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Factors Impacting The Variation In Phase Of The Tcc Seismic Pick, Central Fields Region, Gippsland Basin.

Purdy, Adrian J.

Honours Degree, 1997

University of Adelaide

Abstract

The Gippsland Basin is one of Australia's premier oil and gas producing regions and has been for the last 25 years. By Australian standards it is a mature basin with most of the major structures being well understood. However there exists smaller, more subtle traps that remain future targets for exploration. With these smaller hydrocarbon plays comes a need for greater accuracy when considering well locations.

The Central Fields region of the Gippsland Basin comprises of the Halibut, Cobia and Fortescue Fields, which are approximately 65 km offshore in water depths of 69-79m. The tops of the Latrobe Group reservoir units in this region are defined by an erosional surface locally termed the Top of Coarse Clastics (TCC). Many of the potential traps in the Central Fields region also consist of the Latrobe Group reservoirs truncating beneath the TCC.

In order to facilitate interpretation, the TCC is generally carried as a peak on the seismic data. Analysis of synthetic seismograms from wells across the Central Fields region indicates that the position of the TCC seismic marker is not consistent across the field and minor corrections are required to accurately tie the well data. These minor corrections can be attributed to variation in the presence and thickness of overlying high impedance units.

To gain an understanding of how this error in the TCC seismic pick varies across the Central Fields region synthetic seismograms were created at each well location. The relative shift of the TCC was then expressed as a phase shift, normalised by the loop duration of the seismic peak.

Modelling was then carried out to investigate how the TCC error varied in 2D. This allowed attributes to be extracted and examined to investigate any possible relationship between the seismic attributes extracted and the phase shift observed.

These models were then used as tools to help predict phase across the Central Fields from real 3D seismic data. Seismic attributes such as loop duration and amplitude provided good relationships to phase shift. These two attributes were then used to help the prediction of phase across the Central Fields region.

Predictions were made using attributes extracted from synthetic seismograms and from real seismic data. The results indicated that by extracting attributes such as loop duration and amplitude from real seismic data possible to reduce the TCC seismic pick errors currently incurred.

Australian School of Petroleum
THE UNIVERSITY OF ADELAIDE

SA 5005 AUSTRALIA

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