Chemical enhanced oil
recovery (CEOR) has been around for a while. Recently, interest has grown as it
has been successfully deployed. A July 2023 paper in the journal Energy
& Fuels explains that surfactants work by:
“…changing either fluid/rock and/or fluid/fluid interaction due to ion-pair forming and/or surfactant adsorption on the rock surface. As the main surfactant role in EOR, IFT {inter-facial tension} reduction refers to adsorbing of surfactant molecules on the residual oil/water interface, which causes an increase in capillary number; as a result, trapped oil drops in porous media get free and start to move through the pore space toward the production well.”
That paper also notes that
the downsides of chemical surfactants, including toxicity, cost, and
environmental impact, can be overcome if significant natural surfactants are
developed through methods such as so-called “green chemistry,” via plant-based
surfactants.
A July 2024 paper in the
journal ACS Omega: Advancements in Surfactant Carriers for Enhanced Oil
Recovery: Mechanisms, Challenges, and Opportunities, explores EOR
surfactants and surfactant carriers.
The paper explains some of
the issues with surfactants below:
“Surfactant injection is a widely used chemical EOR
method that aims to change the rocks’ wettability, reduce the interfacial
tension between the oil and water phases, making the oil more mobile and easier
to displace from the reservoir rock. This method has been successfully applied
in several field projects, and recent studies have focused on optimizing the
formulation of surfactant solutions and understanding the mechanisms of oil
displacement by surfactants. Despite their high efficiency, the surfactants
used in EOR processes must be carefully evaluated due to their production cost,
toxicity, and tendency to adsorb on the reservoir surfaces.”
Targeted delivery of the
surfactants via carrier systems has also been a focus in recent years.
Supramolecular technologies have gained in importance “due to their unique
self-assembly properties and ability to form complex, functional structures.”
They explain supramolecular carrier systems below:
“Supramolecular carrier systems exploit noncovalent
interactions, such as hydrogen bonding, van der Waals forces, hydrophobic
interactions, pi-pi stacking, and ion-dipole interactions, to create highly
ordered structures capable of encapsulating and releasing surfactants in a
controlled manner. The self-assembly of these systems enables the formation of
micelles, vesicles, and other nanostructures with tunable characteristics,
designed to respond to external stimuli such as changes in pH, temperature, or
the presence of specific ions. This responsiveness allows for the controlled
and localized release of surfactants, enhancing the efficiency of the EOR
process.”
They also explain
non-supramolecular methods, especially nanoparticle methods, several involving
nanoparticles or nano-structured materials:
“On the other hand, nonsupramolecular carrier systems,
including inorganic or polymer nanoparticles, liposomes, and other
nanostructured materials, such as carbon nanotubes and graphene, have also
demonstrated promising results. These systems often utilize covalent bonding
and physical encapsulation methods to protect and transport active surfactant
molecules. Surface engineering of these materials can be tailored to improve
surfactant transport and release, making them suitable for a wide range of
industrial applications, including EOR.”
Choosing which kind of
surfactant and delivery method can depend on the qualities of the reservoir
rock. These include mineralogy, the rock’s “wettability,” and chemical factors
such as pH and the rock’s ionic charge. Thus, for instance, cationic
surfactants are used with limestone reservoirs and anionic surfactants are used
with sandstone reservoirs.
Surfactant loss is a
challenge that must be mitigated. That is a major reason why transport or
delivery of the surfactants to the reservoir rock is so important. The graphic flow chart below explores strategies to reduce surfactant loss.
The graphic chart below examines the environmental concerns of surfactants.
The paper examines in detail several types of potential surfactant carriers, including inorganic nanoparticles, carbon nanomaterials, polymeric agents and surfactants, and supramolecular systems.
The company Locus Bio-Energy
Solutions, which develops biosurfactants for EOR, says that “biosurfactants
are the future of sustainable and more effective oil recovery.” They define
surfactants as follows, and note that they are used in many industries,
including agriculture, cosmetics, food and beverage, pharmaceuticals, mining,
oil & gas, remediation, wastewater, and many more:
“Surfactants are compounds with inherent properties that
reduce the surface and interfacial tension between two liquids, a gas and a
liquid, or a liquid and a solid.”
“Surfactants, or surface-active agents, are compounds
that contain a hydrophilic, or “water-loving” head, and a hydrophobic, or
“water-fearing” tail—allowing them to lower the surface tension between
liquids, gases or solids. In oilfield applications, surfactants are critical
components of scale and corrosion inhibitors, hydraulic fracturing fluids,
drilling muds and enhanced oil recovery treatments.”
Surfactants can function as cleansers,
detergents, dispersants, foamers, emulsifiers, viscosity builders, and wetting
agents. They are used in several different ways in oil & gas development
and extraction. There is a growing push these days to develop biosurfactants as
a more sustainable approach. Biosurfactants are produced biologically via
microorganisms, which can produce a variety of “surface-active substances.”
