Wellbore: 2/8-6 - Factpages - Norwegian Offshore Directorate

General information

General information
Attribute	Value
Wellbore name Official name of wellbore based on Norwegian Offshore Directorate guidelines for designation of wells and wellbores.	2/8-6
Type Wellbore type. Legal values: EXPLORATION, DEVELOPMENT, OTHER (see 'Purpose' for more information)	EXPLORATION
Purpose Final classification of the wellbore. Legal values for exploration wellbores: WILDCAT, APPRAISAL, WILDCAT-CCS, APPRAISAL-CCS. Legal values for development wellbores: OBSERVATION, PRODUCTION, INJECTION, INJECTION-CCS, OBSERVATION-CCS. Legal values for other wellbores: SOIL DRILLING (drilling in connection with track surveys and other subsurface surveys to investigate the soil conditions prior to placement of facilities), SHALLOW GAS (drilling to investigate shallow gas before the first 'real' drilling on the location), PILOT (drilling to investigate the geology and fluid connectors for location of the main wellbore), SCIENTIFIC (drilling according to Law of Scientific research and exploration), STRATIGRAPHIC (driling according to Law of Petroleum activities §2-1).	WILDCAT
Status Status for the wellbore. Legal values are: BLOWOUT: A blowout has occurred in the well. CLOSED: A development wellbore that has been closed in a shorter or longer periode. Also applies to development wellbores where drilling is completed, but production/injection has not yet been reported. DRILLING: The well is in the drilling phase - can be active drilling, logging, testing or plugging, JUNKED: The drilling operation has been terminated due to technical problems. P&A: Exploration: The well is plugged and abandoned, and can not be reentered for further use. Development wells: The production/injection from/to the well is stopped and the well is plugged. The wellhead is removed or else made unavailable for further well operations. PLUGGED: The wellbore has been plugged, but the upper parts of the wellbore can be re-used. A sidetrack might be drilled at a later stage. PRODUCING: It was produced from the wellbore at the time of the operators last monthly report to the Norwegian Offshore Directorate. INJECTING: It was injected to the wellbore at the time of the operators last monthly report to the Norwegian Offshore Directorate. PREDRILLED: The upper part of the well has been drilled, usually as part of a batch-drilling campaign covering several wellbores. RE-CLASS TO DEV: Exploration wellbore that is reclassified to a development wellbore. RE-CLASS TO TEST: Exploration wellbore that is reclassified to test production. SUSPENDED: The drilling operation in the wellbore has been temporarily stopped. The current plan is to continue drilling later on.	P&A
Factmaps in new window	link to map
Main area Name of the area on the Norwegian Continental Shelf where the wellbore is located. Legal values: BARENTS SEA, NORWEGIAN SEA, NORTH SEA.	NORTH SEA
Field Name of the field the wellbore is related to.	VALHALL
Discovery Name of the discovery the wellbore is related to.	2/8-6 Valhall
Well name Official name of the parent well for the wellbore based on Norwegian Offshore Directorate guidelines for designation of wells and wellbores.	2/8-6
Seismic location Position of spud location on seismic survey lines. SP: shotpoint.	LINE 73-23 SP.102
Production licence Official designation of the production licence the wellbore was drilled or planned to be drilled from ( well head posistion).	006
Drilling operator Name of the licensee starting the drilling operation on behalf of the active production license (well head position). This will usually equal the operator of the production license.	Amoco Norway Oil Company
Drill permit The drilling permit number together with the version of the drilling permit as stated in the drilling permit granted by the Norwegian Offshore Directorate.	124-L
Drilling facility Norwegian Offshore Directorate's name of the facility which the wellbore was drilled from.	WAAGE DRILL I
Drilling days Number of days from wellbore entry to wellbore completion.	85
Entered date The date when he wellbore was spudded. For sidetracks: The date when new formation was drilled by kicking off from the mother-wellbore,	07.04.1975
Completed date Exploration wellbores from moveable facilities: For floating facilities - date when anchor handling is started. For jackups - date the jacking-down started. Exploration wellbores from fixed facilities and all development wellbores: Date when the wellbore is at total depth, and last casing, liner or screen is set. In case of immediate plugging of the wellbore, completed date equals the date the last plug i set in the wellbore. Date when the wellbore is at total depth, and last casing, liner or screen is set. In case of immediate plugging of the wellbore, completed date equals the date the last plug i set in the wellbore.	30.06.1975
