The development and implementation of a new alloyed steel for oil and gas production wells

摘要

To develop an economical new alloyed steel,the effects of alloying elements such as Cr and Cu,and microstructure were investigated in CO_2 environments with and without a little amount of H_2S.In laboratory tests,the Cr steels with martensitic microstructure showed good corrosion resistance.But the double corrosion prevention effect of Cr addition to steels and ferritic-pearlitic microstructure,which are recognized as corrosion improvement factors,was not observed in those corrosion tests.The Cu and Mo additions to Cr steels were not effective in CO_2 environments with H_2S.Field tests were also carried out in some production wells of Statoil.In particularly,long term field test result of 5 months showed superior resistance to general and localized corrosion in 5Cr alloyed steel,and the life extension above 5 times to Steel J55 with ferritic-pearlitic microstructure was confirmed in that steel.The developed-5Cr alloyed steel has been successfully used in Siri Field that is Oil & Gas Field located in the Danish Sector of the North Sea.