by Wolf Tilmann Pfeiffer, Christof Beyer, and Sebastian Bauer Hydrogen storage in a heterogeneous sandstone formation: dimensioning and induced hydraulic effects by Wolf Tilmann Pfeiffer, Christof Beyer, and Sebastian Bauer Petroleum Geoscience Volume 23(3):315-326 August 1, 2017 © 2017 The Author(s)‏

(a) Structural model used in the analysis (a) Structural model used in the analysis. us, Upper Shale; ms, Main Sandstone; ls, Lower Shale. (a) Structural model used in the analysis. us, Upper Shale; ms, Main Sandstone; ls, Lower Shale. (b) Thickness of the reservoir formations. The black stars indicate the positions of the storage wells. The black line depicts the transect along which the observation points are located at 500, 1000, 2500 and 5000 m (positions indicated as black bars). Modified after Pfeiffer & Bauer (2015). Wolf Tilmann Pfeiffer et al. Petroleum Geoscience 2017;23:315-326 © 2017 The Author(s)‏

Exemplary permeability distribution for the individual sub-formations in run #14. Exemplary permeability distribution for the individual sub-formations in run #14. Please note that the Upper Shale of the Middle Rhaetian and the Main Sandstone of the Middle Rhaetian consist of five individual layers of which only three are displayed. Wolf Tilmann Pfeiffer et al. Petroleum Geoscience 2017;23:315-326 © 2017 The Author(s)‏

Initial hydrostatic pressure distribution in the storage formation (left) and the observed pressure change during the sixth storage cycle (right) in run #14. Initial hydrostatic pressure distribution in the storage formation (left) and the observed pressure change during the sixth storage cycle (right) in run #14. Wolf Tilmann Pfeiffer et al. Petroleum Geoscience 2017;23:315-326 © 2017 The Author(s)‏

Evolution of the pressure change at the observation points at (a) 500 m, (b) 1000 m, (c) 2500 m and (d) 5000 m along a transect perpendicular to the well gallery and intersecting with the centre well. Evolution of the pressure change at the observation points at (a) 500 m, (b) 1000 m, (c) 2500 m and (d) 5000 m along a transect perpendicular to the well gallery and intersecting with the centre well. All observation points are located at the central layer of the storage formation. The solid black line depicts the median of all realizations; the dark grey shaded area is the interval spanning between the 25th and 75th percentiles; the light grey shaded area is the interval spanning between the 5th and 95th percentiles. The dashed lines indicate the absolute minimum and maximum values. Wolf Tilmann Pfeiffer et al. Petroleum Geoscience 2017;23:315-326 © 2017 The Author(s)‏

(a) Vertically averaged gas saturations and (b) vertically averaged molar fractions of H2 in gas after the storage initialization and during the sixth storage cycle in run #14. (a) Vertically averaged gas saturations and (b) vertically averaged molar fractions of H2 in gas after the storage initialization and during the sixth storage cycle in run #14. Wolf Tilmann Pfeiffer et al. Petroleum Geoscience 2017;23:315-326 © 2017 The Author(s)‏

(a) Absolute gas saturations before the sixth production period and (b) the change in gas saturation after the sixth storage cycle; (c) molar fractions of H2 in gas before the sixth production period and (d) the change in the molar fractions of H2 in gas after the sixth production period (magnitudes) in the storage formation in run #14. (a) Absolute gas saturations before the sixth production period and (b) the change in gas saturation after the sixth storage cycle; (c) molar fractions of H2 in gas before the sixth production period and (d) the change in the molar fractions of H2 in gas after the sixth production period (magnitudes) in the storage formation in run #14. The displayed formation is vertically exaggerated by a factor of 5. Each grid block is 50 × 50 m in lateral direction. Wolf Tilmann Pfeiffer et al. Petroleum Geoscience 2017;23:315-326 © 2017 The Author(s)‏

Vertically averaged gas saturations in the storage formation before the sixth production period in: (a) run #3, (b) #14, (c) #15 and (d) #19. Vertically averaged gas saturations in the storage formation before the sixth production period in: (a) run #3, (b) #14, (c) #15 and (d) #19. Wolf Tilmann Pfeiffer et al. Petroleum Geoscience 2017;23:315-326 © 2017 The Author(s)‏

(a) Total storage flow rate, (b) volume averaged molar H2 fraction in the produced gas phase per storage and (c) resulting H2 flow rate, as well as equivalent power output, for storage cycles 1, 3 and 6. (a) Total storage flow rate, (b) volume averaged molar H2 fraction in the produced gas phase per storage and (c) resulting H2 flow rate, as well as equivalent power output, for storage cycles 1, 3 and 6. All observation points are located at the central layer of the storage formation. The solid black line depicts the median of all realizations, the dark grey shaded area is the interval spanning between the 25th and 75th percentiles, and the light grey shaded area is the interval spanning between the 5th and 95th percentiles. The dashed lines indicate the absolute minimum and maximum values. Wolf Tilmann Pfeiffer et al. Petroleum Geoscience 2017;23:315-326 © 2017 The Author(s)‏