The Frontier formation in the Moxa Arch (Wyoming) is a complex, tight sandstone reservoir. As with any other tight formations, hydraulic-fracture stimulation is required to unlock the hydrocarbon reserves. This reservoir is also known for having high water and condensate production that seriously diminish the gas production, despite good reservoir quality, and can cause confusion when comparing the effectiveness of different stimulation techniques. A good understanding of reservoir characterization and production analysis is critical when comparing the effectiveness of different stimulation treatments across the field. This work addresses these topics by applying a systematic loop process that begins with reservoir evaluation, followed by completion design and production history analysis to identify the optimal treatment for each area in the field. The measure of success in this model was the accurate prediction of production using a reservoir flow-capacity model based on the parameters obtained from a calibrated log model specific to this reservoir and year-over-year production improvement. Once production capacity of the reservoir was known, an analysis allowed completion designs to be ranked by efficiency, from best to worst. Production-history matching provided additional information for a better understanding of the reservoir, as well as some other completion efficiencies. The results of this analysis were the key to identify necessary changes to improve fracture designs.
In this study, fifty one (51) wells that were completed before 2006 were used to generate the model to predict production. The model was later successfully tested using fourteen wells completed in 2007, where actual production matched model predictions and showed improvement over similar offset completions.
Different hydraulic-fracture treatment-design criteria were presented as a result of this study as optimized designs based on return on investment (ROI) for the Frontier formation. Each design criteria corresponds to specific areas of the field, where very clear and different fluid/gas ratios were identified.