Methane emissions from inactive oil and gas wells in Western Canada

The oil and gas industry is the largest source of methane emissions for many countries, including Canada. In the last 10 years, several new studies have highlighted the underestimation of methane emissions from active wells and facilities compared to national inventories. In contrast, only a few studies have focused on emissions from inactive wells. These studies also suggested underestimation compared to national inventories. In this context, more research is needed, and to address this, we undertook an extensive analysis, mining close to 15,000 vehicle-based measurements acquired across Alberta and Saskatchewan over a span of six years. The results showed averaged emission factors ranging from 0.09 to 0.15 kg/hr for suspended well sites, aligning well with the literature (0.008-0.45 kg/hr with a mean of 0.20 kg/hr) for this region. Similar to previous studies, the most significant sources of emissions were suspended gas wells in Red Deer, Alberta, and heavy oil sites near the border of Alberta and Saskatchewan. No emission factors were computed for plugged well sites because of insufficient observations. Although suspended and plugged wells emit less methane per site or at a lower frequency than active wells, their large numbers can result in significant total methane emissions. Our results support proposed amendments to the federal oil and gas methane regulations that would, for the first time, extend the regulatory scope to all infrastructure, including nonproducing wells. The results from this study also confirmed that vehicle-based surveys can detect emissions from isolated suspended well sites.