Sour gas

Sour gas is natural gas or any other gas containing significant amounts of hydrogen sulfide (H2S).

Natural gas is usually considered sour if there are more than 5.7 milligrams of H2S per cubic meter of natural gas, which is equivalent to approximately 4 ppm by volume under standard temperature and pressure.[1][2] However, this threshold varies by country, state, or even agency or application. For instance, the Texas Railroad Commission considers a sour gas pipeline one that carries gas over 100 ppm by volume of H2S.[3] However, the Texas Commission on Environmental Quality has historically defined sour gas for upstream operations – which requires permitting, reporting, and possibly additional emission controls – as gas that contains more than 24 ppm by volume.[4][5] Natural gas that does not contain significant amounts of hydrogen sulfide is called "sweet gas".

Although the terms "acid gas" and "sour gas" are sometimes used interchangeably, strictly speaking, a sour gas is any gas that specifically contains hydrogen sulfide 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. Thus, carbon dioxide by itself is an acid gas, not a sour gas. In addition to being toxic, hydrogen sulfide in the presence of water also damages piping and other equipment handling sour gas by sulfide stress cracking. Natural gas typically contains several ppm of volatile sulfur compounds, but gas from one well in Canada is known to contain 90% hydrogen sulfide and others may have H2S contents in the tens of percent range.[6]

  1. ^ NaturalGas.org website page Processing Natural Gas
  2. ^ Air Dispersion Modeling Conversions and Formulas
  3. ^ Pipeline Definitions Archived 2012-05-02 at the Wayback Machine Railroad Commission of Texas.
  4. ^ Permit by Rule Chapter 106 - July 31, 2008 Scroll down to PDF page 38 of 58 PDF pages.
  5. ^ Oil and Gas Handling and Production Facilities Title 30 Texas Administrative Code § 106.352(l) Texas Commission on Environmental Quality (TCEQ). Scroll down to page 2.
  6. ^ Cite error: The named reference Ullmann was invoked but never defined (see the help page).

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