The Pelican Lake field in northern Alberta (Canada) is home to the first successful commercial application of polymer flooding in higher viscosity oils (i.e. greater than 1,000 cp), which has opened up new opportunities for the development of heavy oil resources.
The field produces from the Wabiskaw “A” reservoir which has thin pay (2 to 6 meters) and exhibits a significant viscosity gradient across the field, with oil viscosities as low as 600 cp in the existing waterflood and polymer flood area to over 200,000 cp in the current undeveloped “immobile” area. This unique geological feature limits the application of chemical injection to the less viscous areas of the field and calls for different methods for the heavier accumulations.
As a first step to develop alternate technologies capable of recovering oil from heavier areas of the field not ideal for polymer flooding, a hot water injection pilot was designed and implemented in June 2011. The hot water injection scheme was applied to a transition area where dead oil viscosity ranges from 3,000 cp to approximately 15,000 cp. It consists of one horizontal producer supported by two horizontal hot water injectors, with an injector-producer distance of 50 meters for both injectors, and 3 vertical observation wells equipped to monitor pressure and temperature between one injector and the producer.
The pilot was operated in three phases. The first phase consisted of 6 months of primary production period to obtain a baseline of the pilot performance prior to hot water injection. The second phase began in June 2011 and consisted of hot water injection through the edge injectors. The third phase was started in March 2012 and consists of hot water edge injection accompanied by hot water circulation in the production well as a means to stimulate oil production. One of the features of this stage is the use of an insulated coil tubing, which continuously delivers hot water to the toe of the producer and allows continuous stimulation and uninterrupted oil production.
This paper describes the mechanical components of the pilot and discusses the results obtained with an emphasis on the hot water circulation stage which has proven to be very effective. Oil production increased from approximately 6 m3/d during the flood stage, to more than 25 m3/d during the hot water circulation stage and has held relatively steady for more than 2 years.
The data captured has been reconciled with analytical and reservoir simulation models, and results suggest that the technology could help unlock some of the heavier oil accumulations in the field.