SAGD with a Longer Wellbore

This paper investigates the feasibility of bitumen production using SAGD technology with a longer wellbore. A longer wellbore can be used to exploit a greater volume of the reservoir with a single wellpair as opposed to multiple wells; thus, decreasing pad and drilling costs. The major concern in using a longer wellbore from a reservoir engineering point of view is the potentially non-uniform steam chamber growth over the whole well length due to pressure drop in the horizontal well. Reservoir simulation was performed using Computer Modelling Group's STARS (TM) simulator and the QFlow thermal wellbore simulator to address the issue. The pressure drop inside the wellbore was calculated using QFlow. Reservoir simulations were performed using STARS. A sectioned model was constructed, dividing the whole length of the horizontal wellbore into multiple sections, each with its own pressure restriction to match the pressure drop obtained from QFlow. The results showed that with a sufficiently large wellbore size that resulted in a sufficiently low pressure drop, one longer well performed as well as two shorter wells. When a smaller wellbore size was used, production from a longer well was significantly impeded due to the large pressure drop.