There are numerous heavy oil reservoirs in Canada which are underlain by bottom-water zones and are undergoing steam injection. Steam may be injected in the reservoir or the bottom-water zone, depending on the injectivity considerations. Due to gravity override effects, zones swept by steam in these reservoirs may have irregular shapes. Using a new analytical solution for a multi-layer, composite reservoir model, this study investigates transient pressure responses for partially-penetrating, steam injection wells with irregularly-shaped fronts in the presence of infinite or finite bottom-water zones. Pseudosteady-state crossflow is allowed among-adjacent layers to model the vertical flow of fluids. Pressure and pressure derivative responses have been studied to determine the effects of penetration ratio, crossflow parameters, mobility ratio, storativity ratio, and dimensionless front radii in different layers. Results of this study demonstrate the variety of well-tests responses expected in such complex scenarios. Also, this study outlines the difficulties associated with the traditional pseudosteady-state approach to estimate the swept volume in the presence of bottom-water zone effects. However, this analytical transient-pressure model should prove helpful in automated (or automatic) type-curve matching analysis of well-test data obtained from thermal recovery operations with and/or without bottom-water zone effects.
