Nitrate Treatment Strategy, Differences of the Reservoir Scale and the Lab Scale

For years reservoir souring has caused serious economic and environmental damages. High concentration of sulphate in seawater besides the presence of sulphate reducing microorganisms in both seawater and reservoir fluids are a major source of this issue. Even though most of the academic research studies and industrial report propose nitrate treatment as a favourable mitigation strategy, some reports introduce it as an inefficient method. As the available literature data have studied nitrate treatment in the lab scale, to assess nitrate treatment fairly, they cannot be used directly. Therefore, in this study, we use simulation to extend our understanding from the lab scale to the reservoir scale. Results show that if NRM are dominant nitrate reducer community in the reservoir, nitrate treatment strategy might not be promising. In the case that NRSOM are the dominant nitrate reducer community, there can be a concentration of nitrate that can inhibit reservoir souring. In fact, this concentration is the concentration for which carbon source is exhausted through sulphur cycling. Therefore, the success of nitrate treatment, in this case, might depend on the feasibility of injecting this nitrate concentration. Additionally, we suggest that nitrite inhibition mechanism is not of significance in the reservoir scale.