Sweet and sour: A quantitative analysis of methane emissions in contrasting Alberta, Canada, heavy oil developments

Abstract

Cold heavy oil production with or without sand (CHOPS, or CHOP) are prevalent methods of oil extraction in western Canada. CHOP(S) sites account for over 40% of all reported vented methane (CH₄) from oil production in Alberta, and high rates of CH₄ emissions have been confirmed in independent measurement studies. In this study, we used truck-based surveys coupled with qualitative optical gas imaging (OGI) to quantify and characterize methane emission rates and sources at nearly 1350 and 940 well sites in two major CHOP(S) developments respectively in 2016 and 2018. The studies were conducted in Lloydminster, Alberta, where produced gases are sweet (i.e., <0.5% sulfur) and non-olfactory, and Peace River, Alberta, where regulations were implemented in 2017 to manage sour (i.e., >0.5% sulfur) odorous emissions (hydrogen sulfide, BTEX, etc.). Based on results from all surveys, in Peace River, 43% of measured sites were emitting CH₄, compared to 37% in Lloydminster. The measured CH₄ emission rates in Peace River were, however, significantly lower than in Lloydminster for both years, and had fallen from 2016 to 2018. In 2018, emissions in Lloydminster were fairly unchanged relative to previous measurements taken in 2016. OGI showed that tanks in Peace River continue to emit CH₄ despite regulatory interventions and a reported venting rate of zero. The continued emissions were thus classified as "unintended venting", which can be a consequence of the non-routine malfunction (e.g., inappropriate operator action or poor equipment design/sizing) of vapor recovery equipment. Mitigation strategies implemented in Peace River targeting olfactory compounds were beneficial in reducing and keeping CH₄ emissions lower, since these gases are co-emitted, and could even be co-regulated provincially. Reciprocal to that, we might expect future air quality improvements as a consequence of the new provincial requirements to reduce CH₄ emissions under amended Directives 060 and 017.

Keywords: CHOPs; Fugitive emissions; Heavy oil developments; Methane emissions; Methane regulations; Venting.