Enhanced Oil Recovery (EOR) is defined by different techniques used in the petroleum industry to improve the extraction of hydrocarbons from subsurface reservoirs. Conventional primary and secondary recovery methods extract only 20 to 40% of the original oil content. In that context, EOR aims to recover a substantial portion of the remaining oil by altering its physical and chemical conditions within the reservoir [1].
In brief, EOR methods involve the injection of specialized fluids, like gases (e.g., supercritical CO₂), surfactant solutions, polymer solutions, or combinations, into the reservoir to improve the displacement and mobility of trapped oil. These methods are particularly needed in challenging rock conformity, such as tight reservoirs and shales, where natural flow is limited.
This section is not an exhaustive treatment of petroleum engineering but rather an introduction to highlight the concepts at the heart of microfluidic science and their importance for EOR.
Oil recovery process usually happens in very defined steps. Before any recovery of hydrocarbons begins, a geological survey is conducted to identify promising subsurface formations that contain oil and/or gas. Once a reservoir is located, vertical and horizontal drilling operations are carried out to access the oil-bearing rock layers [1].
However, even after these stages, 60 to 80% of the oil often remains trapped in the porous rock matrix due to complex interactions involving capillary forces, wettability, and pore geometry. This inefficiency is particularly noticeable in tight formations, where low permeability severely limits fluid movement.
This is where Enhanced Oil Recovery (EOR) comes into play. EOR aims at modifying the physicochemical environment of the reservoir to displace and mobilize trapped oil. These techniques involve the injection, or “flooding“, of custom-engineered fluids into the reservoir, like:
Despite the complexity of these formulations, their design is often based on empirical knowledge rather than fundamental chemistry, largely because subsurface conditions like being confined, high-pressure, high-temperature, and saline are difficult to replicate and study. This challenge can be overcome with microfluidics, which provides controlled platforms to simulate and observe multiphase fluid behavior in porous geometries.
Also briefly mentioned in our last report from the Annual European Rheology Conference, rheology and microfluidics are closely related. Rheology is the study of the deformation and flow of materials, both solids and liquids. In the context of EOR, the strategies’ performances are highly sensitive to fluid-rock interactions at the pore scale, where phenomena such as capillary pressure, wettability, and fluid rheology dictate the efficiency of oil displacement [2-4].
Microfluidic technologies are capable of mimicking pore-scale geometries and offering real-time visualization suited to investigate these processes. Below are some key fluid mechanics parameters commonly explored in microfluidic EOR research:
Wettability refers to the ability of a fluid to spread over or adhere to a solid surface by displacing a gaseous phase or another liquid phase, not miscible with the wetting fluid. It is a central parameter in determining oil recovery efficiency. Reservoir rocks may range from water-wet to oil-wet, with many systems exhibiting mixed wettability. Surfactants or brine formulations are used to shift wettability towards more favorable conditions, typically water-wet, to enhance displacement. Microfluidic models allow direct visualization of these transitions and their effect on flow pathways.
Interfacial tension is the force required to break the surface between two immiscible liquids. It basically controls the capillary forces that trap oil droplets in pore constrictions. Surfactants are commonly introduced to reduce IFT, facilitating the mobilization of trapped oil. Microfluidic platforms have demonstrated how even modest reductions in IFT can significantly alter displacement efficiency and residual oil saturation.
Capillary forces arise from surface tension and the geometry of the pore space. Capillary pressure (the difference in pressure across the interface of two immiscible fluids) is a determining factor in fluid displacement and entrapment.
Injected fluids often exhibit non-Newtonian behavior. Shear-thinning fluids (e.g., polymer solutions) reduce their viscosity at higher shear rates, enabling better penetration through narrow pores while maintaining sufficient viscosity to displace oil. Conversely, shear-thickening fluids increase viscosity under shear, which can help block high-permeability channels and redirect flow to unswept zones. Understanding this behavior is crucial to designing fluids tailored to the specific permeability profiles of a reservoir.
The permeability of a porous media (like a rock) is a measure of the ability of the fluid to flow through the rock, and depends on the pore volume of the reservoir. Natural reservoirs exhibit heterogeneity in permeability, which can lead to preferential flow paths and inefficient sweep. Microfluidics enables precise modeling of permeability contrasts and the visualization of flow redistribution strategies.
When a less viscous fluid displaces a more viscous one, like water displacing oil, instabilities at the fluid interface can result in viscous fingering, a phenomenon that bypasses much of the oil and reduces recovery efficiency. The geometry and flow rate in microfluidic devices can be controlled to investigate and mitigate these instabilities.
