1. adj. [Geology]

Pertaining to an oil field, an accumulation, pool or group of pools of oil in the subsurface. An oil field consists of a reservoir in a shape that will trap hydrocarbons and that is covered by an impermeable or sealing rock. Typically, industry professionals use the term with an implied assumption of economic size.

See: accumulation,  field,  hydrocarbon,  oil pool,  reservoir,  seal,  trap

2. adj. [Geology]

Pertaining to the surface area above a subsurface oil accumulation.

See: accumulation,  field,  hydrocarbon,  oil field,  oil pool,  reservoir,  seal