Wellbore: 31/2-1 - 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.	31/2-1
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.	SUSPENDED
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.	TROLL
Discovery Name of the discovery the wellbore is related to.	31/2-1 (Troll Vest)
Well name Official name of the parent well for the wellbore based on Norwegian Offshore Directorate guidelines for designation of wells and wellbores.	31/2-1
Seismic location Position of spud location on seismic survey lines. SP: shotpoint.	77 - 6046 SP 461
Production licence Official designation of the production licence the wellbore was drilled or planned to be drilled from ( well head posistion).	054
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.	A/S Norske Shell
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.	219-L
Drilling facility Norwegian Offshore Directorate's name of the facility which the wellbore was drilled from.	BORGNY DOLPHIN
Drilling days Number of days from wellbore entry to wellbore completion.	116
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,	17.07.1979
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.	09.11.1979
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.	09.11.1981
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.	15.02.2006
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/GAS
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 JURASSIC
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.	SOGNEFJORD FM
Kelly bushing elevation [m] Elevation of the rotary kelly bushing (RKB) above mean sea level.	24.0
Water depth [m] Depth in metres betweem mean sea level and sea floor.	324.0
Total depth (MD) [m RKB] Total measured length of wellbore from kelly bushing to total depth (driller's depth).	2433.0
Final vertical depth (TVD) [m RKB] Vertical elevation from total depth to kelly bushing. Shown only for released wells. Referred to as true vertical depth (TVD).	2433.0
Bottom hole temperature [°C] Estimated temperature at final total depth of the wellbore. Shown only for released wells. See discription.	65
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.	LATE TRIASSIC
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.	HEGRE GP
Geodetic datum Reference system for coordinates. Example of legal values: ED50.	ED50
NS degrees Geographic coordinate of the wellhead, north-south degrees.	60° 46' 19.16'' N
EW degrees Geographic coordinate of the wellhead, east-west degrees.	3° 33' 15.87'' E
NS UTM [m] Universal Transverse Mercator coordinate of the wellhead, north-south.	6737677.61
EW UTM [m] Universal Transverse Mercator coordinate of the wellhead, east-west.	530201.60
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.	398

Well 31/2-1 is the Troll West gas and oil Discovery well. The purpose of the well was to establish the basic stratigraphy in the area, and to evaluate the prospectivity of the Jurassic sequence. The structure is formed by a tilted Jurassic fault block on the Sogn Spur High between the North Viking Graben and the Horda Basin. A migration path from the Viking Graben kitchen area is provided by monoclinal fault blocks. The most dominant characteristic of the structure was the presence of a "flatspot", which was believed to be associated with a present hydrocarbon/water contact. Sealing of the potential Jurassic reservoir is provided by Cretaceous and Paleocene Claystones, overlying the reservoir sandstones.

The well is Type Well for the Johansen, Krossfjord, Fensfjord, and the Sognefjord Formations, and Reference Well for the Amundsen, Cook, and Drake Formations.

Operations and results

Wildcat well 31/2-1 was spudded with the semi-submersible installation Borgny Dolphin on 17 July 1979 and drilled to TD at 2433 m in the Late Triassic Hegre Group. Severe problems with setting the 30" casing led to abandoning of the first hole and re-spudding on 24 July, 50 m to the south of the original spud position. The well was drilled with gel polymer down to 793 m, and with gypsum/lignosulphonate mud from 793 m to TD.

The well 31/2-1 proved the existence of a Late - Middle Jurassic gas bearing reservoir sequence in the Flathead A structure (block 31/2). A gross commercial gas column of 134.5 metres with top at 1439.5 m was encountered in good-moderate quality coastal - shallow marine sands. Good oil shows with oil bleeding from cores were encountered from 1567 m to 1597 m, below the gas. It is possible that both a gas-oil contact and an oil-water contact occur in this zone, however, data available suggested tight formation. From the pressure data the plausible interpretation is that a gas-water contact effectively exists at the intersection of the extrapolated gas and water pressure gradients at 1574 m (1550 m SS), which would imply that the oil observed in cores is actually residual. Indications of oil occurred down to 1622 m. The well results showed that the marked seismic flatspot seen on seismic lines across the structure at 1685 msec was closely related to the base of the gas column. For a detailed evaluation of the reservoir it was decided to take diamond bit cores over the whole hydrocarbon bearing Jurassic interval. A total of 18 cores were cut in the interval from 1450 to 1668 m, with a recovery length of 182 m (86%). The cored interval extends from just below the top reservoir to below the hydrocarbon/water contact. Extensive RFT pressure measurements showed the accumulation to be under hydrostatic conditions. Good RFT gas samples were recovered from 1442 m, 1468 m, 1482 m, 1515 m, 1547.5 m, 1573 m, and 1574 m. They showed a consistent dry gas composition with 93% methane, 0.5% CO2, and 1.5% N2. Only trace C4+ and no H2S was recorded. A number of RFT water samples were found to be heavily contaminated by the mud and not representative for the Formation.

The well was suspended on 9 November for re-entry and possible testing at a later stage.

Testing

After RFT testing preparations were made for drill stem testing of the interval where oil had been observed bleeding from cores (1565 to 1622 m). Due to severe weather and technical problems the test was aborted.

