With modem drilling techniques, it is now possible to drill wells with mult
iple branches emanating from the same vertical or even horizontal trunk. Se
veral heavy-crude reservoirs are very thick, and low vertical permeability
would make them unattractive for single horizontal wells. Further the much
higher viscosity of the reservoir fluid results in highly unfavorable mobil
ity. Thus, drilling stacked horizontal branches would create effectively th
inner drainage areas in which the vertical mobility is far more forgiving.
However, the clear benefit derived from thermal recovery favors steam injec
tion and invites investigation of ways to improve on the Steam Assisted Gra
vity Drive (SAGD) application.
As an extension of the SAGD concept, this paper uses thermal reservoir simu
lation to investigate the effects of increasing the spacing between the inj
ector and producer, or adding producers above or below the SAGD configurati
on, to mine more of the heat transferred to the reservoir by the injected s
team. Simulations are performed with the Eclipse 500 thermal simulator usin
g reservoir and fluid properties typical of the Bachaquero field in Venezue
la. Economics confirm the merits of the approach.