Material Selection for CCS applications

Nippon Steel developed a complehensive material selection chart for CCS applications, based on extensive experimental investigations under supercritical CO₂ environments containing various impurities.

The methodology is supported by a material selection chart, which covers a wide range of operating condition

relevant to CCS wells, explicitly accounting for:

  • CO₂ phase conditions
  • Impurity effects
  • Chloride concentration in formation water

Key experimental findings underpinning this methodology have been published in international technical conferences such as AMPP and Eurocorr (e.g. C2026-00140)

Material selection chart for CCS applications

Material applicability is evaluated under representative formation water conditions, defined as:

  • Moderate salinity: 5 wt% NaCl (< 31,300 mg/L Cl⁻)
  • High salinity: 25 wt% NaCl (< 181,000 mg/L Cl⁻)

The material selection chart enables rapid screening of suitable materials based on the combined effects of:

  • Impurity concentration (O₂, SO₂, NO₂, H₂S)
  • Chloride level
  • Pressure and temperature conditions

This approach allows early‑stage material down‑selection while maintaining sufficient conservatism for CCS‑specific risks.

Material Selection Chart for CCS application              in 5% NaCl (< 31,300 mg/L Cl) condition                     in 25% NaCl (<181,000 mg/L Cl) condition

 

New corrosion risks involved in CO2 injection wells

Compared to conventional hydrocarbon production wells, CO₂ injection wells are exposed to fundamentally different and more severe corrosion mechanisms, including:

  • Formation water flowback into the wellbore
  • Strong acidification due to CO₂ dissolution (pH (~)3.0~3.5)
  • Presence of oxidizing and acid-forming impurities (O₂, SOx, NOx)
  • Increased susceptibility to localized corrosion (pitting / crevice) 

👉 These factors significantly increase the severity and complexity of material selection, making conventional oil & gas design concepts insufficient for CCS applications..

comparizon HC prod vs CO2 injection

Required Input Data for CCS Material Selection

The following information must be considered to properly assess the corrosiveness of the environment:

1. Injection conditions

  • Pressure and temperature profile
  • Injection and shut‑in sequences

2. Injection fluid composition
 - CO₂, H2O, H2S, O2, NOx, SOx and any other element considered important

3. Reservoir fluid composition
・Formation water composition (especially, Chloride contents [Cl-], bicarbonate contents [HCO3-])
・Original Reservoir Gas composition in case of injection in a depleted reservoir

Material Selection Analysis for your wells

Nippon Steel provides customized material selection analyses tailored to individual CCS well conditions.

Based on the supplied input data, we will:

  • Evaluate corrosion risks under realistic CCS environments
  • Identify applicable material grades
  • Optimize material selection from both technical and economic perspectives

Please fill in the following spreadsheet and contact us:<https://nipponsteel.box.com/s/4xawkhleq4dlmd574krd6xy3pi66g46t>

 

    Key design considerations for CCS Materials

      A critical characteristic of CCS environments is the significant decrease in pH caused by dissolved CO₂:

      • Typical pH: 3.5 or lower

      This results in:

      • Increased general corrosion rates Enhanced risk of localized corrosion (pitting / crevice) Potential for environmental cracking
      • In addition, CCS wells are expected to operate over extended timeframes (typically 50–100 years or more), requiring:
      • Based on experimental investigations under supercritical CO₂ environments:
      • Experimental experience in super critical CO2 environments

      (1) Effect of Oxygen (O₂)

      • Corrosion rate increases with O₂ partial pressure
      • Pitting and crevice corrosion are promoted even at relatively low concentrations

      (2) Effect of SO₂ / NO₂

      • Even trace levels of SO₂ (~ppm level) significantly increase corrosion rate
      • Strong acidification effect contributes to material degradation

      (3) Chloride Effect (Critical Parameter)

      • Corrosion susceptibility is strongly dependent on chloride concentration
      • High chloride environments drastically reduce the applicability range of lower-grade CRAs
      • High long-term corrosion resistance
      • Robust material reliability under variable conditions

      👉 Therefore, material selection for CCS applications must be based on a comprehensive, data-driven approach, rather than conventional oil & gas practices.

      Recent studies performed by Nippon Steel on the effect of O2 , SO2 and NO2 in CO2 dominant environments carried out on Super Martensitic Stainless Steel (SM13CRS / UNS S41426), Propietary-Cost effective Duplex Stainless Steel (SM25CRU / UNS S82551) and Super Duplex Stainless Steel (SM25CRW /UNS S39274) (see below Figure, just an exapmles)

      corrosion test results in 5%NaCl for CCS applications

      Therefore, for NOx, SOx effect on materials, additional studies are required to define the critical thresholds of these impurities on materials behaviors in CO2 dominant environments.

      Effect of Mixed Gas Conditions

      Testing under simulated CCS gas compositions (including O₂, SO₂, NO₂, H₂S) revealed:

      • Corrosion performance is highly sensitive to combined impurity effects
      • DSS may be applicable under:
        • Low impurity concentration (ISO 27913 level)
        • Lower pressure conditions
      • SDSS maintains robust performance even under severe environments

      👉 Material selection must be environment-specific rather than generic.

      Mixture gas test result_5%NaCl

      Mixture gas test result_25%NaCl

      Low-Temperature Integrity (Joule–Thomson Effect)

      Accidental depressurization of high-pressure CO₂ can cause rapid temperature drops due to the Joule–Thomson effect.

      Charpy impact testing results indicate:

      • Solution-annealed DSS and SDSS maintain sufficient toughness down to low temperatures
      • Cold-worked SDSS shows reduced toughness

      👉 Low-temperature performance could be considered in addition to corrosion resistance.

      Low temp toughness

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