Demulsifier and separation of water from crude oil

Abstract

In the oil and gas industry, one of the main challenges faced by oil extraction, transportation and refining processes is the formation of water-in-oil emulsions. These emulsions are formed especially in oilfield extraction operations and during refinery processes and cause problems in crude oil transportation, end product quality, equipment damage and increased costs. Demulsifiers are special chemicals designed to break water-in-oil emulsions and separate the two phases. This article comprehensively reviews the functional mechanisms, types of demulsifiers, the effects of various factors such as temperature, pH and demulsifier concentration, and their application challenges in the oil industry. Also, the effects of using demulsifiers in improving the water-in-oil separation process under different operating conditions and oilfields are investigated.

Introduction to demulsifier

In the oil extraction process, water is usually extracted as an impurity along with crude oil. This water can form water-in-oil (W/O) emulsions, which are one of the major problems in oil transportation and refining processes. Due to the presence of fine water particles in the oil, these emulsions often prevent the smooth flow of oil and increase the costs of refining and purification. To solve these problems, the use of chemicals called demulsifiers is necessary. Demulsifiers are chemicals that can break down emulsions and separate water from oil by reducing the surface tension between the water and oil phases. These compounds are usually composed of surfactants and can be effectively used in oil and gas industrial processes, oil refining, and oil-contaminated water treatment.

Types of Demulsifiers

Demulsifiers are generally divided into several major categories:

1. Anionic demulsifiers
2. Cationic demulsifiers
3. Nonionic demulsifiers
4. Hybrid demulsifiers

The choice of demulsifier type depends on the characteristics of the emulsion, the type of crude oil, and the environmental conditions.

Anionic demulsifiers

These types of demulsifiers contain anionic groups that are more effective under certain conditions, especially in water-in-oil emulsions in the presence of alkalis and metal ions. These compounds are usually in the form of sulfate and carboxylate salts and reduce surface tension and facilitate the separation process. Due to their special characteristics, anionic demulsifiers are used in various processes such as crude oil refining and oil wastewater treatment.

Cationic demulsifiers

Cationic demulsifiers have cationic groups that are able to effectively interact with water particles in oil and prevent the formation of emulsions. These compounds are usually used in emulsions that contain negative ions, such as oil emulsions derived from heavy oils or those contaminated with various salts.

Nonionic demulsifiers

These types of demulsifiers are electrically neutral and are mainly used to separate complex emulsions and heavy oils that contain fine particles and a lot of water. Nonionic demulsifiers usually work well at high temperatures and in more severe conditions and are used in refineries and in complex oil fields, especially for heavy crude oils.

Combined demulsifiers

These compounds are usually a combination of different types of demulsifiers that can provide the benefits of both anionic and cationic or nonionic types simultaneously. These compounds are much more effective for emulsions that have different characteristics than either type alone.

Mechanisms of action of demulsifiers:

The function of demulsifiers in reducing the stability of emulsions is mainly due to their ability to change the surface properties of the oil and water phases. Demulsifiers break down emulsions and separate oil and water phases through various mechanisms. The most important mechanisms of demulsifiers are:

1. Reduction of surface tension
2. Aggregation of water droplets
3. Stabilization of the oil phase
4. Chemical reactions

Reduction of surface tension:

Demulsifiers cause water droplets to separate from the oil phase by reducing the surface tension between the water and oil phases. This process causes the water droplets to aggregate into larger forms and facilitates separation.

Agglomeration of water droplets:

These compounds cause water droplets to aggregate into larger forms, which are easily separated from the oil phase and can be easily removed from the system.

Oil phase stabilization:

In some cases, demulsifiers can make the oil phase more stable by changing its properties and preventing re-emulsification.

Chemical reactions:

In some cases, demulsifiers bind to particles in the emulsion by performing chemical reactions, causing the separation of water from oil.

Factors affecting the efficiency of demulsifiers:

1. Temperature
2. pH of the environment
3. Demulsifier concentration
4. Type of crude oil

Temperature:

Temperature is a key factor in the efficiency of demulsifiers. At higher temperatures, the rate of the separation process increases. This is especially effective in heavy crude oils and under severe operating conditions.

Ambient pH:

The pH of the environment can have a significant impact on the performance of demulsifiers. Some demulsifiers work better in acidic environments, while others work better in basic environments. Adjusting the pH carefully can increase the efficiency of the water separation process.

Demulsifier concentration:

The concentration of the demulsifier is another important factor. Too much demulsifier concentration can increase costs and have side effects, while too little can lead to poor performance.

Crude oil type:

The type of crude oil, its chemical properties (such as the amount of sulfur, salts, and water present), and the type of emulsion (stable or unstable) can all affect the performance of demulsifiers. Heavy oils usually require special demulsifiers that are capable of breaking complex emulsions.

Applications of demulsifiers in the oil and gas industry:

Demulsifiers have a wide range of applications in the oil industry, including the following:

1. Crude oil refining
2. Oil wastewater treatment
3. Oil transportation in pipelines

Crude oil refining:

In crude oil refining, demulsifiers are used to separate water from crude oil. This process reduces costs and increases refining efficiency.

Oil wastewater treatment:

Wastewater from oil extraction operations usually contains large amounts of water and oil. The use of demulsifiers can help treat these wastewaters and reduce environmental pollution.

Oil transportation in pipelines:

In the process of transporting oil through pipelines, water-in-oil emulsions can cause flow problems and increase friction. The use of demulsifiers can help solve these problems.

Experimental results and research:

Various studies have shown that the use of different demulsifiers can significantly improve the quality of the water-oil separation process. In particular, the use of combined demulsifiers in oil fields with complex emulsions and under extreme operating conditions (high temperatures, high pressures) is much more effective than simple demulsifiers.

Conclusion:

Demulsifiers are known as an effective and economical solution for water-oil separation in the oil and gas industries. The selection of the appropriate type of demulsifier depends on the characteristics of the crude oil, operating conditions, type of emulsion and environmental factors. These compounds can help reduce refining costs, improve the efficiency of oil and gas processes and reduce environmental problems caused by pollutants. Optimal use of demulsifiers in oil processes can increase oil production efficiency and reduce negative environmental impacts.