeability of the resource the displacing means may consist of hot water or hot solvents such as kerosene naptha or a combination of these solvents and water steam is generally the most desirable displacing means because of its high heat content and high mobility in the establishment of the horizontal heated plane hot water hot solvents or combinations thereof mixed with surfactants may be more desirable in order to insure the horizontal plane of communication fully develops before appreciable vertical channeling takes place when full displacement of the horizontal heated plane results improved sweep efficiency may be achieved by the introduction of inert gases flue gas air with steam or any combination thereof with steam at this later stage it may be desirable to promote vertical permeability through the use of these gases to create vertical channels through the laminations of clay and shale to the upper portion of the resource formation 20 steam is introduced into boreholes 24.