Salt-tolerant cationic friction reducers (FRs) have been successfully used in up to 100% of high total-dissolved-solids- (TDS) produced water for hydraulic fracturing applications. However, they might not be compatible with formation rocks, such as sandstone, that are typically negatively charged under normal pH. This study introduces a new cationic FR (C-FR) formulation that switches to anionic conditions under downhole conditions, thereby having minimal effects on the rock wettability of sandstone or clay formation.
Flow loop and zeta potential tests were conducted to demonstrate the benefits of using a C-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 to high levels of iron, allowing 100% reuse of produced water on location. Zeta potential measures the rock's surface charge and determines if there is significant wettability alteration in the presence of this FR.
Flow loop results verify that the new FR is extremely salt tolerant up to 300,000 ppm of TDS that includes up to 200 ppm of iron. An initial multiple well trial program was implemented in the Marcellus during August 2015, and, on average, pumping rates were maintained at approximately 100 bbl/min, and the treating pressure was kept well below 8,000 psi. Zeta potential indicates that the FR became negatively charged after releasing the cationic compound, thereby having minimal impact on the original rock wettability. The normalized long term production data from selected wells were compared to other offset or adjacent wells fractured with a standard anionic FR; no appreciable difference was determined.