During the last years the exploitation of heavy oil reservoirs has gained a great attraction, the application of techniques such as continuous steam injection has increased around the world. Although there are many successful projects, inherent problems such as the overriding effect, where steam moves to the top part of the layer decreasing steamflood efficiency occur. The water alternating steam process (WASP) was designed to reduce the problems associated with continuous steam injection, since the water sweeps the remaining oil in the lower parts of the layer, while lowering the reservoir temperature. Due to the limited information on WASP projects, reservoir simulation is a useful tool to determine the feasibility of a WASP process implementation. In this paper the results of a feasibility study are presented in order to perform a WASP process in a Colombian heavy oil field.
The technique was evaluated by numerical simulation on a heavy oil reservoir located in the Middle Magdalena Valley basin. Following the exploitation scheme implemented in other formations of the reservoir, it began with a brief period of cold production followed by a stage of thermal stimulation then to inject steam continuously up to reaching maturity and demonstrating the phenomena of channeling, steam overriding and associated operational problems. The influence of the operating parameters in the WASP technique was determined by sensitivity analysis to then define the optimal scheme of variables to be used during the implementation of the further process to the steamflood.
The simulation results indicate that there was an maintennace in the cumulative oil production as well as a reduction in the project energetic requirements, which means an increase in the net present value (NPV). The economic life of the project was extended given the observed decrease in steam - oil ratio (SOR). The influence of operational variables such as the length and number of cycles, water temperature and water and steam injection rate in the technical performance is also shown.
This work assessed the potential of the water alternating steam process (WASP) for the recovery of heavy oil in a Colombian reservoir, serving as a basis for a subsequent study in a full field model.