Demulsification law of polyether demulsifier for W/O crude oil emulsion containing hydrophobically modified polyacrylamide in water

Abstract

Hydrophobically modified polyacrylamide (HMPAM) is one of the commonly used polymers for polymer flooding. Because it is water soluble, there are many reports on the impact of HMPAM on the stability and treatment of produced water (it is O/W emulsion), but few reports on its influence on the demulsification of W/O crude oil emulsion. In this paper, firstly, three types of HMPAM containing cationic, anionic, and nonionic hydrophobic monomers (abbreviated as P(AM-AANa-N)Cn, P(AM-AANA-S)Cn, and P(AM-AANA-O)Cn, respectively) were synthesized; Then, demulsification experiments and interface behavior experiments (including dynamic interfacial tension, dilatational rheology and dynamic coalescence time measurement) were conducted to investigate the influence of HMPAM on the demulsification performance of a W/O heavy oil emulsion demulsifier D1. The demulsification results showed that HMPAM reduced the dehydration speed of D1, the type of hydrophobic monomer and the length of hydrophobic chain in HMPAM can affect the final water separated of D1. P(AM-AANa-S)Cn, P(AM-AANa-N)Cn with long hydrophobic chain, and P(AM-AANa-O)Cn with short hydrophobic chains had the negative effect on performance of D1. The results of dynamic interfacial tension experiments indirectly showed that HMPAM had the influence on the D1′s conformation and speed of rearrangement at the W/O interface during the water droplet coalescence process, thereby affecting the reduction of elastic modulus (G′) of W/O interface and the coalescence rate of water droplets. When there was HMPAM in water, the coalescence time of water droplets increased, resulting in the decrease of dehydration rate. At the meantime, HMPAM had an impact on the lg(G1′/Gdemulsifier′)/lgG1′, thereby affecting the final water separated of D1.