Formulation of Spontaneous In Situ Emulsification Using Sodium Lauryl Sulfate Grafted Nanopyroxene for Enhanced Heavy Oil Recovery in Sandstone Reservoirs

Heavy oil recovery presents enormouschallenges during production,especially in thin reservoirs, where thermal recovery is inefficient.To overcome these challenges, chemically heavy oil recovery methodsare extensively used. Herein, we formulated a new class of stablenanofluids from surfactant-coated nanomaterials to improve the microscopicdisplacement efficiency and recover a medium-viscosity heavy oil.Our nanofluid consists of an anionic surfactant, sodium lauryl sulfate(SLS), grafted on the surface of nanopyroxene to be used as an emulsifierthat can instinctively emulsify heavy oil by minimal agitation designedfor heavy oil enhanced oil recovery (EOR). Optimum screening of thedesigned emulsions was performed by interfacial tension (IFT) measurementsand emulsion stability testing. The droplet size distribution andmicroscopic morphology of the created emulsions were observed by anoptical microscope, dynamic light scattering testing, and magneticresonance imaging. Afterward, the EOR mechanism of emulsions was investigatedby core flooding studies with the aid of NMR and/or computer tomography(CT). The characterization results showed that our synthesized nanoparticleswere successfully grafted with the anionic surfactant. Then, the graftedsurfactant-nanopyroxene resulted in an ultralow IFT and hence stableoil/water emulsions (E1). Moreover, the synergy effect between nanopyroxeneand SLS was further enhanced by adding 0.2 wt % NaOH, which greatlyimproved the capability of emulsification (E2). As a result, the designedformulation E1 and/or E2 emulsified heavy crude oil by applying aminimum force. Notably, crude oil in small pores was more effectivelydisplaced by the E2 system than E1. Consequently, E2 exhibited a higherEOR efficiency than the E1, SLS, and SLS+NaOH systems. E2 recovered(34.4%) compared to E1 (18.5%), SLS (16.2%), and SLS+NaOH (1.2%).This work revealed the EOR mechanism of the surfactant grafted nanoparticlesystems from the level of the pore structure using NMR and CT scan.

Automated summary

Researchers have developed a stable nanofluid made from surfactant-coated nanomaterials to improve the displacement efficiency and recovery of heavy oil. It is found that this nanofluid can emulsify heavy oil with minimal agitation. By adding sodium hydroxide, the emulsification capability of the nanofluid is further enhanced. Experimental results show that this new nanofluid has a higher efficiency in enhancing oil recovery compared to traditional methods.