51314-3861-The Laboratory Evaluation of Seawater Injection on H2S Production Incorporating Several Different Treatment Strategies Utilising Fixed Film Upflow Bioreactors

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Product Number: 51314-3861-SG

ISBN: 3861 2014 CP

Author: Heike Hoffmann

Publication Date: 2014

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Reservoir Souring is the unplanned production of increased concentrations of hydrogen sulfide (H2S) in well-stream fluids from production wells that are subjected to water-injection. This is typically associated due to the activity of a specialised group the sulfate-reducing Bacteria (SRB). However in recent years various other micro-organisms are believed to be involved in souring e.g. sulfate reducing Archaea (SRA).In this study fixed film up flow bioreactors (FFBUR) were utilized to assess the potential for H2S production or changes in such H2S production when seawater is injected into a North Sea oil reservoir. The study has demonstrated how changes in fundamental parameters (e.g. bacterial nutrients chemical treatments shut-in periods) can impact sulfide production and alter the microbial communities. The FFBUR’s were soured to create a ‘worst case’ scenario and different nutrient additions or remediation treatments were applied to represent either near injection wellbore or deep field conditions.The following parameters were measured during the testing period: sulfide generation volatile fatty acid organic carbon sources (VFA) iron nitrate and nitrite concentrations. The microbiology of the system was evaluated both by traditional culture techniques and molecular methods such as of fluorescence in situ hybridization (FISH) analysis and DNA-based analyses.Results indicate that once sulfide generation had reached 10 mg/L and a dose of a specific biocide solution was applied almost complete cessation of sulfide generation resulted for a period of 14 days. Following the sulfide inhibition period sulfide generation recommenced and again reached a concentration of slightly greater than 10 mg/L in 13 days. However the changes in the microbial community were found to be somewhat selective to certain SRB families. The various effects of the different treatments and conditional changes are discussed further in this paper.