A Study On The Application Of Internal Corrosion Direct Assessment Technique Of Natural Gas Pipeline Containing CO₂

As the running time of the gas pipeline grows,the pipeline will be gradually entering the aging stage.At present,there are amount of pipelines that have appeared different degrees of corrosion as a result of the increasing service life.This will cause a very serious threat to the safety of the operation of pipeline,the surrounding natural environment and even the social security.In order to accurately grasp the situation of internal corrosion in pipeline and repair the existing or potential pipeline defect in time,the general use of the method is on-line detection.However,the costs of online testing are too high and in addition,online detection can not be suitable for all pipeline because of its physical and geometrical factors.Therefore,how to reasonably predict the internal corrosion of gas pipeline and accurately identified the pipeline's corrosion sensitive area is an urgent need for the safe operation of the gas distribution network.This article mainly aims at the internal corrosion direct assessment method of the dry gas pipeline and the wet gas pipeline.By means of numerical simulation respectively,theoretical analysis method,this article qualitatively and quantitatively analyzed the relationship between the flow state and pipe inclination angle,the gas-flow rate and other gas flow parameters of the pipeline.The law of the influence of various flow parameters on Internal Corrosion Direct Assessment method of the dry gas pipeline are studied and summarized;we also put forward some suggestions when using the DG-ICDA method.At the same time by using object-oriented language—C#,the program of the Internal Corrosion Direct Assessment method of dry gas pipeline was made and packaged into application software in this paper.This software makes the application of DG-ICDA method more convenient and intuitive,so,it has a certain guiding significance in engineering application of direct assessment method of dry gas pipeline.As to the research on Internal Corrosion Direct Assessment method of wet gas pipeline,this paper mainly focus on the study of the core processes of the evaluation methods--corrosion rate prediction,the multiphase flow simulation software and the high-pressure rectilinear oscillation experiment were used to predict the corrosion rate of CO₂ under different multiphase flow parameters.The research mainly aimed at the effect of gas flow rate,entrance temperature,CO₂ partial pressure,oil-water ratio and other parameters on pipeline internal corrosion rate,and analyzed the effect laws of the above parameters from mechanism.At last,the WG-ICDA method was systematically studied and applied,combining with the example of Yacheng submarine pipeline.At the same time,the corrosion rate and residual strength of the target line are respectively predicted in this article.The utility of the WG-ICDA method was evaluated in this example.We also analyzed the reason of the bias between the evaluation results and actual test results,putting forward the correction factor to modify the evaluation result under the study of the operation history of the pipeline.Such contents provided certain reference and effective technical support for the implementation of the WG-ICDA method.