VERTICAL INJECTION WELLS FOR SAGD - A PRACTICAL OPTION OR NOT

The steam-assisted gravity drainage process (SAGD) is a promising meth od for the in situ recovery of bitumen and heavy oil. A horizontal wel l is employed as the producer because its extended contact with the re servoir makes it possible to achieve economic production rates. Either horizontal or vertical injection wells can be used. It is possible to place the injection and the production wells wide apart vertically if the viscosity of the in situ oil is a few thousand cp, e.g., in Lloyd minister type reservoirs, whereas in bitumen reservoirs, a much closer separation is usually employed. A major incentive in the use of verti cal injection wells is that they may already be available from previou s production. The major disadvantage of using vertical wells is that t he steam chamber has to grow in the direction of the axis of the horiz ontal well as well as transversely. Thus the effective length of the p roduction well is less than its physical length at least until the ope ration becomes mature. The present work focuses on the growth of the s team chamber along the production well under different operating condi tions and with varying configurations of injection and production well s. Experiments were carried out using a three dimensional, scaled, cyl indrical, physical model with central vertical injection wells. The ef fect of parameters such as the type of production surface, thermal con ductivity of production well, point of injection along the vertical in jection well, and the effect of the injection of non-condensible gas a long with steam were studied. A theoretical model to predict the growt h of the steam chamber around the Vertical injection well is presented . Predictions from this model are compared to field and experimental d ata.