Foams Stabilized By Nanoparticles And Amphiphiles For Enhanced Oil Recovery

Foams have been widely used in oilfields for effective profile control and displacement.However,foams stabilized by surfactants lack long-term stability,especially in an oil reservoir.Here,we have studied the in situ modification of positively charged AlOOH nanoparticles via the adsorption of the anionic surfactant sodium dodecyl sulfate(SDS)and the characterization of foam stabilized by AlOOH nanoparticles in synergy with SDS under different conditions.The most stable foam was obtained with an SDS/AlOOH concentration ratio of 5:1;further increases of the SDS concentration led to a decrease and subsequent increase in foam stability.The relationships between the zeta potential,three-phase contact angle,nanoparticle aggregate size,and foam stability were comprehensively analyzed,revealing that foam stability was affected by all of these factors.We concluded that nanoparticles with partial hydrophobicity,a positive or slightly negative charge,and small aggregate size can be adsorbed tightly to foam surfaces and form compact networks in the foam's film,thereby resulting in a stable foam.Sandpack flooding experiments showed that the SDS/AlOOH foam can increase and maintain the differential pressure more effectively than the SDS foam.Meanwhile,foam stabilized by hydrophobic modified alumina nanoparticles was systematically studied.Sodium cumenesulfonate(SC)was used to modify nanoparticles and generate foam.A competitive effect between nanoparticles and SC was found.Specifically,foam stability increased with SC concentration at lower SC concentration range.Foam with high stability and relatively high foamability was obtained at an SC concentration of 20 mM,and then,foam stability sharply decreased because of the competitive effect.The presence of an electrolyte slowed down the adsorption of SC at the air-water interface by forming an ion pair between the headgroup of SC and the cation,which influences foamability and stability.Meanwhile,the electrolyte also caused detachment of particles from foam due to the decrease of hydrophobicity as a result of the decreased SC adsorption.Sandpack flooding experiments showed that the oil recovery rate increased with SC concentration because of the enhanced foamability and stability,leading to a higher displacement efficiency and water flush resistance.