The oil and gas industry consists of many complex processes, including drilling, increasing oil recovery, pipeline transportation, and refinery processing.

In crude oil extraction, there are two main challenges and optimizations related to surface interaction processes: the first is to improve crude oil recovery rate, and the other is new methods to treat and prevent pipeline scaling.

The only oil available on this planet makes it necessary to study ways to extract as much crude oil as possible from existing oil fields and improve production processes. One method is to optimize the recovery process and obtain more oil from the reservoir. This can be promoted by improving understanding of the mineral crude oil release process in the reservoir. Another way to increase oil production is by effectively separating crude oil from water and other substances.

Another challenge is scaling that occurs at different stages of oil production, which can lead to reduced transmission efficiency, excessive energy consumption, and increased costs. The main factor causing this issue is asphaltene, which tends to adsorb at the interface of each stage of oil production. Asphalt will aggregate and deposit under various processing conditions, and this high trend of sedimentation is a headache because it may lead to sediment accumulation and blockage, such as heat exchanger accumulation and pipeline blockage.

Improve oil recovery rate

During the oil recovery stage, different optimization recovery methods such as surfactants or carbon dioxide flooding can be used to improve oil recovery efficiency. After injecting surfactants or carbon dioxide into the reservoir, they come into contact with the reservoir and interact with it, thereby changing the equilibrium conditions and fluid properties of the crude oil. This may lead to the settling and accumulation of heavy organic solids, mainly asphaltene. These phenomena lead to changes in the wettability of reservoir rocks and a decrease in permeability, resulting in a decrease in recovery rate.

The interfacial tension between crude oil and oil displacement agent is an important parameter. The lower the interfacial tension value, the better the solubility of the oil displacement agent in crude oil. The interfacial tension between carbon dioxide and crude oil has been extensively studied, as carbon dioxide is one of the most promising oil displacement agents.

The functional relationship chart of interfacial tension vs. pressure between carbon dioxide and crude oil. Tested using the Expansion Theta high-voltage module.

Application Summary: Using Carbon Dioxide to Improve Crude Oil Recovery

QSense QCM-D can simulate surfactant adsorption at the molecular level to optimize oil recovery processes in real-time. It is also possible to simulate adsorption using polymers in experiments, which can reproduce and improve crude oil recovery at the nanoscale.

Adsorption of asphaltene on solid surfaces

In addition to stabilizing the oil-water interface, asphaltene can also adsorb onto solid surfaces at different stages of oil recovery and transfer processes. In order to understand the mechanism of asphaltene deposition, a basic understanding of asphaltene solid interactions is required. QSense QCM-D can be used to characterize the adsorption and scaling of asphaltene on various surfaces under different solvent conditions.

The settling and accumulation of asphaltene can cause changes in the wettability and permeability of reservoir rocks, leading to a decrease in recovery rate. The wettability and interfacial tension relationship between crude oil, fluids, and rocks can be studied through contact angle measurement. Contact angle measurement can also be performed under high pressure and high temperature conditions simulating reservoir conditions.

[Surfactants and lotion/surfactant behavior]

Almost all industrial products use surfactants, from cleaning agents to paints, cosmetics to food. Surfactants can be used as cleaning agents, wetting agents, emulsifiers, foaming agents, and dispersants depending on the system they are applied to. Naturally occurring surfactants may also lead to unnecessary product performance. The characterization of surfactants is crucial for ensuring optimal performance of products and processes.

Surfactants are typically amphiphilic organic compounds, which means they contain both hydrophilic (water-soluble) and hydrophobic (water-insoluble) moieties. Due to their amphiphilic nature, surfactants adsorb at the interface, thereby reducing the surface and interfacial tension between the two phases.

In many industrial processes, surfactants can be added to improve product performance. For example, surfactants are used as cleaning agents to improve the efficiency of cleaning products, and can also be used as wetting agents in paints or emulsifiers in food products. Another aspect of surfactants is that they are natural compounds that act as surfactants. These include asphaltene found in heavy crude oil, which may cause various problems in crude oil production.

