34/10-33
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General information
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Wellbore history
GeneralWell 34/10-33 was the sixth well drilled to reservoir level on the Gullfaks South structure. The main objective of the well was to appraise the oil and gas reserves in the Brent Group on the northern part of the structure. The gas/oil and oil/water contacts were to be confirmed at 3324 m and 3395 m MSL respectively. Secondary objective was to penetrate 50 m of the Statfjord Formation to obtain data to better understand the structural development in the area, and also update the geological model for the upper part of the formation. A positive result would lead to the drilling of a horizontal testing well as a sidetrack from this well.Operations and resultsWell was spudded with the semi-submersible installation West Delta on 25 September 1988 and drilled to TD at 3870 m in the Early Jurassic Statfjord Formation. There was some shallow gas at 477 - 478 m. Due to this the 20" casing was set at 450 m. There was a problem with a leakage in the BOP. The drill string got stuck when setting the 13 3/8" casing and the MWD and drill bit had to be changed. The well was close to vertical down to ca 2500 m. From there the well built inclination gradually up to 20 deg at TD. At TD true vertical depth is estimated to be ca 20 m less than measured depth. The well was drilled with spud mud down to 483 m, with gypsum/polymer mud from 483 m to 3161 m, and with gel/lignosulphonate/lignite mud from 3161 m to TD.Top Brent Group, Tarbert Formation came in at 3186 m with gas and oil. FMT data showed a gas/oil contact at 3268 m, 85 m higher than prognosed. Approximately 150 m of oil was found vertically down to top Dunlin Group at 3424 m, much more than expected. No oil/water contact was seen. There was a pressure shift of 1.5 - 2 bar at around 3350 m, indicating two separate compartments in the oil zone. This had not been observed in the previous wells on Gullfaks South. Due to the large amount of oil in the Brent Group, the oil in place estimate was adjusted to 50 - 60 million Sm3.Eighteen cores were cut in the well. One core was cut from 3152 to 3161.5 m, 14 cores in the interval 3188 to 3435 m and 3 cores from 3799 to 3840 m. The core depth was found to be from 1.00 to 3.75 m less than loggers' depth. Segregated fluid samples were obtained at 3314 m in the Ness Formation and at 3368 m in the thin Etive Formation. Sampling was attempted also at 3406 and 3406.2 m in the Rannoch Formation, but due to very low permeability no formation fluid was obtained.The well was plugged back and classified as an oil and gas appraisal well. West Delta started the sidetrack 34/10-33A 15.12.88 at 18.30 hrs.TestingFour DST tests were performed in this well.DST 1.1 tested the interval 3378 - 3394 m in the Rannoch Formation and produced 289 Sm3 oil and 51000 Sm3 gas /day through a 12.7 mm choke in the main flow. The GOR was 176, the oil density was 0.859 g/cm3, and the gas gravity was 0.680 (air = 1).DST 1.2 tested the combined intervals 3378 - 3394 m in the Rannoch Formation plus 3359 - 3374 m in the Ness/Etive Formations and produced 1318 Sm3 oil and 211900 Sm3 gas /day through a 28.6 mm choke in the final flow. The GOR was 161, the oil density was 0.856 g/cm3, and the gas gravity was 0.685 (air = 1). The reservoir temperature measured in the test was ca 123 deg C at reference depth 3373 m.DST 2.1 tested the interval 3279 - 3307 m in the Ness Formation and produced 850 Sm3 oil and 376700 Sm3 gas /day through a 19.1 mm choke in the main flow. The GOR was 443, the oil density was 0.850 g/cm3, and the gas gravity was 0.665 (air = 1).DST 2.2 tested the combined intervals 3279 - 3307 m and 3311.5 - 3329 m, both within the Ness Formation, and produced 1403 Sm3 oil and 302100 Sm3 gas /day through a 19.1 mm choke in the main flow. The GOR was 215, the oil density was 0.851 g/cm3, and the gas gravity was 0.660 (air = 1). The reservoir temperature measured in the test was ca 122 deg C at reference depth 3301.5 m. -
