Fugitive gas emissions

Fugitive gas emissions are emissions of gas (typically natural gas, which contains methane) to atmosphere or groundwater^[1] which result from oil and gas or coal mining activity.^[2] In 2016, these emissions, when converted to their equivalent impact of carbon dioxide, accounted for 5.8% of all global greenhouse gas emissions.^[2]

Most fugitive emissions are the result of loss of well integrity through poorly sealed well casings due to geochemically unstable cement.^[3] 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).^[3] Approximately 1-3% of methane leakage cases in unconventional oil and gas wells are caused by imperfect seals and deteriorating cement in wellbores.^[3] Some leaks are also the result of leaks in equipment, intentional pressure release practices, or accidental releases during normal transportation, storage, and distribution activities.^[4][5][6]

Emissions can be measured using either ground-based or airborne techniques.^[3][4][7] In Canada, the oil and gas industry is thought to be the largest source of greenhouse gas and methane emissions,^[8] and approximately 40% of Canada's emissions originate from Alberta.^[5] Emissions are largely self-reported by companies. The Alberta Energy Regulator keeps a database on wells releasing fugitive gas emissions in Alberta,^[9] 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.^[1] Some studies have shown a range of 6-30% of wells suffer gas leakage.^{[7][9][10][11]}

Canada and Alberta have plans for policies to reduce emissions, which may help combat climate change.^[12][13] Costs related to reducing emissions are very location-dependent and can vary widely.^[14] Methane has a greater global warming impact than carbon dioxide, as its radiative force is 120, 86 and 34 times that of carbon dioxide, when considering a 1, 20 and 100 year time frame (including Climate Carbon Feedback ^{[15] [16][9]} Additionally, it leads to increases in carbon dioxide concentration through its oxidation by water vapor.^[17]