Impact of salt-tolerant friction reducers on shale stability and fracture conductivity
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One of the main challenges of hydraulic fracturing is the reuse of flowback waters. While it alleviates the disposal and treatment costs of these concentrated brines, it also limits the environmental impacts of the fracking industry by reducing the amounts of fresh water necessary to produce gas. This research aims at optimizing this process by assessing the impacts of salt-tolerant friction reducers on shale stability and fracture conductivity. Polyacrylamide and polyethylene oxide based friction reducers were assessed over a wide range of NaCl and CaCl₂ concentrations, using a hot rolling oven and fracture conductivity experiments. The commonly used polyacrylamide based DR3046 was found to be a good shale stabilizer but did not efficiently reduce friction in the presence of divalent salts. While high molecular weight polyethylene oxides showed a high friction reduction in all brines, and reduced shale cuttings dispersion in the presence of salts, they did not maintain fracture conductivity. The newly developed Dispersion Polymer Friction Reducer (DPFR) showed the best and most consistent results for all salt concentrations, in terms of friction reduction, shale stabilization efficiency, and ability to maintain the highest fracture conductivity.