Anthony E. Kakpovbia

Microbial Corrosion in Linepipe Steel Under the Influence of a Sulfate-Reducing Consortium Isolated from an Oil Field

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 (FexSy), and iron (III) oxide-hydroxide (FeOOH) constituents in the corrosion products for the system exposed to the SRB consortium.

Improvement of the Welding Inspection Process for Projects in the Oil and Gas Industry Using Six Sigma Methodology

At the start of welding activities in oil and gas projects, high welding rejection rates (WRR) are often reported. This is a cause for concern to companies because welding defects that are not identified nor corrected can have serious consequences, such as on asset integrity, cost of rework, and schedule impact. Therefore, the quality organizations immediately investigate the different causes and recommend solutions which eventually contributes toward lowering the WRR.Based on recent field studies conducted in oil and gas projects using the Six Sigma methodology, high WRRs are caused by many factors, including but not limited to the following:1. New and inexperienced welders with poor welding techniques.2. Poor environments surrounding the welding activities.3. Discrepancies and inaccurate data in the welding tracking system (WTS).These contributing factors can be reduced and eliminated by implementing a strong welding inspection and control program with the following recommendations:1. Screen for qualified and experienced welders with a proven successful welding history before starting the welding.2. Test the welders on-site before actual production welding.3. Implement an encouragement scheme for welders by having frequent toolbox meetings and presenting awards for the best welders according to the lowest rejection rates.4. Assess the WTS constantly to prevent any inaccurate data.Copyright