The near disposition of source rock, reservoir rock and cap rock is favorable for oil and gas accumulation in buried hill traps.

The gas-cap oil reservoir is an oil reservoir overtopped with gas phase hydrocarbon that is in a unified hydrodynamic system with the underneath oil deposit and the water body.

There are large number of oil fields developed under gas cap drive in operation currently, however, much less studies on the reservoir behavior of such oil fields have been carried.