Learn how surfactants reduce the surface tension between oil and water and enhance the sweep and displacement efficiency of the injected fluid.

Improved Reservoir Sweep Efficiency: Surfactants contribute to enhanced oil recovery by improving the sweep efficiency of injected fluids through the reservoir. Selectivity in Oil Recovery: Surfactants can be tailored to exhibit selectivity in targeting specific types of oil. This selectivity ensures that the surfactant formulation is optimized to recover a higher percentage of the target hydrocarbons, providing a more customized and efficient oil recovery process. Microemulsion Formation: Surfactants facilitate formation of stable microemulsions, which are colloidal dispersions of oil, water, & surfactant. Presence of microemulsions improves the solubility & transport of oil.

How do surfactants improve oil recovery?

Oil is a valuable and finite resource that is often trapped in hard-to-reach reservoirs. To extract more oil from these reservoirs, oil companies use various methods of enhanced oil recovery (EOR), which involve injecting fluids or gases into the wells to increase the pressure and reduce the viscosity of the oil. One of these methods is surfactant flooding, which uses chemicals called surfactants to improve the mobility and displacement of oil. In this article, you will learn how surfactants work, what types of surfactants are used, and what benefits and challenges they pose for oil recovery.

1 What are surfactants?

Surfactants are substances that reduce the surface tension between two different phases, such as oil and water, or air and water. Surfactants have a dual nature: one part of their molecule is hydrophilic (water-loving) and the other part is hydrophobic (water-hating). This allows them to align themselves at the interface of the two phases and create a thin film that lowers the interfacial tension. Surfactants are commonly used in detergents, cosmetics, and pharmaceuticals, as well as in oil and gas applications.

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2 How do surfactants improve oil recovery?

Surfactants improve oil recovery by enhancing the sweep efficiency and displacement efficiency of the injected fluid. Sweep efficiency refers to the fluid's ability to cover the entire reservoir and contact the oil, while displacement efficiency pertains to how well the fluid pushes the oil out of the rock's pores and fractures. Surfactants achieve this by reducing interfacial tension between the injected fluid and oil, allowing it to overcome capillary forces. Additionally, they alter wettability of the rock, making it more water-wet so that water can displace oil from the rock surface more easily. Furthermore, surfactants create microemulsions which are mixtures of oil and water that form tiny droplets stabilized by surfactants. These microemulsions improve mobility ratio between the injected fluid and oil, so that it can move faster than the oil and avoid viscous fingering or channeling.

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Samad Mulla

Trainee Petroleum Engineer | Quest Global | Unlocking the Future of Subsea Engineering, Production Optimization, and Artificial Lift Technologies | Strategic Innovator and Problem Solver
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Surfactants, acting like soap, lessen the stickiness between oil and rock pores in Enhanced Oil Recovery (EOR), enabling easier oil flow towards production wells, enhancing oil extraction from reservoirs.

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Guan Gregory

Shanghai Howell Petroleum Additives Co.,Ltd. — Sales Manager
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Surfactants reduce the interfacial tension between oil and water, making it easier for oil to detach from rock surfaces and flow to production wells. Surfactants can alter the wettability of the reservoir rock, making it more favorable for water-based fluids to displace oil. Surfactants can form stable emulsions between oil and water, which can help mobilize and displace trapped oil from smaller pores in the reservoir rock. Surfactants can also be used in combination with polymers to improve mobility control within the reservoir. Surfactants are commonly used in foam-based EOR methods to improve the displacement of oil from reservoir rocks.

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3 What types of surfactants are used?

When selecting surfactants for oil recovery, there are many types to consider depending on the properties of the reservoir and the oil. Anionic surfactants, which have a negative charge on their hydrophilic part, are effective in low-salinity water and can reduce the interfacial tension significantly. Cationic surfactants, with a positive charge on their hydrophilic part, are effective in high-salinity water and can alter the wettability of the rock. Nonionic surfactants, without any charge on their hydrophilic part, function well in a wide range of salinity and pH conditions and can form microemulsions. Lastly, amphoteric surfactants, with both positive and negative charges on their hydrophilic part, adjust their charge depending on the pH of the environment and can be used in combination with other surfactants. Examples of these four types of surfactants include sulfonates, carboxylates, phosphates, quaternary ammonium salts, amines, alcohols, ethers, esters, betaines and imidazolines.

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Samad Mulla

Trainee Petroleum Engineer | Quest Global | Unlocking the Future of Subsea Engineering, Production Optimization, and Artificial Lift Technologies | Strategic Innovator and Problem Solver
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Surfactants used in EOR come in different types, like anionic, cationic, nonionic, and amphoteric. They work differently based on their makeup, but all aim to help move oil more easily from underground rocks to production wells, boosting oil recovery.

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4 What are the benefits of surfactants?

Surfactants can offer a variety of advantages for oil recovery, such as increasing the oil recovery factor by 5% to 20% compared to water flooding alone, depending on the reservoir conditions and the surfactant formulation. Additionally, they can reduce the water cut by improving the displacement efficiency and reducing the residual oil saturation. Furthermore, surfactants can reduce the environmental impact by decreasing the amount of fluid and energy needed for extraction, as well as by using biodegradable and eco-friendly surfactants.

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Manish Kumar

Lead Petroleum Engineer @ Cairn Oil and Gas| LinkedIn Top Voice| PGP DS @ McCombs School of Business, Texas | MTech AIML @ BITS Pilani
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Improved Reservoir Sweep Efficiency: Surfactants contribute to enhanced oil recovery by improving the sweep efficiency of injected fluids through the reservoir. Selectivity in Oil Recovery: Surfactants can be tailored to exhibit selectivity in targeting specific types of oil. This selectivity ensures that the surfactant formulation is optimized to recover a higher percentage of the target hydrocarbons, providing a more customized and efficient oil recovery process. Microemulsion Formation: Surfactants facilitate formation of stable microemulsions, which are colloidal dispersions of oil, water, & surfactant. Presence of microemulsions improves the solubility & transport of oil.

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5 What are the challenges of surfactants?

Surfactants can present some challenges for oil recovery, such as high cost, low stability, and low injectivity. The cost of surfactants can be reduced by optimizing the concentration, using cheaper or locally available surfactants, and recycling or reusing them. The stability of surfactants can be improved by selecting the appropriate type, modifying the structure, or adding stabilizers or co-solvents. To enhance injectivity of surfactants, viscosity needs to be reduced, permeability increased, and adsorption of the rock decreased.

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6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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How do surfactants improve oil recovery?

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1 What are surfactants?

2 How do surfactants improve oil recovery?

3 What types of surfactants are used?

4 What are the benefits of surfactants?

5 What are the challenges of surfactants?

6 Here’s what else to consider

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