February 1993
OSO – New Geoscience in the Marketplace
London, UK
Paper
Reservoir Souring: The Involvement of Dormant Thermophilic Sulphate-Reducing Bacteria
Sulphide souring of initially sweet oilfield reservoirs normally occurs due to the growth of sulphide-producing bacteria. These bacteria may be native to the reservoir or, more likely, they are introduced during sea water flooding for secondary oil recovery. Deep oilfields are hot (above 100˚C) and any bacteria in such situations must be able to grow under extreme conditions (i.e. they must be thermophilic). Oil Plus Ltd and the University of Exeter are carrying out an on-going research project, funded jointly by the OSO, Maersk Olie og Gas, Amerada Hess Ltd and Chevron UK Ltd, to define the conditions were thermophilic sulphate-reducing bacteria (tSRB) are able to survive and grow. The aims of the project have been: firstly, to identify the frequency of occurrence of tSRB in North Sea oilfield systems; secondly, to determine temperature and nutrient requirements; thirdly, to determine how tSRB survive adverse conditions (high/low temperatures; nutrient starvation); fourthly, to study bacteria migration in rock; fifthly, what remedial treatments (e.g. chemical boicides) will be appropriate; sixthly, to enhance predictions of the rate and extent of reservoir souring in existing and new fields.