Adsorption of surfactants at gas-liquid or liquid-liquid interfaces

The efficiency of surfactants was measured by measuring their ability to reduce surface or interfacial tension and stabilize lotion, and by studying their hydrophile lipophilic equilibrium (HLB).

By measuring the relationship function between surface and interfacial tension and concentration, the maximum decrease in surface or interfacial tension that a given surfactant or surfactant mixture can produce can be determined. From an economic perspective, this is also important because the amount of surfactant used has a direct impact on the cost of the product. In terms of surfactant concentration and toxicity, environmental factors also need to be considered. Critical micelle concentration measurement is commonly used to determine the optimal amount of surfactant in formulations.

[Download Surface and Interface Tension - What is it and how to measure it?]

Surfactants adsorb on solid surfaces

Understanding the adsorption of surfactants on solid surfaces, such as in paint manufacturing, water filtration, or crude oil production, is crucial. Taking paint as an example, it is a complex water-based mixture consisting of different components such as pigment particles, polymers, and surfactants. Pigment particles impart the desired color to coatings, while polymers increase viscosity and surfactants to enhance the stability and wettability of coatings. If polymers are preferentially adsorbed on the surface of pigments instead of surfactants, problems may arise. This will result in a decrease in the color, appearance, and adhesive properties of the dry film.

Problems caused by the adsorption of asphaltene in crude oil production

Due to the presence of asphaltene (oil sands, heavy oil) in many recently discovered reserves, there is increasing interest in asphaltene. Asphalt is a high molecular weight component of crude oil, and its exact molecular structure is unknown. It is typically classified as insoluble in alkanes such as n-pentane and n-hexane, but soluble in toluene. Asphaltene tends to be adsorbed on the interface, thus increasing the stability of oil-water lotion (related to the stability of lotion) and changing the wetting behavior of the reservoir. The adsorption of asphaltene during crude oil processing can also cause problems such as pipeline pollution.

In order to understand the mechanism of asphaltene deposition, a basic understanding of asphaltene solid interactions is required. QSense QCM-D can be used to characterize the adsorption and contamination of asphaltene on various surfaces under different solvent conditions.

The precipitation and deposition of asphaltene can cause changes in the wettability and permeability of reservoir rocks, leading to a decrease in oil recovery rate. Contact angle measurement can be used to study the wettability and interfacial tension between oil, fluid, and rock. Contact angle measurement can also be performed under high pressure and high temperature to simulate reservoir conditions.

Characterization of adsorption kinetics of surfactants at solid-liquid interface

As we can see, surfactants and their behavior at the solid-liquid interface are at the core of many fields, from biological applications to decontamination and cleaning to improving oil recovery. QSense QCM-D technology can characterize surfactants, surfactant systems, and surfactant mixtures based on the dynamics and behavior at the interface. By utilizing this surface sensitive technology, the adsorption and desorption kinetics of surfactants on different surfaces can be studied, and the adsorption dynamics can be monitored in real-time. The surface can easily change, making it possible to plan the effects of surface materials, surface functionality, and hydrophilicity or hydrophobicity. It is also possible to determine the layer thickness of the adsorbed surfactant and track the morphological changes of the adsorption membrane based on various surfactant concentrations, pH values, salt concentrations, and temperatures. This technology can also explore and characterize the interactions between surfactants and materials such as lipid vesicles, polymers, and polyelectrolyte layers.

[surfactant and lotion/lotion stability]

Lotion is a mixture of two or more liquids, which are usually incompatible with each other. From the thermodynamic point of view, lotion is an unstable system, because the liquid-liquid system has a natural tendency to separate and reduce its interface energy.

The stability of lotion can be defined as the ability of the system to resist the change of its physical and chemical properties with time. The stability of lotion is very important in many industrial applications, including coatings, food, agricultural formulations, personal care and petroleum. Several mechanisms such as emulsification, flocculation, and aggregation can lead to emulsion breaking.

Although the stability of lotion is necessary in most industrial products and processes, there are also some processing processes that do not require the stability of lotion. For example, crude oil recovery requires separating crude oil from water before transportation, or wastewater treatment does not require oil-water emulsions.