The controlled environment of microfluidic systems places it as the best method for studying pore-scale fluid dynamics and EOR strategies. The following sections will further explore how microfluidic platforms are being used to screen EOR formulations, visualize displacement processes, and model real reservoir conditions.
To replicate realistic reservoir conditions in microfluidic experiments, pressurized environments must be precisely controlled. This is where high-performance pressure controllers, such as those developed by Elveflow, become essential. These instruments provide unmatched pressure accuracy and stability, making them ideal for simulating the dynamic injection profiles encountered in Enhanced Oil Recovery. By ensuring reproducibility and fine-tuned control, Elveflow systems allow researchers to push EOR studies closer to real-world field conditions.
Water flooding is one of the standard techniques in oil recovery because of its simplicity and cost-effectiveness. However, the efficacy of water flooding can be improved through optimization of fluid properties such as salinity, chemical composition, wettability modification, and rheological behavior. Thanks to microfluidics, those parameters can be studied in a confined and controlled environment, with clear visibility of the results.
Low salinity water flooding (LSWF) is one of the parameters that scientists and industrials are studying for EOR. Indeed, LSWF is an attractive EOR method both environmentally and economically. Microfluidic studies demonstrate that lowering the ionic strength of injected brine can lead to altered wettability and increased oil mobilization, particularly in sandstone formations.
In particular, divalent cations like Ca²⁺ can influence oil–rock–brine interactions. For instance, studies using borosilicate glass micromodels demonstrated that oil recovery was reduced when Ca²⁺ was present, likely due to increased adhesion between the oil phase and pore surfaces. Conversely, LS brines with only monovalent ions (Na⁺) performed better in water-wet systems [5].
Microfluidic platforms are ideal for understanding these effects, allowing for controlled variation of brine chemistry while directly visualizing displacement fronts.
Wettability is a critical factor controlling capillary forces and displacement efficiency. Natural reservoirs exhibit a range of wettability states, from water-wet to oil-wet, with mixed-wet systems being most common due to the historical saturation pattern and adsorption of crude oil onto pore walls [4].
Microfluidic studies have allowed direct quantification of contact angle changes and observation of fluid displacement in both hydrophilic and hydrophobic pore networks. In hydrophobic systems, a persistent film of oil tends to line the pore walls, leading to reduced oil recovery. By contrast, altering wettability by injecting brine or surfactants increases water wettability and facilitates oil release.
Surfactants play a dual role in EOR: they reduce interfacial tension (IFT) and modify wettability. Lowering IFT helps overcome capillary forces that trap oil in pore and throats, increasing the capillary number (Ca) and thereby enhancing recovery.
Microfluidic observations have shown that surfactant-flooded systems maintain continuous oil displacement without reaching a steady-state recovery plateau, unlike brine-only floods. In particular, the formation of microemulsions, especially bicontinuous ones, has been identified as a dominant mechanism in certain cases, enabling higher sweep efficiency.
Moreover, combining surfactants with low salinity brine can synergistically enhance recovery by promoting both wettability alteration and IFT reduction, while also minimizing surfactant retention and precipitation [6].
Polymers are often added to increase the viscosity of the displacing phase, thereby improving mobility control and minimizing viscous fingering. In microfluidic models, polymer-enhanced floods display more stable fronts, better sweep efficiency, and improved displacement in heterogeneous pore structures.
Polymers with shear-thinning behavior are particularly useful as they provide low viscosity during injection (easy flow through tight zones) and higher viscosity in wide pores (better sweep). When combined with surfactants, they contribute to both mobility control and chemical interaction, forming the basis of Chemical EOR (CEOR).
EOR Strategy
Main Mechanism
Effectiveness in Microfluidics
Visual Observations
Limitations
Low Salinity Brine (LSWF)
Alters wettability, improves displacement
Higher recovery in water-wet networks; sensitive to ion type
Improved front stability, more uniform displacement
Mechanism not fully understood; variable performance
Surfactant Flooding
Reduces interfacial tension, modifies wettability
Continuous oil displacement, effective even in oil-wet systems
Formation of emulsions, sustained recovery
Surfactant loss via adsorption, cost, environmental impact
Polymer Flooding
Controls mobility, reduces viscous fingering
Improved sweep efficiency, better stability of displacement front
More stable flood front, higher displacement uniformity
Shear degradation, sensitivity to salinity and temperature
Another strategy studied for EOR consists in the addition of gas to the flooded phase. Once again, microfluidic platforms are effective for visualizing and analyzing the behavior of gas and foam injection strategies.