Release date Date when raw data which has been reported to the authorities from the wellbore is not confidential any longer. Normally 2 years after finishing the drilling. May be earlier if the area of the production license is relinquished.	30.06.1977
Publication date Date quality control of the wellbore information was completed, so it can be published on the internet as a 'Well Data Summary Sheet' wellbore with more information available than other wellbores.	16.10.2012
Purpose - planned Pre-drill purpose of the wellbore. Legal values for exploration wellbores: WILDCAT, APPRAISAL, WILDCAT-CCS, APPRAISAL-CCS. Example of legal values for development wellbores: OBSERVATION, PRODUCTION, INJECTION.	WILDCAT
Reentry Status whether the wellbore has been re-entered (YES) or not (NO). Re-entered wellbores are not included in the count when wellbores are presented in statistical overviews.	NO
Content For exploration wellbores, status of discovery. Legal values: DRY, SHOWS (trace amounts of hydrocarbons), GAS, GAS/CONDENSATE, OIL or OIL/GAS. SHOWS (GAS SHOWS, OIL SHOWS or OIL/GAS SHOWS) are detected as fluorescent cut (organic extract), petroleum odour, or visual stain on cuttings or cores, or as increased gas reading on the mud-loggers gas detection equipment. Legal values for WILDCAT-CCS and APPRAISAL-CCS: WATER For development wellbores, type of produced/injected fluid. Legal values: WATER, CUTTINGS, NOT AVAILABLE, OIL, GAS/CONDENSATE, OIL/GAS, CO2, GAS, WATER/GAS, NOT APPLICABLE.	OIL
Discovery wellbore Indicator which tells if the wellbore made a new discovery. Legal values: YES, NO. Prior to press-release or other information regarding drilling results, the indicator will be “NO” as a default.	YES
1st level with HC, age Age of lithostratigraphic unit, 1st level, where hydrocarbons were encountered. Examples of legal values: CRETACEOUS, EARLY CRETACEOUS, LATE JURASSIC, EOCENE. See also Norwegian Offshore Directorate bulletins.	LATE CRETACEOUS
1st level with HC, formation Name of lithostartigraphic unit, 1st level, where hydrocarbons were encountered. Shown only for released wells. Examples of legal values: BASEMENT, COOK FM, EKOFISK FM, HEIMDAL FM, SANDNES FM, SOGNEFJORD FM, TARBERT FM, BRENT GP. See also Norwegian Offshore Directorate bulletins.	TOR FM
2nd level with HC, age Age of lithostratigraphic unit, 2nd level, where hydrocarbons were encountered. Examples of legal values: CRETACEOUS, EARLY CRETACEOUS, LATE JURASSIC, EOCENE.	LATE CRETACEOUS
2nd level with HC, formation Name of lithostartigraphic unit, 2nd level, where hydrocarbons were encountered. Shown only for released wells. Examples of legal values: BASEMENT, COOK FM, EKOFISK FM, HEIMDAL FM, SANDNES FM, SOGNEFJORD FM, TARBERT FM, BRENT GP.	HOD FM
Kelly bushing elevation [m] Elevation of the rotary kelly bushing (RKB) above mean sea level.	27.0
Water depth [m] Depth in metres betweem mean sea level and sea floor.	68.0
Total depth (MD) [m RKB] Total measured length of wellbore from kelly bushing to total depth (driller's depth).	2669.0
Bottom hole temperature [°C] Estimated temperature at final total depth of the wellbore. Shown only for released wells. See discription.	83
Oldest penetrated age Age (according to Geologic Time Scale 2004 by F. M. Gradstein, et al. (2004)) of the oldest penetrated formation. May differ from age at TD for example in deviated wellbores. Examples of legal values: CRETACEOUS, EARLY CRETACEOUS, LATE JURASSIC, EARLY PERMIAN, EARLY TRIASSIC, EOCENE.	EARLY CRETACEOUS
Oldest penetrated formation Name of the oldest lithostratigraphic unit penetrated by the wellbore. Shown only for released wells. In most wellbores this is formation or group at total depth. May differ from formation or group at TD for example in wellbores drilled with high deviation or through faults. Examples of legal values: AMUNDSEN FM, BALDER FM, BASEMENT, BLODØKS FM, BRYNE FM, BURTON FM, COOK FM, DRAKE FM, DRAUPNE FM, EKOFISK FM, DUNLIN GP.	SOLA FM
Geodetic datum Reference system for coordinates. Example of legal values: ED50.	ED50
NS degrees Geographic coordinate of the wellhead, north-south degrees.	56° 15' 42.91'' N
EW degrees Geographic coordinate of the wellhead, east-west degrees.	3° 23' 40.81'' E
NS UTM [m] Universal Transverse Mercator coordinate of the wellhead, north-south.	6235439.35
EW UTM [m] Universal Transverse Mercator coordinate of the wellhead, east-west.	524449.07
UTM zone Universal Transverse Mercator zone. Examples of legal values: 31, 32, 33, 34.	31
NPDID wellbore Norwegian Offshore Directorate's unique id for the wellbore.	276

