Internal Corrosion Direct Assessment Research Articles

Application of internal corrosion direct assessment in CO2 slug flow submarine pipelines

This paper aims to establish a direct method for evaluating the internal corrosion in submarine pipelines, including four steps: pre-assessment, indirect inspection, detailed inspection, and post-assessment. The evaluation of corrosion severity and the determination of key monitoring points are particularly important in indirect detection. Taking CO2 gathering and transmission pipeline of an offshore oil field as an example, the overall internal corrosion rate of the pipeline is calculated to be 0.253 mm/a. The 12–45 m long pipeline is selected as the focus of corrosion monitoring. Through the comparative analysis of internal detection data and loss wall thickness, it is found that the results of indirect evaluation and direct evaluation are consistent, indicating the correctness of corrosion rate prediction model and loss wall thickness calculation method. The pipeline reevaluation time is five years. The evaluation method can accurately predict the corrosion status of multiphase flow pipeline and locate the corrosion.

A Numerical Corrosion Rate Prediction Method for Direct Assessment of Wet Gas Gathering Pipelines Internal Corrosion

The paper introduces a numerical internal corrosion rate prediction method into the internal corrosion direct assessment (ICDA) process for wet gas gathering pipelines based on the back propagation (BP), the genetic algorithm (GA) and BP, and the particle swarm optimization and BP artificial neural networks (ANNs). The basic data were collected in accordance with the terms established by the National Association of Corrosion Engineers in the Wet Gas Internal Corrosion Direct Assessment (WG-ICDA) SP0110, and the corrosion influencing factors, which are the input variables of the ANN model, are identified and refined by the grey relational analysis method. A total of 116 groups of basic data and inspection data from seven gathering pipelines in Sichuan (China) are used to develop the numerical prediction model. Ninety-five of the 116 groups of data are selected to train the neural network. The remaining 21 groups of data are chosen to test the three ANNs. The test results show that the GA and BP ANN yield the smallest number of absolute errors and should be selected as the preferred model for the prediction of corrosion rates. The accuracy of the model was validated by another 54 groups of excavation data obtained from pipeline No. 8, whose internal environment parameters are similar to those found in the training and testing pipelines. The results show that the numerical method yields significantly better absolute errors than either the de Waard 95 model or the Top-of-Line corrosion model in WG-ICDA when applying the approach to specific pipelines, and it can be used to investigate a specific pipeline for which the data have been collected and the ANN has been developed in WG-ICDA SP0110.

Overview: Production/Facilities (December 2006)

Welcome back to the Production/Facilities feature. This issue focuses on environmental and corrosion challenges. These challenges are especially important because the global production infrastructure is aging, with much of it more than 30 years old. These issues are, of course, intertwined because the materials and corrosion engineer spends much of his/her time preventing the produced fluids from escaping into the environment. This issue delves into new or revitalized developments in produced-water treatment. Concern has been mounting over the years regarding the effect on the environment of chemical treatments used by the industry when the chemicals are discharged with produced water, for example. New "green" corrosion inhibitors have been developed. As well as preventing corrosion in susceptible materials, the materials and corrosion engineer also must be able to assess the effect of any corrosion that has occurred. State-of-the-art calculation of the corrosion rate is available. Also, a new approach has been developed to assess the internal condition of a pipeline accurately. A low-cost water-purification treatment has been used in the sewage-treatment industry for many decades. It is being transferred to the petroleum industry. The use of reed beds is common as an alternative waste water treatment in remote areas. This method is being used in the Nimr field, onshore Oman. Essentially, the reeds capture the impurities through the root system, where they are held in the plant tissue. The plants then can be harvested and used as biomass fuel, for example, and the residual ash, which contains the inorganic impurities, can be disposed of safely. Production/Facilities additional reading available at the SPE eLibrary: www.spe.org SPE 100673 "Assessment and Comparison of CO2-Corrosion Prediction Models" by R.C. Woollam, BP plc, et al. SPE 98854 "The Path to Zero Flaring in Zadco" by M.M. Misellati, Zadco, et al. SPE 100412 "Prediction Equation of CO2 Corrosion With the Presence of Acetic Acid" by M.C. Ismail, U. Teknologi Petronas, et al. SPE 103922 "Internal-Corrosion Direct Assessment for Multiphase-Flow Pipeline Systems" by P.G. Puente, SPE, Scandpower PT, et al. IPTC 10548 "Produced-Water-Management Strategy Water-Injection Best Practices—Design, Performance, Monitoring" by A.S. Abou-Sayed, Advantek Intl. Corp., et al.