Shikhzarli is a typical active mud volcano (MV) in Azerbaijan with extremely high percentages of fire eruptions reaching 74%. The strong eruption of Shikhzarli MV on 13 March 2011 (Shamakhi–Gobustan region, central Azerbaijan, at 40°29′12.5′′N; 49°02′03.4′′E) was accompanied by gas ignition with a straight-flow vertical gas flare. A large (60 m height) short-living (30 min) gas flare and small (1.5 m height) gas spouts with longer lifetimes (5 h) were simulated in SigmaFlow, and the model was used to evaluate methane flux and the amount of combusted methane. Geological and mineralogical data, field observations, as well as eye witness reports and photographs in mass media were used to choose the boundary conditions for the gas fire simulation. This study provides the first quantitative evaluation for methane emission during an MV catastrophic eruption. As simulation predicts, 14,000 m3 of methane was consumed for the life time (30 min) of the main 60-m high flare, which is equivalent to nine tons of cold gas at ambient conditions; the volume of erupted methane for the 5-h lifetime of a small spout (1.5 m high) was 72.6 m3 (45 kg) of cold CH4. The amount of methane emitted during a single strong flame eruption is commensurate with the annual output of permanently active individual MV vents or may be ten to hundred times as high.