Flare: Solution Gas Combustion, AER Directive 060, and Flare Stack Efficiency in the WCSB
A flare is an engineered arrangement of a vertical stack, a pilot, and one or more burner tips used to safely combust hydrocarbon vapours that cannot be conserved, sold, or otherwise routed to a sales line. Flares appear at the wellsite during drilling, completions, and well testing, and they are permanent fixtures at gas plants, batteries, compressor stations, and refineries where they handle both routine streams and emergency relief from pressure-safety valves. The arrangement is sometimes called a flare stack, and the act of burning the gas is called flaring as distinct from venting, which releases raw gas to atmosphere without combustion. The chemistry is straightforward oxidation: methane and heavier hydrocarbons react with atmospheric oxygen to produce carbon dioxide and water vapour, converting methane (a greenhouse gas roughly 28 times more potent than CO2 over a 100 year horizon) into the far weaker CO2. A well designed flare achieves combustion efficiency of 98 percent or higher, but efficiency falls sharply in high crosswinds, with low heating-value gas, or when the exit velocity is poorly matched to the flow, which is why assist gas, steam, or air is sometimes added to stabilise the flame and suppress smoke. In the Western Canadian Sedimentary Basin, flaring is governed primarily by AER Directive 060, which sets the regulatory framework for flaring, incinerating, and venting and establishes a basin-wide solution-gas conservation expectation: an operator must conserve associated gas where it is economic to do so, evaluated against a defined net-present-value threshold, rather than flare it. Volumes are reported in e3m3 (thousands of cubic metres) and aggregate basin flaring is tracked in millions of cubic metres, with 1 e3m3 equal to roughly 0.0353 million cubic feet, so a 1,000 e3m3 monthly flare equals about 35.3 MMcf. Sour streams carrying hydrogen sulfide demand special handling because incomplete combustion releases toxic H2S and produces sulfur dioxide, so Directive 060 imposes setback, dispersion-modelling, and minimum-efficiency requirements on sour flares. Flaring also intersects with measurement rules under Directive 017, methane-reduction targets that have driven a steep decline in routine WCSB flaring since 2020, and the economics of small or remote solution gas volumes that fall below the conservation cutoff.
Key Takeaways
- Combustion, not release: A flare oxidises hydrocarbon vapour to CO2 and water rather than releasing raw methane, the distinguishing feature versus venting. Target destruction efficiency is 98 percent or better; crosswind, low heating value, and poor velocity matching erode it, so steam or air assist and proper tip sizing are used to hold a clean, stable flame and avoid black smoke.
- AER Directive 060 governs the WCSB: Alberta's flaring, incinerating, and venting framework requires operators to conserve solution gas where economic, judged against a net-present-value test, before flaring is allowed. It sets sour-gas dispersion modelling, minimum combustion efficiency, and reporting obligations, and ties into Directive 017 measurement and provincial methane-reduction targets.
- Dual-unit volumes: WCSB flare volumes are reported in e3m3, where 1 e3m3 equals about 0.0353 MMcf or 35.3 Mcf. A battery flaring 500 e3m3 in a month burns roughly 17.6 MMcf of gas. Aggregating across thousands of sites, basin reporting rolls up to 10e6m3 (million cubic metre) scale for annual conservation accounting.
- Sour service is higher risk: Flaring H2S-bearing gas produces SO2 and, if combustion fails, releases toxic hydrogen sulfide at ground level. Directive 060 mandates setbacks, continuous pilots, and modelling to keep ground-level concentrations below human-exposure limits, which is why sour flares at sites like Duvernay or Nisku sour pools carry stricter design margins than sweet-gas flares.
- Conservation has displaced routine flaring: Tighter economics, methane rules, and gathering-system buildout have cut routine WCSB solution-gas flaring sharply since 2020. Most remaining flaring is non-routine: well-test cleanup, upset relief, and stranded volumes too small or remote to justify a tie-in, where the Directive 060 economic test permits continued flaring.
Flare Efficiency and Why Crosswind Matters
Combustion efficiency is the fraction of hydrocarbon actually oxidised to CO2 rather than escaping as unburned methane or partially burned products. Open-pipe flares lose efficiency in high wind because the flame is bent and air entrainment becomes uneven, allowing pockets of gas to slip past unburned; at sustained winds above 30 to 40 km/h an unassisted flare can drop well below the 98 percent design figure. Operators counter this with enclosed or shrouded flare tips, pilot monitoring, and minimum exit-velocity control. Heating value matters too: lean gas below roughly 7.5 MJ/m3 may not sustain stable combustion, so supplemental fuel is blended in to keep the flame lit and efficient.
Flaring Versus Conservation Economics
Under Directive 060 an operator must conserve solution gas when a gathering tie-in clears a net-present-value threshold, typically modelled over the producing life of the well. A Montney oil well producing 20 e3m3/d of associated gas 8 km from the nearest sales line will usually justify a pipeline tie-in at CAD 250,000 to 600,000 per kilometre, so flaring it long-term would breach the conservation test. A marginal Cardium well making 2 e3m3/d at 25 km, by contrast, may fall below the cutoff, and the AER permits continued flaring with reporting. This calculus shifts with AECO gas price, making conservation more attractive in strong-price years.
Fast Facts
Alberta once flared so much solution gas that satellite night imagery showed the WCSB as a visible cluster of light, prompting the province's 1990s flaring-reduction initiative that cut routine solution-gas flaring by more than 70 percent within a decade. The visible orange flame people associate with flares is actually a sign of incomplete combustion and soot; a perfectly efficient flare burning sweet pipeline-quality gas is nearly invisible in daylight, showing only a faint heat shimmer above the tip.
Related Terms
A flare sits within a cluster of conservation and safety concepts. Venting is the regulated alternative that releases gas without combustion and is restricted under the same Directive 060 framework because raw methane is a far stronger greenhouse gas. Solution gas is the associated gas liberated from oil that most routine flaring once consumed. Hydrogen sulfide defines sour service and drives the stricter dispersion rules on sour flares, while sour gas handling at plants determines whether a stream can be conserved or must be incinerated.
Real-World WCSB Scenario: Duvernay Completion Flowback near Fox Creek
An operator completing a multi-stage Duvernay horizontal near Fox Creek must flow back roughly 4,000 m3 of fracturing fluid and clean up the well before tie-in. During the 9-day cleanup the well unloads sour gas at 80 to 120 e3m3/d, well above the rate any temporary line could take, so the volume is routed to a sour flare engineered per Directive 060 with continuous-pilot monitoring and a 100 m setback from the lease edge. The operator runs AER-required dispersion modelling to confirm ground-level H2S stays below 10 ppm at the boundary, and meters the flared volume under Directive 017 for royalty and emissions reporting.
Total cleanup flaring reaches about 900 e3m3 (roughly 31.8 MMcf), reported to the AER as non-routine well-test flaring. Once flowback stabilises, the well is tied into the existing sour gathering system at an incremental cost near CAD 1.4 million, after which solution gas is conserved and routine flaring drops to zero, satisfying the conservation test for the well's producing life.