Ile Formation (Ileformasjonen)
(From NPD Bulletin no. 4)
Fangst Group
Name
From the Norwegian word for a stone sinker or a drag. The unit corresponds
to the lower part of the informal Tomma formation (Hl-4) or "Tomma III".
Well type section
Well 6507/11-3
(Saga Petroleum), coordinates 65°01'59.8"N, 07°30'42.34"E, from 2536 m to
2471.5 m (Fig. 16). The entire formation is cored except for the basal 2
m.
Well reference section
Well 6407/1-3
(Statoil), coordinates 64°52'25.48"N, 07°02'53.47"E, from 3813 m to 3741 m
(Fig. 19). One core (10 m recovery), from the upper part of the unit.
Thickness
64.5 m in the type well and 72 m in the reference well.
Lithology
Fine to medium and occasionally coarsegrained sandstones with varying
sorting are interbedded with thinly laminated siltstones and shales.
Mica-rich intervals are common. Thin carbonate-cemented stringers occur,
particularly in the lower parts of the unit.
Basal Stratotype
The lower boundary is defined at the base of a generally upwards
coarsening sequence visible on the gamma ray log. In wells where this
coarsening trend is not evident on logs, the base of the formation may be
picked where the overall lithology changes from siltstone to sandstone.
Often this transition is associated of one or more carbonate-rich beds.
Age
Late Toarcian to Aalenian.
Depositional environment
The formation represents various tidal-influenced delta or
coastline settings.
Lateral extent and variation
The Ile Formation generally varies from 50 m to 100 m over most of
Haltenbanken, with a general thickening to the west and a marked thinning
to the northeast. It is also encountered in wells on Trænabanken.
Sandstone-dominated successions of similar age have been located by sea
bottom sampling and shallow drilling on the eastern part of the Trøndelag
Platform. (Bugge et al. 1984).
Correlation
No distinct comparable time equivalent formations are known from the North
Sea area. In the Hammerfest Basin the middle part of the Stø Formation may
be correlated to the Ile Formation.
