Reservoir souring: sulfur chemistry in offshore oil and gas reservoir fluids

Abstract

The injection of sulfate-containing seawater into an oil reservoir, for maintaining the reservoir pressure, can promote the growth of sulfate reducing bacteria and archaea near the injection wells, leading to the formation of sulfides such as hydrogen sulfide. However, intermediate sulfur species with different valence states, such as polythionates and polysulfides have been detected in several produced water samples, likely a result of phase partitioning, and chemical and microbial reactions. These sulfur species could affect the microbial communities (e.g., microbially influenced corrosion) and will impact the efficiency of souring mitigation methods. In addition, the presence of these sulfur species can result in operational, environmental, and treatment problems. Therefore, development and implementation of souring control strategies during production cycle of oil and gas reservoirs require identifying the origins, reactivity, and the partitioning behaviour of these compounds. This paper presents an overview of the known mechanisms responsible for reservoir souring and then focuses on the chemical reactions and sulfur species associated with production and consumption of hydrogen sulfide. In this work we highlight complexity of the sulfur chemistry and that the assumption that all the sulfate is reduced to hydrogen sulfide can lead to inappropriate souring management methods. The paper also reviews the detection and analysis methods used for sulfur compounds. The review demonstrates that there is a gap in the current souring models and methods due to the exclusion of key sulfur compounds and challenges in identifying and quantifying these compounds with respect to speed of analysis and sample stability.

Microbial Surfactants: The Next Generation Multifunctional Biomolecules for Applications in the Petroleum Industry and Its Associated Environmental Remediation

“…Biosurfactants interact with metal surfaces and orient the lipophobic head to the surface and the lipophilic tail to the external environment, thereby creating unfavorable conditions for corrosion. Furthermore, the antimicrobial effect of biosurfactants reduces the biomass of sulfate-reducing bacteria (SRB) and inhibits biofilm formation, which is both corrosion agents in the reservoir [56,57]. For instance, bacterial species, such as Bacillus licheniformis and Pseudomonas aeruginosa , have been shown to have a potential antimicrobial effect on different strains of SRB [58].…”

Water Compatibility Study: Detecting Souring Potential

“…The Mechanisms of controlling reservoir souring using nitrate and biocide have been studied and simulated [12]. The chemical reactions and sulfur species associated with production and consumption of H2S have been reported [13]. Hence, reservoir souring can be detected early prior to water flooding and can be prevented.…”

Flow and Permeability Evolution during Microbial Sulfate Reduction and Inhibition in Fractured Rocks

“…Seawater is high in dissolved sulfate concentration in comparison to typical subsurface brines. The injected sulfate-rich seawater, coupled with available carbon and electron donor sources within the reservoir, stimulates growth of sulfate-reducing microorganisms (SRMs) and production of H 2 S (also known as microbial souring). , H 2 S can lead to structural corrosion, and H 2 S toxicity also poses health and safety hazards to workers . An effective souring treatment remains a challenge as the souring process occurs at the nexus of hydrological, geochemical, and biological processes in the subsurface.…”