The Liatårnet discovery is particular in many ways, and therefore it represents a great example of the more niche plays currently being targeted in the North Sea. Presented yesterday during the NCS Exploration – Recent Discoveries conference, Aasmund Olav Løvestad from Aker BP gave an overview of the work Aker BP so far has done on this very shallow find.
Plumbing system
First of all, the field is a great example of the North Sea oil and gas plumbing system. Aasmund showed nicely how hydrocarbons have been spilling from the Frigg field in the west to the Frigg Gamma field in the east, and from Frigg Gamma upwards into the Lower Miocene Skade Formation reservoir of Liatårnet. Even then, further leakage occurs, as evidenced by the so-called Christmas trees structures observed in seismic above the Liatårnet structure.
Sealed by a sand
Secondly, the team at Aker BP concluded that the accumulation must at least partly be sealed by a sandstone, on the basis of the analysis of the exploration well 25/2-21. This Miocene sandstone was found to be cemented by calcite, which causes the interval to be acting as a seal. Aasmund did stress that overlying mudstones also add to the sealing capacity of the discovery though.
Unconsolidated sands
Thirdly, this find in Miocene sands clearly ranks amongst the “youngest” discoveries in the North Sea. Besides the calcite-cemented sandstones in the sealing unit of the accumulation, the reservoir sands are unconsolidated. As Aasmund highlighted during his talk, when a core barrel was opened on the rig, the sands were held together by the oil that was dripping out of the sediments nicely. Aasmund made the audience aware that this was an experience to never forget.
Aker BP is now planning a further appraisal well on Liatårnet. One of the main aims is to take downhole fluid samples, which the exploration well did not manage to obtain. This will shed further light on the oil quality and viscosity and hence the development strategy.
The in-place volumes are encouraging, with estimates of 600-800 MMbls.
The GeoPublishing Team congratulates Aker BP with the prize and hopes to report on a positive appraisal campaign outcome nearer the time.
HENK KOMBRINK
