Carbon dioxide enhanced hydrocarbon recovery methods coupled with underground hydrogen storage

A method comprising:

• introducing carbon dioxide gas into a subterranean formation via one or more injection wells, the carbon dioxide gas being obtained via carbon capture from an oxy-fuel combustion of a supplied hydrocarbon and a supplied oxygen, and the subterranean formation containing hydrocarbons and optionally water;
• mobilizing at least a portion of the hydrocarbons in a hydrocarbon-bearing zone of the subterranean formation with the carbon dioxide gas;
• after mobilization with the carbon dioxide gas, producing the hydrocarbons from the hydrocarbon-bearing zone of the subterranean formation via one or more production wells;
• introducing hydrogen gas into the subterranean formation via the one or more injection wells, the hydrogen gas displacing the carbon dioxide gas downward in the subterranean formation;
• storing the hydrogen gas in the subterranean formation above the carbon dioxide gas;
• and
• producing at least a portion of the hydrogen gas from the subterranean formation via the one or more production wells, the one or more injection wells, or any combination thereof,
• wherein the supplied hydrocarbon comprises at least a portion of the hydrocarbons produced from the hydrocarbon-bearing zone of the subterranean formation, and/or
• wherein the supplied oxygen is obtained as a byproduct of water electrolysis.

A method comprising:

• introducing carbon dioxide into a subterranean formation via one or more injection wells, the subterranean formation containing hydrocarbons and optionally water;
• mobilizing at least a portion of the hydrocarbons in a hydrocarbon-bearing zone of the subterranean formation with the carbon dioxide;
• after mobilization with the carbon dioxide, producing the hydrocarbons from the hydrocarbon-bearing zone of the subterranean formation via one or more production wells;
• introducing hydrogen to the subterranean formation via the one or more injection wells, the hydrogen displacing the carbon dioxide downward in the subterranean formation;
• storing the hydrogen in the subterranean formation above the carbon dioxide;
• producing at least a portion of the hydrogen from the subterranean formation via the one or more production wells, the one or more injection wells, or any combination thereof;
• and
• generating electricity using a hydrogen fuel cell with at least a portion of the hydrogen produced from the subterranean formation.