ABSTRACT Pressurised sand filled bioreactors have been used to create realistic physiochemical conditions to investigate chemical dosing for the control of oilfield reservoir souring. In a simulation of water injection and wellbore conditions, Molecular Microbiological Methods (MMM) were used to demonstrate that growth of mesophilic and thermophilic sulfate-reducing prokaryotes, including sulfate-reducing bacteria (SRB) and sulfate-reducing archaea (SRA), could be supported. Experimental trials investigated the feasibility of monitoring the onset of reservoir souring by measuring microbially influenced corrosion with an in-line MIC monitor and an integral linear polarization resistance monitoring (LPRM) probe. The subsequent impact of conventional shot dosing and more novel continuous dosing of third generation THPS on established bacterial populations, MIC, hydrogen sulfide generation and dissolution of existing corrosion deposits was evaluated. Key words: Souring, MIC, Pressurised, Bioreactors, SRB, SRA, Third Generation THPS, Molecular Microbiological Methods INTRODUCTION A long term experimental program has been initiated to explore the performance of two biocide dosing strategies and their impact on the near well bore and reservoir environments. Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to NACE International, Publications Division, 1440 South Creek Drive, Houston, Texas 77084. The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association. In addition, the study attempted to measure the impact of reservoir souring upon microbially influenced corrosion (MIC) and ascertained the influence of a chemical treatment program and its ability to limit corrosion rates. In the souring process sulfate ions are reduced to sulfide as part of the SRB's respiration process.