--> 3-D Architecture of the Wilton Package and Geological Attribute Distribution in the Greater McArthur Basin, Northern Territory, Australia

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3-D Architecture of the Wilton Package and Geological Attribute Distribution in the Greater McArthur Basin, Northern Territory, Australia

Abstract

Three-dimensional (3D) modelling is extensively used in the petroleum and mining industry to assist in bridging the gap between scarce geoscientific data and subsurface reality. Over the last decade 3D modelling methods have dramatically improved, including development of the implicit modelling method which reduces the time-cost and difficulty in building a structural 3D model. The Northern Territory Geological Survey (NTGS) is applying the implicit modelling approach to construct geological models to improve understanding of the sub-surface architecture of the greater McArthur Basin, which includes the McArthur Basin and contiguous correlative successions in the Tomkinson Province of the Tennant Region and Birrindudu Basin. The Palaeo- to Mesoproterozoic greater McArthur Basin is located in north-eastern Northern Territory of Australia. The basin covers an area of approximately 480,000 km2. It is composed of a series of stacked basins with thickness ranging between 8 to >15 km of primarily sedimentary rocks and subordinate volcanic rocks. The greater McArthur Basin succession has been subdivided into five lithostratigraphic packages defined by age and lithology and separated by regional unconformities or disconformities. Current modelling focuses on the Mesoproterozoic Wilton package, which includes Roper Group in the Beetaloo-Sub-basin. This package preserves evidence of two main structural phases; syn-depositional NNW-ESE extension and post-depositional N-S compression. The package is comprised of sandstones, siltstones and shales, and includes fine-grained carbonaceous shales of the Kyalla and Velkerri formations. These formations contain proven petroleum source rocks and potentially host unconventional shale petroleum systems. The NTGS 3D modelling project addresses 2 aims, improving understanding of the sub-surface architecture of the Wilton package, and providing a structural and volumetric framework for geostatistical assessment. Multi-scale structural investigations have been conducted on various formations within the Wilton package. These investigations are being used to characterise the timing of fracture events, geometry and continuity of fractures, and to aid in the visualisation of structural relationships within the package. The combination of organic and inorganic geochemical data with this structural framework assists in understanding the distribution of facies used for sweet-spot targeting in potential petroleum shale plays.