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Concept
Fugitive gas emissions
Résumé
Fugitive gas emissions are emissions of gas (typically natural gas, which contains methane) to atmosphere or groundwater which result from oil and gas or coal mining activity. In 2016, these emissions, when converted to their equivalent impact of carbon dioxide, accounted for 5.8% of all global greenhouse gas emissions.
Most fugitive emissions are the result of loss of well integrity through poorly sealed well casings due to geochemically unstable cement. This allows gas to escape through the well itself (known as surface casing vent flow) or via lateral migration along adjacent geological formations (known as gas migration). Approximately 1-3% of methane leakage cases in unconventional oil and gas wells are caused by imperfect seals and deteriorating cement in wellbores. Some leaks are also the result of leaks in equipment, intentional pressure release practices, or accidental releases during normal transportation, storage, and distribution activities.
Emissions can be measured using either ground-based or airborne techniques. In Canada, the oil and gas industry is thought to be the largest source of greenhouse gas and methane emissions, and approximately 40% of Canada's emissions originate from Alberta. Emissions are largely self-reported by companies. The Alberta Energy Regulator keeps a database on wells releasing fugitive gas emissions in Alberta, and the British Columbia Oil and Gas Commission keeps a database of leaky wells in British Columbia. Testing wells at the time of drilling was not required in British Columbia until 2010, and since then 19% of new wells have reported leakage problems. This number may be a low estimate, as suggested by fieldwork completed by the David Suzuki Foundation. Some studies have shown a range of 6-30% of wells suffer gas leakage.
Canada and Alberta have plans for policies to reduce emissions, which may help combat climate change. Costs related to reducing emissions are very location-dependent and can vary widely.
Source officielle
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