Oil is one of the most required and used forms of energy on a global scale. Two-dimensional nanomaterials have evolved as possible options for enhancing oil recovery technology throughout the last decade. This article highlights the latest advancements in various 2D nanomaterials utilized to enhance oil recovery technology.
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Enhanced Oil Recovery Technologies
Enhanced oil recovery (EOR) involves artificially stimulating a resource to recover additional oil. EOR is generally used when secondary recovery procedures are no longer able to maintain the necessary production levels. In addition, EOR is employed when the remaining oil in the reservoir is confined in inaccessible (low-permeability) portions with poor oil-water interaction or irregular faults.
EOR utilizes heat energy, soluble gases, or chemical substances to increase oil recovery. It creates a sophisticated method for modifying intermolecular attraction, facilitating the extraction of residual oil trapped in rock surfaces.
Limitations of Current Enhanced Oil Recovery Technologies
A large proportion of oil is left untreated from traditional EOR procedures such as surfactant flooding or polymer flooding. This behavior is related to issues such as agglomeration, leading to pore throat constriction, polymer breakdown, and polymer adhesion onto the surface of the reservoirs. Problems like these make the EOR method exceedingly expensive. It is therefore essential to develop a more effective EOR approach.
Nanomaterials as Potential Candidates for EOR technology
Nanomaterials have been offered as a possible option for the EOR technique because of their ability to permeate the pore throat and significantly modify reservoir characteristics, enhancing oil recovery. Nanofluid flooding or nano flooding is a revolutionary chemical EOR technique involving the injection of nanoparticles embedded in a heat transfer fluid into an oil reservoir. It can collect around fifty percent of in-place oil reserves that cannot be recovered using the standard EOR technique.
In addition to better oil recovery, nanofluid offers a more steady dynamic pressure variation as well as a robust capacity to break through with minimal impact.
Nanofluids have increased thermos-physical characteristics, such as heat capacity, temperature gradient, fluidity, and thermal diffusivity, compared to base liquids, such as oil or water.
2D Nanomaterials for EOR
In literature, nanomaterials can be categorized into groups based on their structural features, i.e., zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) nanomaterials. The specific surface areas of 2D nanomaterials are often greater than 0D and 1D nanoparticles (NPs) if the same volume (V) is retained. This makes 2D nanomaterial more reactive.
2D nanomaterials exhibit greater surface area, more surface-active sites, better electron affinity, and outstanding charge transport interface than 0D and 1D nanomaterials as their dimensionality increases. Based on these benefits, the usage of 2D nanomaterials is appropriate for nano-fluids enhanced oil recovery.
In addition, amphiphilic 2D nanomaterials, also known as nanosheets, have received interest due to their unique properties. Nanosheets exhibit more interfacial properties than other configurations such as rods, spheres, or wires. Therefore, they have a stronger capacity to decrease interfacial tension, stabilize dispersions, and modify interfacial characteristics.
2D nanomaterials have a highly elastic surface that minimizes reservoir clogging complications. Higher interfacial reactivity than other geometries also led to more adsorption energy from the interface to the bulk phase. This indicates that nanosheets can increase dispersion and emulsion stability once deposited to the interface, enhancing oil recovery.
Common 2D Nanomaterials Used for EOR
Graphene and its derivatives, including graphene oxide (GO), reduced graphene oxide (rGO), and graphene quantum dots, are the most prevalent 2D nanomaterials for EOR.
Graphene is superior to other materials in several ways. For example, graphene has high thermal conductivity and resilience and a larger surface area ratio to volume, enhancing heat transferability. Consequently, graphene is an ideal contender for nanofluid design.
GO is the oxidized state of graphene. The preponderance of the sp2 bonds in graphene oxide nanosheets (GON) comes from the oxygen functional group. It increases its stability in the EOR process. Compounds with very few oxygens functional groups can end up causing pores to become clogged. Additionally, GON includes several negatively charged functional groups, which reduce sedimentation in porous environments and increase the efficacy of nanofluids.
MoS2 and bifunctional boehmite are other ultrathin 2D nanomaterials used in the EOR industry. MoS2 is one of the most investigated Transition Metal Dichalcogenides (TMD) compounds. Its layers are piled due to van der Waals forces. Each TMD monolayer is composed of three atomic layers, with a layer of metal oxides sandwiched between chalcogen layers.
Recent Research in 2D Nanomaterials for EOR
Recent research by Sun et al. on few-layer graphene nanofluids polymeric solutions revealed a 25% increase in thermal conductivity at a modest nanofluid concentration of 0.055%. Amiri et al. also discovered that the addition of dispersant to severely crushed few-layer graphene/water increased heat conductivity by 42.5%. Amiri et al. later discovered an increase in thermal conductivity of more than 25 percent. They tested monolayer graphene/water at various temperatures and concentrations. The nanofluid with the greatest increase in thermal conductivity was composed of 0.01 percent weight nanofluid.
