NANSEN FM

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• General information

  General information

  Attribute	Value
  Lithostrat. unit The lithostratigraphic unit's official name.	NANSEN FM
  NPDID lithostrat. unit Norwegian Offshore Directorate's unique id for lithostratigraphic units.	108
  Level Indicates the lithostratigraphic unit's level. Legal values: GROUP, FORMATION, MEMBER.	FORMATION
  Lithostrat. unit, parent The parent lithostratigraphic unit's official name. See also level. Will be empty if Level = GROUP.	STATFJORD GP

• Level below

  Level below

  Lithostrat. unit

• Description

  Nansen Formation
  
  Name

  After the Norwegian polar scientist, explorer and statesman, Fridtjof Nansen.

  Well type section

  UK well 211/24-1 (Conoco/Gulf/NCB) (Fig 1.17-18) . 1.17) from 3112 m to 3159 m below KB.

  Well reference section

  Norwegian well 33/12-2 (Mobil) (Fig 1.17-18) .

  Thickness

  46 m in the type well and 19 m in the reference well.

  Lithology

  In the type well the formation consists of medium- to coarse-grained, fairly well-sorted, homogeneous, white sandstones with a calcite-cement and a subordinate kaolinite matrix. Occasional horizons with granules or pebbles are present. Carbonaceous material and mica are rare but glauconite is quite common. Thin shale beds containing marine fossils are present, most commonly in its upper part.
  At the top of the formation, from 3112 m to 3135 m in the type well is a more prominent calcareous horizon defined informally as the calcareous sandstone bed. This may grade locally into a sandy limestone, for example in the Brent Field.
  The Nansen Formation thins towards the east and passes laterally into calcareous siltstones and shales in the Norwegian sector (Fig 1.17-18) . Although these siltstones and shales are lateral equivalents of the Nansen Formation they are placed in the overlaying Dunlin Group on lithological grounds.

  Boundaries

  The originally Nansen Member of the Statfjord Formation was elevated to formation level by Lervik, 2006. The lower boundary is marked by the change from the non-calcareous sandstones of the Eiriksson Formation to the cleaner, generally calcareous sandstones of the Nansen Formation. The upper boundary is marked by the change from calcareous sandstone to the argillaceous sediments of the Dunlin Group . Both boundaries are well marked on gamma ray and sonic logs particularly in the UK sector where the formation is best developed. The calcareous sandstone bed at the top of the formation is normally reflected by a distinctive sonic log response (Fig 1.17-18) . However, as this passes laterally into calcareous siltstones and shales the sonic log still responds to the calcareous nature of the sediments.

  Distribution

  The formation is widespread in the northern North Sea. Deegan and Scull (1977) describes the formation as well developed in the Brent Field area. The lower part of the formation overlaps westwards to the Cormorant Field area where it is probably the only representative of the Statfjord Group . The calcareous sandstone bed at the top does not extend as far west as the lower part of the formation.

  Age

  Probably Hettangian to Early Sinemurian.

  Depositional environment

  Subaerial depositional conditions are suggested for parts of the fine-grained units by the presence of calcrete, coals and root-traces. In contrast, delicate lenticular and flaser lamination, wave-ripple laminae and abundant bioturbation suggest that the other parts of the fine-grained units were deposited in standing water (Røe and Steel, 1985). Based on the stacking pattern of facies associations and the presence of marine fossils, the upper part of the sequence is interpreted to have been deposited in a marine environment.
  Although the Nansen Formation in the Gullfaks and Statfjord area has been described as marine (Deegan and Scull, 1977; Røe and Steel, 1985), Nystuen and Fält (1995) interpret this formation as being a massive, rapidly deposited and dewatered fluvial sandstone with evidence of glauconite only near its top at Statfjord. Evidence for marine incursions at the Snorre Field is equivocal, for they may be stratigraphically higher than the Nansen Formaion. Equally the sandstones interpreted as shallow marine in origin may be interpreted as the deposits of a fluvial environment, such as a laterally extensive braided stream or a sheetflood.

