VGP Technical Report 19 - A probabilistic determination of Original Gas in Place for gas fields in the Port Campbell Embayment Onshore Otway Basin
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Product description:About the Victorian Gas Program: The Victorian Gas Program (VGP) is a comprehensive science-led program, incorporating geoscientific and environmental research to assess the risks, benefits and impacts of potential onshore conventional gas exploration and production. The program is also investigating the potential for further discoveries of onshore conventional and offshore gas in the Otway and Gippsland geological basins and assessing the feasibility of additional onshore underground gas storage in depleted reservoirs around the Port Campbell area. The VGP includes an extensive, proactive and phased community and stakeholder engagement program, through which the results of the scientific studies are being communicated. Executive summary: The opportunity for further underground gas storage (UGS) in depleted gas fields in the onshore Otway Basin is being investigated as part of the Victorian Gas Program (VGP). There are currently three depleted gas fields used for UGS in Victoria. These sites are in the Port Campbell area in the onshore Otway Basin. The Geological Survey of Victoria (GSV) engaged SEAL Energy Pty Ltd (SEAL Energy) to carry out a suite of technical studies to investigate UGS potential in the onshore Otway Basin. The probabilistic determination of Original Gas in Place (OGIP) for gas fields in the Port Campbell Embayment forms part of these technical studies. This study was undertaken to calculate probabilistic determinations of Original Gas in Place (OGIP) for all potential UGS sites to ensure consistency in field capacities prior to geological static and dynamic modelling for selected sites. As a result of the ranking study (Bagheri, 2019), Mylor, McIntee, Tregony, Croft, Fenton Creek and Penryn were recommended for full static and dynamic modelling. However, as these two studies were carried out concurrently, all 13 potential sites were included in this probabilistic determination. The OGIP volumes calculated in this study were based on geological structures determined by operators at the time of field discovery. Probabilistic properties derived from a revised petrophysical analysis of reservoir field data (SEAL Energy, 2020a) and an additional study to review the Penryn field (SEAL Energy, 2020b) were also used as inputs to this study. An analysis of Gas Water Contact (GWC) and fluid properties (for gas formation volume factor) was also conducted. The probabilistic determination of Original Gas in Place (OGIP) in 13 gas fields is presented as probabilistic P90-P50-P10 ranges to reflect the uncertainties associated with structural mapping, the measurements and determination of reservoir parameters (net pay, porosity and water saturation) and their spatial distribution across the field areas. The greatest sensitivities were associated with the uncertainties in the determination of Gas Water Contacts. For example, where the pressure data from repeat formation tests or saturation from wireline log data were not conclusive for GWC determination. Other uncertainties arose from rock and fluid property measurements (i.e. porosity, water saturation, net pay thickness and formation volume factor), because of the sparse subsurface data (generally one well per structure). This report describes the methodology and input data used to perform a probabilistic determination of OGIP volumes including a summary of the results. Bibliographic reference: SEAL Energy, 2020. A probabilistic determination of Original Gas in Place for gas fields in the Port Campbell Embayment, Onshore Otway Basin, Victoria. Victorian Gas Program Technical Report 19. Geological Survey of Victoria. Department of Jobs, Precincts and Regions. Melbourne, Victoria. Download: The downloadable version of this report is supplied in PDF format (5.1 MB) and accessible version (DOCX 3.6 MB). | ||||||
