Multibranch Injector/Producer Wells in Thick Heavy-Crude Reservoirs

Abstract

Summary With modern drilling techniques, it is now possible to drill wells with multiple branches emanating from the same vertical or even horizontal trunk. Several 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 mobility. Thus, drilling stacked horizontal branches would create effectively thinner drainage areas in which the vertical mobility is far more forgiving. However, the clear benefit derived from thermal recovery favors steam injection and invites investigation of ways to improve on the Steam Assisted Gravity Drive (SAGD) application. As an extension of the SAGD concept, this paper uses thermal reservoir simulation to investigate the effects of increasing the spacing between the injector and producer, or adding producers above or below the SAGD configuration, to mine more of the heat transferred to the reservoir by the injected steam. Simulations are performed with the Eclipse 500 thermal simulator using reservoir and fluid properties typical of the Bachaquero field in Venezuela. Economics confirm the merits of the approach.