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Thermal Maturation And Fluid Movement Modelling Based On Regional Seismic, Barrow Sub-Basin, Western Australia.

Auld, Kerri Ann

Honours Degree, 1994

University of Adelaide

Abstract

Computerized basin modelling in petroleum exploration is state-of-the-art technology. It is an excellent tool for better understanding the dynamics of petroleum systems, in particular thermal maturation and hydrocarbon fluid flow. The study area for this thesis is the Barrow Sub-Basin within the larger Carnarvon Basin, offshore Western Australia. Three regional seismic lines were modelled, two dip lines and one strike line to determine the timing of migration and trap formation. Two-dimensional simulation of the structural and stratigraphic evolution of the basin was included using the basic modelling package PetroMod. This study is one of the first 2D thermal maturation and fluid flow analyses of the Barrow Sub-Basin.

The methodology behind this study involved the synthesis of a wide range of petroleum related data and the understanding of, the sophisticated basin modelling package, PetroMod. Calibration of a temperature curve through a heat flow model using vitrinite reflectance and bottom hole temperatures was performed. Once thermal maturation had been modelled, migration modelling was performed. Fluid flow modelling was based on capillary pressure alterations and the presence of faults and associated transmissibility values.

The results of the study confirmed that migration in the Barrow Sub-Basin has been occurring from 140 MaBP up until the present-day. Modelled hydrocarbon migration from source beds has revealed pulses of peak migration in the basin. One major peak occurs at around 82 MaBP, but it is suggested that two peaks of migration of hydrocarbons may have occurred if average TOC values of 2% are used for the Dingo Claystone and Anchor Formation. The first peak occurred when the Anchor Formation first entered the oil window and the second when the Dingo Claystone entered the oil window. Migration of hydrocarbons continues to the present within the Barrow Sub-Basin. Based on the modelled results and suggestions, it is concluded that trap formation would have been required prior to 140 MaBP or preferably before 82 MaBP. However, due to migration continuing up until the present, any traps formed after 82 MaBP may still contain hydrocarbons. In the vicinity of Barrow Island it is likely that the majority of hydrocarbons have been trapped within the Barrow Island anticline or lost from the system. The anticlinal structure formed at a modelled age of 82 MaBP allowing the entrapment of large quantities of hydrocarbons.

Finally, the use of computerized basin modelling packages such as PetroMod, should be encouraged as the ability to produce hypothetical scenarios is of considerable value in the generation and confirmation of ideas in hydrocarbon exploration.

Australian School of Petroleum
THE UNIVERSITY OF ADELAIDE

SA 5005 AUSTRALIA

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