A proper characterization of fluid contacts and their uncertainties are an essential input to the development of gas and oil reservoirs. However, during exploration and early appraisal there is usually little information available that can reliably anchor the uncertainty ranges. Depending on the expected fluid type there may be little infrastructure in place to evacuate the reservoir fluids. Particularly the presence of a large gas cap can have a big impact on the economics of a potential development, depending on the evacuation options for the gas. This paper aims to show how PVT data may be used to delineate the size of the gas caps in stacked reservoirs.