Depleted gas reservoirs are underground formations that have already been tapped for their natural gas resources. Over time, the extraction of gas reduces the pressure within the reservoir, making it less capable of producing additional gas. These reservoirs are often found in sedimentary rock formations and can be identified through geological surveys. Once a gas reservoir is depleted, it may still hold value for other uses, such as carbon dioxide storage or natural gas reinjection. Additionally, advancements in technology may allow for the recovery of remaining gas, making these reservoirs a focus for ongoing energy exploration and management.