The 4 main types of reservoirs are: Standard Oil Reservoirs — mostly crude oil with some water and gas. Volatile Oil Reservoirs — high amounts of corrosive gas in addition to oil and water. Dry Gas Reservoirs — mostly natural gas with some water vapor. Gas Condensate Reservoirs. In this video, we take a high-level trip through the flow path of each of these types to explore the commonly used vessels and equipment.