Synthesis of a novel copolymer of block polyether macromonomer and diallyldimethylammonium chloride and its reverse demulsification performance

Produced fluid from polymer flooding is a complicated mixture of water/crude oil emulsion and crude oil/water emulsion. During the treatment of produced fluid, both demulsifier and reverse demulsifier are added into the oil water separator and the function of reverse demulsifier is to reduce the oil content in crude oil/water emulsion for relieving the load of oily wastewater treatment. In this paper, a novel reverse demulsifier was prepared by copolymerization of block polyether macromonomer (PEP-65) and diallyldimethylammonium chloride (DM). Its synthesis condition was optimized by using three indexes including product stability, the effect on dehydration of water/crude oil emulsion and oil removal of crude oil/water emulsion. The best copolymer of PEP-65 and DM (PDMP) had no negative effect on the dehydration of water/crude oil emulsion and had a more than three times of oil removal of crude oil/water emulsion than that of commercial reverse demulsifier. In addition, measurement of partition coefficient, interfacial tension, interfacial dilational modulus and dual polarization interferometry (DPI) test were carried out for investigating the reverse demulsification properties of PDMP. We found that PDMP had better interface activity, higher interface adsorption mass and lower interfacial dilational modulus than that of commercial reverse demulsifier.