Publication Name: The Sedimentary Basins of WA
Authors: K.Auld, B. Thomas, J. Goodall, L. Elliott & J. Benson
Publication Volume: 3
Date Published: December 2002
Number of Pages: 36
Reference Type: Book Section
Abstract:
John Brookes liST 1 discovered an 85 m gross dry gas column within Carnarvon Basin permit WA-214-P during 1998, in the area today forming the John Brookes location. The primary objective was to test a structural closure at the base of the Muderong Shale regional seal, up-dip from Tryal Rocks 1, drilled in 1970. Tryal Rocks 1 was initially considered a dry hole, however, a well review in 1997 suggested that it might contain a hydrocarbon column. The mapping of the structure using initially 2D, then 3D data, indicated that Tryal Rocks 1 was drilled off the crest, with significant closure existing up-dip. The John Brookes 1st 1 location was selected to test this up-dip potential, and the discovery confirmed the structural model. The surprising nature of the reservoir, interpreted to be a well developed Birdrong Sequence turbidite channel of P. burgeri age, changed the emphasis from purelystructural to a play with structural/stratigraphic potential. An amalgamated turbidite complex model was invoked, inferring that the sandstone represents a confined channel system cut into the underlying substrate. This model explains the John Brookes liST 1 gas reservoir being in direct continuity with the sandstones at Tryal Rocks 1. A review of the 3D seismic data over the field and seismic modelling supports the palaeo-depositional model.