Gas Cap 1 : A zone of free gas above an oil deposit. The gas cap occurs where the oil is oversaturated with gas (past the solubility limit). When a gas cap is not present at discovery, the oil is above the bubble point
George E. King Engineering, 5000 Oilfield Terms: A Glossary of Petroleum Engineering Terms, Abbreviations and Acronyms, US 2010. http://gekengineering.com/Downloads/Free_Downloads /Glossary_of_Petroleum_Engineering_Terms_25_August _2010.pdf, (Oil - Amer) {593}