Oil-Water Interface : Oil will lie on top of water due to difference in specific gravity. The bottom level of oil column and top level of water column are at a common level called the interface. (WT)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}