The present invention involves a method and apparatus for
enhanced recovery of
petroleum fluids from the subsurface by
convective heating of the oil sand formation and the heavy oil and bitumen in situ by a downhole electric heater. Multiple propped vertical hydraulic fractures are constructed from the well bore into the oil sand formation and filled with a
diluent. The heater and downhole pump force thermal
convective flow of the heated
diluent to flow upward and outward into the propped fractures and circulating back down and back towards the well bore heating the
oil sands and in situ bitumen on the vertical faces of the propped fractures. The
diluent now mixed with produced products from the oil sand re-enters the bottom of the well bore and passes over the heater element and is reheated to continue to flow in the convective
cell. Thus the heating and diluting of the in place bitumen occurs predominantly circumferentially, i.e. orthogonal to the propped fracture, by
diffusion from the propped
vertical fracture faces progressing at a nearly uniform rate into the oil sand deposit. In situ hydrogenation and thermal
cracking of the in place bitumen can provide a higher grade produced product. The heated low
viscosity oil is produced through the well bore at the completion of the active heating phase of the process.