Microbiologically influenced corrosion in floating production systems

Abstract

The production of oil and gas is of major importance to the stability of the world's energy supply. With the depletion of onshore reserves, offshore exploration and production of oil and gas has increased sharply. In particular, Western Australia's oil and gas industry is a vital component of Australia's national economy, producing over 70 per cent of Australia's natural gas, crude oil, and condensate In particular, microbial contamination and consequent microbiologically influenced corrosion (MIC) represents a serious problem to FPSO operations, which can incur significant costs, and be difficult to control 4,5 . The number of FPSOs that have been in operation for significant time has increased worldwide and the issues are usually common to all operators. However, conditions in Australia can be different from other oil and gas producing regions thus particular challenges can arise. Microorganisms in petroleum reservoirs and FPSOsDue to the in situ presence of substantial amounts of electron donors and electron acceptors for bacteria growth, diverse popula- Source of microbial contamination of FPSOsThe presence of microorganisms in oilfield systems is usually the result of contamination by any number of mechanisms including . Polomka, Confidential Report, 2015). This provides a ready supply of bacteria to the FPSO as well as biogenic H 2 S.Typically, a FPSO is installed initially on a single field and provided the reservoir is consistent across the field, production will be the same. However, in several cases oil production from various reservoirs is co-mingled into one FPSO. In this case, different water chemistries are mixed with subsequent risk of scale formation and additional nutrients and microorganisms, which could result in an increased risk of MIC. Bacteria present at the front end will spread through the entire system including the back end oil offtake system in the water phase. Likewise, a FPSO can combine seawater injection with production that can potentially result in souring (sulphide production) and MIC in the facility thus requiring biocide injection into the reservoir. Values of >3000 ppm of H 2 S Major areas of MIC threatThe vast majority of MIC on FPSOs occurs on carbon steel components. Although MIC of corrosion-resistant alloys (CRAs), e.g. stainless steels, can occur in aerobic environments (e.g. seawater utility systems), hydrocarbon-processing trains on FPSOs are anaerobic and MIC of CRAs is not an issue. Souring of the reservoir is a common outcome of facilities that conduct produced water reinjection. This generally results in a higher than anticipated H 2 S content in well, process and rundown streams.

Complementary DNA/RNA-Based Profiling: Characterization of Corrosive Microbial Communities and Their Functional Profiles in an Oil Production Facility

“…Dominant microorganisms found active in the facility belong to three microbial groups, sulfate reducers, fermenters, and methanogens; all of these previously associated with MIC processes (Machuca et al, 2017; Machuca and Polomka, 2018; Vigneron et al, 2018; Suarez et al, 2019a). Microbial interactions among these populations have been previously studied (Raskin et al, 1996; Morris et al, 2013; Ozuolmez et al, 2015; Sela-Adler et al, 2017).…”

“…Microorganisms change the electrochemical conditions at the metal/solution interface by the attachment of cells, biofilm formation, and subsequent release of metabolites, which induces or accelerates the corrosion process (Moura et al, 2013). MIC is characterized by a particular morphology of damage – localized pitting (Little and Lee, 2007), with corrosion rates reported up to 10 millimeters per year (Machuca and Polomka, 2018). Remarkably, MIC is not constrained to a unique corrosion mechanism (Lewandowski and Beyenal, 2009; Kakooei et al, 2012; Urquidi-Macdonald and Macdonald, 2014; Li et al, 2018).…”

“…Lately, MIC has been reclassified into two different mechanisms, chemical MIC (CMIC) that considers metal deterioration induced by corrosive chemical species produced via microbial metabolic activity (indirect corrosion), and electrical MIC (EMIC) that refers to the damage caused by direct microbial uptake of electrons from the steel (direct corrosion) (Enning and Garrelfs, 2014). Causative microorganisms have been classified in microbial groups according to their metabolic activities, such as sulfide producing prokaryotes that include sulfate and thiosulphate reducers (Machuca et al, 2017; Machuca and Polomka, 2018), acid-producing (Gu and Galicia, 2012; Gu, 2014), methanogens (Uchiyama et al, 2010), iron-oxidizing (Ashassi-Sorkhabi et al, 2012; Liu et al, 2014), and iron-reducing bacteria (Herrera and Videla, 2009). Microorganisms with these metabolic capabilities are part of the normal microbiota of petroleum reservoirs (Magot et al, 2000; Ollivier and Magot, 2005).…”

“…Microbiological assessment is routinely performed to detect the presence of MIC causative microorganisms and to evaluate the effectiveness of biocide treatments used to mitigate against MIC. Traditionally, culture-based techniques have been used to identify the presence of known corrosive microbial groups in industrial facilities (Muyzer and Marty, 2014; Beale et al, 2016; Machuca and Polomka, 2018). Since culture media cannot recover all microorganisms present in the environment (Keasler et al, 2012; Chakraborty et al, 2014), culture-independent techniques are used to complement cultivation based analyses.…”

Assessing Microbial Corrosion Risk on Offshore Crude Oil Production Topsides under Conditions of Nitrate and Nitrite Treatment for Souring

“…The incomplete oxidation of sulfide may also result in the accumulation of corrosive elemental sulfur [ 12 ] and/or nitrite, depending on the proportions of sulfide to nitrate in a given system [ 13 ]. There are many other types of microorganisms that can participate in MIC, including acetogens, iron-reducers, and methanogens [ 14 , 15 , 16 , 17 , 18 ], and several of these microbial groups have been detected in corroded offshore fluids or infrastructure [ 2 , 19 , 20 , 21 ].…”