OSEBERG FM

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• General information

  General information

  Attribute	Value
  Lithostrat. unit The lithostratigraphic unit's official name.	OSEBERG FM
  NPDID lithostrat. unit Norwegian Offshore Directorate's unique id for lithostratigraphic units.	123
  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.	BRENT GP

• Level below

  Level below

  Lithostrat. unit

• Description

  Oseberg Formation
  
  Name

  Named after the Oseberg Field in Norwegian blocks 30/6 and 30/9. Oseberg is the name of a Viking ship, discovered in a large burial mound at the Oseberg farm near Tønsberg in Vestfold county, Norway.

  Well type section

  Norwegian well 30/6-7 from 2739 m to 2786 m, coord N 60°38 '39.49", E 02°45' 21.74".

  Well reference section

  None at present.

  Thickness

  47 m in the type well.

  Lithology

  The name Oseberg Formation should be used for the relatively homogeneous, predominantly coarse-grained sandstone unit, 20-60 m thick, that is well documented from the base of the Brent Group in the Oseberg Field and neighbouring fields. The sandstone unit now defined as the Oseberg Formation has long been considered anomalous in the sense that it does not fit well into the “normal” Brent Group succession as is seen, for example, in well 34/10-8 . The basal unit`s (now Oseberg Formation) anomalous coarseness an homogeneity, its common, sharply defined base and “blocky” log pattern, and the indications of a Late Toarcian/Aalenian age for its lowermost parts in some wells have always been awkward aspects of Brent Group lithostratigraphy where the sand unit was interpreted as Etive Formation or as a combined Rannoch / Etive Formation.
  The Oseberg Formation has a typical “blocky” log motif (gamma-ray and neutron/density logs), reflecting the homogeneous nature of the sand units compared to the underlying and intercalating mudstones. Occasional upwards-coarsening motifs occur in structurally high locations.
  Five types of lithofacies sequences are identified within the formation:

  • bioturbated, micaceous mudstones and siltstones containing wave-generated ripple lamination,
  • bioturbated, flat-lying to low-angle inclined (or undulating), medium- to coarse-grained sandstones, with little internal lamination,
  • inclined sets (10-30o, unidirectional dips), of medium- to coarse-grained sandstones with common “floating” granules and small pebbles, rare bioturbation,
  • units of coarse to very coarse and pebbly sandstone, with internal erosion surfaces and a diffuse flat or irregular lamination
  • massive or low-angle laminated, well-sorted sandstones, occasionally interbedded with poorly sorted sandstones or bioturbated, micaceous mudstones

  Boundaries

  The base of the formation is defined by the first appearance of sandstones or siltstones/mudstones above the shales of the Dunlin Group . The log response is characterised by lower gamma-ray readings when entering the overlying Oseberg Formation. The formation`s top, easily recognised throughout the region, is defined by the aprupt vertical change from the formation`s massive or wispy laminated sandstones to the micaceous mudstones and well-laminated sandstones of the Rannoch Formation and is characterized by higher radioactivity.

  Distribution

  The formation has been clearly recognized in the Oseberg Field area (main reservoir unit) and can also be recognised in the neighbouring fields to the north-east ( Veslefrikk ) and east ( Brage , Troll ).

  Age

  Late Toarcian – Early Bajocian.

  Depositional environment

  The lower part of the formation was deposited in a shallow marine environment, and gravitational processes are suggested. For the upper part of the Oseberg Formation sheetflooding and/or shallow-braided streams in an alluvial environment are suggested. The uppermost part of the formation is interpreted as a wave-reworked “transgressive” sand unit deposited during a relative rise of sea level. The sandstones form a number of fan-shaped sand-bodies that originated from the eastern highlands.

  Compiled from

  • Graue, E., Helland-Hansen, W., Johnsen, J., Lømo, L., Nøttvedt, A., Rønning, K., Ryseth and A., Steel, R. Advance and retreat of Brent Delta system, Norwegian North Sea. 915 - 937 in: Brooks, J. and Glennie, K. (eds.) 1987: Petroleum Geology of North West Europe.

