Study On Corrsion Behavier Of Subsea Gathering Pipeline Steel

The subsea pipeline is.regarded as the main objective of the present study, many aspects of pipeline such as whose structure, service environment, the operational status, the well condition etc were surveyed, and the corrosion types and characteristics of the subsea gathering pipelines were determined. So the detailed experimental programs were developed to solve the actual corrosion problems of a submarine oil field gathering lines encountered in the production process.The pipe sections having the characteristics of corrosion were chose form the pipeline system and were evaluated, the results show that. The corrosion morphology of the whole pipe system is mainly uniform, there are pitting phenomenon appearing in the local area, and the bending region cannot meet the mechanical requirements of API SPEC 5L due to the severe thinning.We have also investigated the corrosion behavior of the product film under the conditions of the mining by laboratory simulation, electrochemical testing and product film analysis. Seawater corrosion of subsea pipeline steel is mainly oxygen corrosion; With the increasing of temperature,the corrosion rate of steel increases first and then decreases, while the carbon dioxide corrosion shows the decreasing tendency; the partial pressure ratio of carbon dioxide and hydrogen sulfide is the dominant factor determining the corrosion of the pipeline steelAccording to the results of physical evaluation and the prediction of the oil pipe corrosion rate from the model made of TGRI, the results show that the maximum operating pressure for the safe production was 20.2MPa and 7.6MPa respectively.