Australia: Octanex Commences Rissa 3D Seismic Survey
Octanex N.L. announces that the first of three new 3D seismic surveys has commenced, with the survey vessel now on location and acquiring the Rissa 3D survey in WA-422-P.
These new 3D surveys are to be acquired within three of the Company’s eight Southern Bonaparte Basin permits. The Company’s wholly-owned subsidiary, Goldsborough Energy Pty Ltd, holds a 100% participating interest in two of the permits (WA-407-P and WA-420-P) where the surveys are to be acquired and a 60% interest in the third permit, WA-422-P.
The names and areas of the three surveys to be acquired in the respective permits are:
• WA-422-P – 295 km2 Rissa 3D survey;
• WA-407-P – 325 km2 Ascalon 3D survey; and
• WA-420-P – 400 km2 Tamar 3D survey.
The 3D surveys follow the successful acquisition during November of three 2D surveys in three other of the Company’s Southern Bonaparte Basin permits. Those 2D surveys were completed on time, within budget and more than fulfilled the Year 3 work obligations of their respective permits.
As with the completed 2D surveys, Seabird Exploration FZ LLC will carry out the 3D surveys using the acquisition vessel, “Voyager Explorer”. It is expected to take approximately 60 days to complete all three surveys.
After a crew change and taking on the necessary 3D cables and equipment, the “Voyager Explorer” carried out streamer deployment and extensive testing of the 3D cables and related equipment prior to commencing the Rissa survey.
Rissa 3D Survey
The Rissa 3D survey area within WA-422-P is located on the northern end of the Londonderry High and is seen as a potential natural focus for oil migration. The survey area is to the south of several oil fields (Laminaria, Coralina, Buffalo, Kitan, Kuda, Tasi and Jahal). Also, the presence of residual oil columns in exploration wells within and to the south of the survey area indicates the existence of an oil migration route through the survey area.
Leads identified on vintage 2D seismic data possess similar west to east oriented horsts and tilted fault blocks to those in the oil discoveries to the north. There are two wells within the Rissa 3D survey area that will be utilised to calibrate the new 3D data; Fulica-1 and Kittiwake-1/ST1.
Fulica-1 was drilled on a large structure which was found to have a residual oil column in Early Cretaceous, Sandpiper Formation sandstones. From the poor resolution vintage 2D seismic, it is uncertain if this well tested a valid trap.
Kittiwake-1/ST1 tested a smaller tilted fault block structure. It found an 11m residual oil column at the top of thick Late Jurassic, Tithonian submarine fan sandstones of the Lower Sandpiper Formation and oil shows in the overlying Early Cretaceous Upper Sandpiper Formation sandstones. The well did not reach the Jurassic target Elang and Plover formations, although at the time the operator of the well thought it had.
The poor resolution of the vintage 2D restricts clear definition of trap closure and cross fault seal juxtaposition. Hence there is a need to acquire a modern 3D seismic survey to better resolve the leads within the survey area at the target reservoirs of the Early Cretaceous Sandpiper sandstones and Jurassic Elang and Plover formations.
Subsea World News Staff , December 21, 2011; Image: Octanex/SeaBird