The Treachery Formation — A Complex Glacially Influenced Reservoir, Blacktip Gas Field, Southeastern Bonaparte Basin, Western Australia

Simeonova, Anelia ¹; Giaj-Via, Paola ¹
(1) Exploration, ENI Australia, Perth, WA, Australia.

The Blacktip Gas field is located in the Southeastern Bonaparte Basin, offshore Western Australia. The field was discovered in 2001 by Blacktip-1, which encountered stacked gas bearing sandstone reservoirs in the Triassic, Permian and Late Carboniferous section. Since then one appraisal and two development wells have been drilled and production from the field commenced in 2009.

The Blacktip structure is an east-west trending four-way dip closure with multiple amplitude anomalies, identified on seismic. The reservoir comprises stacked gas-bearing sandstones in the early Triassic Mt Goodwin Formation, and in the Permian Keyling and Treachery Formations.

This study focuses on the Treachery Formation which is composed of diamictite, sandstone, mudstone and siltstone, deposited in glacially influenced fluvial to shallow marine environments. The Formation was cored in Blacktip-2 appraisal well, and Blacktip North-1 which is located immediately to the North of the Blacktip gas field.

The Treachery Formation is characterized with sharp lateral and vertical facies changes resulting in complex reservoir architecture. Five main lithofacies have been identified within the Treachery Formation, with the best reservoir sandstone developed in fluvial outwash plain or proximal delta plain. The primary sedimentary fabric is the major controlling mechanism for the reservoir distribution and quality, however petrological study indicates complex diagenetic overprint that further hinders reservoir quality predictions.

The study provides better understanding of the complex facies interrelation within the glacially influenced Treachery Formation, and could facilitate optimization of reservoir performance and production.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.