What is the total amount of oil located in the subsurface of a reservoir called?

• A. Oil in place
• B. Reserves
• C. Recoverable oil
• D. Oil on surface

Answer: (A)

Oil in place is the total quantity of oil originally present in the subsurface reservoir. It counts every drop held in the rock’s pore spaces (and any trapped oil still inside the rock) before production begins, including portions that may be unrecoverable with current technology or economics. Reserves refer to the portion that can be recovered profitably with today’s methods, while recoverable oil is the subset that can actually be extracted given the existing technology. Oil on surface isn’t a descriptor for oil located underground.