THE INTEGRATION OF GEOLOGY AND GEOPHYSICS TO POST-WELL EVALUATIONS - EXAMPLE FROM BELUGA-I, OFFSHORE NORTHERN AUSTRALIA

Abstract

The Beluga 1 well was drilled in May 1991 in Permit NT/P41 in the Arafura Sea to test a seismically identified stratigraphic trap in Late Jurassic - Early Cretaceous age syn-rift sediments on the southern flank of the Malita Graben. A continuous high amplitude seismic event defined a lithologic package prognosed as a rift infill sand prone fan sequence interpreted to have been sourced from the adjacent southern platform.

The target section penetrated by the well was found to consist predominantly of a uniform sequence of bioturbated fine sandstones with poor porosity and almost nil permeability indicating distal deposition.

Post well evaluation of Beluga 1, utilizing a variety of well and seismic measurements, showed evidence for several episodes of basin inversion within the juvenile Malita Graben. Reinterpretation resulted in a new structural and depositional model which accounted for the well result and has implications for future exploration in this area and lowstand fan studies in general.