Geological storage refers to the process of safely storing substances, such as carbon dioxide (CO2), deep underground in rock formations. This method is often used to reduce greenhouse gas emissions by capturing CO2 from industrial sources and preventing it from entering the atmosphere. The storage sites are typically selected based on their ability to contain the gas without leakage. The geological formations used for storage can include depleted oil and gas fields, deep saline aquifers, and unmineable coal seams. These formations are chosen for their impermeable rock layers, which act as barriers to keep the stored CO2 contained over long periods, ensuring environmental safety.