Microbiologically Influenced Corrosion in the Upstream Oil and Gas Industry

Torben Lund Skovhus, Dennis Enning, Jason Lee, Torben Lund Skovhus, Dennis Enning, Jason S. Lee

• Publisher: CRC Press
• Year: 2017
• ISBN:
  9781351654692
• Edition: 1
• Topic: Technologie et ingénierie
• Subtopic: Ingénierie de la chimie et de la biochimie

Microorganisms are ubiquitously present in petroleum reservoirs and the facilities that produce them. Pipelines, vessels, and other equipment used in upstream oil and gas operations provide a vast and predominantly anoxic environment for microorganisms to thrive. The biggest technical challenge resulting from microbial activity in these engineered environments is the impact on materials integrity. Oilfield microorganisms can affect materials integrity profoundly through a multitude of elusive (bio)chemical mechanisms, collectively referred to as microbiologically influenced corrosion (MIC). MIC is estimated to account for 20 to 30% of all corrosion-related costs in the oil and gas industry.

This book is intended as a comprehensive reference for integrity engineers, production chemists, oilfield microbiologists, and scientists working in the field of petroleum microbiology or corrosion. Exhaustively researched by leaders from both industry and academia, this book discusses the latest technological and scientific advances as well as relevant case studies to convey to readers an understanding of MIC and its effective management.

Section IV Field Cases and Laboratory Studies

15 MIC under Conditions of Oxygen or Nitrate Ingress

Jaspreet Mand, Yin Shen, Heike Hoffmann, and Gerrit Voordouw

15.1 Introduction

15.2 Nitrate Ingress

15.2.1 Influence of NRB on Steel Corrosion

15.2.2 Biological Sulfur Formation by soNRB

15.2.3 Decreased Corrosion Threat due to Nitrate Ingress

15.3 Oxygen Ingress

15.3.1 Influence of Oxygen in SRB-Dominated Environments

15.3.2 Microbial Sulfide Oxidation to Form Sulfur

15.3.3 Cycling of Anaerobic and Aerobic Conditions

15.4 Corrosivity of Sulfur and Polysulfides

15.5 Case Studies

15.5.1 Albertan Oilfield

15.5.2 North Sea Oilfield

15.6 Conclusions

References

The majority of microbiologically influenced corrosion (MIC) scenarios occur under anoxic conditions and often implicate sulfate-reducing bacteria (SRB). These bacteria catalyze sulfate respiration and form sulfide as a metabolic end product. While SRB may be one of the most aggressive players in biocorrosion and are by far the most often studied, MIC can involve other organisms as well. The ingress of electron acceptors other than sulfate, such as oxygen or nitrate, into an SRB-dominated environment can lead to changes in the microbial community and in the corrosion threat. For instance, the partial respiration of nitrate by nitrate-reducing bacteria forms nitrite, a corrosive metabolite. The chemical reaction of oxygen or nitrite (a by-product of incomplete nitrate respiration) with SRB-produced sulfide forms polysulfides or elemental sulfur. Sulfur and polysulfides are highly corrosive, and evidence of sulfur-mediated corrosion can be seen when examining the metal surface in the form of severe pitting. Furthermore, changes in microbial community composition may also serve as evidence of sulfur- and polysulfide-mediated corrosion.

DNA pyrotag sequencing was used to determine the microbial community compositions of field samples from a North Sea oil production site and from an Alberta oilfield. In both cases, microbial communities associated with sulfur metabolism were uncovered. An abundance of microorganisms able to oxidize aqueous sulfide using oxygen as an electron acceptor (genera Arcobacter, Sulfurospirillum, Sulfurimonas) were discovered. The potential for sulfur formation by these organisms greatly enhances corrosion threat. The fact that other bacteria capable of using elemental sulfur as an electron acceptor (genera Desulfuromonas, Desulfuromusa) were also found in these samples serves as evidence that sulfur is often produced at these sites. The presence of these different sulfur cycle microorganisms and the subsequent activity shown under oxygen or nitrate ingress is evidence for their participation in MIC.

15.1 Introduction

MIC of steel, caused by the presence and activities of microorganisms or by their metabolites, is a serious threat to oil and gas infrastructure. For a steel structure in an aqueous environment, an anodic reaction is as follows:

$${\text{Fe}}^0\to {\text{Fe}}^{2+}+2{\text{e}}^{-}$$

15.1

15.1

A counter-cathodic reaction is required, and in the presence of oxygen, the electrons formed in Equation 15.1 are used for the formation of hydroxide ions:

$$\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.{\text{O}}_2+{\text{H}}_2\text{O}+2e^{-}\to 2\text{O}{\text{H}}^{-}$$

15.2

15.2

Most often, the environment within pipelines is kept anaerobic to limit oxygen ingress to prevent Equation 15.2 from proceeding. In such cases, the cathodic reaction becomes

$$2{\text{H}}^{+}+2{\text{e}}^{-}\to {\text{H}}_2$$

15.3

15.3

An anoxic environment allows the growth of anaerobic microorganisms, such as SRB. There are several ways in which SRB are associated with MIC. SRB are able to use the hydrogen formed in Equation 15.3 as an electron donor to reduce sulfate and form sulfide (Von Wolzogen Kühr and Van der Vlugt 1934). Some strains of SRB have the ability to use steel as an electron donor directly without the formation of a hydrogen intermediate (Venzlaff et al. 2013; Enning and Garrelfs 2014). The production of sulfide by SRB is a process known as souring; sulfide is a corrosive by-product as well (Gieg, Jack, and Foght 2011). The sulfide can precipitate out of solution as metal sulfides and lead to further anodic depolarization of steel surfaces (Spruit and Wanklyn 1951; Wanklyn and Spruit 1952; King and Miller 1977; Hamilton 1985). Sulfide is also known to promote the entry of hydrogen into a metal surface, which can lead to hydrogen embrittlement of steel.

Although SRB are most often connected with MIC, there are many other organisms found in the same environments. Microbial communities found attached to and growing on metal surfaces are generally living as multicellular biofilms. Biofilms consist of microbial cells embedded i...