Increasing the efficiency of bactericide use when using seawater in a reservoir pressure maintenance system

Abstract

Rationale: Since 2018, at the Uzen oilfield, in order to study and control the microbiological contamination with sulfate-reducing bacteria (hereinafter referred to as SRB) of oilfield environment, full-scale bactericidal treatment and monitoring of the effectiveness of reagent use have been carried out. At the equipped control points, water samples are taken for the content of SRB cells before and after injection of the bactericide. Target: Reduce the intensity of sulfidogenesis at the oilfield and, as a consequence, the concentration of hydrogen sulfide in the associated gas. Materials and methods: Since the applied technology of injecting the bactericide in shock dosages did not allow achieving a stable reduction in the concentration of hydrogen sulfide, it was replaced by the technology of constantly injecting the bactericide into seawater at a dosage of 40 mg/l in an experimental mode. This technology showed low efficiency, hydrogen sulfide (H2S) concentrations varied between 352–379 ppm, and the monthly consumption of the reagent increased by 40%. Based on the obtained data on ineffectiveness, the constant injection of bactericide at MPS-4 was stopped and a new technology for injection of bactericide was proposed, aimed at suppressing not only planktonic, but also adherent forms of SRB. Results: Results. Injection of the bactericide using the new technology showed significant efficiency, which was assessed by reducing the concentration of hydrogen sulfide in the associated gas by an average of 45% across the oilfield. Conclusion: The proposed new technology for injecting a bactericide made it possible to effectively suppress the activity of sulfidogenic microorganisms and reduce the level of biogenic hydrogen sulfide in the oilfield.