Abstract
Most mature steamflood projects have the heat injection rates reduced to minimize fuel costs and extend the economic life of the project. However, there is little industry consensus on whether the heat cuts should take the form of 1) mass rate reductions while maintaining the same high steam quality, or 2) steam quality decreases while keeping the same mass rate. Using a commercial three-phase, three-dimensional simulator, oil recovery schedules were generated for several steam mass rate and quality reduction cases under a variety of reservoir and operating conditions. The results indicated that for equivalent heat injection rates, decreasing the steam injection mass rate at a constant high quality will yield more economic oil than reducing the steam quality at a constant mass rate. A sensitivity analysis confirmed this conclusion and demonstrated the importance of the gravity drainage/steam zone expansion mechanism in a low-pressure, heavy oil steamflood with gravity segregation. Furthermore, the impact of discontinuous silts and non-uniform initial temperatures within the steamflood zone was studied, again indicating that a decreasing mass rate injection strategy is a superior operating practice.
