Authors: Jasinge, D; Ranjith, PG; Choi, SK; Kodikara, J

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Jasinge, D, Ranjith, PG, Choi, SK & Kodikara, J 2008, 'Effect of Carbon Dioxide Injection on the Mechanical Properties of Synthetic Brown Coal', in Y Potvin, J Carter, A Dyskin & R Jeffrey (eds), Proceedings of the First Southern Hemisphere International Rock Mechanics Symposium, Australian Centre for Geomechanics, Perth, pp. 301-307.

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There is evidence that global warming has led to climatic changes in many cities around the world. This has drawn attention from governments of many countries to try to reduce greenhouse gas (GHG) emission. One of the options that have been considered is the storage of anthropogenic carbon dioxide (CO2) in unmineable coal seams. This, however, still needs further research. The state of Victoria in Australia has one of the largest high quality brown coal reserves in the world. Research related to the geomechanical aspects of CO2 storage in deep coal seams is important for assessing the economic feasibility and the long-term safe storage of sequestered CO2. Coal is usually highly heterogeneous which depends on its origin and coalification history. This heterogeneous nature causes difficulty in conducting a systematic investigation of coal properties. During this research work we have tried to develop a synthetic coal material to investigate the effect of CO2 injection on the behaviour of brown coal. The main objective of developing the synthetic coal material was to be able to conduct tests on a material which is highly homogeneous, the properties of which are reproducible and similar to some degree to natural coal. A series of uniaxial compression (UC) tests were conducted on synthetic coal samples exposed to carbon dioxide at different pressures and for different durations. Particular attention was focused on the influence of gas pressure and duration of exposure on the mechanical properties of the synthetic coal samples, such as Young’s modulus and compressive strength. The results showed a reduction of compressive strength and Young’s modulus of samples exposed to CO2. An 8 and 2.5% decrease in compressive strength and a 13.5 and 11.5% decrease in Young’s modulus was observed when the samples were exposed to CO2 at 1 and 3 MPa, respectively.

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