Product

Sour gas is a form of natural gas that contains significant concentrations of hydrogen sulfide (H₂S) and often carbon dioxide (CO₂), alongside methane and other light hydrocarbons. The presence of H₂S—which is highly corrosive and toxic—requires specialized processing to remove these impurities before the gas can be sold or injected into pipelines.

In a typical sweetening train, sour gas is first contacted with an amine solvent (such as methyldiethanolamine or diethanolamine), which selectively absorbs H₂S and CO₂ under moderate pressure and temperature conditions. The “rich” amine—now loaded with acid gases—is then heated in a regeneration column, where H₂S and CO₂ are released and the lean amine is recycled. The liberated H₂S is converted into elemental sulfur via the Claus process, while CO₂ may be vented, sequestered, or used for enhanced oil recovery.

Contaminant levels in sour gas vary widely:

• Hydrogen sulfide (H₂S): 0.1 – 10 vol % is common (fields above ~0.05 vol % trigger sour-gas processing)
• Carbon dioxide (CO₂): 1 – 8 vol % in many reservoirs
• Mercaptans, COS, CS₂, and trace nitrogen compounds may also be present at ppm to percent levels

Because sour gas composition varies, its average molecular weight and specific gravity likewise span ranges:

• Average molecular weight: 17 – 22 g/mol
• Specific gravity: 0.55 – 0.75 (air = 1)

Because of its toxicity and corrosiveness, handling sour gas demands robust metallurgy, gas‐tight seals, rigorous leak‐detection systems, and strict safety protocols. Facilities processing sour gas include specialized flare systems and sulfur recovery units to minimize environmental impact and ensure worker safety.

Production of sour gas fields is common where deep reservoirs have undergone bacterial or thermogenic alteration, allowing H₂S and CO₂ to accumulate. Once treated, the resulting sweet natural gas meets pipeline specifications and can be used for heating, electricity generation, or as feedstock for petrochemical complexes.