How can depleted oil and gas reservoirs be used for carbon capture and storage?

In petroleum engineering, depleted oil and gas reservoirs are considered attractive sites for carbon capture and storage (CCS) because they provide ready-made, deep underground storage locations that have historically contained hydrocarbons for geological timescales.1

To utilize these reservoirs for storage, pressurized carbon dioxide (CO₂) is injected into the porous sedimentary rock strata. The effectiveness of this process relies on several key engineering requirements:1

• Geological Integrity: The reservoir must be sealed by impermeable rock layers free from faults to prevent the gas from leaking back into the atmosphere.1
• Depth: Suitable reservoirs are typically located at least 1 km (0.6 miles) underground.1
• Storage Mechanisms: Once injected, the CO₂ occupies pore spaces in the rock. Over time, it may dissolve into groundwater and react to form stable carbonate minerals.1

While some reservoirs are used for carbon dioxide-enhanced oil recovery (CO₂ EOR) to extract remaining oil, the primary goal of CCS is the long-term isolation of CO₂ to mitigate climate change.123