7121/7-2
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General information
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Wellbore history
GeneralWell 7121/7-2 was drilled on the Beta structure on Tromsøflaket, 3.4 km south of well 7121/7-1. It was designed to test the hydrocarbon potential in Middle to Lower Jurassic sandstones. Planned total depth was in rocks of Triassic age.Operations and resultsWildcat well 7121/7-2 was spudded with the semi-submersible installation Ross Isle on 7 July 1986 and drilled to TD at 2156 m in the Late Triassic Fruholmen Formation. At 871 m in the 17 1/2" section the string parted and 9.5 hours was spent fishing to retrieve the lost equipment. At 1698 m, TD in the 17 1/2" section a H2S alarm occurred with 28 ppm H2S in the mud gas. The problem was cured by placing spud mud with a concentration of 15 kg/m3 of ZnCO3 behind 13-3/8" casing to prevent H2S growing in mud. The well was drilled with spud mud down to 667 m and with polymer/"Shale-Trol" mud from 667 m to TD. The well acted as a pilot well for testing this mud on Tromsøflaket. The main reason for using this mud system was that it was expected to stable the hole through sections that from previous experience had proven to cause tight-hole problems. The mud performed better than the ordinary gypsum/polymer mud previously used in the area, but total costs were higher and it was thus not considered a success.Hydrocarbon bearing Middle Jurassic sandstones (Stø Formation) were encountered at 1881.5 m. The gas/water contact in this well was recognized at 1914.4 m, ca 12 m deeper than in the 7120/9-1 Albatross Discovery. The gas zone, 1881.5 m to 1914.4 m, consists of an interbedded silt, shale and very fine sandstone sequence with good reservoir properties. Two cores were cut in the Stø Formation over the interval 1903 m to 1939 m, (1889 m to 1935 m, loggers depth). Three FMT samples were collected, one at 1884.5 m and two at 1899 m.The well was permanently abandoned as a gas discovery on 12 August 1986.TestingThe interval 1881.8 m to 1889.9 m was perforated and production tested. The test produced on average 527000 Sm3 gas and 28 Sm3 condensate pr day through a 15. 8 mm choke during the main flow. This gives a GOR of ca 18800 Sm3/Sm3. The CO2 content was 8 %. No H2S was detected. -
Cuttings at the Norwegian Offshore Directorate
Cuttings at the Norwegian Offshore Directorate Cuttings available for sampling?YESCuttings at the Norwegian Offshore Directorate Cutting sample, top depth [m]Cutting samples, bottom depth [m]430.002160.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom11903.01927.2[m ]21928.51939.5[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]35.2Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
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Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory909.0[m]SWCGEAR925.0[m]SWCGEAR926.5[m]SWCGEAR1007.0[m]SWCGEAR1034.0[m]SWCGEAR1091.0[m]SWCGEAR1149.2[m]SWCGEAR1176.0[m]SWCGEAR1291.0[m]SWCGEAR1349.5[m]SWCGEAR1379.5[m]SWCGEAR1405.0[m]SWCGEAR1433.0[m]SWCGEAR1461.0[m]SWCGEAR1519.0[m]SWCGEAR1550.0[m]SWCGEAR1556.0[m]SWCGEAR1615.9[m]SWCGEAR1722.5[m]SWCGEAR1729.0[m]SWCGEAR1732.0[m]SWCGEAR1807.0[m]SWCGEAR1812.0[m]SWCGEAR1817.0[m]SWCGEAR1824.0[m]SWCGEAR1831.0[m]SWCGEAR1841.0[m]SWCGEAR1848.0[m]SWCGEAR1858.0[m]SWCGEAR1862.0[m]SWCGEAR1868.0[m]SWCGEAR1877.0[m]SWCGEAR1895.8[m]SWCGEAR1911.0[m]SWCGEAR1914.2[m]SWCGEAR1915.6[m]SWCGEAR1918.8[m]SWCGEAR1921.5[m]SWCGEAR1924.6[m]SWCGEAR1929.3[m]SWCGEAR1932.7[m]SWCGEAR1934.4[m]SWCGEAR1991.0[m]SWCGEAR1999.0[m]SWCGEAR2048.0[m]SWCGEAR2062.0[m]SWCGEAR2087.0[m]SWCGEAR2110.5[m]SWCGEAR2114.0[m]SWCGEAR2119.0[m]SWCGEAR2124.0[m]SWCGEAR2143.0[m]SWCGEAR2149.0[m]SWCGEAR -
Oil samples at the Norwegian Offshore Directorate
Oil samples at the Norwegian Offshore Directorate Test typeBottle numberTop depth
MD [m]Bottom depth
MD [m]Fluid typeTest timeSamples availableDSTDST12180.002153.0007.08.1986 - 00:00YESFMT0.001899.0001.08.1986 - 00:00YESMDT0.000.00YES -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit347430430889889923923157817281806188018821882193820282073 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.18 -
Geochemical information
Geochemical information Document nameDocument formatDocument size [MB]pdf0.26 -
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 nameDocument formatDocument size [MB]pdf17.56 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.01882189915.9Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.014.000Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.0285270000.7750.78018800 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]ACBL VDL3451677ACBL VDL12641400ACBL VDL16711925CDL DNL GR CAL16772154COREGUN8751615COREGUN17122150DIFL BHC AC CDL GR SP CAL6541628DIFL BHC AC GR SP CAL345675DIFL BHC AC GR SP CAL16002155DLL MLL GR18702004FMT18822068FMT18991899FMT18991899HR DIP16772154MWD - GR RES428674RLL - GR RES16802028VSP4052140 -
Casing and leak–off tests
Casing and leak–off tests Casing typeCasing diam.
[inch]Casing depth
[m]Hole diam.
[inch]Hole depth
[m]LOT/FIT mud eqv.
[g/cm3]Formation test typeCONDUCTOR30422.036426.00.00LOTSURF.COND.20654.026675.01.74LOTINTERM.13 3/81680.017 1/21698.01.53LOTINTERM.9 5/82156.012 1/42156.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured4251.08WATER BASED6781.101100.0WATER BASED7951.111500.0WATER BASED12961.1421.0WATER BASED16801.202000.0WATER BASED18501.261500.0WATER BASED19391.251800.0WATER BASED21141.261800.0WATER BASED21561.251800.0WATER BASED -
Pressure plots
Pressure plots The pore pressure data is sourced from well logs if no other source is specified. In some wells where pore pressure logs do not exist, information from Drill stem tests and kicks have been used. The data has been reported to the NPD, and further processed and quality controlled by IHS Markit.Pressure plots Document nameDocument formatDocument size [MB]pdf0.25