In oil: typically onland tankage facilities for short- or long-term storage of crude or products; sometimes used in economic parlance interchangeably with the concept of oil stocks.

In natural gas: facilities used to store natural gas which has been transferred from its original location. Usually consists of natural geological reservoirs like depleted oil or gas fields, water-bearing sands sealed on top by an impermeable cap rock, underground salt domes, bedded salt formations, or in rate cases, abandoned mines.