BASEMENT

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• General information

  General information

  Attribute	Value
  Lithostrat. unit The lithostratigraphic unit's official name.	BASEMENT
  NPDID lithostrat. unit Norwegian Offshore Directorate's unique id for lithostratigraphic units.	10
  Level Indicates the lithostratigraphic unit's level. Legal values: GROUP, FORMATION, MEMBER.	GROUP

• Level below

  Level below

  Lithostrat. unit

• Description

  Basement
  
  

  On the Norwegian Continental Shelf bedrock of pre-Devonian age are regarded as basement in a petroleumgeological context. More than 50 wells in the North Sea, Norwegian Sea and Barents Sea have penetrated pre-Devonian rocks. Most of these wells were drilled on structural highs with depth to top basement quite evenly distributed between 1200 and 4000m.

  The thicknesses drilled have generally been in the order of a few meters. 5 wells have drilled more than 100m of basement rock:
  2/6-3 (142m),
  16/1-4 (146m),
  16/1-5 (195m),
  35/3-2 (233m),
  6306/10-1 (207m).

  Some of the pre-Devonian rocks have been dated by the K/Ar-, Ar/Ar- or Rb/Sr-methods, indicating pre-Middle Devonian metamorphic ages. The age of formation of the rocks are ranging from the Precambrian to the Early Paleozoic.

  The pre-Devonian rocks normally encountered include diverse rocks of low to high metamorphic grade, including metamorphosed igneous rocks such as granitic gneiss, and metasedimentary rocks such as mica schist, greenschist, quartzite and marble. The existing data indicate that these rocks are highly fractured and record a history of polyphase deformation from at least late Proterozoic times onward. In some wells weathered rock material forms an intermediate zone between basement and overlying sediments.

  In more than 30 of the wells basement rocks were cored. The cores were taken to confirm that the wells had reached basement, and coring was therefore usually carried out below any weathering. All wells have information from cuttings and logs.

  Gas condensate was tested from fractured crystalline basement in well 16/1-4 . Minor shows in basement fractures are recorded in various wells. Highly fractured and/or weathered basement rocks can have some potential as conduits for hydrocarbon migration or as reservoirs.

  Compiled from

  • Basset, M. G. Sub-Devonian geology. 61 – 63 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.
  • and NPD-observations.

• Wellbores penetrating

  Wellbores penetrating

  Wellbore name	Wellbore completion date	Top depth [m]	Bottom depth [m]
  2/6-3	25.02.1983	3918	4060
  2/6-5	11.01.1997	3231	3260
  2/9-5 S	18.09.2014	3671	3679
  3/7-1	13.09.1973	3218	3227
  8/3-1	10.10.1966	2965	3015
  10/5-1	26.06.1976	1818	1843
  11/5-1	12.09.2007	1920	1950
  16/1-2	07.08.1976	2912	2919
  16/1-3	27.09.1982	3440	3498
  16/1-4	13.04.1993	1864	2010
  16/1-5	21.11.1998	2265	2460
  16/1-12	08.09.2009	1913	2055
  16/1-15	05.04.2011	1920	2150
  16/1-15 A	13.05.2011	2069	2175
  16/1-17	20.03.2013	1988	2070
  16/1-18	14.05.2014	2360	2391
  16/1-19 S	25.10.2013	1891	1995
  16/1-23 S	25.08.2015	2094	2130
  16/1-25 S	26.12.2015	2004	2210
  16/1-27	11.04.2017	2240	2258
  16/1-28 S	23.08.2018	2336	2336
  16/1-28 S	23.08.2018	2807	3050
  16/1-28 S	23.08.2018	3050	4060
  16/1-28 S	23.08.2018	4060	4295
  16/1-28 S	23.08.2018	4295	4880
  16/1-29 S	03.06.2018	1915	2024
  16/1-30 A	19.07.2019	2041	2075
  16/1-30 S	01.07.2019	2094	2140
  16/1-34 A	15.09.2021	2109	2195
  16/2-1	09.08.1967	1873	1906
  16/2-3	28.09.2007	1894	1905
  16/2-4	15.12.2007	1879	2000
  16/2-5	13.05.2009	2342	2373
  16/2-9 S	24.09.2011	1986	2082
  16/2-12	06.09.2012	1939	2067
  16/2-17 B	16.06.2013	2133	2200
  16/2-18 S	08.08.2013	1864	1970
  16/2-19	03.04.2014	1989	2023
  16/2-19 A	03.05.2014	2310	2348
  16/2-20 A	16.02.2014	2183	2215
  16/2-20 S	21.11.2013	2114	2150
  16/2-22 S	28.01.2017	1950	1993
  16/2-U-19	12.12.2016	1943	2017
  16/3-2	08.03.1976	2015	2019
  16/3-4	28.06.2011	1940	2020
  16/3-4 A	18.07.2011	2082	2128
  16/3-6	16.07.2013	1965	2050
  16/3-7	08.11.2013	2089	2100
  16/3-U-1	24.12.2016	1959	2005
  16/3-U-1 A	10.01.2017	2861	2882
  16/3-U-1 B	15.01.2017	2646	2665
  16/4-1	18.11.1984	2885	2909
  16/4-5	07.03.2010	1898	2020
  16/5-1	08.02.1971	1925	1943
  16/5-7	12.07.2019	1916	2028
  16/5-8 S	22.08.2019	2202	2468
  16/6-1	19.01.1968	2055	2061
  17/3-1	20.08.1995	2811	2852
  18/11-1	31.03.1974	2060	2086
  25/6-1	03.02.1986	2851	2881
  25/7-1 S	19.07.1986	3551	3592
  25/8-19 A	19.03.2020	2806	2950
  25/8-19 S	30.12.2019	2716	2760
  25/8-21 S	20.06.2021	2633	2703
  25/8-22 S	20.07.2021	2589	2622
  25/10-2 R	08.07.1972	3152	3181
  25/11-1	09.07.1967	2391	2459
  25/11-17	22.03.1993	2243	2256
  25/11-28	25.09.2015	2574	2590
  25/11-29 S	13.05.2019	2304	2313
  31/6-1	28.10.1983	4014	4070
  32/4-1	04.12.1996	3132	3186
  35/3-2	26.10.1980	4167	4400
  35/3-4	06.06.1981	4069	4089
  35/3-5	31.03.1982	4092	4114
  35/6-3 S	25.08.2022	2970	2993
  35/9-1	07.05.1989	2314	2350
  35/9-1 R	27.07.1989	2314	2350
  35/9-2	03.04.1991	2856	2885
  35/9-3	11.11.1997	2770	2783
  36/1-1	14.06.1975	1568	1596
  36/1-2	27.10.1975	3233	3256
  36/1-3	25.03.2019	2863	2913
  36/1-4 S	30.01.2022	3228	3255
  36/4-1	01.10.1996	2712	2717
  36/7-1	07.05.1996	2834	2841
  36/7-2	22.09.1997	1429	1435
  6204/10-1	23.11.1995	2670	2709
  6204/10-2 R	21.11.1997	2073	2095
  6204/11-3	14.09.2020	1271	1321
  6305/12-2	17.12.1993	3145	3162
  6306/3-1 S	11.12.2021	2345	2384
  6306/3-2	12.07.2022	1789	1799
  6306/6-1	05.07.1994	1312	1317
  6306/6-2	17.11.2009	2072	2080
  6306/9-1	18.01.2022	967	1055
  6306/10-1	17.12.1990	2980	3187
  6407/10-3	27.06.1992	2959	2973
  6407/10-4	19.01.2016	3169	3224
  6609/7-1	03.08.1983	1912	1969
  7120/1-1 R2	21.07.1986	3947	4003
  7120/2-1	29.10.1985	3471	3502
  7120/12-2	11.09.1981	4664	4680
  7128/4-1	26.02.1994	2503	2530
  7128/6-1	08.11.1991	2534	2543
  7220/6-1	29.03.2005	1483	1540
  7220/6-2 R	22.11.2016	1270	1318
  7220/11-2	03.05.2015	1955	2050
  7220/11-2 A	14.06.2015	2068	2121
  7226/11-1	11.04.1988	5137	5200

