Research ArticleENVIRONMENTAL STUDIES

Long-term viability of carbon sequestration in deep-sea sediments

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Science Advances  04 Jul 2018:
Vol. 4, no. 7, eaao6588
DOI: 10.1126/sciadv.aao6588
  • Fig. 1 Schematic illustration of carbon sequestration in deep-sea sediments.

    The captured CO2 is transported through ships to the platform and then injected into the submarine sediments.

  • Fig. 2 Spatial distribution of different variables at specific times.

    (A to E) Saturation of CO2 hydrate. (F to J) Saturation of liquid CO2. (K to O) Mass fraction of component CO2 in the aqueous phase. (P to T) Mass fraction of salt in the aqueous phase. The time of each column is the same and specified at the top of the figure.

  • Fig. 3 Time evolution of the mass distribution of the CO2 component in different phases.

    The value is defined by the ratio of the total mass of the CO2 component in a specific phase to the total mass of injected CO2. The dashed-dotted line represents the liquid CO2 phase. The solid line represents the hydrate phase. The dashed line represents the aqueous phase.

  • Table 1 Results of the sensitivity study.

    LHFZ, thickness of HFZ; LNBZ, thickness of NBZ; dPI, distance between the seafloor and the front of the CO2 plume at the end of the injection; dmin, minimum distance between the seafloor and the front of the CO2 plume; Td, time spent for the CO2 plume to reach the minimum distance; dHFZ, distance between the front of the CO2 plume and the base of HFZ at Td; dup, distance of upward migration of the CO2 plume after injection ceases.

    ParametersValueLHFZ (m)LNBZ (m)dPI (m)dmin (m)Td (years)dHFZ (m)dup (m)
    Ocean depth (m)1000252287292742223258
    20002952931074698188186
    3500*3442252992813636318
    Vertical permeability (mD)10*3442252992813636318
    503442252992512679348
    10034422529322727211766
    Vertical permeability (mD) with ocean depth = 1000 m10252287292742223258
    502522570189252257
    100252227089252227
    Geothermal gradient (K/m)0.03*3442252992813636318
    0.0425915329923310382666
    0.052061162991979709102
    Seafloor temperature (°C)3*3442252992813636318
    43151782992697714630
    52801312992578182342
    Carman-Kozeny factor3*3442252992813636318
    5344225299292235527
    734422529929879461
    Porosity0.153442252812632688118
    0.25*3442252992813636318
    0.353442253112933945118
    Injection depth (mbsf)35034422525123934410512
    400*3442252992813636318
    5003442254013351150966
    Injection rate (metric tons/day)750*3442252992813636318
    15003442252752516739324
    225034422525723359511124
    Injection time (years)10*3442252992813636318
    5034422523320954313524
    100344225191161100918330
    Injection temperature (°C)15*3442252992813636318
    203442252992754736924
    253442252992696037530

    *Base case.

    †For the case of changing vertical permeability, the ratio of horizontal permeability to vertical permeability remains the same (5:1) to ensure the same anisotropy.

    Supplementary Materials

    • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/7/eaao6588/DC1

      Section S1. Determination of NBZ and HFZ

      Section S2. Development of the simulation code for CO2 sequestration in deep-sea sediments based on TOUGH+HYDRATE

      Section S3. Code verification

      Section S4. Description of the base case

      Fig. S1. Illustration of the NBZ and HFZ with a geothermal gradient of 0.03 K/m, a salinity of 3.5%, and an ocean depth of approximately 3500 m.

      Fig. S2. Possible phase changes in the model.

      Fig. S3. Phase diagram of CO2 hydrate.

      Fig. S4. Comparison of the analytical Buckley-Leverett solution and the results from the numerical simulation.

      Fig. S5. Comparison of the analytical solution and the results from the numerical simulation in the 1D diffusion problem.

      Fig. S6. Schematic of the 1D hydrate formation problem.

      Fig. S7. Time evolution of pressure at x = 2 m.

      Fig. S8. Time evolution of saturation of each phase obtained from the numerical simulation at x = 2 m.

      Table S1. Phases and corresponding components in the model.

      Table S2. PVSM for CO2 sequestration in deep-sea sediments.

      Table S3. Hydrate-related properties.

      Table S4. Physical properties of CO2 and seawater.

      Table S5. Parameter setting for the Buckley-Leverett problem.

      Table S6. Parameter setting for 1D diffusion problem.

      Table S7. Parameter setting for 1D hydrate formation problem.

      Table S8. Parameter setting of the base case.

      Table S9. Thermal and hydraulic properties of the formations.

      Movie S1. Time evolution of spatial distribution of hydrate saturation in the base case.

      Movie S2. Time evolution of spatial distribution of CO2 saturation in the base case.

      Movie S3. Time evolution of spatial distribution of mass fraction of CO2 in aqueous phase in the base case.

      Movie S4. Time evolution of spatial distribution of mass fraction of salt in aqueous phase in the base case.

      References (4664)

    • Supplementary Materials

      • Section S1. Determination of NBZ and HFZ
      • Section S2. Development of the simulation code for CO2 sequestration in deep-sea sediments based on TOUGH+HYDRATE
      • Section S3. Code verification
      • Section S4. Description of the base case
      • Fig. S1. Illustration of the NBZ and HFZ with a geothermal gradient of 0.03 K/m, a salinity of 3.5%, and an ocean depth of approximately 3500 m.
      • Fig. S2. Possible phase changes in the model.
      • Fig. S3. Phase diagram of CO2 hydrate.
      • Fig. S4. Comparison of the analytical Buckley-Leverett solution and the results from the numerical simulation.
      • Fig. S5. Comparison of the analytical solution and the results from the numerical simulation in the 1D diffusion problem.
      • Fig. S6. Schematic of the 1D hydrate formation problem.
      • Fig. S7. Time evolution of pressure at x = 2 m.
      • Fig. S8. Time evolution of saturation of each phase obtained from the numerical simulation at x = 2 m.
      • Table S1. Phases and corresponding components in the model.
      • Table S2. PVSM for CO2 sequestration in deep-sea sediments.
      • Table S3. Hydrate-related properties.
      • Table S4. Physical properties of CO2 and seawater.
      • Table S5. Parameter setting for the Buckley-Leverett problem.
      • Table S6. Parameter setting for 1D diffusion problem.
      • Table S7. Parameter setting for 1D hydrate formation problem.
      • Table S8. Parameter setting of the base case.
      • Table S9. Thermal and hydraulic properties of the formations.
      • Legends for movies S1 to S4
      • References ( 4664)

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    • Other Supplementary Material for this manuscript includes the following:
      • Movie S1 (.mp4 format). Time evolution of spatial distribution of hydrate saturation in the base case.
      • Movie S2 (.mp4 format). Time evolution of spatial distribution of CO2 saturation in the base case.
      • Movie S3 (.mp4 format). Time evolution of spatial distribution of mass fraction of CO2 in aqueous phase in the base case.
      • Movie S4 (.mp4 format). Time evolution of spatial distribution of mass fraction of salt in aqueous phase in the base case.

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