Performance Evaluation of Novel Polymers for CO2 Foam Enhanced Oil Recovery

Abstract

The oil recovery from foam flooding mainly depends on the stability of the foam flow in porous media. At severe reservoir conditions, CO2 foam becomes unstable due to water drainage and gas diffusion through the lamella. The petroleum industry is using several foaming agents to produce and stabilize the CO2 foams. These are mainly water-soluble surfactants, CO2 soluble surfactants, nanoparticles, and water-soluble polymers. Addition of a water-soluble polymer in a conventional foam can increase foam stability, viscosity, and oil tolerance. Most of the previous studies utilized partially hydrolyzed polyacrylamide (HPAM) for CO2 foam stabilization. However, the data on CO2 foam stabilization using other polymers is limited. In this work, CO2 foam stability was assessed using several novel polymers. The foam was generated using alpha olefin sulfonate (AOS) surfactant at a constant concentration. These polymers were mainly acrylamide-based sulfonated polymers that contain thermally stable monomers that increase salt tolerance and thermal stability. The foamability, foam stability, foam diameter and bubble count per unit area of different foaming systems were measured using a dynamic foam analyzer. The result showed that the addition of polymers enhanced foam stability and reduced liquid drainage. Novel sulfonated polymers showed much better performance compared to the conventional HPAM polymer. Reduction in liquid drainage rate was much higher for sulfonated polymers compared to the conventional HPAM due to viscosity of the foaming solutions. For HPAM, the viscosity of the solution reduced at high temperature in presence of salts whereas sulfonated polymers maintained a high viscosity in the presence of salts that resulted in less liquid drainage and enhanced foam stability. The foam stability was also assessed using foam structure analysis. This is the first systematic study on the application of sulfonated polymer with varying molecular weight and structure for CO2 foam stabilization. This study helps in understanding the role of polymer molecular structure, molecular weight, and degree of hydrolysis on foam stabilization for CO2 -EOR.

A Review on Foam Stabilizers for Enhanced Oil Recovery

“…There is usually an optimum concentration that gives the best results for producing the most stable foam. After reaching that particular concentration, further addition of polymer will start to destabilize the foam . The foam stability of surfactant–polymer-NPs systems usually increases by increasing the concentration of the polymer due to steric repulsion but up to a specific concentration.…”

“…However, the stability of polymer enhanced foam is also impacted by the molecular weight of the polymer in play. Majeed et al 101 did a series of experiments on eight polymers of different molecular weights and different DOH. They found that the foam stability decreases with the higher molecular weight; i.e., the polymer with the lowest molecular weight gives rise to the best foam stability.…”