As simple as the media portrays the oil and gas industry sometimes, in reality, it is quite a sophisticated and elaborate process. With the many stages involved at a macro level, including drilling, production, and refining, the oil and gas process can be broken down to many more micro levels as well.
What is the Separation Process?
A separator is a vessel in which a mixture of fluids that are not soluble in each other are segregated from one another.
In the oilfield, separators are used to segregate gas from liquid; or one liquid, such as crude oil, from another liquid, such as water.
There are more separators on oil and gas locations or process facilities than any other type of process equipment. Sometimes they are called scrubbers, slug catchers, FWKO’s, centrifuges, and many other names.
Regardless of what the vessel is called, the function is to segregate two or more fluids (like when using shaker screens), usually gas and liquids.
The Seven Principles of Oil Separation
There are seven principles that affect separation.
- Pressure change
- Temperature change
- Scrubbing action
- Chemical action
- Retention time
Depending on the properties of the well fluid and the required task at hand, these are the principles governing separation.
In some cases, only one of the seven may be used at any given time.
In other cases, it may be more expedient to use a combination of two or more of the principles to get the required results within a given timeframe.
1. Pressure Change
Depending on what needs to be done, pressure on a hydrocarbon containing vessel may be manipulated to enhance the separation process.
If the vapor pressure in a vessel containing hydrocarbons is decreased, some of the lighter hydrocarbons will flash from the liquid phase into the vapor phase.
On the other hand, if vapor pressure in a vessel containing hydrocarbons is increased, some of the lighter hydrocarbons will condense from the vapor phase back into the liquid phase.
These statements are true if the temperature remains constant.
2. Temperature Change
Temperature changes go hand-in-hand with pressure changes when it comes to separation in a hydrocarbon containing system or vessel.
If the pressure in a vessel remains the same, a rise in temperature will cause some of the lighter hydrocarbons to flash from liquid to vapor phase.
Likewise, a drop in temperature at a fixed pressure will cause some of the hydrocarbons to condense into the liquid phase.
Gravity, or more specifically, the difference in specific gravity of the components being separated is the biggest factor in the time it takes for the components to separate.
The greater difference in the specific gravity of the components, the faster separation will occur.
There is a significant difference in the specific gravity between gas, oil and water, so the gas does not take long to break out and rise to the top of the liquids.
The less difference between the specific gravity of the components means there must be more settling or retention time for the components to separate out. If there is a greater difference in the specific gravity of the components, such as in the gas and oil example, gross separation will take place rather quickly.
Want to Learn More About the Other Principles?
Click below to Download our eBook containing the remaining five principles of the oil and gas separation process.
Also, learn more about the key factors to consider for separator optimization.
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