Method for producing viscous hydrocarbons from discrete segments of a subterranean layer

Method for producing viscous hydrocarbon from a productive substrate layer in which the hydrocarbon is releasably held, which method includes the steps of;

• segregating a discrete vertical subsection of said substrate layer which is marginated between a pair of laterally spaced, substantially vertically oriented wells, and at least one other well, a portion of the latter being disposed substantially horizontal, and positioned adjacent to the bottom of the laterally spaced vertical wells,
• said respective vertical walls and at least one other well, being perforated along a portion of the lengths thereof which contacts the productive substrate layer,
• preheating said discrete vertical subsection,
• introducing multi-directional flows of a pressurized heating medium concurrently from one of said vertical wells and the horizontal well respectively, into said vertical subsection to form thermal fronts in the productive layer, which fronts combine to establish an aggregate thermal front which is urged toward the other of said laterally spaced vertically oriented wells,
• producing hydrocarbon from said other vertically oriented well,
• and the production of hydrocarbon from said vertical subsection by way of said at least one other well is achieved prior to the introduction of said multi-directional flows of heating medium thereto, and subsequent to said vertical subsection becoming preheated.