A method for treating a relatively permeable formation containing heavy hydrocarbons
in situ may include providing heat from one or more heat sources to a selected
section of the formation. The heat provided to the selected section may pyrolyze
at least some hydrocarbons in a lower portion of the formation. A mixture of hydrocarbons
may be produced from an upper portion of the formation. The mixture of hydrocarbons
may include at least some pyrolyzed hydrocarbons from the lower portion of the formation.