西南石油大学学报(自然科学版)

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Safety Evaluation of Production Casing Considering Corrosion in Gas
Well with Sustained Casing Pressure

Zhang Zhi1, Huang Yi2, Li Yanjun2, Zhang Chao2, Zeng Chunmin2   

  1. 1. State Key Laboratory of Oil & Gas Reservoirs Geology and Exploitation,Southwest Petroleum University,Chengdu,Sichuan 610500,China
    2. Drilling and Completion Department of Zhanjiang Branch,CNOOC,Zhanjiang,Guangdong 524057,China
  • Online:2014-04-01 Published:2014-04-01

Abstract:

In the high temperature and high pressure(HTHP)gas wells with CO2 and H2S,once sustained casing pressure
builds up in the annulus of tubing and production casing,the production casing above packer will be exposed to the corrosive
environment. Because of the interaction of corrosion and sustained casing pressure,production casing will face big challenges.
A model of the max sustained casing pressure has been established;and based on the corrosion rates of casing,this paper
predicts the safe service life of casing. Meanwhile safe service life has been predicted considering the sustained casing pressure
and corrosion. The paper provides casing residual strength and its safety situation in limited production cycle by casing service
life design,which will not only ensure the safety of casing but also cut the cost of production. For the HTHP sour gas wells,
if the production casing is carbon steel,the performance of annulus protection fluid needs to be tested,and annulus protection
fluid needs to be optimized;and in order to avoid casing security risks,it is necessary to strengthen security supervision annulus
over protection fluid.

Key words: gas well, CO2 corrosion, residual strength, safety evaluation, sustained casing pressure