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]480.003668.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom23188.03197.0[m ]33199.03218.7[m ]43223.03234.7[m ]53235.03250.9[m ]63251.03271.0[m ]73273.53283.2[m ]83285.53298.0[m ]93289.53307.6[m ]103308.03336.0[m ]113336.03348.9[m ]123349.53373.0[m ]133373.03382.5[m ]143382.53410.3[m ]153410.53434.9[m ]163799.03815.7[m ]173815.53825.9[m ]183830.03840.0[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]279.7Cores 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 typeLaboratory3147.5[m]DCGEOCH3152.0[m]CGEOCH3152.5[m]CGEOCH3152.9[m]CGEOCH3153.4[m]CGEOCH3153.8[m]CGEOCH3154.0[m]CGEOCH3154.5[m]CGEOCH3155.6[m]CGEOCH3156.0[m]CGEOCH3156.5[m]CGEOCH3157.0[m]CGEOCH3158.5[m]CGEOCH3159.0[m]CGEOCH3159.5[m]CGEOCH3160.0[m]CGEOCH3161.2[m]CGEOCH -
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 availableDSTTEST1,13378.003394.0029.11.1988 - 00:00YESDSTTEST20.000.0008.12.1988 - 09:00YESDSTTEST2,13279.003307.00OIL08.12.1988 - 07:31YES -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit1639159569801035114512531520156816161827182719072055205523503014301430283028305731863186323433653374342434243514362936763799 -
Geochemical information
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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]pdf3.19pdf47.33pdf40.30 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.03378339412.71.33359337428.62.13279330719.12.23279332919.1Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.021.0001.330.0001232.132.0002.243.500122Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.0288510000.8540.6801761.313182119000.8560.6801612.18503767000.8500.6654432.214033021000.8500.660218 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]AC WAVETRAIN28313432ACDIP GR MISRUN00CBL VDL GR1631829CBL VDL GR24103146CBL VDL GR29943771CDL CN GR37713871CDL GR CAL2253150DIFL ACL GR2253150DIFL ACL GR37713871DIFL CDL CN SL31463768DIPS GR28503870DLL MLL ACL GR31463772FMT GR31883414FMT GR31883406FMT GR33683517FMT GR34063406MWD - SN GR2313152MWD - SN GR31613186MWD - SN GR34353776VESLOCITY8003770 -
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 typeCONDUCTOR30225.036226.00.00LOTSURF.COND.20459.026466.01.43LOTINTERM.13 3/81828.017 1/21844.01.53LOTINTERM.9 5/83148.012 1/43161.01.99LOTLINER73769.08 1/23776.01.96LOTOPEN HOLE3870.063870.00.00 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured4701.1012.03.0WATER BASED06.10.19885921.1012.03.0WATER BASED07.10.198821531.2518.53.5WATER BASED14.10.198823221.2515.03.0WATER BASED17.10.198825901.2518.03.8WATER BASED17.10.198827091.2517.05.5WATER BASED17.10.198829311.2816.04.8WATER BASED18.10.198830141.3418.06.2WATER BASED19.10.198831111.4023.08.6WATER BASED20.10.198831611.4521.06.0WATER BASED24.10.198831611.4518.05.5WATER BASED24.10.198831741.4521.06.0WATER BASED26.10.198831991.4520.04.5WATER BASED26.10.198832231.4921.06.0WATER BASED27.10.198832511.4921.06.0WATER BASED01.11.198832801.4923.07.0WATER BASED01.11.198832861.5321.06.5WATER BASED01.11.198832931.5324.06.0WATER BASED01.11.198833291.5324.07.0WATER BASED02.11.198833501.5324.06.5WATER BASED02.11.198833771.5322.06.0WATER BASED03.11.198834111.5320.06.0WATER BASED04.11.198836021.5375.08.0WATER BASED07.11.198836191.5021.04.0WATER BASED29.11.198837631.4919.05.0WATER BASED21.11.198837651.5023.08.5WATER BASED11.11.198837661.5017.06.5WATER BASED14.11.198837761.5019.08.5WATER BASED14.11.198837761.5019.09.0WATER BASED14.11.198837761.5019.06.5WATER BASED15.11.198837761.5017.06.0WATER BASED17.11.198837761.5021.06.0WATER BASED21.11.198837761.5026.09.0WATER BASED17.11.198837931.4022.06.5WATER BASED21.11.198838151.4023.06.5WATER BASED22.11.198838311.4019.05.0WATER BASED25.11.198838701.4022.05.5WATER BASED25.11.1988 -
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