Multifunctional, Salt-Tolerant Friction Reducer Stabilizes Clay Formations and Minimizes the Alteration of Rock Wettability Under Downhole Conditions after Hydraulic Fracturing

摘要

Salt-tolerant cationic friction reducers (FRs) have been successfully used in up to 100% high total dissolved solids (TDS) produced water for hydraulic fracturing applications. Cationic FRs, however, may not be compatible with formation rocks that contain quartz or clay that is typically negatively charged under normal pH. In this study, a new cationic FR formulation is introduced that does not appear to alter rock wettability and that releases a clay stabilizing agent over time under downhole conditions. Flow loop, capillary suction time (CST), turbidity, and zeta potential (ZP) tests are conducted to demonstrate the benefits of using a multifunctional FR that tends to have minimal formation damage toward formation rocks. Flow loop tests qualify the FR as a robust polymer that is salt-tolerant and enables up to 100% re-use of produced water on location. Both CST and turbidity evaluates the efficacy of the clay stabilizing agent that is released from the FR under downhole conditions. ZP measures the surface charge on the rock's surface and determines whether or not significant wettability alteration occurs in the presence of this FR. Flow loop results verify that the new FR is extremely salt-tolerant up to 300,000 ppm TDS, which was further demonstrated in the Marcellus Shale formation. Both CST and turbidity results suggest that the performance of the clay stabilizer is equivalent to that of a 4% KCl solution, a common temporary clay stabilizer. ZP indicates that the FR became predominantly negatively charged after releasing the clay stabilizing agent, thereby having minimal effect on the original rock wettability.