Wet sour gas pipelines are subjected to corrosion deterioration mechanisms resulting from interactions between the fluid and piping material. Acid gases, condensation rates, water chemistry, and temperature are the key factors in determining the corrosivity of sour gas streams. This work investigated the corrosion risk of a new wet gas pipeline through laboratory experiments and corrosion modeling. The tests were carried out in Hastelloy autoclave rotating cage system used to generate controlled dynamic conditions inside the reactor to mimic the environment inside the pipeline. The results showed high bottom of the line corrosion (BLC) rate reaching 38.9 mpy (0.99 mm/year), while the measured pitting rate was 17 mpy (0.43 mm/year). The corrosion modeling results showed a severe BLC rate exceeding 200 mpy (5.08 mm/year). The observed high BLC was attributed to the absence of bicarbonate which led to a low pH of 3.9. At this pH, the formation of stable iron sulfide is unlikely. Top of the line corrosion (TLC) rate was observed to be moderate reaching up to 7.8 mpy (0.20 mm/year). This is mainly because of the low condensation rate and formation of a protective iron sulfide layer, which confirmed that iron sulfide scale characteristics are the main factor influencing the TLC rate in sour environments. The expected threshold concentration required of bicarbonate to show some reducing effect on the corrosion rate and pH based on historical data analysis and predictive modeling of real-field conditions is discussed in this work. The results and conclusion detail the path forward for the findings.

Aged oil pipeline production systems, historically designed without corrosion protection due to predominantly oil-wetted conditions, now face significant changes as increased water content in produced oil arises from field maturation. This work investigates the corrosion inhibition properties of sweet crude oil on carbon steel 1018 in a CO2-saturated NaCl solution using electrochemical testing (open circuit potential, polarization resistance, electrochemical impedance, potentiodynamic polarization) and surface characterization (SEM, EDS) techniques at 50 degrees C and pH 6. Carbon steel specimens were immersed in crude oil for durations ranging from 0 to 144 h before undergoing corrosion testing. Results showed that a 144-h immersion in crude oil led to an 88 % reduction in corrosion rate, comparable to the efficiency of standard quaternary ammonium-based inhibitors. Furthermore, a semi-empirical model predicting uniform CO2 corrosion rates for varying oil immersion durations is proposed and validated by comparing its predictions with experimental data from the electrochemical tests.

Top of Line Corrosion (TLC) occurs in a multiphase flow when water vapor condenses at the top and the sides of the pipeline, leading to a severe corrosion attack. This study investigated the probabilistic risk of TLC for wet sour gas subsea pipeline using flow modeling and corrosion predications. The flow assurance hydraulic study showed that most of water drops out over the first few kilometers as the gas is cooled and becomes much less through the rest of the offshore part until they reach onshore area where the gas temperature drops further due to Joule-Thomson effect. It was anticipated that corrosion activities will be higher at the high condensation locations. The corrosion prediction modeling revealed high corrosion severity driven by Top of Line Corrosion (TLC). In order to maintain the system integrity the internal coating supplemented by V-jet batch inhibitor injection has been selected to protect against TLC. This study has realized the challenge to apply the batch treatment as it requires process interruption to meet scraper speed limitations. Therefore, the industry path forward should consider the development of novel TLC treatments to be applied with no impact on operations.

