The Stress Variations In Coal Seam Gas Wells At Surat Basin In South-Eastern Queensland
Engineering Honours Degree, 2012
University of Adelaide
Application of present-day stress information is increasingly used in hydrocarbon exploration and production. Stress is a critical parameter in wellbore stability assessment, well design and hydraulic fracture stimulation. The regional stress field of Australia has been well documented at the Basin-scale. However, current understanding of local variations in stress orientations and magnitudes in Australian coal sequences is limited. This project examines the present-day stress magnitudes and orientations in two coal seam gas wells located in Surat Basin in south-eastern part of Queensland.
In order to construct 1-D mechanical earth models of the state of stress and rock mechanical properties, stress parameters were investigated. The orientation of maximum horizontal stress was determined from borehole breakouts in resistivity image logs, 27 breakouts investigated indicate south-west to north-east maximum horizontal stress orientation while vertical stress gradient calculated from density log is approximately 22.4 MPa/km within the coal sequence. Petrophysical log data is used to identify elastic rock properties and associated variations in minimum horizontal magnitudes using 1-D mechanical earth models. The minimum horizontal stress magnitude was estimated from rock elastic properties and ranging from 1.6 MPa at the surface and 13.6 Mpa at 800 metres depths.