Prediction of emulsion stability through interface rheology testing

Interface rheology is a special branch of rheology that involves the study of specific two-dimensional systems formed at interfaces. Just as rheology studies fluid flow, interface rheology studies the flow characteristics of fluid interfaces.

Interface rheology in food and beverages

Proteins can be used as surfactants in food, but other stabilizers can also be added to improve stability. Phosphatidylcholine is one of the few natural surfactants. With the increasing attention to environmental and health issues, natural surfactants are becoming increasingly of interest to people.

Application Abstract Download: Protein Adsorption and Interfacial gel at Gas Liquid and Oil Water Interfaces

Application Digest Download: Interface Rheology of Single Molecular Layers at Gas Liquid Interfaces

Watch Webinar: Interface Rheology: From Fundamentals to Applications

Surface characterization of industrial grade non-ionic emulsifiers

Polyoxyethylene surfactants are widely used in industrial applications, such as coatings, food, agricultural formulas, personal care and petroleum, among which the stability of lotion and foam is important. Alcohol ethoxylates are replacing the more toxic alkylphenol ethoxylates traditionally used as emulsifiers in many applications. However, straight chain alcohol ethoxylates did not exhibit the same good emulsifier performance as alkylphenol ethoxylates, mainly due to the latter having a larger tail. This is due to the different sizes of polarity heads and hydrocarbon tails, which hinder the formation of tightly packed thin films at the interface.

We have studied the adsorption and surface rheological properties of two industrial grade non-ionic surfactants based on different numbers of EO groups of C10 Guerbet alcohol. They are C10EO6 and C10EO14.

The surface pressure isotherms of the two surfactants conform to the reorientation model. However, there are different interpretations of surface rheological data. It indicates that C10EO6 can be explained within the model framework of diffusion relaxation process, while C10EO14 deviates from the diffusion relaxation process and its surface rheological reaction is close to that of non-ionic polymer surfactants. Figures 1 (C10EO6) and 2 (C10EO14) show the storage modulus (E ') and loss modulus (E ") obtained by oscillating perturbations of two surfactants at two frequencies (0.02 Hz and 0.5 Hz). The solid and dashed lines are suitable experimental data obtained from the diffusion model. The results showed that only the experimental data of C10EO6 surfactant showed good consistency with the proposed model.

Figure 1. The relationship function between the storage modulus (E ', hollow symbol) and loss modulus (E ", solid symbol) of C10EO6 surfactant at two frequencies (0.02Hz triangle) and (0.5Hz diamond) and the concentration of the surfactant itself. The solid and dashed lines are the best fitting curves for the diffusion model experimental data.

Figure 2. The relationship function between the storage modulus (E ', hollow symbol) and loss modulus (E ", solid symbol) of C10EO14 surfactant at two frequencies (0.02Hz triangle) and (0.5Hz diamond) and the concentration of the surfactant itself. The solid and dashed lines are the best fitting curves for the diffusion model experimental data.

The surface rheological properties of the two surfactants indicate that they form a viscoelastic layer at the air/water interface. However, due to the different number of ethylene oxide groups, the adsorption film exhibits different behaviors. For smaller surfactants, adsorption and rheological data conform to the diffusion model, while larger C10EO14 surfactants exhibit surface behavior closer to that of polymer surfactants. Moreover, the comparison of the swelling elasticity and viscosity of the two surfactants indicates that increasing the number of EO groups can enhance elasticity. The elasticity of adsorbed surfactant film is directly related to the stability of foam and lotion. Therefore, compared to shorter C10EO6 surfactants, C10EO14 surfactants may form a more stable anti aggregation layer. However, due to the high diffusivity of surfactant in the former, C10EO6 is more capable of forming foam than C10EO14. Therefore, these results may find interesting applications to reasonably develop stable foam and lotion by using non-ionic surfactants containing oxyethylene groups.

文献依据: P. Ramírez, L.M. Pérez-Mosqueda, L.A. Trujillo-Cayado, M. Ruiz, J. Munoz, R.Miller, Equilibrium and surface rheology of two polyoxyethylene surfactants (CiEOj) differing in the number of oxyethylene groups, Colloids Surf., A 375(2011) 130–135.

