Abstract

Ten years of research has resulted in a new satellite gravity dataset for screening, evaluating and ranking hydrocarbon basins over all the continental margins of the world. New processing methods have re-picked, edited and transformed the altimeter data from the ERS-1 and GEOSAT satellites, to recover gravity anomalies with wavelengths down to 10 km.

The methodology has resulted in:

• geologically meaningful and coherent gravity signatures to within 5 km of the coast

• the suppression of noise that is prevalent and dominates existing solutions at wavelengths of between 30 and 40km.

The resulting improvements in the quality of the data are primarily due to three separate processing steps:

• The 'first breaks' of the radar waveforms from the ERS-1 satellite were re-picked using synthetic waveform matching techniques.

• The altimeter profiles along every track were inspected and edited for dc-shifted data, spikes and noise arising from near shore radar returns.

• The final altimeter profiles were levelled using cross-over and micro-levelling techniques to calculate a geoid grid. By definition, the height of the sea surface is the geoid. Free air gravity is derived from the first vertical derivative of the geoid.

This new dataset will significantly help in S.E. Asia to:

• better define the extent and structure of offshore basins, perhaps where little or no other data are available

• identify subtle but important lineations running from the deep water onto the shelf

• plan and assist the interpretation of 2D seismic surveys

• trace sediment pathways and canyons into distal depocentres

In the Gulf of Thailand, hints of the Pre-Cambrian basement structure can be traced through the dominating gravity signature arising from the base of the Tertiary basins. Further examples from the Java Sea and Northern Sulawesi are discussed.