Where does seal collide?

A formality of the common law under which a written instrument, once sealed and delivered, binds its maker by that act rather than by any exchange of value, so a promise made in a deed under seal (a covenant) is enforceable without the consideration an ordinary contract requires. Blackstone's 1766 Commentaries on the Laws of England counted sealing among the essentials of a deed, and Simpson's 1975 A History of the Common Law of Contract traced how the sealed instrument carried obligation for centuries before the action of assumpsit. Here the seal is a legal act that confers binding force on a document, distinct from the geologist's trapping rock and from the confessor's duty of silence.[5][1][2]

Unit

One sealed instrument whose execution binds its maker

Recovery means

Not applicable

Measured by

Established by the formal act of sealing and delivery, and judged valid or not by a court

The impermeable rock, often shale or evaporite, that overlies a reservoir and stops buoyant oil and gas from escaping upward, so that hydrocarbons collect beneath it. White's 1885 The Geology of Natural Gas set out the anticlinal theory, that gas gathers in the crests of folds beneath an impervious cover, and Downey's 1984 Evaluating seals for hydrocarbon accumulations made the seal a quantity to assess, judged by how much pressure it takes to force fluid through the rock and by how unbroken the barrier is. Here the seal is a barrier rock in the subsurface, graded by the column of oil or gas it can hold, unlike the legal formality that binds a deed or the secrecy that binds a confessor.[3][4]

Unit

One barrier rock above a reservoir, rated by the oil or gas column it can hold

Recovery means

Not applicable

Measured by

Assessed by the pressure needed to force fluid through the rock and by its thickness and continuity