Well 2/8-6 was drilled to test the chalk approximately on the crest of the Valhall structure in the southern North Sea. The Valhall structure was mapped as a large northwest-southeast trending anticline at the Tertiary level covering approximately 65 km2 with a vertical relief of ca 490 m. The crestal portion of the Valhall structure, ca 26 km2 in area, was blanketed by a low velocity "bright spot" zone in the overlying Tertiary (Miocene). Such "bright spot" had been observed also over the Hod discovery, the Ekofisk and the Eldfisk. The 2/8-6 and 2/11-2 wells had confirmed that these "bright spot" anomalies were caused by oil and gas present in the younger Tertiary beds, creating extremely low velocities.

Operations and results

Wildcat well 2/8-6 was spudded with the semi-submersible installation Waage Drill I on 7 April 1975 and drilled to TD at 2669 m in the Early Cretaceous Sola Formation. The well was drilled in 38 days. Of these a total of 9 days were lost due to drilling problems; 2 days cementing between the 20 and 13 3/8-inch casing to stop gas entry into the annulus, 1.5 days to repair BOP stack connector, and 5.5 days to combat gas kick and lost circulation while drilling at 2438 m. The well was drilled with seawater and hi-vis mud down to 155 m, with shale-Trol gel mud from 155 m to 1890 m, and with lignosulphonate mud from 1890 m to TD.

The chalk was encountered at 2463 m. Good oil shows were encountered in the intervals 2465 - 2472 m and 2526 - 2551 m with minor oil saturations occurring between the above intervals and down to approximately 2560 m resulting in a gross oil column thickness of 110 m. Log derived porosity in the oil column ranged between 27 and 43%, averaging 33 %. Core porosity ranged between 26 and 52%. The maximum horizontal core permeability was 18 mD; however, most values ranged between 0.1 and 1.0 mD. Water saturations within the two most promising intervals were generally less than 40%. Cores and ditch cuttings showed that the chalk within the upper 12 - 15 m has considerable horizontal and vertical fracturing.

Two core samples were taken from 2465.5 m to 2501.5 m, with 56% recovery. No wire line fluid samples were taken.

The well was permanently abandoned on 30 June 1975 as the oil discovery well on the Valhall Field.

Testing

Five production tests were conducted over the chalk pay. Four mechanically successful tests were conducted over the lower sections. However, the fifth test, which was to test the uppermost pay in the well, failed due to split/collapsed casing.

Test No 1 tested the interval 2570 m to 2582.3 m. The test produced 95 Sm3 oil/day on open choke. GOR was 201 Sm3/Sm3, oil gravity was 34.0 deg API and the gas gravity was 0.665 (air = 1). The interval was supposed to be water saturated, so the oil flow was possibly due to poor cement bonding.

Test No 1A was a retest of Test No 1, after acidizing. This test produced only small amounts of oil and gas together with bottom sediments and water.

Test No 2 tested the interval 2525.9 m to 2553.3 m. Prior to acidizing the test flowed 89 Sm3 oil/day on a 4/64" choke. GOR was 810 Sm3/Sm3, oil gravity was 33.0 deg API and the gas gravity was 0.69 (air = 1). After acidizing the test produced 175 Sm3 oil/day on a 48/64" choke. The GOR was 134, the oil gravity was 34.0, and the gas gravity was 0.68.

