Effect of Wellbore Steam Quality Variation on Steamflooding Thick Formations

ABSTRACT In designing steamfloods for thick formations, usually steam quality is assumed to be uniform over the formation face, even if multiple offtake points are present. This can lead to errors in steamflood oil recovery predictions. This paper addresses this question, and examines, first, the effect of multiple offtakes on steam quality and pressure, and second, the effect of variable vs. uniform steam pressure and quality on steamflood recovery predictions. A wellbore model was developed, which accounts for steam pressure, quality, and flow regime variation, and the added feature of multiple offtake of the steam stream. The model was used to examine a variety of steam injection situations, with steam offtake at a halfway point. Effects of steam splitting on steam quality and pressure was examined for various wellhead pressures and injection rates. The wellbore simulator thus developed was then coupled with a three-dimensional steamflood simulator, to study steam injection performance in formations of various thicknesses, when steam is divided into two streams. The results show that if the wellbore steam quality variation is not allowed significant errors in the predicted steamflood recovery can result. A number of examples are presented, showing discrepancies as large as 50%.