What is a 3 Stage Separator?

Do you know what a 3 stage separator is and how it works? If you are involved in the oil and gas industry, you should be familiar with this essential equipment that separates well fluids into gas, oil, and water phases. A 3 stage separator is a type of vessel that uses gravity and pressure to achieve this separation process.

It is installed near the wellhead and can be either horizontal or vertical in configuration. This blog post will explain what a 3 stage separator is, how it works, And what are the benefits of a 3 stage separator.

What is a 3 Stage Separator and Why Do You Need It?

A 3 stage separator is a device that splits a multi-phase well stream into three phases: gas, oil, and water. This is done to measure and control the flow rates of each phase, as well as to treat and dispose of the unwanted phases. A 3 stage separator is also known as a three-phase separator or a 3-phase separator.

The reason why you need a 3 stage separator is because the well fluids that come out of the ground are not pure. They contain various amounts of oil, water, natural gas, and sediment. These components have different densities, viscosities, and pressures, and they need to be separated before they can be processed, stored, or transported. A 3 stage separator helps you to achieve this separation efficiently and safely.

How Does a 3 Stage Separator Work?

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A 3 stage separator works by using gravity and pressure to separate the well fluids into gas, oil, and water phases. The separation process can be divided into three stages: primary, secondary, and tertiary.

Primary Separation

The primary separation stage is where the bulk of the gas is separated from the liquid. The well fluid enters the separator through an inlet and hits an inlet diverter. This causes a sudden change in momentum and direction, which initiates the separation of gas and liquid. The gas rises to the top of the separator, while the liquid falls to the bottom. The gas exits the separator through a mist extractor, which removes any liquid droplets that may be entrained in the gas. The gas then passes through a pressure control valve, which maintains a constant pressure inside the separator.

Secondary Separation

The secondary separation stage is where the oil and water are separated from each other. The liquid that falls to the bottom of the separator consists of oil, water, and emulsion (a mixture of oil and water that does not separate easily). The liquid flows through a liquid collection section, where the oil and emulsion form a layer above the free water.

A weir controls the oil level, while an interface level controller controls the water level. The oil spills over the weir and exits the separator through an oil dump valve, which is operated by a level controller. The water drains from the separator through a water dump valve, which is operated by an interface level controller.

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Tertiary Separation

The tertiary separation stage is where the emulsion is broken down and the remaining oil and water are separated. The emulsion that forms a layer between the oil and water is treated with chemicals, heat, or electricity to break the bonds between the oil and water molecules. This allows the oil and water to separate more easily. The oil and water then exit the separator through their respective dump valves.

What are the Benefits of a 3 Stage Separator?

A 3 stage separator offers several benefits for the oil and gas industry, such as:

Improved product quality

A 3 stage separator can remove up to 99% of the water and solids from the oil and up to 99% of the oil and solids from the water, resulting in cleaner and purer products that meet the industry standards and customer expectations.

Reduced operating costs

This can reduce the amount of waste and disposal costs, as well as the energy and maintenance costs, associated with the separation process. It can also increase the recovery and utilisation of valuable resources, such as oil and gas, which can boost the profitability and efficiency of the product supply business.

Enhanced environmental performance

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They can minimise the environmental impact of the separation process by reducing the emissions of greenhouse gases and volatile organic compounds, as well as the risk of spills and leaks. It can also help comply with the environmental regulations and policies that govern the product supply industry.

Increased safety and reliability

A 3 stage separator reduces the risk of fire, explosion, corrosion, and fouling that may occur due to the presence of water, solids, and gas in the oil and water phases. It can also prevent the damage and wear of downstream equipment and pipelines that may result from the impurities in the fluids. A 3 stage separator can therefore increase the safety and reliability of the product supply operation and extend the lifespan of the assets.

Flexible and adaptable

They handle a wide range of fluid compositions, flow rates, pressures, and temperatures, making it suitable for various applications and industries. It can also be customised and configured to meet the specific needs and requirements of the product supplier. A 3 stage separator can therefore adapt to the changing conditions and demands of the product supply market and provide optimal performance.


To sum up, a 3-stage separator is an indispensable tool in the oil and gas industry, playing a crucial role in the efficient and safe processing of well fluids. By utilising gravity and pressure, it adeptly separates well fluids into gas, oil, and water phases, ensuring improved product quality, reduced operating costs, enhanced environmental performance, and increased safety and reliability. Its flexibility and adaptability make it a versatile solution across various applications and conditions.

For those in the industry looking to optimise their operations and ensure the highest standards of separation and processing, Resolute Civils offers advanced 3-stage separator solutions tailored to meet your specific needs. Contact Resolute Civils today to explore how we can enhance your operations with our cutting-edge technology and expertise.

Frequently Asked Questions

What exactly does a 3 Stage Separator do?

A 3 Stage Separator is crucial in the oil and gas industry for separating well fluids into their constituent phases: gas, oil, and water, using gravity and pressure differentiation.

How does a 3 Stage Separator differ from a 2 Stage Separator?

Unlike a 2 Stage Separator, which only separates gas from liquids (oil and water), a 3 Stage Separator further separates the liquid phase into oil and water, offering more precise phase separation.

Where is a 3 Stage Separator typically installed?

It’s commonly installed near the wellhead and can be oriented either horizontally or vertically, depending on space and process requirements.

What are the key components of a 3 Stage Separator?

Key components include an inlet diverter, gas mist extractor, weir plates for liquid separation, and dump valves for the controlled release of separated phases.

Can a 3 Stage Separator handle emulsions?

Yes, it can manage emulsions during the tertiary separation stage, where emulsions are broken down, allowing oil and water to be further separated.

How does a 3 Stage Separator enhance environmental performance?

By efficiently separating well fluids, it significantly reduces the potential for spills and leaks and minimises the emission of harmful gases, contributing to safer and more environmentally friendly operations.

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