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Book Chapter

In situ stress distribution and mechanical stratigraphy in the Bowen and Surat basins, Queensland, Australia

By
EMMA TAVENER
EMMA TAVENER
Santos Ltd, Santos Place, 32 Turbot Street, Qld 4000, Australia
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THOMAS FLOTTMANN
THOMAS FLOTTMANN
Origin Energy, 339 Coronation Drive, Qld 4064, Australia
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SAM BROOKE-BARNETT
SAM BROOKE-BARNETT
Origin Energy, 339 Coronation Drive, Qld 4064, Australia
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Published:
January 01, 2017

Abstract:

We present regional in situ stress analyses based on publicly available log and pressure data from coal seam gas developments in the Permian Bowen basin, Australia. Together with earlier data from the eastern part of the Jurassic Surat basin, our results show a broad, but systematic, rotation of SHmax azimuths in this part of eastern Australia as well as systematic changes in stress state with depth. Overall, the geomechanical state of the region appears to reflect the interplay between basin-controlling structures and a complex far-field stress regime. At the reservoir level, within and between Permian coal seams, this stress complexity is reflected in highly variable stress states both vertically and laterally. Stress data, including direct pressure measurements and observations of borehole failure in image logs, have been used to calibrate sonic-derived one-dimensional wellbore stress models that consistently exhibit a change in tectonic stress regime with depth. Shallow depths (<600 m) are characterized by a reverse-thrust stress regime and deeper levels are characterized by a strike-slip regime. Changes in the stress state with depth influence the mechanical stratigraphy of rocks with widely contrasting mechanical attributes (coals and clastic sediments). Our results highlight the interdependency between regional tectonic, local structural and detailed rheological influences on the well scale geomechanical conditions that have to be taken into consideration in drilling and completion designs.

Supplementary material: Database of additional wells with image log data are available at https://doi.org/10.6084/m9.figshare.c.3785849

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Contents

Geological Society, London, Special Publications

Geomechanics and Geology

Geological Society of London
Volume
458
ISBN electronic:
9781786203397
Publication date:
January 01, 2017

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