Study on Oppositely Charged Polymer and Surfactant Mixture for EnhancingOil Production

摘要

Polymer-surfactant mixtures in aqueous solutions present unique rheological and interfacial propertiesthat promote their applications in chemical flooding.The objective of this study is to investigate theinteraction between anionic polyacrylamides and cationic surfactants in different temperature and salinityconditions and the potential application of the polymer-surfactant mixtures in carbonate reservoirs.Cationicsurfactants were selected owing to low adsorption on carbonate rocks.Compatibility tests of polymer-surfactant mixtures were conducted in brine with different salinities to study the interaction between anionicpolymers and cationic surfactants in the presence of salts.The effect of cationic surfactants on polymerviscosity at different temperatures was investigated.The compatibility of the mixtures of the cationic surfactants and the anionic polymers was significantlyimproved in high salinity injection water (with a total dissolved solid of 57,670 mg/L),compared with thecompatibility in deionized water.This is attributed to the shielding of polymer and surfactant charges bythe salts,which diminishes the electrostatic interaction between the chemicals.Rheological measurementsindicated that the polymer viscosity increased in the presence of the cationic surfactant CAS-S or CAS-B.This effect was decreased at 90?C.Other cationic surfactant CAS-1 or CAS-3 slightly increased the polymerviscosity at 25?C and significantly decreased the viscosity at 90?C.These observations can be explainedbased on the surfactants self-assembly.At room temperature,CAS-1 and CAS-3 form spherical micelleswhile CAS-S and CAS-B form wormlike micelles.The entanglement of the polymers with wormlikemicelles explains the observed viscosity enhancement.At 90?C,wormlike micelles became shorter whichweakens this viscosity enhancement effect.In conclusion,the charges and self-assembly structures ofsurfactants play an important role in the performance of polymer-surfactant mixtures that should be takeninto account in the design of optimal formulations.This work provides the insight of interaction betweenanionic polymers and cationic surfactants with different self-assembly structures for the potential applicationin improving oil production.