Sentence:  Underground natural gas <WSD>storages</WSD> are underground facilities for storing natural gas. At present, there are three types of underground natural gas <WSD>storages</WSD> worldwide, which include depleted oil and gas reservoir gas <WSD>storages</WSD>, salt-cave gas <WSD>storages</WSD> and aquifer <WSD>storages</WSD>. 
Meaning of the word marked with <WSD> tags:  An object or place in which something is stored.