Publication Name: Eastern Australian Basins Symposium 2001
Authors: E.M. Johnstone, C.C. Jenkins and M.A. Moore
Date Published: November 2001
Number of Pages: 33
Reference Type: Magazine Article
Abstract:
This new revised structural/stratigraphic model for the Eocene erosional events in the Central/Eastern Gippsland Basin has delineated the key play elements of trap formation and seal development. Integrated structural and palaeogeographical studies have shown that compressional structural inversion commenced in the Early Eocene. This inversion resulted in a relative lowering of base level which initiated fluvial incision of theuplifted coastal plain and the formation of meandering canyon-like features, stream-cut terraces and erosional remnants. Subsequent transgression deposited fine-grained marine facies over the erosional surface, creating potential hydrocarbon traps under the transgressive fill sequences. The Eocene channel fill records repeated pulses of compressional structuring, erosional modification and subsequent deposition within the resultant incised valley fill complex.
Top of Latrobe Group erosional remnant prospects located in the fairway can now be assessed and risked appropriately. The Great White prospect (located in 658 m of water on the present day shelf/slope break)
was selected to test these structural/stratigraphic concepts. Great White-1, drilled in 1996, validated the existence of excellent reservoir, trap and seal parameters for the play as predicted by the new interpretation. The absence of hydrocarbons in the Great White prospect, however, raises questions regarding the presence of an adequate hydrocarbon migration pathway, structural focussing and trap charge elements in this region. This risk was identified pre-drill as the key concern for the success of the prospect.