Synthesis and emulsion stability of salt resistant viscosity reducer for heavy oil reservoirs with varying salinities

To address the inadequate salt resistance of viscosity reducers and their limited applicability to reservoirs with single salinity, we synthesized salt-resistant viscosity reducers PAN x A n in this study. These compounds were derived from fatty alcohol polyoxyethylene ether acrylate, N-alkyl acrylamide, acrylamide, and 2-acrylamido-2methylpropanesulfonic acid. The structures were identified using nuclear magnetic hydrogen spectroscopy. We investigated the effects of the hydrophilic group ethoxy-chain length (n = 14, 16, 18, 20 and 22) and hydrophobic group alkyl-chain length (x = 12, 14, 16, and 18) on the salt resistance, interfacial activity, wettability, interfacial viscoelasticity and emulsification viscosity reduction performance of the viscosity reducers. Futher, the structures of the viscosity reducers which can adapt to different salinities were determined. Based on the emulsification viscosity reduction effect, PAN 14 A 16 , PAN 12 A 16 , PAN 12 A 18 , PAN 12 A 20 /PAN 16 A 16 and PAN 12 A 22 / PAN 18 A 16 adapted to salinities range of 2 x 10 4 -6 x 10 4 , 4 x 10 4 -8 x 10 4 , 6 x 10 4 -10 x 10 4 , 8 x 10 4 -12 x 10 4 and 10 x 10 4 -14 x 10 4 mg/L, respectively. At the optimal salinity, PAN x A n reduced the oil - water interfacial tension from 28.3 to 5.0 mN/m, dynamic contact angle from 130.0 degrees to 61.0 degrees , and heavy oil viscosity from 454.6 to 60.0 mPa & sdot; s with a viscosity reduction rate of 86.80 %. The synthesis of salt-resistant PAN x A n provides theoretical guidance and application value for enhancing the recovery efficiency of viscosity-reducer flooding in high-salinity heavy oil reservoirs.