Nanoparticles as foam stabilizer: Mechanism, control parameters and application in foam flooding for enhanced oil recovery

Abstract

Recently, numbers of studies have been conducted by using nanoparticles as novel foam stabilizer to enhance oil recovery (EOR). However, previous studies have not classified the nanoparticles into hydrophilic and hydrophobic/modified to explain the influence factors and mechanisms of different wettability nanoparticles stabilizing foam. Moreover, the mechanisms of nanoparticles stabilizing foam for EOR and the nanoparticles modification mechanism have not been discussed amply. In this review, the control parameters and the mechanisms of hydrophilic and hydrophobic nanoparticles on foam stability were discussed, and methods to evaluate foam stability were summarized. Meanwhile, the mechanisms of nanoparticles modification were introduced. Finally, the direction of the future studies and their application limitations were also pointed out. The main factors affected the application of nanoparticles stabilized foam included the types of nanoparticles, the modifiers for nanoparticles, the salinity, temperature and the concentration ratio between nanoparticles and surfactant. Both hydrophilic and hydrophobic nanoparticles could enhance the detachment energy, form network structure to stabilize foam. The synergistic effects between nanoparticles and surfactant and the existence state of nanoparticles on lamellae were different between hydrophilic and hydrophobic nanoparticles. NPs-foam could improve sweep efficiency in reservoir, emulsify the crude oil and flow into low permeability pores by fluid diversion. The foam stability measurement methods included viscosity measurement, core flooding experiment, foam thickness and size measurement, drop pressure measurement in dynamic state, and half-life time of foam in static state. It can be concluded that the synergistic effects influenced the hydrophobicity of nanoparticles, the moderate hydrophobic (contact angle ~90°) nanoparticles were the optimum for stabilizing foam. For modified nanoparticles, the modified routes should be refined to identify the optimal modifier and synthesis route. The control parameters of nanoparticles stabilized foam should be studied further, and the low-cost and environmentalfriendly nanoparticles could be the potential foam stabilizer.