Test No 3 tested the interval 2502.4 m to 2511.6 m. Prior to acidizing test flowed 4 - 26 Sm3 oil/day on open choke. After acidizing the test produced surges of oil, gas, acid water, emulsions and solids with open choke. Oil gravity was 35.6 deg API.

Test No 4 tested the interval 2478 m to 2488.7 m. No acid stimulation was applied. The test produced 135 Sm3 oil/day on a 32/64" choke. GOR was 223 Sm3/Sm3, oil gravity was 38.2 deg API and the gas gravity was 0.714 (air = 1). A maximum temperature of 92.2 degC was measured at gauge depth 2471.3 m in this test.

Cuttings at the Norwegian Offshore Directorate

Cuttings at the Norwegian Offshore Directorate
Cuttings available for sampling?	YES

Cuttings at the Norwegian Offshore Directorate
Cutting sample, top depth [m]	Cutting samples, bottom depth [m]
192.00	2668.83

Cores at the Norwegian Offshore Directorate

Cores at the Norwegian Offshore Directorate
Core sample number	Core sample - top depth	Core sample - bottom depth	Core sample depth - uom
1	8089.0	8116.0	[ft ]
2	8153.0	8192.0	[ft ]

Cores at the Norwegian Offshore Directorate
Total core sample length [m]	20.1

Cores at the Norwegian Offshore Directorate
Cores available for sampling?	YES

Lithostratigraphy

Lithostratigraphy
Top depth [mMD RKB]	Lithostrat. unit
95	NORDLAND GP
2422	ROGALAND GP
2422	BALDER FM
2432	SELE FM
2463	SHETLAND GP
2463	TOR FM
2485	HOD FM
2603	BLODØKS FM
2606	HIDRA FM
2627	CROMER KNOLL GP
2627	RØDBY FM
2652	SOLA FM

Documents – older Norwegian Offshore Directorate WDSS reports and other related documents

Documents – older Norwegian Offshore Directorate WDSS reports and other related documents
Document name	Document format	Document size [MB]
276_01_WDSS_General_Information	pdf	0.26

Documents – reported by the production licence (period for duty of secrecy expired)

Documents – reported by the production licence (period for duty of secrecy expired)
Document name	Document format	Document size [MB]
276_2_8_6_Completionlog	pdf	1.91
276_2_8_6_Completion_report	pdf	14.39

Drill stem tests (DST)

Drill stem tests (DST)
Test number	From depth MD [m]	To depth MD [m]	Choke size [mm]
1.0	2570	2582	25.4
2.0	2526	2553	19.0
3.0	2502	2514	0.0
4.0	2478	2489	12.5
5.0	2466	2488	0.0

Drill stem tests (DST)
Test number	Final shut-in pressure [MPa]	Final flow pressure [MPa]
1.0	44.900	26.900
2.0	41.500	11.700
3.0
4.0	44.600	15.800
5.0

Drill stem tests (DST)
Test number	Oil [Sm3/day]	Gas [Sm3/day]	Oil density [g/cm3]	GOR [m3/m3]
1.0	94	19283	0.850	1152
2.0	262	40691	0.840	872
3.0
4.0	136	30270	0.830
5.0

Logs

Logs
Log type	Log top depth [m]	Log bottom depth [m]
BHC	1284	2668
CBL	2331	2637
CDM	2442	2668
CDM AP	2442	2668
CDM PP	2442	2668
CNL	106	1310
DLL MSFL	1285	2668
FDC	2443	2668
FDC CNL	2443	2668
IES	2444	2667
SRS	1284	2668

Casing and leak–off tests

Casing and leak–off tests
Casing type	Casing diam. [inch]	Casing depth [m]	Hole diam. [inch]	Hole depth [m]	Formation test type
CONDUCTOR	30	155.0	36	155.0	LOT
SURF.COND.	20	366.0	26	381.0	LOT
INTERM.	13 3/8	1284.0	17 1/2	1298.0	LOT
INTERM.	9 5/8	2444.0	12 1/4	2446.0	LOT
LINER	7	2668.0	8 1/2	2669.0	LOT

Drilling mud

Drilling mud
Depth MD [m]	Mud weight [g/cm3]	Mud type
767	1.49	seawater
1298	1.63	seawater
2438	1.78	seawater
2459	1.84	seawater
2668	1.97	seawater

2/8-6