Gas injection, particularly using supercritical CO₂ and N₂, is another effective recovery method. These gases can mobilize residual oil by reducing interfacial tension and swelling the oil phase. In the study by Sun et al. [7], a glass microfluidic chip was used to simulate huff-and-puff cycles with both CO₂ and N₂ under controlled conditions and the following results were obtained:
These results highlight the importance of gas type, phase behavior, and cyclic design in optimizing gas-based EOR approaches. The direct visualization enabled by microfluidics provides critical insight into how supercritical gases interact with trapped oil at the pore level.
Foam injection is an established method to reduce gas mobility, block high-permeability zones, and divert displacing fluids into previously unswept regions. In the study by Quennouz et al. [8], PDMS-based microfluidic devices were used to model foam flow at the pore scale, investigating both foam generation and diversion capabilities. Two foam generation strategies were examined:
To assess flow diversion, a “comb-shaped dual-permeability” model was used. Foam preferentially flowed into low-permeability zones after plugging high-permeability paths, demonstrating its effectiveness in redirecting flow and improving displacement uniformity. Foam injection for EOR is still a subject of discussion among researchers regarding its formulation and mode of injection. This is mainly because it has often been studied under ambient conditions, whereas reservoir conditions can drastically affect foam behavior. Additionally, due to Oswald ripening (over time gas bubbles merging) generating stable foams remains difficult. Foam formulations could greatly benefit from the addition of nanoparticles, polymers, or surfactants to improve their stability and performance under realistic reservoir conditions [9].
Heterogeneous liquids, including deformable microgels, engineered nanoparticles, and microbial cultures, are a versatile toolbox for EOR. These materials can modify in situ fluid behavior, alter wettability, and improve sweep efficiency through a combination of mechanical, interfacial, and biochemical effects. Microfluidic devices allow direct observation of their dynamics within controlled porous environments, making them valuable tools for screening and mechanism studies.
Microgels are soft, crosslinked polymer particles that swell in water and deform to navigate complex pore geometries. Their primary EOR function is conformance control, meaning blocking high-permeability zones and redirecting flow into lower-permeability, oil-rich areas.
Compared to polymer flooding with hydrolyzed polyacrilamides (HPAM) for example, microgel suspension induces significant fluctuation of pressure thanks to the nonuniform concentration distribution of the particles. In Lei et. al study [10], microgels particle suspension (MGPS) improved the oil recovery by almost 50% compared to only 17% with polymer suspension.
Hydrophilic silica-based nanoparticles are studied in the context of EOR because of their capacity to alter interfacial properties, stabilize emulsions, and modify wettability [6].
Furthermore, their small size allows for deep penetration into porous networks without significant permeability reduction.
Microbial Enhanced Oil Recovery (MEOR) is one of the innovative methods using bacteria and their metabolic products (biosurfactants, gases, and biopolymers) to improve oil mobilization.
Even though more research is needed to fully understand their dynamics and risks, these live systems offer a biologically sustainable alternative for EOR.
If you are interested in more content regarding how microorganisms are studied with microfluidics, we invite you to have a look at our latest research summary regarding pathogen invasion on gut-on-chip models.
Microfluidic chips are essential tools in EOR research, enabling direct visualization and quantitative analysis of fluid behavior at the pore scale. The materials used to fabricate these chips (glass, PMMA, and PDMS) each offer specific advantages and limitations, particularly in the context of chemical resistance, fabrication complexity, and relevance to reservoir-like conditions.
Glass has been a gold standard for EOR-related microfluidics due to its high chemical stability, transparency, and thermal resistance [4,6]. It is especially well-suited for simulating harsh subsurface environments such as high salinity or temperature, and it enables detailed visualization of displacement mechanisms like droplet coalescence, emulsification, and fingering. For example, Xu et al. [6] fabricated dual-permeability glass chips via hydrofluoric acid etching and thermal bonding to investigate nanoparticle-stabilized emulsions in fractured reservoirs.
If you are interested in alternative material for microfluidic chip prototyping, we’ve recently interviewed Dr Hugo Salmon from Université Paris Cité about his research with thermoplastic chips.
