The Dugong Tail prospect can be seen as another compartment in the NE-SW trending fault block – or relay ramp between the Marulk Basin in the NW and the Tampen Spur High. Similar to Dugong, the targeted reservoir of Dugong Tail is the Middle Jurassic Brent succession.
Discovered in July last year, the Dugong and the smaller Sjøpølse accumulation in overlying Intra-Draupne sands were drilled by well 34/4-15 S and A. Initially, the reported range of recoverable volumes on the basis of these wells was between 40 and 120 MMboe, but the subsequent appraisal well 34/4-16S drilled this year narrowed down this range slightly to 40-108 MMboe.
With the Dugong Tail prospect having an expected volume of 33 MMboe but at the same time a much bigger areal extent than Dugong, it may be suggested that the structure is different from the truncation trap that is the main mechanism in Dugong. As the cross-section below illustrates, the area in which the Dugong Tail prospect is situated is probably having less relief than in Dugong. On that basis, it is likely that the oil column in Dugong Tail is fairly thin.
According to partner Concedo, one of the crucial hints for oil being present in Dugong was the seismic mapping of the base reservoir reflector anomaly. The amplitude is softer where hydrocarbons are present and harder downdip where the reservoir is water bearing. The amplitude anomaly attached to the base reservoir had a similar extent to that of the mapped prospect, thereby providing further support for the validity of the observation.
If the Dugong Tail prospect turns out to be a success, well 33/6-6 S will be drilled later this year, testing the Shamu prospect five kilometres to the southwest of Dugong and probably on trend with Dugong Tail.
HENK KOMBRINK
