# Demulsification of Fluids Produced from Polymer Flooding in Oilfields: A Molecular Dynamics Simulation Study

## TL;DR

This study uses simulations and experiments to compare two demulsifiers for separating oil from water in oilfield fluids containing polymers.

## Contribution

The novel contribution is combining molecular dynamics simulations with experimental validation to understand and compare demulsifier performance in polymer-containing oil-in-water emulsions.

## Key findings

- Demulsifier Y outperformed Demulsifier X in dehydration rates with lower dosages and shorter settling times.
- Molecular simulations showed demulsifiers displaced HPAM molecules at the oil-water interface, increasing interfacial tension.
- Experimental tests confirmed the effectiveness of the simulation results under optimal conditions.

## Abstract

In this study, a combined approach of molecular dynamics (MD) simulations and experimental bottle tests was employed to systematically investigate the demulsification performance and underlying mechanisms of two distinct demulsifiers—Demulsifier X (SP/BP series and alcohol-initiated polyethers) and Demulsifier Y (AP/AE series and amine-initiated polyethers)—targeting polymer-containing oil-in-water (O/W) emulsions derived from heavy oil polymer flooding. Molecular models for heavy oil, saline water, partially hydrolyzed polyacrylamide (HPAM), and demulsifiers were constructed using BIOVIA Materials Studio software. Their dynamic behaviors at the oil–water interface were simulated within three distinct saline systems containing NaCl, CaCl2, and MgCl2, respectively. Simulation results indicated that the demulsifiers effectively displaced interfacial HPAM molecules, increased interfacial tension, and reduced interfacial interaction energy. Experimental bottle tests, evaluating the effects of settling time, temperature, and concentration on dehydration rates and oil content, confirmed that Demulsifier Y outperformed Demulsifier X. Specifically, Demulsifier Y achieved superior dehydration rates with lower dosages, shorter settling times, and reduced temperature requirements under optimal conditions. This work provides both microscopic mechanistic insights and macroscopic experimental validation for the screening and application of high-efficiency demulsifiers.