Abstract
As the demand for water volumes needed to complete wells increase, limitations on freshwater availability and increasing water disposal costs, are driving produced water re-use efforts. These waters must be treated to reduce potential of damage to the formation and to ensure compatibility of other fracturing chemical additives. While treatment methods can improve chemical compatibility, the variability of the water composition presents challenges in selection of friction reducers (FR). FRs are the main component of Slickwater fracturing fluids and their performance impacts the ability to achieve desired pump rates. Changes in water quality can negatively affect friction reduction and lead to an increase in chemical usage and associated costs. Current methods for selection vary by equipment and those laboratory results have limited correlation with field results. This work outlines the methodology for monitoring produced or recycled waters during hydraulic fracturing operations, the evaluation of friction reducer performance in the laboratory and subsequent successful field validation.
Process evaluation and optimization showed that a unified monitoring approach can generate data that allow the selection of fluids that can meet the changing water conditions in the field. Standardized criteria were used along with on-site monitoring and testing to track changes in water composition and the effect of water quality on friction reducer performance and dosage requirements. The data was used to validate field results and to provide input on fluid design changes during the fracturing process to improve efficiency and drive cost-savings.
Monitoring showed the water composition varied greatly from site to site, highlighting the need for an in-depth understanding of water composition. Friction reducer performance also varied from pad to pad on the same lease. Performance changes correlated with changes in water composition over the span of the hydraulic fracturing operations. This suggested that standardizing a fluid design based on prior water data does not always result in optimal performance. The ability to optimize FR selection to existing water conditions, could result in chemical and water treatment cost-savings to operators when produced waters are used.
The use of produced water will continue to present challenges in fluid design; however, with proper understanding of produced water composition and its impact on fluid chemistry, fluids can be optimized to work in changing conditions. Definition of lab-based performance criteria for friction reducer performance, allowed for the selection of top performers for field trial. These could then be systematically ranked based on cost and performance and validated in the field based on fracture pressures and volumes used. Hydraulic fracturing operations using the top performing FRs for the specific water conditions allowed to operators to use harsher produced water quality while reducing the total FR spend.
