A petroleum reservoir is a body of rock that contains crude oil, natural gas, or both, that can be extracted by a well. Two conditions must be met in tapping such resources. First, to contain and permit extraction of its fluids, the reservoir rock must be porous and permeable. Second, there must be a reservoir trap, a set of conditions that concentrates the petroleum and prevents its migration to the earth’s surface.

Salem Press Encyclopedia of Science, 2023. 3p.