Viking Stimulation: Case History

Abstract This paper presents case history results documenting the impact of changes to oil and water production in the Viking formation. This body of work applies in general to stimulation of the Viking as well and potentially other formations with high clay content. By understanding which variables have had the most impact on Viking production, it is possible to more effectively design future stimulation treatments. Some areas that previously lagged in production have now become the best producing Viking assets. The areas studied were Red Water, Plato, and Dodsland. The wells studied were drilled horizontally using cemented casing. Hydrajet perforating was used for each fracture stage. The fracturing treatments were pumped through coiled tubing at a typical rate of 1.5 m3/min, or less using inflatable packers above and below the desired set of perforations to provide isolation. Typical fracturing treatments used 7 tonnes of 16/30 proppant and were placed using a borate crosslinked guar fluid system. The primary design changes that have led to these improvements in production include the following: Control of clay fines migration, given that clay content in the Viking formation can exceed 50 vol%.Control of clay swelling.Prevention of paraffin precipitation caused by injected fracturing fluids having a temperature below the cloud point of the wax in the crude.Paraffin crystal structure modification to help mitigate production issues associated with any precipitated paraffin.Use of larger proppant sizes, higher proppant concentrations, and more aggressive proppant schedules.Optimization of fracture size and spacing. Because this has been the basis of much of the success in the Viking formation in recent years, a detailed discussion follows.