The Application of Investigative Workflows for Sour Field Mitigation and Remediation

Abstract Reservoir souring is simply defined as the predicted or observed increase in production of sulphide in oil, water or gas phase. The potential causes are far less simply defined, and can, in many cases, lead to a significant disruption to operations through concerns over HS&E, integrity and process efficiency. The consequences of sour production can be far reaching, and almost always expensive, perhaps to the point of making a field un-economical to produce. One of the reasons for this is that, in many cases the response to souring is to mitigate, long term and short term, the consequences of souring, rather than the cause of souring. This paper examines the application of both high level and detailed investigation workflows which have led to significant improvements in understanding both the risks associated with souring and the most techno-economically feasible long term and short term mitigations of both causes and effects. The aim of the workflow is to define causes and develop solutions to either mitigate souring and/or the effects of souring, maximising the techno-economic benefit to the operator and reducing HS&E risks as much as possible. The workflows themselves are phased and flexible, they aim to examine pre-existing data, examine their validity, and/or collect new data to identify the probable causes of souring in each specific case. Once the cause(s) have been defined it then becomes possible to estimate worst case souring potential and integrity threat based upon biochemical and geochemical interactions, phase behaviours and the physical condtions for either microbiological and/or non-microbiological throughout the system. This approach has been applied numerous times to great effect in sub-sahran Africa, North America and Europe.