An Assessment of Top Seal Integrity in the Seaspray Depression, Gippsland Basin: a Study on the Wombat Field
Mahmood, Adi Iskandar
Geoscience Honours Degree, 2010
University of Adelaide
The Gippsland Basin is a world-class oil and gas province since 1969. Many exploration and discoveries were achieved in the giant oil field. The basin is expected to reach its maximum potential in not so distant future. Attempts are made to prolong the prospect of the basin and recently, the Gippsland Basin was chosen as a site for potential carbon dioxide sequestration initiatives. Therefore, the understanding of the Gippsland Basin petroleum systems will benefit greatly in Carbon Capture and Storage (CCS) projects.
This project in assessing the top seal integrity has taken the approach of detecting direct evidence seal breaching such as the presence of gas chimneys and fluid inclusion stratigraphy.
The detection of gas chimneys was done using the OpendTect, open source seismic data interpretation software. The use of neural network and multi attributes seismic data aids the detection of gas chimneys within the Wombat field to great detail. Six gas chimneys were detected around the Wombat field, and the mapped gas chimneys in the study area gave insights on vertical migration pathways.
The fluid inclusion stratigraphy analaysis (FIS) was applied on the Wombat-3 well. The FIS technique highlighted the presence of a seal. The observing the trace level of different chemical species based on the different horizons indicated this. The FIS technique to suggested minimal communications between chemical on both side of the seal.
Based on well completion reports of 4 wells (Macalister-1, Merriman-1, McCresh-1 and Wombat-1), gas chimney detection and FIS technique, the study indicates the seal of the area (Lakes Entrance formation) is effective and rated as moderate to good in terms of seal retention capacity.
This information is then analysed for the purpose of carbon dioxide sequestration.