TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn this paper we present two methods for calculating uncertainty ranges for connected hydrocarbon volumes as applied to the Sunrise gas-condensate field, Timor Sea. 1) A "quick look" approach which uses a simplified, exploration scale fault data set. 2) A more detailed fault interpretation which is integrated with 3-D geological and dynamic reservoir modelling techniques.Despite the differences in sophistication, the two methodologies generate similar results in terms of absolute connected hydrocarbon volume ranges.In both studies the fractal relationships between the fault throws, lengths and frequency of occurrence were used to determine the minimum throw of faults fully interpreted on the seismic. This structural interpretation was then augmented by the probabilistic infill of sub-seismic faults with throws greater than the critical juxtaposition-sealing throw of 20 m. The resulting maps were then used to estimate a range of potentially connected gas volumes.The large number of across fault sand-sand juxtapositions within the areally extensive field suggests that as a most likely case the reservoir is 100% connected due to effective communication across faults or around fault tips. Sensitivities were analysed around this most likely case. As a worst case scenario all faults were assumed to be totally sealing due to the potential effects of shale gouge or cataclasis. The quick look study, which took no account of any sedimentological connectivity issues, predicted a worst case connectivity of 77% whilst the detailed 3-D dynamic simulator study predicted a connectivity of 72%.Although the areal distribution of connected hydrocarbons was different for the two approaches, the similarity of the final connected volume figures suggests that the quick look methodology provides a useful technique for the rapid estimation of connected hydrocarbon volume ranges in fields with limited data content and perceived simple sandbody architectures.