In SAGD operation the start-up phase is intended to establish inter-well communication in an initial low mobility or immobile fluid reservoir. Establishing the communication early and uniformly along a SAGD well pair allows one to achieve a quick ramp up to the targeted peak production. In an ideal case a uniform start-up of inter-well communication and steam chamber should occur with parallel wellbores in a homogeneous reservoir. In reality the wellbore undulation and reservoir heterogeneity will lead to non-uniform start-up of inter-well communication along the well pair, localized growth of steam chamber, and delayed production ramp-up. In addition the wellbore hydraulics may also affect well flow behavior and the start-up operation.
This paper evaluates the effects of wellbore undulation on the start-up of SAGD process. The STARS' FlexWell model was used to assess the effects of wellbore undulation, wellbore fluid heating and wellbore/grid alignment. The simulation reveals localized steam chamber initiation due to wellbore undulation and delayed production ramp-up.