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]
480.00	2433.00

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	1450.0	1453.5	[m ]
2	1454.0	1455.5	[m ]
3	1456.6	1465.6	[m ]
4	1465.6	1474.6	[m ]
5	1474.6	1485.6	[m ]
6	1488.0	1493.3	[m ]
7	1514.0	1521.8	[m ]
8	1523.6	1532.7	[m ]
9	1533.0	1541.8	[m ]
10	1542.0	1559.0	[m ]
11	1560.0	1577.4	[m ]
12	1577.4	1595.5	[m ]
13	1595.5	1613.5	[m ]
14	1613.5	1616.6	[m ]
15	1617.5	1634.1	[m ]
16	1634.1	1638.4	[m ]
17	1638.4	1652.1	[m ]
18	1652.3	1662.7	[m ]

Cores at the Norwegian Offshore Directorate
Total core sample length [m]	183.6

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

Core photos

Core photos

1450-1452m	1452-1453m	1454-1455m	1456-1459m	1459-1462m

1462-1464m	1464-1465m	1465-1468m	1468-1471m	1471-1473m

1373-1474m	1474-1477m	1477-1480m	1480-1482m	1482-1485m

1485-1486m	1488-1490m	1490-1493m	1514-1516m	1516-1519m

1519-1521m	1523-1526m	1526-1529m	1529-1531m	1531-1531m

1533-1535m	1535-1538m	1538-1541m	1541-1542m	1542-1544m

1544-1547m	1547-1550m	1550-1552m	1552-1555m	1555-1558m

1558-1559m	1560-1562m	1562-1565m	1565-1568m	1568-1570m

1570-1573m	1573-1576m	1576-1577m	1577-1580m	1580-1582m

1582-1585m	1585-1588m	1588-1590m	1590-1593m	1593-1595m

1595-1598m	1598-1600m	1600-1603m	1603-1606m	1606-1609m

1609-1611m	1611-1613m	1613-1616m	1616-1617m	1620-1622m

1622-1625m	1625-1628m	1628-1631m	1631-1633m	1633-1634m

1634-1636m	1636-1638m	1638-1641m	1641-1643m	1643-1646m

1646-1649m	1649-1651m	1651-1652m	1652-1655m	1655-1657m

1657-1660m	1660-1663m

Lithostratigraphy

Lithostratigraphy
Top depth [mMD RKB]	Lithostrat. unit
348	NORDLAND GP
525	HORDALAND GP
1184	ROGALAND GP
1184	BALDER FM
1250	SELE FM
1322	LISTA FM
1393	VÅLE FM
1405	CROMER KNOLL GP
1414	VIKING GP
1414	DRAUPNE FM
1440	SOGNEFJORD FM
1532	HEATHER FM
1595	FENSFJORD FM
1742	KROSSFJORD FM
1880	HEATHER FM
1881	BRENT GP
1985	DUNLIN GP
1985	DRAKE FM
2093	COOK FM
2134	AMUNDSEN FM
2176	JOHANSEN FM
2273	AMUNDSEN FM
2293	STATFJORD GP
2381	HEGRE GP

Composite logs

Composite logs
Document name	Document format	Document size [MB]
398	pdf	0.35

Geochemical information

Geochemical information
Document name	Document format	Document size [MB]
398_1	pdf	0.74
398_2	pdf	3.93
398_3	pdf	1.13
398_4	pdf	0.63

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]
398_01_WDSS_General_Information	pdf	0.12
398_02_WDSS_completion_log	pdf	0.17

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]
398_31_2_1_COMPLETION_REPORT_AND_LOG	pdf	16.05

Logs

Logs
Log type	Log top depth [m]	Log bottom depth [m]
BGT GR	426	798
BGT GR	793	1324
CBL VDL	1310	2074
CBL VDL GR	344	2035
DLL MSFL SP GR	1310	1703
FDC BHC GR SP	1310	1703
FDC CNL CAL GR	426	575
FDC CNL CAL GR	793	1323
FDC CNL CAL GR	1310	1381
FDC CNL CAL GR	1550	2070
FDC CNL CAL GR	2063	2432
HDT	1310	2070
HDT	2063	2432
ISF BHC GR SP	426	578
ISF BHC GR SP	793	1322
ISF BHC GR SP	1310	1379
ISF BHC GR SP	1310	1703
ISF BHC GR SP	1550	2070
ISF BHC GR SP	2063	2432
ISF GR SP	793	1220
LSS GR	426	479
LSS GR	793	1321
LSS GR	1310	2070
MSFL GR CAL	1310	1379
RFT	1308	1336
RFT	1308	1701
RFT	1308	2433
VELOCITY	0	0

Casing and leak–off tests

Casing and leak–off tests
Casing type	Casing diam. [inch]	Casing depth [m]	Hole diam. [inch]	Hole depth [m]	LOT/FIT mud eqv. [g/cm3]	Formation test type
CONDUCTOR	30	423.0	36	470.0	0.00	LOT
SURF.COND.	20	793.0	26	805.0	1.52	LOT
INTERM.	13 5/8	1308.0	17 1/2	1322.0	1.67	LOT
INTERM.	9 5/8	2061.0	12 1/4	2074.0	1.60	LOT
OPEN HOLE		2433.0	8 1/2	2433.0	0.00	LOT

Drilling mud

Drilling mud
Depth MD [m]	Mud weight [g/cm3]	Mud type
793	1.09	waterbased
1308	1.37	waterbased
2080	1.33	waterbased
2433	1.33	waterbased

31/2-1