The Implications of Hydrogen Sulphide in the Oil and Gas Industry - Case Studies and Lessons Learned

The presence of Hydrogen sulphide in the produced fluids and gases in the hydrocarbon industry worldwide has long been an issue. In many parts of the world hydrogen sulphide is naturally occurring from geological origin, such as experienced in the Middle East and North Africa. However, there are other instances where hydrogen sulphide has been generated in-situ within oil reservoirs as a direct result of deliberate intervention in the oil recovery process, through secondary oil recovery practices such as seawater injection. The presence of hydrogen sulphide from either source, present almost identical challenges; hydrogen sulphide is very toxic, exposure to relatively low concentrations can lead permanent disability or death. Hydrogen sulphide is classified as an acidic gas and can create in the right circumstances a very corrosive environment both in terms of accelerating the more normal corrosion mechanisms but also more specifically in the form of sulphide stress corrosion cracking.

This paper discusses the mechanisms and practices leading to the presence of hydrogen sulphide in hydrocarbon systems. It considers not only sulphides present as a result of geochemical activity but also those derived from microbial reduction of sulphate by sulphate reducing microbes such as sulphate reducing bacteria (SRB) and sulphate reducing archaea (SRA) metabolising in-situ or injected sulphate. What practices can be pursued to mitigate against its generation or in controlling its effects. Case histories are presented anonymised where appropriate, which from an industrial safety standpoint, detail the effects of the uncontrolled and in some cases unknown presence of hydrogen sulphide within hydrocarbon production systems.