Authors / CoAuthors
Spencer, L. | Xu, J. | La Pedalina, F. | Weir, G.
Abstract
The Australian Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) is planning a pilot project to inject, store, and monitor carbon dioxide in a depleted gas field (Naylor Field) in the Otway Basin, Victoria, in Southeast Australia. Approximately 100,000 tonnes of CO2 are planned to be injected over a 2 year period in a new well to be located down dip of the existing crestal well. An accurate and detailed geological assessment and characterization is essential to the selection/evaluation of any potential carbon storage site, as this provides the inputs for the reservoir models that are needed to design the monitoring and verification programs. For the proposed Otway Basin Pilot Project, the stratigraphy and structure of the Early Cretaceous Waarre Formation in the Port Campbell Embayment has been studied. Detailed geological models for reservoir simulation have been established based on geological, geophysical and history matching studies. Particular emphasis has been placed on the Early Cretaceous Waarre Formation (the main regional and proposed injection reservoir) in the Naylor Field. Uncertainties in the geological model (based on good 3D seismic but poor well data) will be ultimately minimized through the drilling and logging of a new well and the re-logging of the existing well. Prior to this, there is a need to understand the geological uncertainties as they stand, so that an effective well location and well testing program can be defined. Based on limited palynological control (from neighboring wells) the Waarre Formation is not notably time transgressive within the study area; beyond this only a broad breakdown is possible. The Waarre Formation is divisible into units A, B, C and D, A being the oldest. Only the Waarre C reservoir unit is of immediate interest. From regional work it is interpreted that the top of unit B is associated with minor erosion and incision, prior to the onset of significant growth faulting associated with continental breakup. Initial Waarre C deposition is sandy incised valley fill deposits on this eroded surface. The configuration of these basal Waarre C deposits has been seismically mapped. Core interpretation establishes that subsequent Waarre C deposition occurred on a sandy low sinuosity fluvial braid plain. study area; although there are indications that the upper Waarre C was partially eroded prior to transgression of the overlying marine Waarre D unit. The Waarre C section is characterized by clean high permeability sandstones, interpreted as abandoned channel fill ~2m thick, within which there are thin shales. These shales form the only significant flow barriers within this upper unit; and appear to comprise less than 10% of the section, but mapping their distribution is difficult. Several PETREL reservoir models were created to capture the uncertainty and potential reservoir heterogeneity of the Waarre C in the Naylor Field; key parameters (for example: porosity, permeability, channel orientation, shale content, connectivity, and gradient of the top structure) have been systematically varied to provide the most likely and extreme cases for the subsequent reservoir simulation studies. The reservoir properties have been characterized through history matching of the well-head pressure and water-cut data over the 18-month production history of the well using systematic numerical simulation approaches. The results indicate that the reservoir has an average permeability of 500-1000 mD, the original gas-water contact was at 2020 meters depth and that there was a significant aquifer support to the reservoir. This reservoir characterization and history matching study has provided additional and essential knowledge of the field and helped to constrain the injection location. The study establishes a sensible current reservoir condition, which will subsequently be used as the initial condition in the simulation of CO2 injection in the depleted gas field.
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nonGeographicDataset
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64009
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- External PublicationAbstract
- ( Theme )
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- geological storage of CO2
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2006-01-01T00:00:00
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