Mobile measurement of methane emissions from natural gas developments in Northeastern British Columbia, Canada

Abstract

<p><strong>Abstract.</strong> North American leaders recently committed to reducing methane emissions from the oil and gas sector, but information on current emissions from Canadian unconventional developments is lacking. This study examined the incidence of methane in an area of unconventional natural gas development in northwestern Canada. In August to September 2015 we completed almost 8000 km of vehicle-based survey campaigns on public roads dissecting developments that mainly access the Montney formation in northeastern British Columbia. Six survey routes were repeated 3–6 times and brought us past over 1600 unique well pads and facilities developed by more than 50 different operators. To attribute on-road plumes to infrastructural sources we used gas signatures of residual excess concentrations (anomalies above background) less than 500 m downwind from infrastructural sources. All results represent emissions greater than our minimum detection limit of 0.59 g/s at our average detection distance (319 m). Unlike many other developments in the US for which methane measurements have been reported recently, the methane concentrations we measured at surface were close to normal atmospheric levels, except inside natural gas plumes. Roughly 47 % of active wells emitted methane-rich plumes above our minimum detection limit. Abandoned and under-development well sites also emitted methane-rich plumes, but the incidence rate was below that of producing wells. Multiple sites that pre-date the recent unconventional Montney development were found to be emitting, and in general we observed that older infrastructure tended to emit more often (per unit) with comparable severity in terms of measured excess concentrations on-road. We also observed emissions from facilities of various types that were highly repeatable. Emission patterns in this area were best explained by infrastructure age and type. Extrapolating our results across the Montney development, we estimate that the emission sources we located (emitting at a rate > 0.59 g/s) contribute more than 111,800 tonnes of methane annually to the atmosphere. This value exceeds reported bottom-up estimates of 78,000 tonnes for all oil and gas sector sources in British Columbia, of which the Montney represents about 55 % of production. The results also demonstrate that mobile surveys could be used to exhaustively screen developments for super-emitters, because without our intensive 6-fold replication we could have used single-pass sampling to screen 80 % of Montney-related infrastructure. This is the first bottom-up study of fugitive emissions in the Canadian energy sector, and these results can be used to inform policy development in an era of methane emission reduction efforts.</p>

Methane emissions from upstream oil and gas production in Canada are underestimated

“…Gas concentrations (CH 4 , CO 2 , C 2 H 6 , H 2 S) were measured in real time using laser spectrometers (Picarro Inc., Santa Clara, CA, USA), (2) computational signal processing and geochemical analysis were used to distinguish oil and gas emissions from biogenic, naturally occurring sources, or other anthropogenic emissions, (3) we conducted a back-trajectory analysis to attribute emission anomalies observed on-road to specific upwind sites, (4) volumetric emissions rates were estimated via a point-source Gaussian Dispersion Model (GDM). Each of these steps, and uncertainties therein, have been explained previously 9 , 17 , 18 . Thus, only a brief overview is included in the next three subsections.…”

“…The uncertainties related to our methods of plume detection, attribution, and emission rate estimation have been previously evaluated 9 , 17 , 18 . Plume detection uncertainty (i.e.…”

“…Canada’s CH 4 reduction targets are based on component-level inventory estimates reported annually in the national inventory report (NIR), which are based in part on industry self-estimation and self-reporting 4 . Field measurement studies in Canada and the US have shown that actual emissions range from equivalent to substantially higher than inventory estimates 9 – 16 . But a national understanding of discrepancies is lacking because most measurement studies in Canada consist of relatively region-specific sample populations which may not be extensible to regions with varying extractive techniques, geology, and geochemical properties.…”

“…Our findings are consistent with previous CH 4 emission studies within Canadian developments; no studies have yet identified a Canadian oil and gas producing region with emissions lower than the inventory estimate. In previous studies, factors of 1–15 have been estimated, with most being in the range of 1.5–3.0 9 – 11 , 14 , 15 . This implies that CH 4 abatement costs could be lower per ton of CO 2 equivalent than previously reported, due to higher volumes of CH 4 (i.e.…”

Field Performance of New Methane Detection Technologies: Results from the Alberta Methane Field Challenge

“…Field studies have been conducted as part of recent methane measurements campaigns. Mobile truck-based platforms were deployed in British Columbia and Alberta to measure site-level emissions, while plane-based systems were used to detect site-and basin-level emissions in the US [25]- [31]. More recently, scientists deployed drone-based systems for methane detection and quantification at O&G facilities [29], [30], [32].…”