Air

Sour gas

Sour gas is natural gas that contains hydrogen sulphide, a colorless flammable compound that has a strong rotten egg odor. This gas is toxic to humans and animals in low concentrations, and can be dangerous if not handled properly.

More than 30 per cent of the natural gas produced in Western Canada is considered sour. Sour gas can also occur as solution gas in crude oil.

• safety measures during drilling
  Special precautions are taken during drilling critical sour gas wells (wells with the potential for large hydrogen sulphide releases or for any release that might affect population centres). These include specific requirements for drilling plans and procedures, well design, specialized worker training and supervision, safety specialists, detailed emergency response plans and community consultation. When the drill bit enters the critical zone where sour gas is likely to be encountered, additional precautions include providing continuous gas “sniffing” or testing, supplying breathing apparatuses for rig personnel and notifying people living nearby.
  
  
• emergency response planning
  Companies and governments have developed computer models to predict how sour gas would disperse in the event of a blowout or other accidental release. Emergency response planning for sour gas wells is based on the results of these models. Plans specify steps that would be taken to protect people’s health and safety in the event of a release. When wells produce high levels of sour gas, the measures include igniting the gas, which converts hydrogen sulphide into sulphur dioxide. (Sulphur dioxide is also toxic but disperses more effectively because heat carries it upward, resulting in lower ground-level concentrations. It can result in a detectable odour of sulphur.) One of the first activities initiated in a sour gas blowout is the monitoring of air quality downwind from the well. Mobile equipment is set up to track the plume and to identify concentrations of gas both inside and outside the emergency planning zone. If the emergency response team determines there is a danger, residents would be evacuated or the well ignited to protect the public.
  
  
• multi-stakeholder consultation
  Industry is committed to working with governments, communities and other stakeholders to improve public confidence in the way sour gas is regulated, developed and produced. In 2000, for example, the upstream oil and gas industry participated with government and public stakeholders in an independent committee formed by the Alberta Energy and Utilities Board to improve the understanding, handling and regulation of sour gas in the province. This advisory committee developed 87 recommendations to improve regulatory and operating practices, understanding of health effects and public communication and information on sour gas. The Board has committed to addressing all recommendations. In response to the recommendations, the Canadian Association of Petroleum Producers (CAPP) developed a set of recommended practices for planning sour gas developments.