Detection And Evaluation Of Corrosion Protection Of Buried Steel Pipelines In S Gas Field

In the process of oil and natural gas transportation, the pipeline transportation is the most economical, the most efficient and the most widely used mode of transportation. It has an irreplaceable position. In China, the gathering pipe network and long distance oil and gas pipeline network are mainly composed of buried steel pipelines. These pipelines travel across a wide area, complex terrains, hence the soil properties vary a lot. As a result, these pipelines are easily damaged by environmental corrosion, stray current interference and different kinds of natural disasters. S gas field is located in the northern part of China, and its surface is mainly covered by desert. As it is China's large onshore monolithic gas field, we should attach more importance to safe operation. Once there is an accident, the consequences will be inestimable. In order to avoid accidents, it will be a necessary and urgent task to develop different kinds of corrosion protection technologies, take effective and economical pipeline inspection technologies and evaluation methods, and develop more effective and more reasonable protection and maintenance measures. Taking comprehensive test and evaluation of the corrosion protection for buried steel pipelines in S gas field is vital to prevent energy leakage, avoid environment pollution, so as to ensure the normal production and operation of the pipelines, and it also has important economic and social benefits.In this paper, the methods to detect and evaluate the soil corrosion properties, external corrosion protection layer conditions, stray current interference, cathode protection effectiveness and discharge protection effect of buried steel pipelines are established. In reference to the relevant foreign standards and combined with China's rich geological conditions and environmental impact factors,the grading evaluation criterions and comment set of asphalt corrosion resistant layer, rigid polyurethane foam anti-corrosion layer, three layer PE coatings, epoxy powder anticorrosive layer of RG and damaged point density were formulated.Aiming at the complex issues about multi index evaluation of the buried steel pipeline corrosion protection system, a set of complete and featured secondary fuzzy comprehensive evaluation models were established. Regarding the corresponding grade of the second level fuzzy evaluation as single factor evaluation vector of the first level fuzzy evaluation, it perfectly retained the information of multi index evaluation, also enabled the model to be simple. In the choice of the weight of each index, using the expert scoring method and the AHP method made the model become more flexible and more operational.The buried steel pipelines in the Fifth block of S field were conducted systematic and comprehensive field detection and laboratory research. The test and research work mainly include:macro inspection, environmental corrosion detection, pipeline map drawing, anticorrosion layer inspection without excavation, excavation test, and the detection pictures were classified.Based on the comprehensive evaluation model of corrosion protection for buried steel pipeline, comprehensive evaluation software for corrosion protection of buried steel pipeline was developed by using C++/QT framework. Using the idea of software engineering, the software requirements analysis, overall design, the main module design and process design were conducted.With the joining of new project storage engineering management function, query function, basic information management functions, import of detection data function and image display of evaluation results function, data report export function, the evaluation becomes more convenient and the results become more intuitive. Comprehensive corrosion protection evaluation of buried steel pipelines in the Fifth block of S gas field and W-Q buried steel pipelines were conducted through software.While giving the graded properties of each pipe segment, inspection periodic, repair advice and repair priority, the practicability and applicability of the software are also verified at the same time.