Asphaltene stabilized oil water lotion

When the oil is recycled, a complex oil-water lotion is formed. Asphaltenes adsorbed at the oil-water interface tend to increase the stability of these lotion. Stable oil-water lotion is usually not required because it increases pumping and transportation costs and will corrode pipes, pumps and distillation towers.

The surface activity of asphalt can be evaluated using an optical tensiometer through simple interfacial tension measurements. By combining high-pressure chambers into the system, measurements can be taken under high pressure and high temperature.

Another widely used method is to study the interfacial rheology of oil-water interfaces. The elasticity of the interface is related to the stability of oil-water emulsions. The interfacial rheology of adsorbed asphalt layer can be studied using the oscillation droplet method. Another method is to use interface shear rheology (ISR) based on a floating needle rheometer to characterize the relationship function of asphaltene bulk density.

Brewster angle microscope can visualize the morphology of asphalt at the air-water interface.

Application Abstract Download: Protein gel Adsorption at Air Water and Oil Water Interfaces

Download Application Digest: Imaging of Thin Film Structures: Brewster Angle Microscope

Watch Webinar: Interface Rheology: From Fundamentals to Applications

[Surfactants and lotion/demulsifiers]

As the stability of lotion is important in many industrial processes and products, demulsification is also crucial in other environments.

Anti emulsification or demulsification is particularly important in crude oil production and wastewater treatment. In crude oil production, water in oil lotion is usually produced. These lotion may be very stable due to asphaltenes and resins naturally present in many crude oils. The effective separation of crude oil and water is crucial in terms of crude oil quality, while also ensuring the separation of high-quality aqueous phase at low cost.

Demulsifier is used to make water in oil lotion unstable

From a process perspective, demulsification has two aspects: the rate of separation and the amount of water remaining in the crude oil. The produced oil usually must comply with company and pipeline specifications. Typically, oil loaded from wet crude oil processing facilities may contain no more than 0.2% BS&W (basic sediment and water) or 4.5 kilograms of salt per thousand barrels of crude oil. This relatively low concentration requirement is to reduce corrosion and salt deposition.

The process of separating emulsions into oil and water involves the instability of the emulsion film around the water droplets. Several methods can be used to destroy the stability of lotion, such as adding chemical demulsifier, increasing the temperature of lotion, applying electric field to promote the aggregation of lotion and change the physical properties. The addition of chemical demulsifiers is currently a commonly used method.

A demulsifier is a surface active reagent used for the migration of oil-water interfaces and the neutralization of the effects of emulsifiers. Choosing the appropriate demulsifier is crucial in the process of demulsification. Due to the wide variety of components in crude oil, it is important to choose demulsifiers based on the type of crude oil. The interfacial rheological parameters, especially the interfacial expansion elasticity, are related to the stability of lotion. The effectiveness of demulsifiers can be determined by measuring the interfacial rheology of the oil-water interface in the presence of demulsifiers.

[surfactant and lotion/foam]

Foam is very important in many industrial products and processes. Foam is usually needed in body care and food, but in some industrial processes such as printing, pumping and lubrication, foam is not needed, and defoamers are needed. Foam is used in many processes such as flotation and enhanced oil recovery.

Foam can be considered as air water lotion. As in oil-water lotion, surfactant molecules are needed to reduce the surface tension between the gas water interface to form foam.

Foam for enhancing oil recovery

Gas injection (such as carbon dioxide, methane, or nitrogen) is commonly used to improve crude oil recovery. However, due to the lower viscosity and density of gases compared to water and oil, problems such as gas channels passing through high permeability regions and gas migration to the upper part of porous media may arise. Therefore, the volumetric scanning efficiency of gas drive is often poor. In order to improve the efficiency of gas drive, it is recommended to use foam injection.

Foam provides a method to reduce the gas fluidity to improve the displacement and purging efficiency. One of the main problems of EOR method based on foam is the stability of foam. The foam must be stable in the porous structure to become an effective recovery agent. Surfactants play a key role in the stability of foam. For example, in order to produce stable carbon dioxide in water foam plastics (one of the most studied foam systems), it is important to develop surfactants that can stabilize the carbon dioxide water interface under storage conditions.