Catalytic Heaters at Oil and Gas Sites May be a Significant yet Overlooked Seasonal Source of Methane Emissions

Abstract

Successful reduction of oil and gas sector methane emissions to meet near-zero intensity targets requires the identification and mitigation of all possible sources. One potentially important source is catalytic heaters, which have largely escaped attention in regulatory and mitigation efforts despite being ubiquitous at upstream production sites in cold climate regions. This study reports direct in situ measurements of the exhaust streams of 38 natural gas-fired catalytic heaters at upstream production sites in British Columbia, Canada. All heaters in the sample showed consistently poor methane conversion with mean destruction efficiencies of 61 ± 5% while releasing 235 [+31/-28] g of methane per cubic meter of fuel. Although individual units are generally small methane sources (mean of 0.28 ± 0.04 kg/h), their prevalence means they could represent 6% of the total provincial upstream methane inventory and as an aggregate methane source could be 5× more significant than abandoned wells. Notably, these heaters are seasonal sources whose emissions would be missed in measurement campaigns occurring solely in summer months. However, additional measurements from a small number of heat medium burners demonstrate that, where feasible, methane emissions can be reduced by approximately 425× by replacing catalytic heaters with centralized heat systems.

Figure 1

(a) Schematic of a catalytic heater showing the location of the sampling point within the fume hood, accompanied by pictures of a heater and the outdoor vent typically used. (b) Picture showing sampling of exhaust gases from a heater.

Figure 2

Example exhaust gas species fractions for two catalytic heaters, showing the measured time history of oxygen, carbon dioxide, and methane. (a) Typical result for a heater with stable exhaust flow. (b) Sampled unit with the least stable exhaust flow, including periods where oxygen concentrations spiked as exterior air flowed into the exhaust duct.

Figure 3

Carbon conversion efficiency (blue dots) and methane emission rate (red diamonds) of all catalytic heaters when operating at 100% fuel flow rate. Error bars represent 95% confidence bounds on the individual mean values. Dashed lines and shaded regions denote the 95% confidence interval on the derived mean CCE and emission rate.