Oil deposits in granitic basement rock on the Norwegian shelf have not been considered commercial due to the density of the rock. Lundin Norway hopes to disprove this notion on Rolvsnes in the North Sea.
Series: New reservoir types on the Norwegian shelf. Part 1:4 – Fractured basement
Lundin Norway is working to recover oil and gas from entirely new reservoir types on the Norwegian shelf. The potential is enormous if we succeed.
In simple terms, the reservoir rock must be sufficiently porous to have room for hydrocarbons. This is not usually the case for granitic basement rock. However, if the granite is sufficiently fractured, and has also been subjected to weathering in that water has flowed through the fracture system and dissolved the minerals, then it could have cracks and pores that are saturated with hydrocarbons.
If there is a strong degree of weathering, the granite can be nearly dissolved, thus developing very good reservoir properties. This is the case for the oil discovery made by Lundin Norway on Rolvsnes, located to the south of the Edvard Grieg field in the North Sea.
Oil has also previously been proven in weathered basement rock on the Norwegian shelf, but these deposits have not been considered commercial. When the discovery was made on Rolvsnes in 2009, and in connection with appraisal drilling in 2015, a number of formation tests were conducted to learn more about the production properties in the reservoir. These tests yielded positive results; however, more testing is still needed as there is little or no experience with this type of reservoir on the Norwegian shelf.
We have already gained important experience from the so-called Tellus area of the Edvard Grieg field. Production performance from this area of the field shows that the reservoir in the fractured basement contributes better than expected, and indicates that there is communication between the sand and the basement rock. This reinforces our optimistic view on Rolvsnes.
A horizontal well in weathered, fractured granite will be drilled on Rolvsnes (16/1-28S) during the first half of 2018 with an initial test production that will give us information about how the production properties develop over time. If the results from this well test are positive, we will start planning for a potential long-term test to the Edvard Grieg platform.
If this is successful, it could pave the way for further opportunities on the Utsira High as well as in other areas of the Norwegian shelf.