Abstract
Steam-Assisted Gravity Drainage (SAGD) is a widely used in situ recovery process for heavy oil and bitumen reservoirs. The performance of the SAGD process is tied with growth of the steam chamber which in turn depends on uniform steam delivery along well length and the underlying geology and fluid properties in the near wellbore region. If the reservoir has poor injectivity due to poor underlying geology oil production suffers. This can be avoided in by examining the interwell subcool. The subcool is the temperature difference between the injected steam and produced fluids. In this study, Proportional-Integral-Derivative (PID) feedback control has been employed to control inflow control valves settings to promote subcool to a target value. This control strategy is examined by using a PID algorithm to control SAGD in a detailed three-dimensional heterogeneous reservoir model with properties typical of an Athabasca bitumen reservoir. Specifically, the SAGD injector is divided into six intervals each with its own steam injection pressure. The interwell subcool is calculated and the PID feedback control algorithm is used to direct the subcool to a target value by changing the steam injection pressure in each well interval. The results show that this control method can be used to enhance uniform steam chamber growth and ultimately more oil production with less steam injection. The key benefit of dynamic well control is that the injection strategy is adjusted dynamically to fit the underlying geological and fluid compositional heterogeneity to obtain improved steam conformance along the wellpair. This implies that potentially a priori detailed knowledge of the geological and fluid compositional heterogeneity may not be as critical for well placement for uniform steam conformance.
