VGP Technical Report 1 - New porosity and permeability measurements from legacy core
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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: New porosity and permeability measurements have been acquired as part of the Victorian Gas Program (VGP) from selected legacy core samples from key reservoir units in the onshore Otway Basin. These new analyses complement the existing Geological Survey of Victoria (GSV) dataset. As part of the VGP geoscience program, GSV is studying petroleum systems components (reservoir, seal and source) to assess the petroleum prospectivity of the Victorian Otway Basin and estimate the potential for further conventional gas discoveries, onshore and offshore within Victoria’s jurisdiction. Reservoirs are an important component of a working petroleum system, and it is necessary to understand characteristics of these rocks, such as porosity and permeability. A thorough assessment of reservoir quality, including porosity, permeability and petrology (origin and composition of rocks), requires the analysis of rock samples from drill cores. Core Laboratories Australia Pty Ltd (Core Laboratories) in Perth was commissioned to measure porosity, grain density and permeability at ambient and overburden pressures from 234 legacy core samples provided by GSV. The core samples were selected from onshore Otway Basin reservoir units including the Waarre, Eumeralla and Pretty Hill formations. The cores are held at GSV’s Drill Core Library in Werribee. Profile permeability was measured on a cut surface of each core piece using a probe permeameter prior to plug preparation. Pore volume (porosity) and permeability of the core plugs were determined using an integrated porosimeter and pressure decay permeameter at ambient pressure conditions (800 psi). Analysis to determine porosity and permeability under simulated overburden pressure conditions was also carried out. The objective of the latter is to understand the fluid flow behaviour of the different reservoir units at their expected depth of burial. Core plugs were photographed and lithological descriptions for each sample were recorded. Conventionally measured porosity and permeability data acquired from the new analyses are broadly comparable with equivalent legacy/regional data for the Waarre and Pretty Hill formations, whereas the results for the Eumeralla Formation show significantly higher porosity values in many samples. Porosity values greater than 30 per cent from the Eumeralla Formation are mostly from relatively shallow depths. As part of the VGP, the resultant data set will be integrated with lithological data (including sedimentary core logs and petrology), palaeontological data and wireline log and seismic data to develop a better understanding of the distribution, thickness and quality of the principal reservoir units across the Otway Basin. Maps summarising the distribution of sedimentary environments at the time of deposition of the reservoir units will be used to assess gas prospectivity. Bibliographic reference: Whittam, D.B., Tomlinson, J., Goldie Divko, L.M. & Herley, S.S., 2019. New porosity and permeability measurements from legacy core, Onshore Otway Basin, Victoria VGP Technical Report 1. Department of Jobs, Precincts and Regions. Download: The downloadable version of this report is supplied in PDF format High Res (24.0 MB), Attachments (xlxs 215 kb) and Word accessible version (docx 77MB). Related products:
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