Produced wellhead gas is wet, saturated with heavy hydrocarbons and contained with salt and sand.
Gas Conditioning Unit varies from a small station that handle 10 million SCFD to a big station that process 500 Million SCFD.
Wells scattered throughout the remote regions, and then carried by export line to the processing unit. Liquid are separated from gas. The liquids consist of salt water and condensate.
The condensate is collected to oil refinery, where the condensate is blended into gasoline. The water is removed and then injected back into the ground in disposal wells.
The gas pressure varies from a few psig to thousands. Wells may contain H2S. The temperature may be over 200 degF and the BTU content ranges from 1000 to 1400 BTU scfd.
The gas will flows to a Knock out drum to removed entrained liquids, the filtered to removed sand and corrosion products, compressed and scrubbed with amine solution to remove H2S.
By circulating ethylene glycol system. Gas is dehydrated. The gas is dried so it will not precipitate water at temperature down to -35 deg F. After dehydration, ethane, propane, isobutane, butane and gasoline is recovered.
The propane is sold as LPG, butane is blended into gasoline, isobutane becomes a feedstock for refinery alkylation unit and ethane is used to a chemical ethylene unit.
The gas is traded on its BTU content.