Narve Formation (Narveformasjonen)
After Fritsen, A. & Riis, F. 2000. A revised chalk lithostratigraphic nomenclature; NPD Report, unpublished)
Chalk Group
Name
After the Norse god Narve, who was the son of Loke and Sigyn (Sturluson, 1954).
Well type section
Well 1/3-8 4520-4337 m MD.
Well reference section
2/8-A-1, 2581.5 - 2501.5 m MD.
Thickness
The thickness of this formation ranges from zero to a few hundred metres in the study wells.
Lithology
Lithofacies associated with the crestal biofacies on Valhall are typically (textural) mudstones and wackestones.
Those associated with the “shallow water” pelagic biofacies are varied, though typically bioturbated to laminated
chalks or interlaminated chalks and clays indicative of slow sedimentation. Those associated with the “deep water”
pelagic biofacies are typically massive chalks. Recognition of allochthonous as against autochthonous chalks is
difficult, for which high-resolution study is desirable of the paleobathymetry of foraminifera. Lithofacies in core
from the 2/8-A-1 well include bioturbated chalks with Chondrites, Planolites and Zoophycos, and also allochthonous
debris flows and slumps with micritic matrices and polymict/non-chalk clasts, indicating affinity with the “shallow water”
and “deep water” pelagic biofacies of the Valhall structure respectively. Allochthonous chalks are also observed in core
from Mona-1.
Characteristics of the lower boundary
Picked primarily on biostratigraphic and log criteria. The biostratigraphic criterion is penetration of microzone FCS13
or nannozone UC3. The log criterion is a downhole gamma increase indicating penetration of the shales of the
Blodøks Formation.
Characteristics of the upper boundary
Picked primarily on seismic and biostratigraphic criteria. The seismic criterion is an onlap surface. The biostratigraphic
criterion is penetration of nannozone UC11.
Log pattern or seismic characteristics
The Narve Formation has been penetrated in many wells in the Valhall area (Lindesnes Ridge) and in the Ål Basin to
the west of the ridge. The gamma log patterns of these wells correlate well in this area, and a detailed correlation of
different subzones is possible. A zone of clean chalk with consistently low gamma values, overlain by a gamma spike,
is situated in the middle of the Narve Formation. This zone (informally named Hod4 by BP) constitutes an important
reservoir in the Valhall Field, and it can easily be recognised on the logs. However, its biostratigraphic age is not
consistent between the wells, and it is possible that the “Hod4” subzone is diachronous.
Geographical distribution
It is absent in the 2/2 wells in the Norwegian Sector and in the Lulu-1 well in the Danish Sector. It is thin
(typically less than 100m thick) in wells on structural highs such as Valhall-Hod and Tor in the Norwegian Sector,
and thickest in wells in basinal lows such as that in the Roar area in the Danish Sector, and in the northern and
western depocenters in the Norwegian sector.
Occurrences of formation tops in wells
Isochore map BLODØKS-NARVE
Biostratigraphy and Stage/Age
Latest Cenomanian-earliest Santonian (for practical purposes, Turonian-Coniacian).
Microzones FCS14-FCS18pp; nannozones UC4-UC11. The base is taken near 94 Ma.
Remarks
Eroded on crests of structures.
