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<p>Underground hydrogen storage (UHS) in depleted gas reservoirs is an effective strategy for balancing renewable energy supply and demand, with cushion gases being used to maintain storage pressure. Here CO<sub>2</sub> is investigated as a cushion gas via measurements of the dispersion between hydrogen and CO<sub>2</sub> in a (Bentheimer sandstone) rock core, performed at reservoir-relevant conditions using a novel core flooding apparatus. Such data is required to quantify undesirable mixing between the stored hydrogen and the cushion gas. Dispersion coefficients (<i>K</i><sub><i>L</i></sub>) were measured at 50–100&#xa0;bar and 22–60&#xa0;°C, with injection velocities up to 170&#xa0;m/day, employing benchtop NMR spectroscopy for effluent composition analysis. The value of <i>K</i><sub><i>L</i></sub> ranged from 0.018 to 0.06&#xa0;m<sup>2</sup>/day, with most of the measurements performed for H<sub>2</sub> extraction (CO<sub>2</sub> displacing H<sub>2</sub>). At 22&#xa0;°C and 50&#xa0;bar, a representative comparison showed higher dispersion during H<sub>2</sub> injection (H<sub>2</sub> displacing CO<sub>2</sub>) than during H<sub>2</sub> extraction. This behaviour is attributed to the viscosity ratio (ratio of displaced to displacing fluid) exceeding unity during H<sub>2</sub> injection, promoting viscous fingering. Extrapolation of <i>K</i><sub><i>L</i></sub> to its value at minimal flow velocity produced a tortuosity value that ranged from 2.24 to 2.63 depending on the diffusion coefficient used, which was consistent with the independent measurement of 2.32 ± 0.20 produced using pulse field gradient (PFG) NMR measurements. Values of the molecular diffusion coefficient (<i>D</i><sub>12</sub>) estimated using Thorne-Enskog theory resulted in the normalised <i>K</i><sub><i>L</i></sub>/<i>D</i><sub>12</sub> data collapsing onto a single curve for all of the temperature and pressure conditions considered.</p>

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Dispersion Measurements for Underground Hydrogen Storage over Sequestered CO2

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年8月1日

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  • Sam Kobeissi,
  • Nicholas N. A. Ling,
  • Minzhen Li,
  • Eric F. May,
  • Michael L. Johns

摘要

Underground hydrogen storage (UHS) in depleted gas reservoirs is an effective strategy for balancing renewable energy supply and demand, with cushion gases being used to maintain storage pressure. Here CO2 is investigated as a cushion gas via measurements of the dispersion between hydrogen and CO2 in a (Bentheimer sandstone) rock core, performed at reservoir-relevant conditions using a novel core flooding apparatus. Such data is required to quantify undesirable mixing between the stored hydrogen and the cushion gas. Dispersion coefficients (KL) were measured at 50–100 bar and 22–60 °C, with injection velocities up to 170 m/day, employing benchtop NMR spectroscopy for effluent composition analysis. The value of KL ranged from 0.018 to 0.06 m2/day, with most of the measurements performed for H2 extraction (CO2 displacing H2). At 22 °C and 50 bar, a representative comparison showed higher dispersion during H2 injection (H2 displacing CO2) than during H2 extraction. This behaviour is attributed to the viscosity ratio (ratio of displaced to displacing fluid) exceeding unity during H2 injection, promoting viscous fingering. Extrapolation of KL to its value at minimal flow velocity produced a tortuosity value that ranged from 2.24 to 2.63 depending on the diffusion coefficient used, which was consistent with the independent measurement of 2.32 ± 0.20 produced using pulse field gradient (PFG) NMR measurements. Values of the molecular diffusion coefficient (D12) estimated using Thorne-Enskog theory resulted in the normalised KL/D12 data collapsing onto a single curve for all of the temperature and pressure conditions considered.