Til toppen

Searching for oil in the Oslo fjord

Just a stone’s throw from the offices at Lysaker, Lundin’s geologists are learning lessons that bring us closer to new oil discoveries in the North Sea … and perhaps even in the Skagerrak strait?

There is a wealth of geology for rockhounds to study along the Vækerø beach, ranging from 460 million-year-old sedimentary rocks, limestone containing fossils, volcanic hypabyssal rocks to faults and joint systems.

Displaced: The rock layers are displaced and tilted so that ‘up’ (what was the surface of the seabed 460 million years ago) now faces out toward the sea.

“You can imagine what the rocks thousands of metres below the earth’s surface actually look like. Such a practical approach gives us a better understanding of what we see on our computer screens in the office,” says Elisabeth Osaland, one of the students working at Lundin this summer.

Important to see and touch

Lundin’s geologists have very good reason to take regular strolls along the beach during working hours.
“Seeing geology in the field is essential for understanding the subsurface in areas where we search for oil. At the Vækerø beach, you can wander through a geological system that has many of the same elements we interpret from seismic data on the screen. But the more geology we actually see and touch, the better our interpretations of the subsurface,” says Jon Halvard Pedersen, exploration geology manager.
The Utsira High in the North Sea is one of Lundin’s core areas, where Johan Sverdrup and Edvard Grieg are the most prominent examples of the company’s exploration success. The Loppa High in the Barents Sea is another area where Lundin feels certain there is more oil to be found. The pebbles on the beach can teach us more about both these areas.

Oil discovery: The image shows volcanic hypabyssal rock from the Permian period which cuts through the Ordovician sedimentary rocks. Volcanic hypabyssal rock types containing light oil are found near Tvedestrand. Perhaps more of this oil could be found in Skagerrak?

“For example, we have good analogies to the basement rock at Rolvsnes on the Utsira High that we can see exposed on the island of Bømlo. Limestone in the Oslo field acts as an analogy to limestones in the Barents Sea and we can find wind-blown sand deposits from the Permian to Triassic Age in Brumunddal,” says Pedersen.

Oil in the Oslo fjord?

Fossils: Fossil deposits can be found on the Vækerøstranda beach. Here we see an octopus that lived on the seabed about 460 million years ago.

Oil is something we associate with the North Sea and Western Norway. But the Vækerø beach proves that the Oslo fjord could theoretically also be hiding the black gold.
The dark shale that pops up here and other places in the Oslo area has a high organic content, which can indicate examples of source rocks. Oil and gas form in the source rock when it is heated to 80-120 degrees Celsius, at depths of about 3-4 kilometres. The shale types at Vækerø were around 4 kilometres deep about 420 million years ago. It’s likely that large volumes of oil and gas were formed in the geological province we call the Oslo field at that time.
Pedersen hopes that this theory can be studied someday.
“We find traces of oil many places in the Oslo field, as well as in Sweden. Maybe there are oil-filled structures preserved in similar geological systems in Skagerrak? Maybe, we can drill wells in Skagerrak to test the play models we see examples of in the Oslo field.

Joints: Here Lundin’s summer students are studying Ordovician limestone with white, calciferous joints. The joints were formed in the early Permian period (300 million years ago) when the Oslo area was ravaged by fracturing of the earth’s crust and massive volcanism.
Shale: Here you can see dark grey shale from the Ordovician. The brown basin in the middle is a concretion. These are formed through precipitation of a mineral in the sediment, often a lime mineral.