VGP Technical Report 2 - New seal capacity measurements from legacy core and cuttings
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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 seal capacity measurements have been acquired as part of the Victorian Gas Program (VGP) from selected legacy core and cuttings samples taken from known and potential sealing units in the Victorian onshore Otway Basin. These new analyses complement the existing dataset. As part of the VGP geoscience program, the Geological Survey of Victoria 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. Seal rocks are an important component of a working petroleum system, and it is necessary to understand the capacity of these geological units to trap hydrocarbons that may be found in underlying reservoirs. A thorough assessment of seal rocks (known as seal potential), including seal geometry, capacity and integrity, requires the laboratory analysis of rock samples together with desktop studies. Core Laboratories Australia Pty Ltd (Core Laboratories) in Perth was commissioned by the Geological Survey of Victoria to measure threshold pressures and calculate seal capacities from legacy core and cuttings samples. Samples were taken from the Pretty Hill Formation, Laira Formation, Eumeralla Formation, Waarre Formation, Flaxman Formation, Belfast Mudstone, Nullawarre Greensand, Skull Creek Mudstone, Paaratte Formation and the Pebble Point Formation. Seventy-nine rock core and cuttings samples were collected from 45 legacy petroleum wells and boreholes held at the Werribee core library by the Geological Survey of Victoria (GSV). The samples were all from the onshore Otway Basin apart from one sample taken from offshore in Halladale-1 DW-1. Mercury Injection Capillary Pressure (MICP) analysis was conducted on the samples following standard Core Laboratories preparation and procedures. Summary results for the 79 samples are presented in this report with full results provided in the attachments. The new threshold pressure data set fits broadly within the range of existing threshold pressure measurements. The greatest mercury injection threshold pressures (>10000 psia) were recorded from the Belfast Mudstone, Eumeralla Formation, Laira Formation and Pretty Hill Formation. Except for results for single samples, a range of threshold pressures (in psia) were recorded for all formations. As part of the VGP, these new seal capacity results will be integrated with existing data and other new VGP data sets. Stratigraphic analyses will be used to determine seal geometry and presence or absence of sealing facies. New mineral analysis has been carried out on most of the samples that were analysed for seal capacity. Resultant mineral composition and textural rock information will be used to ascertain the potential contribution of these characteristics to seal capacities between and within formations. Seal potential assessments will incorporate geometry and capacity results with fault seal studies. Seal potential maps will be prepared and used to assess gas prospectivity. Bibliographic reference: Goldie Divko, L.M. & Karolia, M., 2019. New seal capacity measurements from legacy core and cuttings, Onshore Otway Basin, Victoria VGP Technical Report 2. Department of Jobs, Precincts and Regions. Download: The downloadable version of this report is supplied in PDF format (7.4 MB), Attachments (ZIP 7.3 MB) and Word accessible version (docx 1.7 MB). Related products:
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