f Troll West Gas Province - A reservoir depth conversion study

In this paper a depth conversion study of the top and base of the reservoir in an area in the Troll West Gas Province (TWGP) will be presented. The main objective of the study has been to use different depth conversion methods and vetocity models in order to get an uncertainty estimate of the reservoir rock volume present. The work includes the use of standard 2D- and 3D depth conversion methods as well as more sophisticated techniques. In particular, the GOC-method based on the mapping of the gas-oil contact (GOC) in the area, has been applied as the "base-case" method. The excellent seismic definition of the GOC in the area and the uncertainties associated with the correct time-picking of the GOC has been investigated in detail. The velocity fields used in the depth conversion are generated from different sources of velocities available. This includes well velocities, calibrated stacking velocities (3D) and velocities obtained from both pre-stack and post-stack vetocity modelling on selected 2D-lines.