Recently we compared gathering gas at the wellhead to your buddies gathering at your house to watch a big game. Everybody gathers in one place, for one reason.
Now, after the game is over, your wife is ready for your loud, obnoxious friends to get off the couch. “You don’t have to go home, but you can’t stay here,” she says.
It’s similar to the gas gathering process, in that, the gathered gas can’t stay in the gathering lines. It has to be moved to a processing facility, to a larger transmission system, to storage or a shipping point.
Much of the gas that comes from the ground in not ready to be used by consumers; it must be treated and processed first. This means the various contaminants, natural gas liquids and water must be separated to leave behind the purest natural gas possible. You may hear it referred to as “pipeline quality” natural gas.
If there are impurities such as carbon dioxide in the gas stream, they are removed in the treating process.
Water is removed from the gas stream in a dehydration process. Other components that may be separated include natural gas liquids (NGLs) such as propane, ethane and butane. The NGLs must be broken down further to be useful during a process called fractionation (discussed in our next series entry).
The pipeline quality natural gas moves from the processing plant to transmission lines which take the product to different parts of the country and ultimately to your home.
As for the products such as propane that must be fractionated…we’ll cover that in the next Midstream 101 post.