While microbes produce the biosurfactants, the biosurfactants themselves are
not alive. They are also sterile.
“All biosurfactants are amphiphiles, they consist of two
parts—a polar (hydrophilic) moiety and non polar (hydrophobic) group.”
As noted below,
biosurfactants have several advantages over chemical surfactants and bio-based
chemical surfactants:
“Biosurfactants, specifically fermentation-produced
biosurfactants, offer significant advantages over synthetic surfactants and
other bio-based surfactants. These include enhanced multifunctional
performance, better environmental compatibility, 10x lower toxicity, higher
biodegradability and maintained activity under extreme conditions of
temperatures, salinity and pH values.”
While biosurfactants have
been around for a while, in the past, they have been cost-prohibitive. Locus
Bio-Energy says they have developed a cheaper way to produce them via
fermentation. They say they can provide them with less than 10% of the CAPEX
required for traditional recovery methods. They note that past methods of
microbial enhanced oil recovery (MEOR) developed in the 1980s and 90s sought to
produce the microbes in situ, essentially growing them downhole. The results
were inconsistent, and the process was hard to control. Locus Bio-Energy’s
final product is different since it does not contain the microbes, which are
confined to the fermentation vats. They also design biosurfactant treatment to
remediate wells from paraffin and wax buildup and for use in frac fluids during
hydraulic fracturing of wells.
Surfactant flooding has long
been used to aid heavy oil recovery. It creates an emulsion that can separate
out the oil for extraction. In a March 2026 paper in Physics of Fluids, Wang et
al. studied the use of nano-emulsions in surfactant flooding to increase the
efficacy of oil recovery.
“When surfactants are added to [an] oil-sand mixture,
the hydrophobic tails can penetrate into the oil phase to reduce the heavy oil
viscosity and oil-water interfacial tension,” said author Wanying Wang.
“Consequently, the oil can be effectively removed from the oil-sand mixtures.”
Nano-emulsions contain
smaller drops than traditional emulsions, which results in more uniform droplet
dispersion and long-term stability.
“The team found that combining a nonionic surfactant,
fatty alcohol polyoxyethylene ether (AEO-7), and an anionic surfactant, sodium
dodecyl sulfate (SDS), showed the best oil-washing efficiency.”
“This is attributed to the synergistic stabilization of
the oil-water interface by AEO-7 and SDS … which promotes oil peeling and
enhances oil–sand separation,” Wang said.
“This study provides novel interfacial mechanical
insights for developing high-performance nano-emulsion systems.”
It appears that surfactants
and especially biosurfactants will continue to be used and further developed to
be used more and with better results for improving oil recoveries as the
science progresses.
References:
Advancements
in Surfactant Carriers for Enhanced Oil Recovery: Mechanisms, Challenges, and
Opportunities. Kelly C B Maia, Agatha Densy dos Santos Francisco, Mateus
Perissé Moreira, Regina S V Nascimento, and Daniel Grasseschi. American
Chemical Society. ACS Omega. 2024 July 22; 9 (35):36874–36903. Advancements in Surfactant Carriers
for Enhanced Oil Recovery: Mechanisms, Challenges, and Opportunities - PMC
Improving
surfactant flooding for heavy oil recovery using nano-emulsions: A combination
of a nonionic and an anionic surfactant showed the most effective oil-washing
efficiency. Hannah Daniel. AIP Publishing. April 10, 2026. Improving surfactant flooding for
heavy oil recovery using nano-emulsions | Scilight | AIP Publishing
Review
of the Application of Natural Surfactants in Enhanced Oil Recovery:
State-of-the-Art and Perspectives. Sarkar Muheedin, Hama Abbas, Khaksar Manshad,
and Jagar A. Ali. ACS Energy & Fuels. Vol 37/Issue 14. July 4, 2023. Review of the Application of Natural
Surfactants in Enhanced Oil Recovery: State-of-the-Art and Perspectives |
Energy & Fuels
Oil
Industry, Remember this Word for Enhanced Performance: Biosurfactants: Why?
Because Biosurfactants are the Future of Sustainable and More Effective Oil
Recovery: The Basics of Surfactants. Locus Bio-Energy (website). Oil Industry, Remember This Word For
Enhanced Performance: Biosurfactants | Locus Bio-Energy
On the
effects of surfactant charge on interfacial stability in nano-emulsions. Wanying
Wang, Zhe Li; Bobo Zhou; Yilu Zhao; Yulong Cheng; Xuesong Yang; Lei Wang;
Yaowen Xing; Xiahui Gui. Physics of Fluids. Volume 38, Issue 3. March 2026. On
the effects of surfactant charge on interfacial stability in nano-emulsions |
Physics of Fluids | AIP Publishing
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