The extraction of natural gas from underground to the wellhead is just the beginning of a complex journey. Natural gas, as it reaches consumers, is remarkably different from its raw form. This is where gas processing plants play a crucial role. These facilities specialize in ‘cleaning’ the raw natural gas by removing impurities, non-methane hydrocarbons, and fluids. The outcome is ‘pipeline quality’ dry natural gas, ready for distribution. Gas processing plants also recover valuable natural gas liquids such as condensate, natural gasoline, liquefied petroleum gas, and other substances like sulfur.
Key Takeaways
Understanding the Basics
Natural gas used by consumers primarily consists of methane. However, major transportation pipelines have specific requirements regarding the composition of the gas allowed into the system. To meet these standards, natural gas must undergo processing. While some preliminary processing may occur at or near the wellhead, the complete processing takes place at dedicated plants situated in natural gas producing regions. A vast network of small-diameter, low-pressure gathering pipelines transports the natural gas from the wellhead to these processing plants. In some cases, a complex gathering system can span thousands of miles, connecting the processing plant with over a hundred wells in the area.
The Process Unveiled
Gas processing is an intricate procedure designed to separate various hydrocarbons and fluids from pure natural gas, resulting in ‘pipeline quality’ dry natural gas. Additionally, natural gas liquids (NGLs) can be extracted during this process. NGLs, such as ethane, propane, butane, isobutane, and natural gasoline, have numerous applications. They boost oil recovery in oil wells, serve as raw materials for oil refineries or petrochemical plants, and can be utilized as energy sources.
While the actual processing of natural gas can be complex, it typically involves four main stages:
1. Oil and Condensate Removal
The first step focuses on eliminating any oil and condensate present in the natural gas. This is achieved through specialized equipment and processes that effectively separate the unwanted substances.
2. Water Removal
To prevent the formation of natural gas hydrates, which can obstruct the flow of gas through valves and gathering systems, water must be removed from the gas. Heaters and scrubbers are installed at or near the wellhead to accomplish this goal. The heaters maintain the gas temperature, ensuring that it does not drop too low. Meanwhile, the scrubbers serve to remove larger impurities such as sand particles.
3. Separation of Natural Gas Liquids
The separation of natural gas liquids is a crucial phase in gas processing. NGLs are typically more valuable than pure natural gas. During this stage, the different components of NGLs are separated, enabling their extraction for various applications.
4. Sulfur and Carbon Dioxide Removal
The final step involves the removal of impurities such as sulfur and carbon dioxide. Advanced processes and equipment are employed to ensure that the resulting natural gas is of the highest quality.
The Journey Continues
After processing is complete, the ‘pipeline quality’ natural gas is injected into gas transmission pipelines for transportation to end users. Often, this necessitates transporting the gas over extensive distances, as gas production sites are typically situated far from major consumption areas.
For more information on natural gas processing plants, visit the Ames Farm Center.
Date of Revision: 10252017
