Experiments examined the effects of flow conditions and fuel chemistry on the soot emissions from turbulent buoyant diffusion flames burning methane-dominated alkane fuels mixtures representative of upstream oil and gas sector flares. Soot (elemental carbon) in the captured plumes was measured via thermal-optical analysis. Yields were calculated within precisely-quantified uncertainties following a mass-balance procedure using CO2, CO, and CH4 gas analyzers. Experiments considered six flare diameters (12.7−76.2 mm), exit velocities up to 9.5 m/s, and thirteen multi-component fuel mixtures. Reynolds number times Froude number squared was shown to be a useful criterion to separate differing soot emissions trends which were aligned with the transition buoyant and transition shear sub-regimes of turbulent buoyant flames as defined by Delichatsios (1993). Soot emission rates in each regime were well-predicted by new empirical models based on flame volumetric flow and global mixing rate and were lower than emission factors used in current pollutant inventories.