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Title: Understanding the role of erosion/corrosion interactions in degredation of steel and stainless steel alloys in systems containing sand and oil
Author: Zawai, Khaled Al
ISNI:       0000 0004 2717 5273
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2011
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Erosion and corrosion of piping and 'equlpments continues to be a problem for the oil and gas sector. This primarily occurs where water and entrained sand are present in produced water. The pipelines used to transport these products are often subjected to multiphase flow regimes, which can result in severe degradation of the internal surfaces with the presence of solid particles and an oil phase in the flow system, and the erosion-corrosion mechanisms become more complicated when compared with those seen in single-phase systems. Therefore, it is essential to understand the degradation mechanisms involved to enable effective material selection to be achieved. In this project, a study on sand mobility was conducted, which focused on the effect of the corrosion inhibitor and oil phase adsorption on the sand particles and the effect of the mobility of sand particles in a flow system. A flow loop coupled with a high-speed camera was designed to enable the sand transport to be visualised. With such a system, the consequence of the corrosion inhibitor and hydrocarbon phase, ISOPAR M, on the adsorption process of the sand particles, and the effect of adsorption on reducing the kinetic energy of sand particles were studied. Zeta potential, which is a function of the mobility of an electrical charge at the slip plane beyond which the electrical charges form a stable entity with the solid particle, was also introduced in this work to confirm the result of the sand transport and to define the condition at which adsorption is possible. The results of zeta potential were in good agreement with the results of the sand mobility obtained by the designed flow loop and adjusted jet impingement rig. The results showed that the adsorption of corrosion inhibitor on the surface of sand particles is only possible if the corrosion inhibitor acquires an opposite charge to the sand particles dispersed in solution (the attraction force is dominant). In the study, the erosion-corrosion of a carbon steel (API-5L-X65), 13Cr martensitic stainless steel and duplex/superduplex stainless steel (22Cr and 25Cr) were assessed by jet impingement using a combination of electrochemical tests and metal loss analysis. The assessments were conducted under a simulated CO2 erosive-corrosive oil and gas surface pipeline with the presence of hydrocarbon and corrosion inhibitor to understand the material degradation mechanisms under different testing media to enable supportive information to be provided for the mitigation of erosion-corrosion in the oil and gas industry. In-situ electrochemistry, LPR, was conducted in order to assess the contribution of the corrosion process on the total degradation of materials. Despite the significant effect of the solution containing 5 vol% ISOPAR M on the total weight loss (TWL), the addition of 5% ISOPAR M did not show a clear reduction in the corrosion rate (higher slope of I'1E/l'1i plot). It was proved in this project that the presence of 5 vol% ISOPAR M not only has an important role in reducing the impact velocity of sand particles, but using CFD simulation it was also proved that the particles had a lower impact angle, and, hence, reduced the overall damage to the mechanical component (erosion-corrosion). The other interesting feature identified in this study is the interaction between the corrosion inhibitor and oil phase, which resulted in enhancing the stability of the emulsion flow and the change in the wettability of the metal surface. Unlike other testing media, the measured contact angles of water droplets on API-5L-X65 surfaces, pre-exposed to the solution containing 100 ppm of corrosion inhibitor and 5 vol% hydrocarbon, led some sites on the surface to change to an oil wet, hydrophobic surface, thereby increasing the corrosion resistance. A three-level experimental design with full replication was developed for the purpose of developing a statistical model (using the commercial package Minitab™) relating to the total weight loss of API-5L-X65. Such a model will enhance the understanding of the performance of a material in a multiphase flow environment. This methodology allows the interaction between the most significant parameters on erosion corrosion to be studied. Finally, this thesis has added to the understanding of erosion-corrosion in conditions containing a hydrocarbon phase and sand particles.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available