Casing design in sour gas well mitigating SSC

Abstract

Sulfide stress corrosion cracking (SSC) is the major failure form for casing string in sour gas wells contained H2S. The equivalent tri-axial stress of casing string should be controlled below the threshold stress of SSC occurrence to minimize SSC initiation and improve the integrity and service life of casing. The principles and methods regarding anti-SSC casing design are presented and two methods commonly used for anti-SSC casing design are comprehensively discussed. The accurate strength check formulae for burst and collapse design are derived under tri-axial stress condition. The design method described in this paper can be used to guide casing design in sour environment contained H2S.