• Wellbores with cores

  Wellbores with cores

  Wellbore name	Wellbore completion date	Core length [m]
  2/6-3	25.02.1983	4
  2/6-5	11.01.1997	2
  3/7-1	13.09.1973	6
  8/3-1	10.10.1966	12
  16/1-4	13.04.1993	6
  16/1-12	08.09.2009	23
  16/1-15	05.04.2011	47
  16/1-15 A	13.05.2011	8
  16/1-17	20.03.2013	6
  16/1-19 S	25.10.2013	19
  16/1-25 S	26.12.2015	20
  16/1-30 S	01.07.2019	8
  16/2-1	09.08.1967	3
  16/2-4	15.12.2007	2
  16/2-9 S	24.09.2011	1
  16/2-12	06.09.2012	13
  16/2-17 B	16.06.2013	7
  16/2-18 S	08.08.2013	11
  16/2-19	03.04.2014	5
  16/2-22 S	28.01.2017	3
  16/3-2	08.03.1976	2
  16/3-4	28.06.2011	12
  16/3-4 A	18.07.2011	1
  16/3-6	16.07.2013	3
  16/4-1	18.11.1984	2
  16/4-5	07.03.2010	27
  16/5-1	08.02.1971	13
  16/5-7	12.07.2019	28
  16/5-8 S	22.08.2019	27
  16/6-1	19.01.1968	4
  17/3-1	20.08.1995	3
  18/11-1	31.03.1974	4
  25/7-1 S	19.07.1986	6
  25/8-19 A	19.03.2020	17
  25/10-2 R	08.07.1972	0
  25/11-1	09.07.1967	14
  25/11-17	22.03.1993	8
  31/6-1	28.10.1983	1
  35/3-4	06.06.1981	1
  35/6-3 S	25.08.2022	1
  35/9-1	07.05.1989	2
  36/1-1	14.06.1975	6
  36/4-1	01.10.1996	0
  6305/12-2	17.12.1993	3
  6306/10-1	17.12.1990	4
  6407/10-3	27.06.1992	1
  6609/7-1	03.08.1983	3
  7120/1-1 R2	21.07.1986	2
  7120/2-1	29.10.1985	3
  7120/12-2	11.09.1981	6
  7128/4-1	26.02.1994	3
  7128/6-1	08.11.1991	2
  7220/11-2	03.05.2015	8
  7226/11-1	11.04.1988	5