31/5-3
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General information
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Wellbore history
GeneralWell 31/5-3 was drilled in the southern part of the Troll West Field. The main objectives were to appraise and test the reservoir qualities and the lithology of the Late Jurassic Sognefjord Formation.Operations and resultsWell 31/5-3 was spudded with the semi-submersible installation Treasure Saga on 10 April 1984 and drilled to TD at 2250 m in the Late Jurassic Drake Formation. At 1426 m circulation was lost, and 450 bbls mud was lost to formation before the well was stabilized. The well was drilled with spud mud down to 950 m, with KCl/polymer mud from 950 m to 1497 m, and with a Pro-wate/NaCl-brine/pro-salt mud from 1497 m to TD.The well proved the existence of a stratigraphy ranging from Lower Jurassic to Quarternary. The Tertiary and Quaternary sections were mainly composed of claystones, with a minor sand developed in Pleistocene at the base of the Nordland Group. The Jurassic was composed of sandstone and siltstones in the Viking and Brent Groups, and mainly claystone with an interbedded sandstone layer in the Dunlin Group. One major unconformity was found between Early Portlandian and Maastrichtian. Four other unconformities were also observed in the well, from Aalenian to Bathonian, from Early Kimmeridgian to Early Portlandian, from Late Oligocene to Pliocene, and one intra-Oligocene.The Sognefjord Formation was hydrocarbon bearing with a 39.5 m hydrocarbon column, of which 17.5 m was gas and 22 m was oil. Top reservoir was found at 1555 m, the GOC was at 1572.5 m, and the OWC at 1594.5 m. Oil shows persisted further down, but decreased from 1595 m and disappeared below 1622 m. No other interval in the well was hydrocarbon bearing.Three cores were cut from 1550 m to 1622.5 m in the Late Jurassic Sognefjord Formation. FMT gas samples were taken at 1557 m and 1567. Three more FMT fluid samples were taken in the oil zone at 1577 m, 1591 m, and at 1592 m.The well was permanently abandoned on 9 June 1984 as a gas and oil appraisal well.TestingTwo drill stem tests were performed in the Sognefjord Formation. Both the intervals were gravel packed. DST # 1 from 1606 - 1610 m produced formation water. DST # 2 from 1582.3 - 1586.3 m produced 1100 Sm3/day of oil with a constant GOR of approximately 55Sm3/Sm3. Gas coning occurred as the rate was increased to 1550 m /day. The GOR stabilized at its original value as the rate was reduced to 1050 Sm3 /day -
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]440.002250.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom11550.01568.0[m ]21568.01594.4[m ]31595.01622.0[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]71.4Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
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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 availableDSTDST21582.301586.30OIL02.06.1984 - 19:00YES -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit35378013401340140214771547154715551666171818481905199221032103 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.35 -
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]pdf12.08 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.0160616180.02.01582158644.5Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.0712.0Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.02.01230590400.65048 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CDL CNL GR14971911CDL CNL GR19052244CDL GR425964CDL GR9501506DIFL LSBHC GR425965DIFL LSBHC GR9501512DIFL LSBHC GR14971914DIFL LSBHC GR19052246DIPLOG14921900DIPLOG19052243DLL MLL GR14971912FMT15551663FMT19482168GR327430SPECTRALOG14971906VELOCITY9702230 -
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 typeCONDUCTOR30425.036430.00.00LOTSURF.COND.20950.026963.01.89LOTINTERM.13 3/81497.017 1/21515.01.57LOTINTERM.9 5/81905.012 1/42236.01.73LOTOPEN HOLE2253.08 1/22253.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured4261.03WATER BASED30.04.19844301.03WATER BASED30.04.19844401.08WATER BASED30.04.19847911.14WATER BASED30.04.19848371.16WATER BASED30.04.19849631.2047.025.0WATER BASED30.04.19849631.2047.025.0WATER BASED30.04.19849631.18WATER BASED30.04.19849651.14WATER BASED30.04.198410801.3049.028.0WATER BASED30.04.198411771.2547.024.0WATER BASED30.04.198413951.3049.028.0WATER BASED30.04.198414261.3046.024.0WATER BASED30.04.198415151.3046.023.0WATER BASED30.04.198415151.3046.023.0WATER BASED30.04.198415151.3046.023.0WATER BASED30.04.198415181.1880.060.0WATER BASED30.04.198415681.1878.050.0WATER BASED30.04.198415951.0078.051.0WATER BASED03.05.198416231.1869.045.0WATER BASED03.05.198417301.1877.052.0WATER BASED03.05.198418801.1880.054.0WATER BASED03.05.198419151.1879.056.0WATER BASED03.05.198419151.1878.053.0WATER BASED03.05.198419151.1885.060.0WATER BASED03.05.198419151.1987.058.0WATER BASED04.05.198419151.1975.052.0WATER BASED07.05.198419151.1987.058.0WATER BASED04.05.198419151.1878.053.0WATER BASED03.05.198419151.1885.060.0WATER BASED03.05.198419151.1975.052.0WATER BASED07.05.198422361.2061.042.0WATER BASED07.05.198422501.2061.042.0WATER BASED08.05.198422500.0061.042.0WATER BASED07.06.1984 -
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]pdf0.22