Radnia et al. investigated the adsorption characteristics of GO onto sandstone, which is a crucial feature for the material's use in chemical EOR procedures. They discovered that the concentration of GO has a greater impact on adsorption than acidity and salinity. Significant effects of pH on GO adsorption are seen at high GO quantities and low salinity.
Bao et al. developed a very stable nanofluid and good thermal conductivity in a brand-new 2D nanomaterial called MXene. In 30 days, they discovered that MXene/ethylene glycol nanofluid increases heat conductivity by 64.9% without any sedimentation. This amazing quality makes the nanofluid a great choice for enhancing oil recovery. In a similar manner, Das et al. discovered that the addition of 1,3-Dimethylimidazolium dimethyl-phosphate ionic liquid to water/MXene nanofluid enhanced the stability and optical quality with a maximum thermal efficiency of 13.95%.
Raj et al. manufactured amphiphilic MoS2 nanosheets by changing the permeability of the core at very small concentrations (0.005%). The produced MoS2 nanosheets displayed amphiphilic properties following modulation with an alkylamine chain. They designed an alternate modifying particle comparable to surfactant to address high cost, probable formation defects, and chemical waste. MoS2 was synthesized via a one-step hydrothermal technique, which is suited for largescale manufacturing and modified with octadecyl amine (ODA).
The modified MoS2 nanosheet shifted the wettability from oil-wet to water-wet at a lower concentration (0.005 wt.%) than traditional surfactants. Oil recovery of 21.8% was found from low permeability (25 mD) cores.
Conclusion
This study discussed the capability of 2D nanomaterials in the area of EOR. Several 2D nanomaterials, including graphene and its compounds, MoS2, and functionalized boehmite nanosheets, have been evaluated as EOR agents.
Due to their huge surface area, high surface-to-volume ratio, and abundance of atoms on the surface, these 2D nanomaterials exhibit exceptional electrical and thermal conductivity, wetting, and mechanical properties. These extraordinary qualities enable its usage in a variety of applications of EOR. Although few 2D nanomaterials have been experimentally evaluated as EOR agents, it is anticipated that their use will increase in the future.
References and Further Reading
Natalya, S. A., Kadja, G. T., Azhari, N. J., Khalil, M., & Fajar, A. T. (2022). Two-dimensional (2D) Nanomaterials for Enhanced Oil Recovery (EOR): A Review. FlatChem, 100383. https://doi.org/10.1016/j.flatc.2022.100383
Sun, Z., Pöller, S., Huang, X., Guschin, D., Taetz, C., Ebbinghaus, P., & Muhler, M. (2013). High-yield exfoliation of graphite in acrylate polymers: A stable few-layer graphene nanofluid with enhanced thermal conductivity. Carbon, 64, 288-294. doi.org/10.1016/j.carbon.2013.07.063
Amiri, A., Ahmadi, G., Shanbedi, M., Etemadi, M., Zubir, M. N. M., Chew, B. T., & Kazi, S. N. (2016). Heat transfer enhancement of water-based highly crumpled few-layer graphene nanofluids. RSC advances, 6(107), 105508-105527. doi.org/10.1039/C6RA22365F
Radnia, H., Rashidi, A., Nazar, A. R. S., Eskandari, M. M., & Jalilian, M. (2018). A novel nanofluid based on sulfonated graphene for enhanced oil recovery. Journal of Molecular Liquids, 271, 795-806. https://doi.org/10.1016/j.molliq.2018.09.070
Bao, Z., Bing, N., Zhu, X., Xie, H., & Yu, W. (2021). Ti3C2Tx MXene contained nanofluids with high thermal conductivity, super colloidal stability and low viscosity. Chemical Engineering Journal, 406, 126390. doi.org/10.1016/j.cej.2020.126390
Das, L., Habib, K., Saidur, R., Aslfattahi, N., Yahya, S. M., & Rubbi, F. (2020). Improved thermophysical properties and energy efficiency of aqueous ionic liquid/MXene nanofluid in a hybrid PV/T solar system. Nanomaterials, 10(7), 1372. https://doi.org/10.3390/nano10071372
Raj, I., Qu, M., Xiao, L., Hou, J., Li, Y., Liang, T., & Zhao, M. (2019). Ultralow concentration of molybdenum disulfide nanosheets for enhanced oil recovery. Fuel, 251, 514-522. https://doi.org/10.1016/J.FUEL.2019.04.078
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