Fig. 1: Change of H2 and CO2 concentrations during H2 co-storage in the Lehen test reservoir.
From: Hydrogen storage and geo-methanation in a depleted underground hydrocarbon reservoir
a, Monitoring of H2 across one storage cycle comprising injection (circles), gas is pressed into the reservoir; shut-in (grey shading, squares), gas is sealed and stored in the reservoir; production (triangles), gas is produced from the reservoir. The yellow horizontal line indicates the mean H2 concentration during injection. b, Zoom in on the H2 concentration trajectory during the production phase. The red vertical line signifies the threshold beyond which the withdrawal of cushion gas took place. A dashed, blue horizontal line indicates the H2 concentration at the end of the field trial. c, Monitoring of CO2 concentration across all phases of the field trial. d, Zoom in on the CO2 concentration trajectory during the production phase: CO2 concentration drops following short breaks in gas production termed ‘mini shut-ins’. A vertical dashed line indicates the beginning of each mini shut-in.
