Hydrodynamics to assess hydrocarbon migrationin faulted strata-methodology and a case study from the North West Shelf of Australia

Abstract

The North West Shelf hydrodynamics pressure database currently contains about 8000 pressure data points and hundreds of stress, temperature and water salinity data. All data have been ranked using a newly developed quality-control system (Pressure QC ™ ). A hydrodynamic workflow was used to interpret fluid migration pathways in faulted strata and to identify fault seal integrity in the Barrow sub-basin on the North West Shelf. The comprehensive database and methodology investigate hydrocarbon migration from basin-centred source rocks to the eastern and south-eastern edge of the basin across the Flinders Fault zone. The different structural styles and orientations along the basin-edge Flinders fault zone determine hydraulic connection to the basin margin and potential up-dip migration of hydrocarbons. Hydrodynamic data show that north of 21 °S latitude, the fault zone acts as a fluid barrier and hydraulic communication occurs only at specific locations where individual faults lose displacement at their tips and in relay zones. A convoluted migration pathway is required to migrate oil from the mature regions to the basins' edge. South of 21 °S latitude, the Flinders Fault zone changes orientation and the hydrostratigraphic unit is in hydraulic communication with the basin margin, increasing the prospectivity of oil migration into this region, as is documented by oil shows.