Application Research Of H₂S/CO₂ Corrosion Prediction Model Based On Pipeline In Northern Shan Xi Oilfield

With the continuous development of China's oil and gas industry,steel corrosion and protection has been a difficult problem in the process of oil and gas development and transportation.The use environment of steel is usually complex and harsh,and the corrosion prevention work in oil and gas fields is particularly urgent due to the combined action of various corrosion factors.According to the research,most of the corrosion in the oil industry comes from H2S and CO2,which has caused a huge obstacle to the development of China's oil industry.Therefore,it is necessary to study the corrosion prediction model of H2S and CO2.Scholars at home and abroad have done a lot of research on the mechanism and influencing factors of CO2 corrosion,and put forward various types of prediction models,including empirical model,semi-empirical model and mechanism model.However,there is little research on H2S corrosion and CO2/H2S coexistence.Based on the Norsok model,the Top of Line model and the De Waard model of the target pipeline,this paper selects a collection and transportation pipeline in northern shan xi as the research object and selects the Norsok model,the Top of Line model and the De Waard model to predict the target pipeline.According to the operating conditions and corrosion types of the target pipeline,the prediction model under the coexistence of CO2/H2S was selected,and the corrosion prediction model was obtained by MATLAB fitting solution.When the temperature was changed,the error between the calculated value of the prediction model and the measured value was found to be large,so the temperature term was added for correction.Through comparison,it is found that the influence factors of temperature,H2S content and CO2 content are considered in the Cassandra model.Based on the consistency with the field situation of the target pipeline,this model is selected as the basic model in this paper and the temperature term is added to establish a new modified model.New correction model is obtained by fitting to solve method,and the correction model of target line model,and calculates correction model of the average error between the calculated values and measured values is small,the results are better than the predictive results of the above several basic models,so the correction model more suitable for the pipeline corrosion prediction.Based on the improved model,the internal corrosion prediction software is compiled,which can calculate the pipeline corrosion rate according to the basic parameters input,and provide some reference and effective technical support for the internal corrosion evaluation.The residual life of the target pipeline is predicted by the modified model,and it is concluded that the residual life of the target pipeline is 24 years,which satisfies the 20 years commonly used in pipeline design in China.Therefore,although the target pipeline is corroded to a certain extent,it still has the ability to continue its operation.OLGA software can also be used to calculate the corrosion rate of pipelines,including three models,namely the Norsok model,the Top of Line model and the De Waard model.In this paper,OLGA software was used to simulate the gathering and transportation pipelines in northern shan xi,and the influence of temperature and pressure on the corrosion rate was mainly studied and analyzed.The results show that the relationship between pressure and corrosion rate is linear,while the relationship between temperature and corrosion rate is not linear.By comparing with the results of the modified model,it is found that the results are consistent and the feasibility of the modified model is further verified.