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Stratigraphic Modelling Of Sediment Distribution In The West Dixon Area, Dampier Sub-Basin.

Hirning, Colin David

Honours Degree, 1997

University of Adelaide

Abstract

The principal aim of this project was to investigate the nature of sediment distribution during the Late Jurassic Epoch in the West Dixon area. The project was to use a 3D chronostratigraphic forward modelling approach to provide additional control on the nature, location and geometry of stratigraphic variations, in areas of low seismic resolution. A modified version of SEDSIM3.03 was to be used to accomplish these objectives.

The study area (33 km by 28 km) is located offshore in the Dampier Sub-basin, North West Shelf, proximal to exploration well West Dixon #1. It includes a portion of the Rankin Platform and extends towards the Kendrew Trough. Three exploration wells have penetrated Late Jurassic sediment at this locality: all three wells exhibit high sand to shale ratios. Depositional environments range from submarine fans to near-shore environments.

A preliminary input data set was developed. This included a relative sea-level curve, palaeotopographic surfaces, tectonic files, source sediment characteristics, flow parameters and palaeoenvironmental parameters. Development of the palaeotopographic surface was the most critical requirement in formulating the data set. All other parameters were affected by, and hence were calibrated against it. The tectonic files altered that surface through time. Several styles of tectonic files were proposed. The most effective proposal involved operating the program on an increasing mass system that synthesises erosion through subsidence. This could be achieved by morphing successive palaeotopographic surfaces between their respective times.

Preliminary simulations were conducted to calibrate the initial input data set. The simulations mostly extended for periods less than 1000 yrs: the rnaximum simulation period was 10,000 yrs. The extent of the simulations was restricted by two factors: time and software problems. Coding errors resulted in the development of simulation artifacts. These artifacts included apparent holes in the topography, sediment mountain building at source locations, and unrealistic depositional patterns.

Corrections to the code are in progress. Although the principal objectives of the project were not satisfied, the data collected from this thesis should be able to be incorporated into a simulation in the near future in an attempt to satisfy those objectives. A comprehensive account of the considerations and methodology used to develop the data set is provided within the thesis.

Australian School of Petroleum
THE UNIVERSITY OF ADELAIDE

SA 5005 AUSTRALIA

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