page_title: Fugitive gas emissions
section_title: Reporting and regulating emissions
hierarchical_section_title: Fugitive gas emissions / Reporting and regulating emissions
caption_attribution_description: English: Surface Casing Vent Flow (SCVF) vs Gas Migration (GM)
context_page_description: Fugitive gas emissions are emissions of gas to atmosphere or groundwater which result from oil and gas activity. Most 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 or via lateral migration along adjacent geological formations. 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.
context_section_description: Policies regulating reporting of fugitive gas emissions vary, and there is often an emphasis on self-reporting by companies. A necessary condition to successfully regulate greenhouse gas (GHG) emissions is the capacity to monitor and quantify the emissions before and after the regulations are in place.
  Since 1993, there have been voluntary actions by the oil and gas industry in the United States to adopt new technologies that reduce methane emissions, as well as the commitment to employ best management practices to achieve methane reductions at the sector level. In Alberta, the Alberta Energy Regulator maintains a database of self-reported instances of gas migration and surface casing vent flows at wells in the province.
  Reporting of leakage in British Columbia did not start until 1995, when it was required to test wells for leakage upon abandonment. Testing upon drilling of the well was not required in British Columbia until 2010. Among the 4017 wells drilled since 2010 in British Columbia, 19%, or 761 wells, have reported leakage problems. Fieldwork conducted by the David Suzuki Foundation, however, has discovered leaky wells that were not included in the British Columbia Oil and Gas Commission's (BCOGC) database, meaning that the number of leaky wells could be higher than reported. According to the BCOGC, surface casing vent flow is the major cause of leakage in wells at 90.2%, followed by gas migration at 7.1%. Based on the methane leakage rate of the reported 1493 wells that are currently leaking in British Columbia, a total leakage rate of 7070 m³ daily (2.5 million m³ yearly) is estimated, although this number may be underestimated as demonstrated by the fieldwork done by the David Suzuki Foundation.
  Bottom-up inventories of leakage involve determining average leakage rates for various emission sources such as equipment, wells, or pipes, and extrapolating this to the leakage that is estimated to be the total contribution by a given company. These methods usually underestimate methane emission rates, regardless of the scale of the inventory.
caption: Illustration of surface casing vent flow and gas migration pathways in the subsurface near a producing well. The cement plug in the lower portion of the well makes this an example of an abandoned well.
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