• Wellbores penetrating

  Wellbores penetrating

  Wellbore name	Wellbore completion date	Top depth [m]	Bottom depth [m]
  30/2-2	04.05.1985	4098	4135
  30/2-3	05.10.1992	3974	3983
  30/3-1 R	26.04.1982	3866	3874
  30/3-2 R	16.02.1981	2891	2950
  30/3-5 S	19.06.1992	4155	4243
  30/3-6 S	06.03.1994	5503	5688
  30/3-7 A	29.01.1998	6526	6620
  30/3-7 B	04.08.1998	4304	4350
  30/3-7 B	04.08.1998	5259	5326
  30/3-7 B	04.08.1998	5693	5777
  30/3-7 BR	17.11.2001	4304	4350
  30/3-7 BR	17.11.2001	5259	5326
  30/3-7 BR	17.11.2001	5693	5777
  30/3-7 S	12.12.1995	4928	4930
  30/3-7 S	12.12.1995	5070	5122
  30/3-8 A	23.05.2000	4286	4554
  30/3-8 A	23.05.2000	4830	4858
  30/3-8 S	04.05.2000	4256	4486
  30/3-8 S	04.05.2000	4488	4554
  30/3-9	01.07.2000	3904	3923
  30/3-11 S	09.09.2022	4545	4612
  30/4-1	14.05.1979	5359	5400
  30/6-7	24.08.1982	2739	2786
  30/6-19	21.06.1986	2920	2989
  30/6-19 R	25.05.1994	2919	2988
  30/6-21	09.04.1987	2615	2670
  30/6-22	13.07.1988	2943	2998
  30/6-22 R	02.06.1994	2942	2997
  30/6-23	01.07.1990	2839	2902
  30/6-25 S	06.01.1999	2712	2713
  30/6-25 S	06.01.1999	2916	2918
  30/6-30	18.11.2018	3361	3447
  30/9-4 S	30.03.1985	3568	3633
  30/9-7	23.12.1988	3137	3168
  30/9-8 R	25.09.1989	3140	3149
  30/9-10	21.09.1990	3114	3117
  30/9-11	19.11.1990	2514	2516
  30/9-11 A	29.12.1990	2679	2680
  30/9-13 S	11.10.1991	3444	3452
  30/9-13 SR	17.07.2002	3448	3456
  30/9-23	21.08.2009	2814	2845
  30/9-28 S	26.02.2016	3304	3311
  30/9-B-18	25.09.1992	3831	3941
  30/9-B-18 A	23.10.1992	3701	4751
  31/1-2 A	29.01.2021	3711	3761
  31/1-2 S	12.01.2021	3319	3364
  31/2-21 S	04.06.2014	3032	3074
  31/4-A-13 C	26.07.2022	7070	7225
  31/7-1	22.06.2016	2425	2449
  35/10-4 S	10.10.2018	3801	3834
  35/10-7 A	27.12.2021	3492	3561
  35/10-7 S	11.12.2021	3398	3464
  35/11-2	04.12.1987	3524	3601
  35/11-3 S	09.09.1989	3573	3640
  35/11-4	29.12.1990	2707	2785
  35/11-4 R	27.01.1992	2717	2795
  35/11-5	03.11.1991	3342	3396
  35/11-6	20.04.1992	3678	3721
  35/11-7	29.09.1992	2528	2584
  35/11-8 S	11.05.1996	3505	3576
  35/11-10	23.06.1997	2746	2801
  35/11-10 A	14.07.1997	3212	3259
  35/11-11	22.05.1998	3119	3177
  35/11-17	01.05.2014	2773	2837
  35/11-18	27.09.2015	3657	3695
  35/11-18 A	16.12.2015	3705	3750
  35/11-20 B	15.09.2016	4789	4862
  35/11-21 A	17.10.2018	2847	2874
  35/11-21 S	05.09.2018	2724	2758
  35/11-22 S	02.02.2019	3377	3417
  35/11-23	06.11.2019	2835	2894
  35/11-25 A	04.06.2021	3723	3741
  35/12-4 S	26.06.2011	3250	3255
  35/12-5 S	19.06.2015	3554	3570
  35/12-7	25.07.2018	2708	2750

• Wellbores with cores

  Wellbores with cores

  Wellbore name	Wellbore completion date	Core length [m]
  30/2-2	04.05.1985	37
  30/2-3	05.10.1992	9
  30/3-1 R	26.04.1982	7
  30/3-2 R	16.02.1981	55
  30/3-5 S	19.06.1992	51
  30/3-7 B	04.08.1998	29
  30/3-11 S	09.09.2022	2
  30/6-7	24.08.1982	44
  30/6-19	21.06.1986	34
  30/6-21	09.04.1987	54
  30/6-22	13.07.1988	54
  30/6-23	01.07.1990	63
  30/6-30	18.11.2018	86
  30/9-4 S	30.03.1985	18
  31/1-2 S	12.01.2021	45
  35/10-7 S	11.12.2021	67
  35/11-5	03.11.1991	14
  35/11-6	20.04.1992	28
  35/11-7	29.09.1992	13
  35/11-10	23.06.1997	24
  35/11-18 A	16.12.2015	44
  35/11-21 S	05.09.2018	6