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In-situ Stress, Fracture Characterisation and Structural Geology of the Batten Trough,
McArthur Basin, Northern Territory

Rachael A. Clark
Master of Science (Petroleum Geoscience) 2015
Australian School of Petroleum
The University of Adelaide


Armour Energy drilled the Cow Lagoon-1 well mid-2012. Encouraging gas shows were
encountered from the Mid-Proterozoic Lynott Formation and Reward Dolomite, warranting
further investigation. Initial assessment of resistivity image logs acquired from the well
indicated the presence of conductive and resistive fractures. The fundamental aim of this
study was to characterise fracture sets and orientations and provide a permeability
assessment. As part of this assessment the in-situ stress, structure of the well and
susceptibility of fractures were taken into account.
A combination of wireline log, resistivity image log, seismic and well data was used in this
study. Some uncertainty of results exists due to the type, quality and availability of data at the

Results conclude that NNW orientated fractures at 150°N are the predominant striking
feature. This correlates to major structures seen within the Batten Fault Zone such as the Emu
and Tawallah Fault, as well as the Batten Fault Zone itself. It is interpreted that these NNW
orientated fractures are more likely to be permeable away from the wellbore, particularly in
the Lynott Formation and Reward Dolomite. Similarly orientated fractures below 1169.75
mMDRT may or may not be open and permeable in the far field stress environment due to
the possibility of stress rotation around faults. E-W striking subsidiary fractures are only
observed in the discontinuous conductive fracture populations and are not interpreted to be
natural fractures.

The most prospective formation for further exploration is the Upper Lynott Formation. This
hosts a large cluster of NNW conductive fractures that are optimally orientated for shear

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