Identification of Bacteria Causing Souring and Biocorrosion in the Halfdan Field by Application of New Molecular Techniques

Abstract

Abstract Nitrate has been added to the injection water in the Halfdan field since January 2001 in an attempt to prevent reservoir souring. As with any new technique, it is important that the treatment is monitored and optimized. In this paper it is demonstrated that cultivation-independent methods are superior for identification of bacteria compared to the traditional cultivation methods. Hence, cultivation-independent methods help improve the quality of monitoring. In situ techniques were implemented on field samples from the Halfdan water injection system. For bacterial quantification and determination of identity, fluorescence in situ hybridization (FISH) was applied. The bacterial functional groups were quantified using microautoradiography (MAR). The results demonstrated that: The MAR and FISH techniques measure at least 100 times greater counts than obtained with the most probable number (MPN) technique, which have an impact on the interpretation.Sulfate reducing bacteria (SRB) made up to 10% of all bacteria present when measured by cultivation-independent techniques. By comparison, the MPN method showed no SRB to be present.Cultivation-independent techniques can be applied much faster (few hours to few days) compared to traditional MPN techniques (30 days incubation time), resulting in a potentially faster response time to e.g. maltreatments.