Seismic Tectono-Stratigraphic Study Of The Pleistocene In The Sunrise/Troubadour Area In Relation To Development Of Future Infrastructure.

Chapman, Timothy Ray

Honours Degree, 1998

University of Adelaide

Abstract

The analysis of Pleistocene sequences in the Timor Sea was a project devised by Woodside to gain an understanding of depositional geometries and anomalies in the shallow substrate of the Sunrise/Troubadour (STL) region. This understanding was required to aid the positioning of a production platform and several sub sea completions. An area of 16500 square km within permit blocks ZOCA 95-19 and NT/RL 2 was investigated using available 2-D seismic data to define near-surface and surface features that could impact on the platform location. On the basis of the seismic interpretation, a seismic sequence stratigraphic model for the Neogene-to-Recent deposition in the Timor Sea region was produced.

The STL area has a number of risk areas that should be avoided when considering infrastructure location. A large slump feature of approximately 720 sq km, identified by this study, was defined within the Holocene/Late Pleistocene section. The slump is located on the palaeo-slope to the west of Troubadour #1 and Sunrise #1 and #2 and includes the Sunset West #1 location. Overall, the continental shelf is flat and stable whereas the continental slope is unstable in places with areas of mass wasting and slumping. Any location on the slope area should be considered carefully as any seismic activity in the area could result in further slope failure and movement.

Prior to identifying a platform location high resolution 3D seismic is required over the area to accurately record the sea floor topography and possible slump scarps. Bathymetric maps generated from 2-D seismic and focused on deep petroleum reservoirs are only accurate vertically to within 10-15 milliseconds and should not be used for detailed site planning. Confirmation of the proposed model of deposition would also benefit from shallow coring and isotope studies.