Eastern Australasian Basins Symposium IV Brisbane, QLD, 10–14 September, 2012 1 1 1 GeoScience Victoria, Victorian Department of Primary Industries, Level 9, 55 Collins Street, Melbourne VIC 3001, Australia Lead author: john.miranda@dpi.vic.gov.au 2 The University of Edinburgh, Grant Institute, Room 400, The King’s Buildings, West Mains Road, Edinburgh, Midlothian EH9 3JW, United Kingdom 3 National Offshore Petroleum Titles Administrator, Level 1, 451 Little Bourke Street, Melbourne VIC 3000, Australia 4 CSIRO Petroleum Geoscience, Earth Science and Resource Engineering Division, 26 Dick Perry Avenue, Kensington, Perth WA 6151, Australia Gippsland Basin stratigraphic and CO 2 migration modelling: workflows for building regional, geological carbon storage (GCS) reservoir models John Miranda 1 , Rami Eid 2 , Mark McLean 1 , Geoffrey O’Brien 3 , Cedric Griffiths 4 , Chris Dyt 4 , Tristan Salles 4 , Peter Tingate 1 , Louise Goldie Divko 1 , Monica Campi 1 Keywords: Gippsland Basin; geological carbon storage (GCS); CO2; reservoir modelling; stratigraphic forward modelling outcomes have important implications for both petroleum exploration and production activities within the Gippsland Basin. The integrated approach allows the development of efficient CO2 migration simulations and conceptual models of fluid migration to be tested. A similar workflow should be transferable to other sedimentary basins, particularly during the early phases of GCS assessment. Moreover, the ability to incorporate updated or newly acquired data (such as stratigraphic, seismic, well and/or structural data) into the workflow, creates an iterative process whereby the reservoir model can be promptly updated and ultimately results in an improved regional fluid migration simulation model. Introduction GeoScience Victoria (GSV) is currently involved in a number of collaborative projects, with the overall aim to determine the suitability of Victoria’s major sedimentary basins as potential sites for geological carbon storage (GCS). Victoria’s carbon dioxide (CO2) emissions result mainly from brown coal-fired electricity generation, the continued use of which over the next 20 years will be largely contingent on adopting technologies—such as GCS—that will allow for significant reductions in greenhouse gas emissions. The Victorian Geological Carbon Storage (VicGCS) initiative focuses on the Gippsland Basin, located approximately 200 km east of the city of Melbourne (Fig. 1). This region hosts both Victoria’s largest greenhouse gas emission sites (the coal-fired power stations within the Latrobe Valley) and the attendant brown coal deposits onshore, as well as giant oil and gas fields offshore. The focus for VicGCS has been centred on several key issues associated with the geological storage of CO2: (1) containment, (2) injectivity-capacity and storage potential, and (3) potential impacts. Results from VicGCS which have been previously reported include: O’Brien et al. (2008); Goldie Divko et al. (2009a; 2009b; 2010); Tingate et al. (2011) ; Ciftci et al. (2012) ; and Miranda et al. (2012). The combination of the basin’s proximal location to major emission sources and its potential to store very large amounts of injected CO2 resulted in the National Carbon Storage Taskforce identifying the Gippsland Basin as Australia’s premier potential geological site for carbon storage (Carbon Storage Task Force 2009a). In order to better understand the injectivity-capacity and storage potential of the basin, it has been necessary to develop a regional 3D, attributed geological model that permits CO2 injection scenarios to be investigated. This model needs to include Abstract A geoscientific workflow has been developed to model CO2 migration and storage potential within the Gippsland Basin. The result is an attributed, basin-scale reservoir model that can be used as the basis for simulating CO2 injection and migration scenarios within the Latrobe Group reservoirs. The first stage in the workflow uses regional interpreted seismic horizons combined with CSIRO’s Sedsim stratigraphic forward modelling code to simulate sediment accumulation, distribution and lateral variability across the basin, from the base of the Golden Beach Subgroup (85 Ma) up to the present day (0 Ma). The second stage uses Permedia to construct a regional structural model of the basin, based on five regional seismic surfaces, with intra-formational seals (baffles) determined from petrophysical and fluid inclusion data. In the third stage Gocad is used as the platform within which (1) the simulated porosity data, derived from Sedsim, is combined with (2) well-log derived porosity data and incorporated into (3) the Permedia model. The combined porosity distribution within the resulting attributed model is accordingly biased towards petrophysical- derived values near wells, whereas Sedsim data informs the model in data-poor areas. Regional porosity-permeability transforms are then applied to the updated model and used for simulating CO2 injection using Permedia’s migration and black oil simulators (CO2BOS). Early simulation results using this workflow within selected structures in the nearshore/onshore Gippsland Basin compare well with existing hydrocarbon migration models. The migration pathways and volumes of the simulated CO2 plumes (from various injection scenarios) provide an important geoscientific scoping tool for assessing areas that may be suitable for CO2 storage within the basin. This new reservoir model provides an important assessment tool not only for the purposes of GCS, but also for inferring (1) the distribution of reservoir and seal facies (and thus reservoir compartmentalisation), (2) past/present hydrocarbon migration pathways, and (3) the distribution of organic-rich facies. These