Study On Corrosion State Evaluation Technology Of WC19-1B To WC19-1A Submarine Pipeline

Internal corrosion of pipelines is universal in oil and gas industry, it has brought great risks to the operation safetyof pipelines. For subsea pipelines, its environment is different from land pipelines, so the consequences will be more seriousby internal corrosion accident. In recent years, there have been dozens of subsea pipeline damage accidents due to internal corrosion,and the problemsare increasingly outstanding.Therefore, it is necessary to accurately evaluate the internal corrosion state of subsea pipelines.The WC19-1B to WC19-1A subsea pipeline in CNOOC WenChang19-1oil field is a multiphase pipeline, it’s transport medium contains oil, gas and water more than or equal to5%and Internal corrosion has been very serious This paper has established internal corrosion direct assessment method for this pipeline. This assessment hasa guidance and reference function to similar pipelines. The main contents are as followed.(1) This paper investigates the internal corrosionprediction methods domestically and abroadand collects the relevant data contains design,operation,internal inspection,etc.All data shows the internal corrosion degree along the pipeline and the corrosion characteristics of CO2corrosion.(2) Based on the internal corrosion characteristics.the main corrosion influence factors and operation conditions,this paper reasonablydesign the internal corrosion and corrosion sensitive factors analysis experiment,completes17groups dynamic corrosion rate testing experiments.The experiment shows the corrosion rules and sensitive factors at different temperature, CO2partial pressure, flow rate and the experimental cycle. In addition, based on dynamic corrosion test of the C inhibitor, HYH151Binhibitor and TS719B3inhibitor, this paper determined the corresponding average corrosion rate is40%-80%, it provide the basic parameters for the establishment ofinternal corrosion prediction method.(3) Based on the internal corrosion characteristics, multiphase simulation results and internal inspection results, the average condition is chosen as typical condition. This paper uses three kinds of corrosion prediction methods to predict the internal corrosion rate of researched pipeline, including the NORSOK M506model and De Waard95model, Back Propagationneural network and Genetic algorithm optimized Back Propagation neural network. Then, by comparing the prediction results,this paper chooses the best prediction method and validates it.(4) Based on the established prediction method and its prediction results, the ASME B31standard can be used to assess the pipeline state. The assessment results show that the corrosion defects depth of some pipeline section will be run to80%of the pipeline wall thickness so thatit will hole or leak. Therefore, it is necessary to assess the pipeline state regularly and take effective measures to ensure safe transportation. Based on the field data, indoor experiment, software simulation, internal corrosion rate prediction optimization and state assessment of WC19-1B to WC19-1A subsea pipeline, this paper establishes the internal corrosion direct assessment method for this subsea pipeline, and the method is a guidance and reference for similar pipeline.