The application of triazine-based H2S scavengers are often used for the removal of H2S during oil and gas production processes. Most oil and gas production installations today use monomethylamine (MMA) and monoethanolamine (MEA) based triazines for H2S removal. Although triazine products have a good capacity to reduce the sulfide concentration, they are associated with several drawbacks, such as significant calcium carbonate scaling issues due to an increased pH of process waters. Issues in downstream refineries processing crudes are also reported.

This paper presents feedback on the impact of triazine scavengers in North Sea and American installations in terms of performance and technical issues1. Attention has been focused on the development of alternative scavenger chemistries with good scavenging capability, limited impact on carbonate scaling and which do not interfere with existing scale control strategies. The evaluation of a range of H2S scavengers based on different chemistries, looking at both influence on scaling and scavenging ability, is described.

It has been shown that the chemistry of the scavengers can have a significant influence on carbonate scaling.2,3 In general, scale formation correlates with pH, with a large increase in the rate of carbonate scaling observed in the presence of the amine-based scavengers due to their high pH. Scavenger products based on triazine and oxazolidine structures show the best scavenging performance where an aqueous phase is present. However, this work has highlighted that an oil soluble zinc carboxylate product formed deposits in the water-based test.

Correlation of both carbonate scaling tendency and H2S scavenging ability by these products has been studied to assess suitability for application in environments where carbonate scale is either known or has the potential to form.

This work has demonstrated that it is possible to identify alternative scavenger chemistries that are able to scavenge efficiently, but do not increase the carbonate scaling tendency following scavenger dosing and validates the approach of investigating different chemistries as a way of improving the process of H2S removal during oil and gas production.

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