Cooling systems are prone to many corrosion deterioration mechanisms, one of which is Microbiologically Influenced Corrosion (MIC). Microbes are ubiquitous, they have been implicated in many major failures, and their control measures have a high economic impact on the oil and gas industry. This work investigates unexpected leaks observed on several cracked admiralty brass tubes that failed after 7 years in operation. Both metallurgical and molecular microbiological methods were used to understand the root cause of these failures. Scanning Electron Microscopy (SEM) analysis in all examined tubes (Cu-Zn alloy) showed localized pitting associated with cracks. X-Ray Diffraction (XRD) analysis carried out on the corrosion products confirmed presence of ammonic compounds (copper nitrate hydroxide-Cu2(NO)3(OH)3). The quantitative polymerase chain reaction (qPCR) technique used for microbiological DNA analysis revealed the coexistence of various strains of Sulfate Reducing Archaea (SRA), Acid Producing Bacteria (APB), Iron Reducing Bacteria (IRB) and Denitrifying Bacteria (DNB). It was postulated the lube oil cooler failed due to microbial assisted cracking driven by a collaborative metabolic reaction by the presence of microbial community. The study resulted in the development of a comprehensive control and monitoring plan to safeguard the integrity of the system and prevent damage recurrence in similar systems.

Subsea pipelines network represents a key component of oil and gas offshore operations, thus determining the integrity status for each pipeline to ensure a safe, reliable and cost-effective operation is crucial. It is always difficult to regularly check pipelines of tremendous length and large diameter, which are frequently laid in places that are not easily accessible. This paper presents a risk assessment model developed as part of a holistic study conducted to evaluate the condition of subsea pipelines. A systematic semi-quantitative risk-based model was developed to identify, analyze and evaluate risk associated with each subsea pipeline. The risk calculation combines the Probability of Failure (PoF) and the Consequence of Failure (CoF). The PoF calculations considered different factors, which believed to have direct impact on the likelihood of pipelines failure including: internal corrosion, hydrogen induced cracking (HIC) susceptibility and mechanical integrity. The CoF calculations factor safety, environment, economic and reputation impact. In overall, the study determined the risk level of each pipelines and provided measures and recommendations to lower the total risk.

Aboveground Storage Tanks (AST) degradation is mainly caused by bottoms corrosion, which occurs on bottoms product-side and soil-side as a result from the interaction between the steel and the surrounding environments. Different corrosion control and mitigation measures have been deployed to minimize the corrosion damage and subsequently increase tanks reliability and integrity. This paper evaluated the effectiveness of different applied AST bottoms corrosion control systems. The paper includes a case study, where historical inspection records of more than sixty (60) AST with different hydrocarbon fluid services and bottoms corrosion control systems were reviewed and analyzed. The study reveals that applied product-side corrosion control systems were effective, whereas, examined soil-side corrosion control systems shared similar shortcomings. In addition, the analysis results were discussed against inspection requirements of two internationally adopted AST inspection codes, namely, American Petroleum Institute API standards 653 and Equipment Engineering Material Users Association EEMUA Publication No. 159.

Refining industry cooling systems are prone to many different corrosion deterioration mechanisms, one of which is Microbiologically Influenced Corrosion (MIC). Bacteria are ubiquitous, they have been implicated in a number of major failures and their control measures have a high economic impact on the refining industry. This work investigates the unexpected failures and leaks observed in several seawater heat exchanger tubes, which resulted in plant shutdowns and significant production losses. Both metallurgical and molecular microbiological methods were deployed to comprehend the root cause of these failures. Metallurgical analysis in all examined tubes (70-30 Cu-Ni and Al-Brass) revealed localized pitting with circular and cup-like morphology typical of those formed by MIC attack. The DNA subsequent sequential analysis revealed the co-existence of various strains of Acid Producing Bacteria (APB) and Iron Oxidizing Bacteria (IOB) in the collected corrosion products with a noticeable absence of Sulfate Reducing Bacteria (SRB). Lack of adequate chlorination and presence of hydrocarbons and other organic matters that naturally end up in the open transport channel as a nutritional source led to flourishing microbial population including corrosion-causing species and subsequent rapid MIC attacks. Cost effective short and long term action plans including criticality assessment, timed replacements, selective cleaning, chlorination dosage adjustments and carbon source identification monitoring were considered. The study resulted in the development of a comprehensive control and monitoring plan to safeguard the integrity of the system.