  Compiled from

  • Deegan, C. E. and Scull, B. J. (compilers) 1977: A standard lithostratigraphic nomenclature for the Central and Northern North Sea. UK Institute of Geological Sciences, Report 77/25. The Norwegian Petroleum Directorate, NPD-Bulletin No. 1, 36 pp.
  • Goldsmith, P. J., Hudson, G. and Van Veen, P. Triassic. 105 – 127 in: Evans, D., Graham, C., Armour, A. and Bathurst, P. (editors and coordinators) 2003: The Millennium Atlas: petroleum geology of the central and northern North Sea. The Geological Society of London, 389 pp.
  • Lervik, K.-S. 2006: Triassic lithostratigraphy of the Northern North Sea Basin. Norwegian Journal of Geology, Vol. 86, pp. 93-116.

• Wellbores penetrating

  Wellbores penetrating

  Wellbore name	Wellbore completion date	Top depth [m]	Bottom depth [m]
  25/6-6 S	22.04.2019	2927	2972
  25/7-8 S	09.01.2020	2976	2995
  25/8-19 A	19.03.2020	2211	2286
  25/8-19 S	30.12.2019	2245	2263
  25/10-12 S	18.01.2015	2241	2249
  25/10-17 S	10.02.2023	3944	3978
  30/2-3	05.10.1992	4288	4294
  30/3-2 R	16.02.1981	3228	3298
  30/6-1	22.09.1979	2712	2786
  30/6-9	16.12.1982	3046	3226
  30/6-9 R	12.05.1990	3044	3224
  30/6-14	08.02.1984	2784	2799
  30/6-15	05.09.1984	3241	3272
  30/6-16	21.01.1985	2960	2967
  30/6-19	21.06.1986	3255	3275
  30/6-19 R	25.05.1994	3254	3274
  30/6-23	01.07.1990	3163	3179
  30/6-28 S	29.03.2012	2483	2590
  30/8-1 SR	01.03.1996	4691	4729
  30/9-4 S	30.03.1985	4173	4209
  30/9-7	23.12.1988	3535	3565
  30/9-9	06.11.1989	2757	2775
  30/9-16	08.08.1994	3457	3476
  30/9-28 S	26.02.2016	3645	3717
  31/11-1 S	28.06.2021	3008	3043
  33/6-3 S	24.07.2012	4267	4285
  33/12-2	23.08.1974	2700	2719
  33/12-8 S	26.04.2002	3647	3731
  34/2-2 R	08.05.1981	3840	3865
  34/2-4	11.06.1985	4063	4107
  34/4-14 S	19.05.2015	4640	4658
  34/6-2 S	05.11.2012	4055	4095
  34/6-3 S	24.09.2014	4360	4407
  34/7-6	30.05.1985	2510	2527
  34/7-10	29.10.1986	2531	2562
  34/10-1	08.09.1978	2268	2329
  34/10-2	08.12.1978	3325	3379
  34/10-3	07.06.1979	2495	2561
  34/10-3 R	10.10.1987	2492	2558
  34/10-4	15.10.1979	2340	2435
  34/10-5	02.01.1980	2562	2649
  34/10-7	23.03.1980	2053	2140
  34/10-7 R	14.07.1983	2050	2137
  34/10-9 R	03.07.1980	2375	2421
  34/10-11	05.03.1981	1890	1935
  34/10-21	22.10.1984	3906	3914
  34/10-32	13.07.1987	3353	3386
  34/10-32 R	10.08.1987	3353	3386
  34/10-43 S	11.04.2001	3878	3946
  34/10-44 S	08.07.2001	3720	3776
  34/10-47 A	14.11.2002	2964	3020
  34/10-54 A	18.04.2014	4467	4512

• Wellbores with cores

  Wellbores with cores

  Wellbore name	Wellbore completion date	Core length [m]
  25/7-8 S	09.01.2020	20
  25/8-19 S	30.12.2019	10
  30/3-2 R	16.02.1981	3
  30/6-1	22.09.1979	10
  30/6-14	08.02.1984	14
  30/6-15	05.09.1984	18
  30/9-16	08.08.1994	17
  30/9-28 S	26.02.2016	55
  33/12-2	23.08.1974	10
  34/7-6	30.05.1985	9
  34/7-10	29.10.1986	29
  34/10-2	08.12.1978	39
  34/10-4	15.10.1979	6
  34/10-9 R	03.07.1980	4
  34/10-11	05.03.1981	27
  34/10-32	13.07.1987	25
  34/10-54 A	18.04.2014	38