Superior Salt-Tolerant High Viscoelastic Friction Reducer Polymer Enables 100% Re-Use of Ultrahigh TDS Produced Water in Hydraulic Fracturing

Abstract

Abstract The water usage per well has considerably increased over the last decade, putting tremendous pressure on freshwater resources. Rather than paying to treat and dispose of produced and flow back water, most hydraulic fracturing companies prefer to reuse it in subsequent stimulation treatments by using salt-tolerant high-viscoelastic friction reducers (HVFR) to conserve freshwater resources, reducing operations costs, reducing carbon footprint, and improving environmental stewardship. The objective of this study is to systematically evaluate the compatibility of salt-tolerant HVFR products in extremely high-salinity environments to enable 100% reuse of produced and flow back field water in stimulation operations. The HVFR performance was evaluated based on three criteria: i) friction reduction accomplishment, ii) viscoelastic properties performance, and iii) proppant transport capability. Two anionic HVFR slurry product was used with highly desired water sources of salinity varying up to 300,000 ppm. Four dosages at 0.5, 1, 4, and 6 gpt were investigated. Water source samples from oilfields in Northeast Texas and in Midland Texas with a salinity of 200,000 ppm and 62,563 ppm were used to hydrate HVFR. A flow loop was used to determine the friction reduction of the HVFR product. Anton Paar rheometer was used to determine the viscosity and elastic properties of HVFR. Proppant settling studies using 30/60 mesh sizes were conducted in a confined fluid tube. The performance of salt-tolerant HVFR was compared with a widely used commercial friction reducer fracture fluid. Results show that salt-tolerant HVFR is a "self-healing product" compatible with producing water salinity, it developed both high viscosity and elastic profiles with high isothermal viscosity stability at 122 °F and 167 °F in 200,000 TDS. Even at 200,000 TDS, low dosages of HVFR (0.5 gpt) still produce a high stable friction reduction rate of approximately 75% across 11 minutes of testing with high quick hydration in less than 20 seconds. Salt-tolerant HVFR shows a good proppant settling performance with a long proppant suspension time varying from 10 minutes to 20 minutes. Proppant suspension time is controllable by changing the HVFR concentration. Finally, the salt-tolerant HVFR shows much better rheological properties than the commercial HVFR. This study demonstrates that salt-tolerant HVFR products have excellent friction pressure reduction performance, very well-accepted viscoelastic properties, and high proppant transport capability using oilfield-produced water salinity. The laboratory results illustrate the true benefits of the use of salt-tolerant HVFRs as a base fluid with the increasing demand for re-cycled and flow-back water use in fracturing fluid systems.