Natural Gas Processing

Natural gas formed hundreds of millions of years ago. The heat and gravity decomposed the dead plants and animals and turned them into petroleum, oil, or natural gas. Most of the time natural gas can be found near oil reservoirs, and because of that, a separation is needed after extraction.

The extraction process depends on how deep the natural gas is below the surface and if there is anything unconventional (rocks that need to be broken up) that could make the extraction less efficient.

Natural gas processing starts with the extraction and begins in the wells. Natural gas can come up through crude oil wells, gas wells, and condensate wells. Natural gas is sometimes just an associated gas that was found and extracted with oil.

However, some reservoirs include only natural gas: in fact, it is called non-associated gas.

Separation starts with oil. The most common method is to use equipment called Conventional Separator which is placed near wellheads so it can start separating right after natural gas came to the surface. It works with gravity: in a simple, closed tank the heavier oil separates from the lighter gas.

Groundwater comes with natural gas many times. Removing the associated water happens right after oil separation and is a more complex procedure. The process involves absorption, or adsorption, depending on the water’s condensation.

Natural gas liquids are not the same as LNG (liquefied natural gas). Additional liquids like oil, butanes, and pentanes have to be removed from the natural gas. The cryogenic expansion process removes lighter hydrocarbons too (such as ethane). The process starts with a dramatic dropping in the temperature: the gas stream reduces to around -85 degrees C. The cryogenic expansion process produces a cleaner natural gas.