PMMA (polymethyl methacrylate), or acrylic, is a low-cost, optically clear thermoplastic that offers an easier fabrication route using laser cutting or CNC micromilling. While not as chemically robust as glass, PMMA is ideal for prototyping and educational setups. The study by Mahani et al. demonstrated the use of PMMA-based micromodels to visualize aqueous-phase displacements, showing good flow stability under moderate pressure and temperature conditions. Although PMMA is less resistant to organic solvents and high salinity, its affordability and ease of customization make it valuable for screening experiments or testing flow pattern hypotheses [13].
PDMS (polydimethylsiloxane) is a silicone-based elastomer favored for its ease of replication, flexibility, and excellent optical properties. Soft lithography enables the rapid fabrication of microchannel networks that can mimic porous structures. However, PDMS is less chemically stable compared to glass or PMMA, it swells in contact with many organic solvents and absorbs surfactants, which may bias results in EOR scenarios. Despite these limitations, PDMS is still used to study aqueous-phase displacement and observe droplet formation and mobility patterns [2].
Material
Advantages
Typical Applications in EOR
Glass
High chemical and thermal resistance; excellent optical clarity; ideal for harsh subsurface simulation
Expensive fabrication; brittle; complex processing (e.g., hydrofluoric acid etching)
Nanoparticle-stabilized emulsions; dual-permeability modeling; capillary-driven displacement
PMMA
Low cost; easy fabrication (laser cutting/CNC); good optical clarity; suitable for prototyping
Lower chemical resistance (e.g., to solvents, salinity); limited use under extreme conditions
Aqueous-phase displacement visualization; screening experiments; educational use
PDMS
Flexible; rapid prototyping via soft lithography; good optical properties; mimics porous media
Swells in organic solvents; absorbs surfactants; less chemically stable
Droplet formation and transport; aqueous-phase flow studies
Microfluidics has significantly advanced our understanding of Enhanced Oil Recovery (EOR) by enabling direct, pore-scale visualization of complex fluid interactions. From water flooding optimization to gas injection and nanoparticle-based methods, microfluidic models can provide valuable insights into the mechanisms that govern oil mobilization.
However, most current studies rely on 2D micromodels, which do not fully capture the three–dimensional complexity of real reservoir rocks. As a result, flow behaviors such as vertical connectivity, gravity–driven segregation, and realistic fingering patterns remain underexplored.
To overcome these limitations, the development of 3D microfluidic models is essential. Coupled with advanced imaging and data analysis, these models could bridge the gap between lab-scale experiments and field applications, paving the way for more predictive and efficient EOR strategies. In particular, when working with heterogeneous liquids, researchers require platforms capable of precise control over complex fluid behavior.
At Elveflow, we provide flexible solutions to support such research efforts from our PDMS Chip Station, ideal for fast and flexible prototyping of porous media micromodels and the Easy Droplet Generation Pack designed for controlled studies of multiphase flow, emulsions, and interfacial dynamics. Together, these systems empower researchers to replicate and visualize pore-scale processes with clarity, bringing microfluidic EOR research closer to real-world conditions.
[1] V. A. Lifton, “Microfluidics: An enabling screening technology for enhanced oil recovery (EOR),” Lab on a Chip, vol. 16, pp. 1777–1796, Jan. 2016, doi: 10.1039/c6lc00318d.
[2] M. A. Nilsson et al., “Effect of fluid rheology on enhanced oil recovery in a microfluidic sandstone device,” Journal of Non-Newtonian Fluid Mechanics, vol. 202, pp. 112–119, Dec. 2013, doi: 10.1016/j.jnnfm.2013.09.011.
[3] M. Fani, P. Pourafshary, P. Mostaghimi, and N. Mosavat, “Application of microfluidics in chemical enhanced oil recovery: A review,” Fuel, vol. 315, p. 123225, May 2022, doi: 10.1016/j.fuel.2022.123225.
[4] M. Saadat, J. Yang, M. Dudek, G. Øye, and P. A. Tsai, “Microfluidic investigation of enhanced oil recovery: The effect of aqueous floods and network wettability,” Journal of Petroleum Science and Engineering, vol. 203, p. 108647, Aug. 2021, doi: 10.1016/j.petrol.2021.108647.
[5] M. Saadat, P. A. Tsai, T.-H. Ho, G. Øye, and M. Dudek, “Development of a microfluidic method to study enhanced oil recovery by low salinity water flooding,” ACS Omega, vol. 5, pp. 17521–17530, Jul. 2020, doi: 10.1021/acsomega.0c02005.
