High-Resolution Aeromagnetics as an Exploration Tool in the Timor Sea, Northwestern Australia

O'BRIEN, GEOFFREY W., and PETER WELLMAN, Bureau of Mineral Resources, Canberra, Australia

The Mesozoic Vulcan Graben in the Timor Sea, northwestern Australia, is one of Australia's most active oil exploration areas, with a number of discoveries made within the last five years. To further assist in understanding the structural setting of the region, the Australian Bureau of Mineral Resources (BMR) carried out a regional high-resolution aeromagnetic survey over the Vulcan Graben in late 1989. Three to twelve km wavelength, 0.2-2.0 nT amplitude magnetic anomalies have northeast strikes and correlate well with the position and orientation of the rift faults, as defined by seismic reflection data. Significantly, the magnetic trends closely match the fault trends at the prospective Valanginian unconformity horizon, where all of the major producing reservoirs are located. Numerou northwest-trending (strike-slip?) faults have also been mapped as zones of low anomaly, some of which correspond with offsets in the major northeast-trending anomalies. These faults, which are probably due to the reactivation of either Mesozoic transfer faults or Paleozoic normal faults, may have a major role in the entrapment of hydrocarbons in the Timor Sea, as most producing fields are located close to a northwest-trending fault or its extension. The northwest-trending faults have not previously been defined using seismic data. This survey shows that even in an area with extensive seismic coverage such as the Timor Sea, high-resolution aeromagnetics can provide important information that both complements and supplements the seismic data.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)