Microbiologically influenced corrosion is not a distinct type of corrosion, but rather involves synergistic interaction of microorganisms with resulting biofilms and metabolic biogenic products that enhance corrosion processes. Therefore, it is important to obtain insights about the nature of the biogenic products resulting from microbial metabolic process. In this research, the biogenic products produced by sulfate reducing bacteria (SRB) cultivated from a sour oil field were characterized using X-ray photoelectron spectroscopy (XPS). Moreover, the zeta potential and magnetic susceptibility of SRB cells and biogenic products were evaluated using a microelectrophoretic apparatus and a magnetometer that is based on superconducting quantum interference methods, respectively. The results reveal that the biogenic sludge is mainly composed of different compounds of iron sulfides such as pyrrhotite and pyrite. Furthermore, it was found that the SRB consortium used in this investigation have negative surface charges of -53 mV as indicated by the zeta potential measurements and were able to generate paramagnetic sludge particles with an average calculated magnetic susceptibility of 1.4 x 10-6 m3/kg Fe. The implications of biogenic products physical and chemical characteristics on MIC will be presented.

This study was conducted to establish the root cause of premature cracking failures detected on several firewater hydrants handling untreated seawater. Quantitative polymerase chain reaction (qPCR) was used to characterize the microbial diversity of corrosion products collected from failed structures. In addition, scanning electron microscopy (SEM), coupled with energy dispersive X-ray spectroscopy (EDS) was used to gain insight into the corrosion mechanism. The qPCR results indicated that microbial communities were dominated by nitrate reducing bacteria (NRB) with limited contamination of other corrosion causative microorganisms such as sulfate reducing bacteria (SRB). Fracture examination revealed the effects of two distinctive failure modes: stress corrosion cracking (SCC) and selective leaching (dezincification). SEM examination revealed intergranular corrosion with preferential attack on grain boundaries whereas EDS results confirmed the depletion of zinc on examined fracture surface grains. Environmental cracking of copper alloy C86300 was attributed to ammonia produced by the metabolic activities of nitrate reducing bacteria.

Increasing plant capacity is one of the critical changes that should be assessed thoroughly to avoid the possibility of increasing corrosion risks and introducing hazards to operations, processes, and control parameters. A systematic approach was developed and utilized to directly assess the impact of the capacity increase in a hydrocracking unit. This study has determined the possible changes in corrosion drivers and subsequent corrosion loops, risk matrix, and inspection strategies using a quantitative risk-based decision process. The sensitivity analysis revealed that increased capacity requires focus in the following areas: erosion-corrosion due to velocity increases and ammonium bisulfide (NH4HS) fouling. Process simulations along with Risk Based Inspection assessments were employed. The study concluded that the capacity increase is feasible provided: the water wash treatment is increased to account for additional NH4HS, additional on-stream inspection points are provided for systems susceptible to erosion-corrosion, and selective metallurgical upgrades are planned for improved sulfidation resistance.

This work investigates the inhibition effect of Neem (Azadirachta indica) extract on microbiologically influenced corrosion (MIC) of API 5L X80 linepipe steel by a sulfate-reducing bacterial (SRB) consortium. The SRB consortium used in this study included three phylotypes; Desulfovibrio africanus, Desulfovibrio alaskensis and Desulfomicrobium sp. Steel coupons were incubated in the presence of the SRB consortium without and with 4 wt.% Neem extracts for different periods of time. The morphology, compositions of the interfaces and subsequent corrosive pitting were characterized with field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectroscopy (EDS). In addition, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and open circuit potential (OCP) were used to investigate the in situ corrosion behavior under the two different conditions. The results revealed that Neem extract has the capability to reduce the biocorrosion rate by approximately 50%. Neem has significantly reduced the propensity of linepipe steel to SRB caused MIC by minimizing the cell growth and has subsequently suppressed the sulfide productions, sessile cell density and biofilm development. (C) 2013 Elsevier Ltd. All rights reserved.

The aim of this work is to investigate the effect of plastic deformation on the corrosion susceptibility of casing and tubing steels; i.e., API 5CT K-55 and P-110. The steels were cold-rolled to obtain a reduction in thickness of 10%, 20% and 30%, and tested in synthetic formation water purged with CO2 gas. The corrosion behavior and the evolution of interfacial layers were investigated using linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). Corrosion products morphologies, structures and compositions were evaluated using field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectroscopy (EDS). The results show that when the amount of cold work increased, K-55 steel exhibited an increased corrosion rate, and P-110 steel showed a decreased corrosion rate when compared to the as received values. The mechanisms are characterized based on the impedance response that shows a one-time constant for K-55 steel and two time-constants for P-110 steel which was attributed to different scale developments. The induced plastic deformation enhanced the corrosion rate and altered the evolution of the covering layers with time.

Microbiologically influenced corrosion (MIC) is a major problem that impacts crude oil production, transportation and storage infrastructures. Indigenous microorganisms that naturally reside in oil reservoirs are able to induce localized changes in the aqueous environment and lead to catastrophic damages. The study herein applies molecular techniques to investigate the microbial communities associated with corrosion products collected from crude oil pipelines. Small subunit ribosomal rRNA gene pyrosequencing was used to identify microbial communities present in each system. The results indicated that that the microbial communities in the corrosion products obtained from both the sour oil pipeline and sweet crude pipelines were dominated by bacteria, though archaeal sequences (predominately Methanobacteriaceae and Methanomicrobiaceae) were also identified in the sweet and sour crude oil samples, respectively. The dominant bacterial phylotypes in the sour crude sample include members of the Thermoanaerobacterales, Synergistales, and Syntrophobacterales. In the sweet crude sample, the dominant phylotypes include members of Halothiobacillaceae. Interestingly, common bacterial phylotypes that are related to Thermotogaceae were identified in all investigated samples. The impacts of these microorganisms in MIC are presented in this paper. This work will increase the knowledge related to the complex microbial diversity associated with crude oil systems and guide future MIC research.

It has been accepted that corrosion protection systems and non-destructive inspection methods produce remnant magnetic fields (RMF) to pipeline steel. The present study investigates the influence of remnant magnetic fields inducted by these tools on microbiologically influenced corrosion (MIC) by a sulfate reducing bacteria (SRB) consortium. The corrosion behavior of carbon linepipe steel exposed to different conditions having either a magnetized or nonmagnetized biotic medium, was investigated by electrochemical impedance spectroscopy (EIS), linear polarization resistance (Rp) and open circuit potential (OCP). The corrosion products, biofilm and pit morphology that developed with time were characterized using field emission scanning electron microscopy (FE-SEM). The results confirm substantial increases of bacteria cell attachment, biofilm mass, corrosion and pitting under magnetized biotic conditions compared to a nonmagnetized biotic system. The significant enhancement of MIC under magnetized biotic conditions has been attributed to the synergetic interaction between SRB cells and associated metabolic products with magnetic fields.

This work investigates microbiologically influenced corrosion (MIC) of API(1) 5L X52 linepipe steel by a sulfate-reducing bacteria (SRB) consortium. The SRB consortium used in this study was cultivated from a sour oil well in Louisiana, USA. 16S rRNA gene sequence analysis indicated that the mixed bacterial consortium contained three phylotypes: members of the Proteobacteria (Desulfomicrobium sp.), Firmicutes (Clostridium sp.) and Bacteroidetes (Anaerophaga sp.). The biofilm and pit morphology that developed with time were characterized with field emission scanning electron microscopy (FESEM). In addition, electrochemical impedance spectroscopy (EIS), polarization resistance (Rp) and open circuit potential (OCP) were used to analyze the corrosion behavior. Through circuit modeling, EIS results were used to interpret the physicoelectric interactions between the electrode, biofilm and solution interfaces. The results confirmed that extensive localized corrosion activity of SRB is due to a formed biofilm in conjunction with a porous iron sulfide layer on the metal surface. Energy dispersive spectroscopy (EDS) revealed the presence of different sulfides and oxide constituents in the corrosion products for the system exposed to the SRB consortium.

