Authors / CoAuthors
Brown, N.J. | Garthwaite, M.C. | Lawrie, S. | Dawson, J.
Abstract
In this presentation we describe analytical techniques that can be used to predict the magnitude and areal extent of surface deformation for the purpose of designing baseline geodetic monitoring networks. Furthermore, we discuss how this forward modelling capability can be combined with geodetic observations from radar satellites (InSAR) and Global Navigation Satellite Systems (GNSS) in an inversion to enhance our understanding of the geophysical properties of reservoirs or aquifers and improve future surface deformation predictions. This technique can be applied to a variety of geophysical studies including CO2 sequestration and groundwater withdrawal. In this presentation we demonstrate our capability with a case study of the extraction of Coal Seam Gas (CSG). We apply the analytical Finite Element Modelling (FEM) technique of Geertsma and Van Opstal (1973) to predict surface deformation in Australia. Simulation of subsidence associated with CSG extraction reveals the possibility of surface deformation due to the cumulative impact of multiple operators extracting large volumes of groundwater within a limited area (and volume). Our hypothesis is that the combined influence of groundwater drawdown associated with CSG extraction from adjoining leases could result in decimetres of subsidence depending on the properties of the reservoir, depth of the coal seams and extraction rates. Surface deformation of this magnitude has the potential to impact on infrastructure (e.g. buildings, houses, well structures, gas transport pipelines) and the environment (e.g. re-routing river systems, alteration of drainage on flood plains, inducing earthquakes, etc.) within and proximal to the areas of CSG operation. Our analysis suggests that surface deformation could occur at distances up to three times the radius of the drawdown zone, potentially resulting in subsidence in regions outside the leases of CSG operators. This highlights the need for predictive modelling to ensure that geodetic networks are designed to extend beyond the deformation zone. GNSS observations and InSAR time series analysis can be used: 1) to directly validate the surface deformation predictions, and 2) in an inversion to constrain geological properties of the reservoir. We apply the Neighbourhood algorithm of Sambridge (1999a, 1999b) to identify the optimal solution based on an ensemble of forward models. This technique allows us to constrain and improve our estimates of reservoir properties and allow for more accurate surface deformation predictions in the future.
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nonGeographicDataset
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75868
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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- External PublicationAbstract
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2013-01-01T00:00:00
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Abstract written by Nicholas Brown based on work developed within the NGRS Section.
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