Publication Name: Eastern Australian Basins Symposium 2001
Authors: P. Lipski
Date Published: November 2001
Number of Pages: 29
Reference Type: Magazine Article
Abstract:
The Maryborough Basin is a mainly Mesozoic basin that straddles the coastline of southeastern Queensland. The sequence ranges in age from Late Triassic to Early Tertiary. Sequences generally can be correlated across the Surat and Eromanga basins to the west. Subsidence and downfaulting resulted in the deposition of over 6,000 metres of Jurassic and Cretaceous sediments in the central part of the basin. Late Cretaceous transpressional deformation formed northwest-trending anticlines, creating the structural traps that form the basin's primaryexploration targets. The main reservoir objective is the Gregory Sandstone Member, being the basal unit of the Early Cretaceous Maryborough Formation. There is also potential for fracture porosity in the crests of anticlines. Source rocks are provided by thick marine and lacustrine shales of the Early Cretaceous Maryborough Formation, and also coals and shales of the Early to Middle Jurassic Tiara Coal Measures and the Early Cretaceous Burrum Coal Measures. Most of the source sequences are presently within the mature gas window over much of the
basin. Structure, gas charge and seal are considered to be relatively low risk in the Maryborough Basin. With respect to reservoir risk, future exploration should address:
1. targets that exhibit favourable reservoir facies , fracture porosity, or secondary porosity enhancement,
2. prospects where maximum depth of burial of reservoir objectives, prior to inversion, has not been prohibitive, and
3. implementation of underbalanced drilling, similar to that employed in low porosity gas fields such as Palm Valley and Mereenie, to maximise the flow potential of any future discovery.