Method of producing drive fluid in situ in tar sands formations

A method for treating a tar sands formation, comprising:

• providing heat to at least part of a hydrocarbon layer in the formation from one or more heaters located in a first portion of the formation;
• allowing the heat to transfer from the heaters to at least a part of the first portion of the formation such that a drive fluid is produced in situ in the first portion of the formation;
• allowing the drive fluid to move at least some mobilized, visbroken, and/or pyrolyzed hydrocarbons from the first portion of the formation to a second portion of the formation, the second portion being at least partially horizontally displaced relative to the first portion;
• producing at least some of the mobilized, visbroken, and/or pyrolyzed hydrocarbons from the second portion of the formation;
• and
• providing heat to at least a part of the second portion from one or more heaters located in the second portion after moving at least some of the mobilized, visbroken and/or pyrolyzed hydrocarbons into the second portion.