1)+Societal+Impacts+of+Sour+Gas+Corrosion

=Societal Impacts of Sour Gas Corrosion=

Natural gas is a very important fuel in today’s society, and is one of the more environmentally friendly fossil fuels. Natural gas is mainly composed on methane (CH 4 ), in the range of 65 – 96 % 1. In addition to methane, natural gas contains impurities such as water (H 2 O), carbon dioxide (CO 2 ), hydrogen sulphide (H 2 S), and oxygen (O 2 ). One of the most important impurities of natural gas that must be considered is hydrogen sulphide, commonly referred to as sour gas. Hydrogen sulphide has the ability to cause corrosion in steel pipes, and given that natural gas is often transported long distances in large networks of pipelines the prevention of hydrogen sulphide corrosion is crucial. Among other issues related to hydrogen sulphide impurities are sulfide stress cracking (SSC) and hydrogen embrittlement (HE), which can cause damage to natural gas pipelines as well 2.

Corrosion is one of the major contributors to pipeline rupture and leakage. In Canada corrosion is responsible for 57% of pipeline ruptures, and in the US 25% of pipeline ruptures are a result of corrosion 1. In Alberta specifically, there are over 6000 sour gas wells and 18 000 km of sour gas pipelines 3. Hydrogen sulphide poses large health and environmental risks and therefore the treatment of the gas is very important. Sour gas is toxic to both humans and animals even at low concentration. Its odor can be detected at less than 1 part per million (ppm), and exposure to sour gas can lead to death within minutes at concentrations greater than 750 ppm 4. For this reason corrosion prevention in order to prevent pipe damage and ultimately pipeline rupture is a very important area of consideration surrounding sour gas extraction.

In Alberta, sour gas is marketable if the H 2 S is removed, and elemental sulphur is recovered as the marketable product. Elemental sulphur is recovered from sour gas through the Claus process: //H 2 S + 1.5O 2 // // à SO 2 + H 2 O// //__SO__ __2__ __+ 2H__ __2__ __S__// //__ à 1.5S__ __2__ __+ 2H__ __2__ __O__// //2H 2 S + O 2 // // à S 2 + 2H 2 O (overall)// Sulphuric acid (produced via the Contact process) is the largest chemical produced (on a volume basis), and is often considered to be an indicator of economic strength in industrialized nations. For this reason, the production and transport of sour gas is extremely important, especially in Alberta, where approximately one third of natural gas wells are sour gas wells. In Alberta various methods are used to ensure the prevention of pipeline rupture due to corrosion (e.g. cathodic protection). While the release of hydrogen sulphide into the atmosphere (i.e. through pipeline rupture) is a major concern, the economic benefits far out weigh the risks. Therefore the necessary precautions must be taken in order to ensure the safety of the environment, as well as the public in all sour gas operations.