A method for treating a hydrocarbon containing formation may include providing heat to a first hydrocarbon layer in the formation from a first heater located in an opening in the formation. The opening and the first heater may have a horizontal or inclined portion located in the first hydrocarbon layer and at least one connecting portion extending between the horizontal or inclined portion and the surface. Isolation material is placed in the opening such that the isolation material partially isolates the layer in which the horizontal or inclined portion of the first heater is located. An additional horizontal or inclined opening portion that extends from at least one of the connecting portions of the opening is formed in a second hydrocarbon layer. A second heater to provide heat the second hydrocarbon formation is placed in the additional substantially horizontal opening portion.