The area to the west of the prolific South Viking Graben/East Shetland Basin and east of the Shetland Islands is called the East Shetland Platform. This name may suggest the area is just a stable block to the west of the Jurassic graben system, but that would be a false assumption. In contrast, the East Shetland Platform is an area where important thickness differences occur within the Palaeozoic and Triassic sedimentary successions and therefore an evaluation of its potential to host untapped hydrocarbons needs to be addressed.
As part of the UKCS Regional Mapping project Lloyd's Register is working on for the Oil and Gas Authority, we interpreted a set of legacy and newly acquired 2D seismic lines on the East Shetland Platform and integrated this with all available well data. In addition, we used studies recently carried out by Frogtech and PGS in the same area.
One of the challenges in the area, as described in an earlier blog, is the difficulty in differentiating between Triassic/Permian and Devonian rocks. This can be exemplified by well 7/16-1, which before this study was interpreted to contain a section of Permo-Triassic rocks. Through our regional interpretation, which is in line with the study carried out by PGS, we concluded that 7/16- 1 did not penetrate the Triassic, but the Rotliegend and Devonian instead. This has an impact on Triassic distribution maps, as shown in the map below.
The map shows the distribution of the Triassic as presented in the Millennium Atlas (Goldsmith et al., 2003) in grey lines and the newly obtained outline from this study in yellow. The pink area represents the locations where the Base Triassic could not be interpreted on seismic. Overall, there is good agreement as to where Triassic rocks can be found; e.g in the East Shetland Basin. However, there are a few differences too, the main one being the example just presented above. As well 7/16- 1 is now interpreted not to have a Triassic succession, the Triassic has a more limited distribution across the Dutch Bank Basin area. In turn, the Rotliegend and Devonian are thicker which may have a positive impact on the hydrocarbon potential of the area; this will be the subject of a future blog.
Lloyd's Register secured two major UKCS projects with the OGA for the UK Continental Shelf (UKCS), for the provision of Regional Exploration Maps and Regional and Field Support Engineering Services to help the OGA independently assess remaining undiscovered resources and improve geotechnical understanding. Read the full detail of the project win here.
This is article eight in a series of posts dedicated to our project for the OGA. Read the previous blog post here.