Role of Foam, Non-Newtonian Flow, and Thermal Upgrading in Steam Injection

Abstract

ABSTRACT Foam formation and flow, non-Newtonian behaviour, and thermal upgrading phenomena play a role in steam injection processes, which is still not clearly understood. This investigation addresses these effects in the context of steamflooding. The results are based upon a steam injection simulator, which was modified to account for foam, non-Newtonian oil viscosity, and thermal upgrading. Steam-foam flow was represented by means of a shear-dependent mobility, which was also a function of pressure, temperature, foam quality, and flow velocity. The relative permeability to gas was also a function of surfactant concentration. Non-Newtonian flow behaviour was implemented in the conventional manner, making the apparent viscosity of oil a function of local shear rate. Thermal upgrading was represented as a permanent decrease in oil viscosity depending on the residence time and temperature. These effects were incorporated into a three-phase, three-dimensional, fully implicit steam simulator. It was found that a steam foam led to an increase in oil production rate, compared to steam alone. However, the increase was small, since the foam acted to increase steam viscosity, although the blocking effect was present to a small extent. The oil production behaviour in the case of a non-Newtonian oil was superior to that for a Newtonian oil, because the apparent viscosity of oil decreased in the cold part of the reservoir. Thermal upgrading, on the other hand, was less effective in increasing oil recovery, because the oil viscosity decrease due to cracking, over and above that due to temperature, was small.