This work investigates microbiologically influenced corrosion of API 5L X52 linepipe steel by a sulfate-reducing bacteria (SRB) consortium. The SRB consortium used in this study was cultivated from a sour oil well in Louisiana, USA. 16S rRNA gene sequence analysis indicated that the mixed bacterial consortium contained three phylotypes: members of Proteobacteria (Desulfomicrobium sp.), Firmicutes (Clostridium sp.), and Bacteroidetes (Anaerophaga sp.). The biofilm and the pits that developed with time were characterized using field emission scanning electron microscopy (FE-SEM). In addition, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and open circuit potential (OCP) were used to analyze the corrosion behavior. Through circuit modeling, EIS results were used to interpret the physicoelectric interactions between the electrode, biofilm and solution interfaces. The results confirmed that extensive localized corrosion activity of SRB is due to a formed biofilm in conjunction with a porous iron sulfide layer on the metal surface. X-ray diffraction (XRD) revealed semiconductive corrosion products predominantly composed of a mixture of siderite (FeCO3), iron sulfide (Fe (x) S (y) ), and iron (III) oxide-hydroxide (FeOOH) constituents in the corrosion products for the system exposed to the SRB consortium.

Hydrocarbon transporting pipelines and seawater injection networks are subject to many different corrosion deterioration mechanisms, one of which is microbiologically influenced corrosion (MIC). MIC is caused by a wide range of microorganisms that naturally thrive in the oil reservoirs and associated secondary seawater injection systems. To gain insight into the impact of microbes on corrosion in oil and sea water injection pipelines, the microbial diversity of corrosion product samples collected from a sour oil pipeline and a seawater injection pipeline were evaluated. As cultivation-based methodologies can greatly underestimate the microbial diversity associated with an environment, the microbial populations of sour crude oil and seawater pipeline samples were evaluated with a 16S rRNA gene pyrosequencing approach. The sequence results indicate that the microbial communities in the corrosion products obtained from both the sour oil pipeline and seawater pipeline were dominated by bacteria; though archaeal sequences (predominately Methanobacteriales) were also identified in the sour sample. For the sour sample, the dominant phylotypes include members of the Synergistales, Thermoanaerobacterales and Syntrophobacterales; while for the seawater injection sample, the dominant phylotypes include members of the Rhodobacterales, Flavobacteriales, Kiloniellales and Desulfovibrionales. This paper discusses the microbial diversity of the collected samples and their potential contribution to MIC for both systems.

Stringent corrosion management programs are being deployed by oil and gas industry to ensure the integrity of pipeline systems. Parts of this program are the corrosion protection systems and inspection detection methods included non-destructive techniques. Those measures induce remnant magnetic field (RMF) in the pipeline steel. Potentially the RMF could affect the corrosion process in the pipeline including microbiologically influenced corrosion (MIC). Microorganisms in pipelines have surface charges and produce a wide variety of metabolic products. Consequently, when they are exposed to RMF generated at the linepipe steel surface by the aforementioned sources there will be potential effects. This sequentially will increase the likelihood of biofilm formation and hence enhance/promote MIC. This study investigates the potential effects of RFM on the MIC by sulfate reducing bacteria (SRB).

During oil and gas operations, pipeline networks and associated infrastructures are subjected to different corrosion deterioration mechanisms, one of which is microbiologically influenced corrosion (MIC). MIC results from accelerated deterioration initiated by different microbial activities present in oil and gas systems. This paper provides a review of MIC in the oil and gas pipelines systems and includes a discussion of causative microbes, biofilm, diagnostics and mitigation methods.