BOKNFJORD GP

hide details Export:  PDF

• General information

  General information

  Attribute	Value
  Lithostrat. unit The lithostratigraphic unit's official name.	BOKNFJORD GP
  NPDID lithostrat. unit Norwegian Offshore Directorate's unique id for lithostratigraphic units.	15
  Level Indicates the lithostratigraphic unit's level. Legal values: GROUP, FORMATION, MEMBER.	GROUP

• Level below

  Level below

  Lithostrat. unit
  BØRGLUM UNIT
  EGERSUND FM
  FLEKKEFJORD FM
  SAUDA FM
  TAU FM

• Description

  Boknfjord Group
  
  Name

  From the main fjord in Rogaland, Norway.

  Type area

  The Fiskebank and Egersund Sub-Basins comprise the type area. The group is illustrated in the Norwegian well 9/4-3 (Conoco), (Fig 3.36) .

  Thickness

  In the type area wells show thicknesses of up to 500 m. In well 9/4-3 the thickness of the group is 290 m. Towards the basin margins the section thins considerably.

  Lithology

  The sediments of the group are dominated by shales. Varying amounts of siltstone, sandstone, limestone stringers and differences in organic content make it possible, however, to subdivide the group into formations (Olsen and Strass, 1982).

  Boundaries

  The lower boundary is characterized by a distinct log break with the underlying sandstones of the Vestland Group . The upper boundary is usually characterized by abrupt changes in log response to lower gamma ray and interval transit times in the overlaying Valhall Formation1). In the Egersund Sub-Basin this boundary may be difficult to identify due to a large supply of clastic material.

  Distribution

  The group is confined to the Fiskebank and Egersund Sub-Basins although the upper two formations extend further westwards than those lying below.

  Age

  The group ranges in age from Callovian to Ryazanian.

  Subdivisions

  The group can be subdivided into four formations, the Egersund (base), Tau , Sauda and Flekkefjord formations (top).

  Remarks

  The term "Bream Formation" was first used by Deegan and Scull (1977) to describe a Callovian-Portlandian (Volgian) sequence, mainly clay-stones and siltstones, distributed throughout the Norwegian-Danish Basin. The formation comprised the Egersund Member, Børglum Member and Fredrikshavn Member. The Bream Formation was adopted with some modification by Michelsen (1978) for the Danish Sub-Basin where it comprises the Børglum and Fredrikshavn Members. Recent correlation work in the Egersund and Fiskebank Sub-Basin (e.g. Olsen and Strass, 1982) shows the existence of four argillaceous units, ranging in age from Callovian-Ryazanian, which are considered stratigraphically useful. They are widespread enough to deserve formation status and different enough from the Danish deposits to merit separate nomenclature. These units are the Egersund , Tau , Sauda and Flekkefjord formations. The formal definitions of the unit in this volume outline their relationship to the Egersund/Børglum/Fredrikshavn Members of Deegan and Scull (1977). Note that the Flekkefjord Formation was formerly part of the early Cretaceous Vallhall Formation, also defined by Deegan and Scull.
  The four formations fall naturally into a single "claystone" group. It is not however considered proper to elevate the former Bream Formation to a "Bream Group" which would encompass these units, since it may still desirable to retain the formation status of the Bream Formation and the member status of the Børglum/Fredrikshavn Members in the Danish sector.
  It is therefore proposed that the term "Bream Formation" should be abandoned for the Fiske-bank and Egersund Sub-Basins, and replaced by the Boknfjord Group, which is defined above.

  Source

  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.

  Footnotes

  • 1) Åsgard Formation according to Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.

• Wellbores penetrating

  Wellbores penetrating

  Wellbore name	Wellbore completion date	Top depth [m]	Bottom depth [m]
  7/3-1	10.06.1969	2598	2655
  8/1-1	07.02.1972	2379	2606
  8/3-1	10.10.1966	1628	2040
  8/3-2	04.12.1982	2025	2375
  8/4-1	25.07.1977	2351	2397
  8/5-1	28.03.2013	2176	2339
  8/9-1	10.02.1976	2103	2156
  8/10-1	01.07.1969	2775	2793
  8/10-2	17.03.1980	2657	2667
  8/11-1	29.06.1975	2807	2835
  8/12-1	23.07.1971	2574	2663
  9/1-1 S	21.11.2011	1934	2392
  9/2-1	28.04.1987	2483	3162
  9/2-2	21.09.1987	2381	3123
  9/2-3	08.02.1990	2625	3252
  9/2-4 S	11.04.1994	2730	4094
  9/2-5	21.07.1995	2595	3146
  9/2-6 S	15.10.1996	3297	4783
  9/2-7 S	10.06.1997	3062	3854
  9/2-8 S	02.02.1998	4762	5823
  9/2-9 S	17.09.1999	2710	3844
  9/2-11	29.03.2010	2101	2629
  9/2-12	14.10.2019	2530	2991
  9/2-A-4	13.08.1996	3758	4631
  9/3-1	04.09.1986	1446	1788
  9/3-2	09.12.2005	1970	2660
  9/4-1	19.05.1968	1985	2288
  9/4-2	29.08.1970	2155	2490
  9/4-3	19.08.1972	2200	2490
  9/4-4	20.08.1977	2310	2718
  9/4-5	01.08.2006	2300	2703
  9/8-1	29.06.1968	1777	1922
  9/11-1	19.08.1971	1957	2040
  9/12-1	06.05.1969	1905	2038
  10/4-1	12.07.2015	1842	2274
  10/5-1	26.06.1976	1275	1472
  10/7-1	30.07.1992	1298	1539
  10/8-1	17.01.1971	1367	1494
  11/5-1	12.09.2007	1086	1276
  11/10-1	19.08.1969	1655	1860
  16/11-1 S	31.10.1967	2124	2165
  16/11-2	23.07.1973	2127	2202
  17/3-1	20.08.1995	1875	2388
  17/6-1	07.02.2011	2020	2630
  17/8-1	23.10.2021	2297	2435
  17/9-1	23.10.1973	1933	2220
  17/9-1 R	11.06.1974	1933	2220
  17/10-1	24.03.1969	2515	2682
  17/11-1	30.06.1968	2083	2211
  17/11-2	17.05.1976	2410	2521
  17/12-1 R	21.06.1972	1902	2290
  17/12-2	09.10.1973	1932	2157
  17/12-3	03.02.1980	1957	2370
  17/12-4	10.07.2009	1992	2277
  17/12-4 A	15.08.2009	2142	2606
  17/12-4 B	26.08.2009	2101	2536
  18/10-1	01.01.1980	1991	2405
  18/11-1	31.03.1974	1609	1878

• Wellbores with cores

  Wellbores with cores

  Wellbore name	Wellbore completion date	Core length [m]
  9/2-1	28.04.1987	13
  9/11-1	19.08.1971	9
  17/12-4	10.07.2009	9