Distribution pattern of hydrogen sulphide-bearing gas in the former Soviet Union

H2S is an unwelcome accompaniment to natural hydrocarbon gas but, in sufficient volumes, it can provide an economic source of sulphur, termed a 'gaseous sulphur' accumulation. Such accumulations are an important component of the sulphur reserves of Russia and other countries. A comparative study of the distribution of economic gaseous sulphur accumulations, together with native sulphur deposits, in the Amu Dar'ya, Volga-Urals, North Caspian and other basins of the former Soviet Union and elsewhere shows that they occur only within large hydrocarbon basins and are restricted to thick and regionally persistent evaporite-carbonate successions. The lithological and geochemical controls and various types of sulphur paragenesis result in a zoned series of accumulations, from gaseous sulphur to sulphur-rich oils to native sulphur, which can be traced from the deep central regions of hydrocarbon-bearing basins with sulphate-evaporite successions towards the shallow basin margins.