Calculating the large leakage flux of a breached hydrocarbon trap using geophysical interpretation of a paleo-gas-water contact

Integration of three-dimensional seismic and well data from the Northern Carnarvon Basin on North West Shelf Australia was used to assess evidence for top seal breach a paleo-gas accumulation. Several indicators vertical hydrocarbon leakage crest stratigraphic Mungaroo Trap point significant flux gas within past few hundred thousand years. Mapping reservoir Triassic aged Formation revealed strong paleo-gas-water contact (GWC), approximately 100 m down flank erosional trap. This conforms structure delimits an original volume 1.1 trillion cubic feet (Tcf), based property calibration nearby wells. also present-day gas-water with closed 0.2 Tcf, 30 crest. displays discordant geometry indicative dynamic contact. The zone is located directly above structure. It seismically imaged comprises seafloor pockmarks, shallow anomalies hydrate anomalies. presence distributed vertically containing present paleo-GWC provides compelling this trap has leaked by breaching seal. Volumetric calculations using two GWCs indicate that been depleted 0.9–1.1 Tcf. A dynamic-GWC indicates event occurred recently. Analysis dating horizons correlated pockmarks places at sometime last 300 Ka.