Materials for sour gas H2S
Sour gas at high pressure, temperature and in mixtures of other acids like formic acids found typically indown hole oil well stimulation environments is extremely corrosive. In these environments few materials could survive. Tantalum surface alloys are immune to sour gas environments showing no measurable corrosion rate. This far exceeds the performance of traditional materials like Hastelloy C276 and various grades of titanium metals.
Sour Gas (H2S) and Acid Gas Definition
Sour gas is natural gas or any other gas that is corrosive due to significant content of hydrogen sulfide (H2S). Natural gas is considered sour if there are more than 5.7 milligrams of H2S per cubic meter of natural gas (4 ppm H2S by volume). Natural gas that contain less amounts of hydrogen sulfide is called "sweet gas".
The terms "acid gas" and "sour gas" are often used interchangeably, strictly speaking, a sour gas is any gas that contains hydrogen sulfide (H2S) in significant amounts, whereas an acid gas is any gas that contains significant amounts of acidic gases such as carbon dioxide (CO2) or hydrogen sulfide (H2S). Thus, carbon dioxide by itself is an acid gas but it is not a sour gas.
Corrosion of sour gas under transportation
Natural gas that have high sulfur and carbon dioxide contents (sour and acid gas) is reconized being extremely corrosive and dangerous. Special corrosion resistant material will have to be applied as Carbon steel is not suitable. Transportation from the wellhead to the sweetening plant must be done carefully
Sour gas corrosion in elevated temperature systems
At elevated temperature hydrogen sulfide acid gas may become severely corrosive. Corrosion rates in the rang inches per year or mils per day has been reported on Hastelloy C-276 (Hastelloy) autoclaved used in laoratories. In these systems offer an essentially zero corrosion rate.
