sulphur is found in heavy crude oils or extra heavy crude oils. These oils does not flow easily that's why they are called heavy. These crude oils have hig molecular weight and boiling point as they contain over 60 carbon atoms. Presence of high amounts of NSO's, and high ratio of naphthenes and aromatics to paraffins make them heavy. This heaviness is high proportional to non-paraffinic compounds, high molecular weight and low proportional to low molecular weight. Here are the name of some heavy and extra heavy crude oil with high molecular weight-
Canadian extra heavy crude oil with viscosity range 5000-10,000 cP.
Venezuela's Orinoco extra-heavy crude oil with viscosity range 1000-5000 cP.
Two main types of heavy crude oils-
High sulphur crude oils: Contain over 1% sulphur with asphaltenes and aromatics. Mostly found in North America including Canada (Alberta, Saskatchewan), United States (California, Mexico), South America (Venezuela, Colombia and Ecuador) and the Middle East (Kuwait, Saudi Arabia).
Low sulphur crude oils: Contain less than 1% sulphur with naphthenes, aromatics and resins. Mostly found in Western Africa, East Africa and Central Africa (Chad, Angola, Madagascar).