[6] K. Xu, P. Zhu, T. Colon, C. Huh, and M. Balhoff, “A microfluidic investigation of the synergistic effect of nanoparticles and surfactants in macro-emulsion-based enhanced oil recovery,” SPE Journal, vol. 22, pp. 459–469, Sep. 2016, doi: 10.2118/179691-pa.
[7] P. Nguyen, J. W. Carey, H. S. Viswanathan, and M. Porter, “Effectiveness of supercritical-CO2 and N2 huff-and-puff methods of enhanced oil recovery in shale fracture networks using microfluidic experiments,” Applied Energy, vol. 230, pp. 160–174, Nov. 2018, doi: 10.1016/j.apenergy.2018.08.098.N.
[8] Quennouz, M. Ryba, J.-F. Argillier, B. Herzhaft, Y. Peysson, and N. Pannacci, “Microfluidic study of foams flow for enhanced oil recovery (EOR),” Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles, vol. 69, pp. 457–466, May 2014, doi: 10.2516/ogst/2014017.
[9] A. Bell, A. Ivanova and A. Cheremisin, “Foam EOR as an Optimization Technique for Gas EOR: A Comprehensive Review of Laboratory and Field Implementations” Energies, January 2023, doi: https://doi.org/10.3390/en16020972
[10] W. Lei, T. Liu, C. Xie, H. Yang, T. Wu, and M. Wang, “Enhanced oil recovery mechanism and recovery performance of micro‐gel particle suspensions by microfluidic experiments,” Energy Science & Engineering, vol. 8, pp. 986–998, Dec. 2019, doi: 10.1002/ese3.563.
[11] K. Xu, D. Agrawal, and Q. Darugar, “Hydrophilic nanoparticle-based enhanced oil recovery: Microfluidic investigations on mechanisms,” Energy & Fuels, vol. 32, pp. 11243–11252, Oct. 2018, doi: 10.1021/acs.energyfuels.8b02496.
[12] J. Pang, T. Wu, C. Zhou, J. Gao and H. Chen, “Microbial Community Distribution in Low Permeability Reservoirs and Their Positive Impact on Enhanced Oil Recovery,” Microorganisms, vol. 13, May 2025, doi: https://doi.org/10.3390/microorganisms13061230
[13] Y. Fan, K. Gao, J. Chen, W. Li, and Y. Zhang, “Low-cost PMMA-based microfluidics for the visualization of enhanced oil recovery,” Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles, vol. 73, p. 26, Jan. 2018, doi: 10.2516/ogst/2018026.
OtherUpgradeSupportAdvanced RangeOEMServices / Training / Installation / RentalsMicrofabricationEssential RangeAccessories
Get in Touch
Do you want tips on how to best set up your microfluidic experiment? Do you need inspiration or a different angle to take on your specific problem? Well, we probably have an application note just for you, feel free to check them out!
Explore how microfluidics is revolutionizing cosmetic research from formulation to toxicology with ethical, precise, and scalable testing.
Microfluidics for the diagnosis and treatment of tuberculosis
Revolutionizing Microfluidics with Acoustic Particle Manipulation
There are three main classes of systems to control liquid motion in microfluidic and nanofluidic devices.
Microfluidic low-flow Liquid flow meters are a compulsory element of microfluidic systems requiring a control of the sample volume dispensed and/or, obviously, the sample flow rate.
This short note will introduce you to the key takeways about microfluidic T junction among other microfluidic junctions.
Fluid mixing at microscale is of importance for many fields of application. This short review summarises the key takeaway aspects of fluid mixing at microscale.
In the past two years, several new microfluidic syringe pump systems have changed the use of syringe pumps in microfluidic experiments.
This review presents a few examples of applications where magnetic flux sources, magnetic particles and microfluidics are combined in order to perform particle sorting and handling.
In microfluidic laminar flows, traditional turbulent mixing between two liquids cannot occur. However, controllable and fast mixing is critical for microfluidic and lab-on-chip devices. So different mixing techniques were developed and are here presented.
One of the great challenges for researchers using microfluidics is miniaturizing analysis processes in very small microchip.
Microfluidic flow controllers are designed to control flows in microfluidic chips.
Despite their sturdiness & simplicity, syringe pumps are often problematic in microfluidics.
The performance of your flow control instruments depends on your experimental conditions.
What are the strengths and weaknesses of each type of microfluidic flow control system? Pressure controller, syringe pump...?
Need customer support?
Name*
Email*
Serial Number of your product*
Support Type AdviceHardware SupportSoftware Support
Subject*
Message
I hereby agree that Elveflow uses my personal data Newsletter subscription
[recaptcha]