Design Of Direct Electrical Heating And Thermal Effect On Deepwater Subsea Pipelines

With the exploit development of oil and gas into deep water,the low temperature and high pressure in working environment have a higher possibility of forming hydrate wax crystallization in exploitation process.The problem of transportation safety of oil and gas has become a science and engineering issue in recent years.Nowadays,the technology of direct electrical heating(DEH)has been widely used to solve the problem of pipe insulation overseas.To further investigate the heating efficiency of pipes,this thesis studies the DEH technology based on the fields including electromagnetic,heat and flow physical from the perspective of thermodynamics.Firstly,an electromagnetic model is established to investigate the joule heating effect of steel pipe.The current,current frequency,the distance of the steel pipe and cable and the pipe size have been studied to reveal the effect of joule heat generated by the DEH technology,and then the weight factors of thus indexes has been given.Secondly,this thesis has studied the temperature distribution of fluid in pipeline with the application of DEH through the establishment of the electromagnetic-flow coupling model.Lastly,the entire pipeline temperature change rule has been calculated with the application of DEH in the well stop working conditions through the establishment of the electromagnetic-thermal coupling model.The relationship between the temperature and heating time,heating current size has been revealed.Through the fitting of large amount data,the formula has been established between the temperature and heating time,heating current size.This formula can calculate the lowest temperature in any time,and it's an important reference for practical engineering design of DEH.