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ABSTRACT: 4D Migration pathway analysis in the Vulcan sub-basin, Timor Sea

Chen, Gang, Kevin Hill, Nick Hoffman , La Trobe 3D-GEO, Melbourne, Australia

Analysis of regional migration pathways typically involves constructing depth structure maps on the main source unit and top reservoir horizon and marking updip flow paths. However, migration most likely occurred in the past when units had a different geometry, overburden, water depth and temperature gradient. Flattening on an intermediate horizon and varying the heat flow provides limited compensation, but this can be significantly improved upon. Additionally, migration effects along/across faults are hard to include.

Applying 3D-Move, the reservoir can be restored to its true configuration at the time of hydrocarbon migration. This involves stripping off the overburden and decompacting the underlying sediments for a more accurate burial depth estimate. Full 3D restoration of major fault geometries and smoothing of minor faults adjust the detailed flow paths. Inclusion of appropriate bathymetry based on sequence analysis and palynology improves estimates of relative depths across the basin, yielding highly accurate depth maps at the chosen critical instant for the source unit and the reservoir.

Using thermal modelling, the extents of the kitchen are delineated and 3D-Move plots updip migration paths on the key reservoir/seal interface with faults allowed as barriers, neutral objects, or conduits.

This method has been applied in the Timor Sea where 2D profiles and 3D datasets in the Vulcan graben define the palaeogeometries for migration and highgrade key play fairways.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia