Sour gas is an unconventional fuel consisting mainly of methane (CH4), carbon dioxide (CO2), and hydrogen sulfide (H2S) that constitutes a considerable, currently untapped energy source. However, little is known about its combustion characteristics. In this work, we used our recently assembled and validated detailed chemical reaction mechanism to examine some of the combustion properties of sour gas with different compositions in both conventional air combustion and oxy-fuel combustion, the latter being motivated by application in carbon capture and storage. The calculations suggest that raising the H2S content in the fuel leads to relatively small changes in the flame temperature and laminar burning velocity, but a considerable reduction in the ignition delay time. At elevated pressures, H2O diluted oxy-fuel combustion leads to higher burning velocities than CO2 diluted oxy-fuel combustion or air combustion. Mixed CH4/H2S flames exhibit a two-zone structure in which H2S is oxidized completely to sulfur dioxide (SO2) while CH4 is converted to carbon monoxide (CO). Formation of corrosive sulfur trioxide (SO3) mainly occurs during CO burnout. (C) 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved.