Abstract
Screening tests were conducted to determine the relative efficacy of six proprietary dual biocide-dosing regimes against planktonic bacteria and sessile bacteria in biofilms. Test conditions represented those encountered in the West Kuwait oil fields where Zubair aquifer water and effluent water are injected into the reservoir. Tests were performed using mixed cultures (sulfate-reducing bacteria (SRB), general aerobic bacteria (GAB) and general anaerobic bacteria (GAnB’s)) of mesophilic bacteria enriched from produced water associated with oil production. In all cases, the dual biocide treatments effectively reduced the numbers of planktonic bacteria to below detection and the numbers of sessile bacteria to low levels. All treatments produced a satisfactory effect in significantly reducing the SRB populations. Overall both aldehyde and quaternary biocide formulations provided suitable laboratory results to support them being employed in the field. A gluteraldehyde-based biocide also gave acceptable performance but the effectiveness of gluteraldehyde can be significantly decreased at acid pH such as is found in the Zubair aquifer System. An extensive discussion section of oilfield biocide strategies and the merits of dual biocide treatments are included.
