The amount of oil and/or gas produced from a reservoir by the reservoir's natural sources of energy. This includes gas-cap drive, dissolved-gas drive, water drive, or any combination of these. (ITOGP)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}