Key issues related to modelling of internal corrosion of oil and gas pipelines - A review

The present mechanistic understanding and practical implications of carbon dioxide (CO2) corrosion of carbon and low-alloy steels in hydrocarbon production have been reviewed. This is base...

Carbon Dioxide Corrosion in Oil and Gas Production—A Compendium

The measurement of the electrochemical noise associated with corroding metals places a number of requirements on the measurement system if good quality data are to be obtained. In particular, aliasing and quantization noise should be avoided. Analysis methods may ignore the ordering of the measured potential or current values by using sequence-independent parameters such as the mean, standard deviation, skew, and kurtosis, or they may take the sequencing into account by computing the autocorrelation function, power spectra, or higher-order spectra. When potential and current noise are measured simultaneously, additional methods are available, including the calculation of electrochemical noise resistance, electrochemical noise impedance, characteristic charge, characteristic frequency, and various cross-correlation methods. Newer, somewhat more speculative methods include wavelet and chaos analysis. One of the most attractive prospects of electrochemical noise measurement methods is the ability to...

Interpretation of Electrochemical Noise Data

A mechanistic model of uniform carbon dioxide (CO2) corrosion is presented that covers the following: electrochemical reactions at the steel surface, diffusion of species between the metal...

A Mechanistic Model for Carbon Dioxide Corrosion of Mild Steel in the Presence of Protective Iron Carbonate Films—Part 1: Theory and Verification

Corrosion is a subject of interest to interdisciplinary research communities, combining fields of materials science, chemistry, physics, metallurgy and chemical engineering. In order to understand mechanisms of corrosion and the function of corrosion inhibitors, the reactions at the interfaces between the corrosive electrolyte and a steel surface, particularly at the initial stages of the corrosion process, need to be described. Naturally, these reactions are strongly affected by the nature and properties of the steel surfaces. It is however seen that the majority of recent corrosion and corrosion-inhibition investigations are limited to electrochemical testing, with ex situ analysis of the treated steels (post-exposure analysis). The characterization of materials and their surface properties, such as texture and morphology, are not being considered in most studies. Similarly, in situ investigations of the initial stages of the corrosion reactions using advanced surface characterization techniques are scarce. In this review, attention is brought to the importance of surface features of carbon steels, such as texture and surface energy, along with defects dislocation related to mechanical processing of carbon steels. This work is extended to a critical review of surface analytical techniques used for characterization of carbon steels in corrosive media with particular focus on examining steel surfaces treated with corrosion inhibitors. Further, emerging surface analysis techniques and their applicability to analyse carbon steels in corrosive media are discussed. The importance of surface properties is commonly addressed by surface scientists as well as researchers in other chemistry fields such as nanotechnology, fuel cells, and catalysis. This article is expected to appeal to a broad scientific community, including but not limited to corrosion scientists, material chemists, analytical chemists, metal physicists, corrosion and materials engineers.

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Carbon steel corrosion: a review of key surface properties and characterization methods

Electrochemical Noise (ECN) and Electrochemical Impedance Spectroscope (EIS) measurements were made simultaneously in a 75 mm I.D., 10 m long acrylic pipeline using salt-water/carbon dioxide mixtures. Full pipe flow was studied for liquid velocities of 0.5, 0.75, 1.1, 1.5 m/s and slug flow for Froude numbers 4, 6 and 9. Experiments were carried out at a constant pressure of 136 kPa and temperature of 40 C. ECN data were measured with a fast auto zero resistance ammeter. The ECN technique is able to detect changes in flow regime, showing distinct differences between full pipe flow and slug flow. The choice of sampling rate when using ECN is very important. For slug flows, sampling rates as high as 100 Hz are necessary to include most of the transients in the flow. Distinct differences can be seen in the Fast Fourier Transforms where dominant frequencies exist which correspond to possible bubble action in the slug body. EIS can be used to measure corrosion rate in multiphase flows. It does show an increase in the corrosion rate with liquid flow rates for full pipe flow and Froude numbers for stationary slug flow. A simple statistical analysis of ECN response gives a correlation withmore » corrosion rate. These show ECN could be a very powerful tool for determining corrosion rate and corrosion mechanism in multiphase flow.« less

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Comparison Of Ecn And Eis Measurement For Corrosion Monitoring Under Multiphase Flow Conditions

An ultrasonic measuring system is provided including a plurality of upstream and downstream ultrasonic transducers coupled to a multiflow pipeline and positioned along first and second cross-sectional portions of the multiflow pipeline. A transducer control system is coupled to the upstream and downstream ultrasonic transducers for selective activation of the transducers. In one embodiment, the ultrasonic measuring system is utilized to determine a flow velocity of a selected fluid in a multiflow pipeline by generating and detecting velocimetric ultrasonic pulses in the selected fluid. In another embodiment, the ultrasonic measuring system is utilized to determine film heights of fluids flowing within the pipeline.

Ultrasonic measuring system and method of operation

Predictive Model for Sweet Corrosion in Horizontal Multiphase Slug Flow

Model For Sweet Corrosion In Horizontal Multiphase Slug Flow

A mechanistic model has been developed to predict corrosion rates in multiphase (water/oil/CO{sub 2}) flow conditions. The model takes into account electrochemistry, reaction kinetics, and, mass transport effects. This paper describes the equations used to determine pH and bulk concentrations of various ions, which are then used to calculate the mass transfer rates to the corrosion surface. The result includes the determination of the mass transfer coefficients of various ionic species and corrosion rates. Details of relations used for determination of mass transfer coefficients for multiphase flows, and rates of electrochemical reaction kinetics are discussed and predicted results are compared with experimental observations. Agreement between model results and experimental data is good.

Madan Gopal

Papers

Comparison Of Ecn And Eis Measurement For Corrosion Monitoring Under Multiphase Flow Conditions

Ultrasonic measuring system and method of operation

Predictive Model for Sweet Corrosion in Horizontal Multiphase Slug Flow

Model For Sweet Corrosion In Horizontal Multiphase Slug Flow

Development Of A Mechanistic Model For Predicting Corrosion Rate In Multiphase Oil/Water/Gas Flows