Abstract
The effect of acidizing process on the stress corrosion cracking of HP-13Cr stainless steel in the ultra-depth well environment was studied by the slow strain rate test, the electrochemical measurement, the microstructure observation, and the finite element modeling. The results indicated that the acidizing process significantly increased the stress corrosion cracking susceptibility of HP-13Cr stainless steel and induced the fracture mode to the brittle characteristic in the high temperature and CO2 pressure environment. The stress corrosion cracking susceptibility also increased with the increase of temperature and CO2 pressure. There were dense defects including pits and cracks in the fracture section from the transverse view. After the acidizing process, under tensile stress condition, the increasing roughness will cause the stress concentration and promote the local anodic dissolution, which induces the initiation of stress corrosion cracking.
Highlights
For the abundant oil and gas reservoir, ultra-depth well exploitation was widely carried out in northwestern China
The aim of this work is to reveal the effect of the acidizing process, especially the lived acid (LA) process, on the stress corrosion cracking (SCC) susceptibility of HP-13Cr stainless steel (SS) in formation water (FW) and clarify the interaction of surface roughness, water chemistry, and stress concentration on SCC by slow strain rate test (SSRT) (Henthorne, 2016), electrochemical measurements, micromorphology observation, and numerical simulation
Compared to the mechanical property at normal conditions, with the temperature and CO2 pressure increasing from 95°C/2.8 MPa to 120°C/3.2 MPa, Iδ and Iψ increased from 18.8 to 22.2% and from 13.9 to 48.1% without LA immersion
Summary
For the abundant oil and gas reservoir, ultra-depth well exploitation was widely carried out in northwestern China. Among the above effective methods, acidizing has been recognized as the most accessible means to exploit the carbonate and sandstone reservoirs around the northwest of China (Mu and Zhao, 2010; Zhao et al, 2019a). The corrosion protection techniques, such as coating, inhibitors, and developing novel materials, are not effective in such an aggressive environment (Cui et al, 2021; Liu et al, 2021; Song et al, 2021). HP-13Cr stainless steel (SS), containing lower C and higher Ni and Mo than traditional 13Cr SS, was widely used as tubing material in the oil and gas industry because of its appropriate mechanical properties, excellent corrosion resistance, and costeffectiveness.
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