A Revised Study of Iron Stress Testing in Hydraulic Fracturing Fluid and Treated Produced Water: Insights from the Bakken

ABSTRACT: This study presents an iteration of a previous novel iron stress test to evaluate the potential of iron-induced precipitation of anionic partially hydrolyzed polyacrylamide (PHPAM) in an industry-formulated hydraulic fracturing fluid sample and some treated and repurposed produced water samples. Samples from various Williston Basin Counties were examined to assess their susceptibility to form gel-like precipitates when exposed to ferric ions under simulated reservoir conditions. Results confirmed that McKenzie County produced water and the tested hydraulic fracturing fluid sample both exhibited iron-stressed behavior, forming visible Fe-PHPAM gel precipitates that transitioned from yellow to brown after heating. These precipitates pose significant risks of formation damage by blocking pore throats and fractures in reservoir rocks, potentially reducing hydrocarbon production rates by up to 80% in the worst cases. The iron stress test offers operators a simple yet effective diagnostic tool to identify problematic fluids before reuse or injection, enabling proactive measures to prevent formation damage. This research provides valuable insights for improving hydraulic fracturing efficiency in tight reservoirs where PHPAM-based friction reducers are commonly employed and supports the integration of routine iron stress testing into fluid treatment/pre-fracturing workflows in a proactive move to minimize reservoir damage.