The invention provides methods for treating a source oil phase consisting of heavy oil, bitumen, a mixture of heavy oil and bitumen, a mixture of solvent and heavy oil or bitumen or both. The method comprises: introducing the source oil phase to a lower reservoir section of a device, flowing the source oil phase through an array of vertically extending heated pipes with an inert gas so as to thermally separate a vaporized light oil phase component from a heated liquid source oil phase, and segregating fluid flows by density in an upper fluid separating manifold to provide a light product fluid and a heavy product fluid.