A method and system for heating a subsurface formation using electrical resistance heating is provided. In one aspect, two or more wellbores are provided that penetrate an interval of solid organic-rich rock within the subsurface formation. At least one fracture is established in the organic-rich rock from at least one of the wellbores, and electrically conductive material is provided in the fracture. In this way electrical communication is provided between the two or more wellbores. The electrically conductive material may include a first portion placed in contact with each of the two or more wellbores, and a second portion intermediate the two or more wellbores. The first portion has a first bulk resistivity while the second portion has a second bulk resistivity. The method also includes passing electric current through the fracture such that heat is generated by electrical resistivity within the electrically conductive material sufficient to pyrolyze at least a portion of the organic-rich rock into hydrocarbon fluids. The resistive heat generated within the first portion of the electrically conductive material is less than the heat generated within the second portion of the electrically conductive material.