29/6-1
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General information
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Wellbore history
GeneralWell 29/6-1 was drilled ca 2 km west of the UK border on the eastern margin of the East Shetland Basin. The primary objective was the Brent Group in a fault block separate from the Hild structure some few km to the southwest. The secondary objective was the Statfjord formation.Operations and resultsWildcat well 29/6-1 was spudded with the semi-submersible installation SEDCO 707 on and drilled to TD at 4832 m.The well was spudded by "Sedco 707" on 12.10.81. When drilling the 17 1/2" pilot hole (with 1.1 sg mud) in the 24" section, mud losses occurred at 870 m. The hole was displaced to seawater and operations continued down to 1205 m where the 24" casing was set. Further drilling went with increasing mud weights due to tight hole problems, to a point where the overbalance considerably reduced penetration rate. Due to high deviation the pipe became differentially stuck at 4664 m. The well was planned to be vertical, but ended up severely deviated. From 3973 m to 4097 m hole inclination increased from 5 degrees to 10.5 degrees, increasing to 15.5 degrees by 4155 m, as a result of the increased dip of the bedding planes. At 4155 m a pendulum drill assembly was used but the hole inclination continued to increase to 19.5 degrees. By 4211 m the angle had reduced to 17 degrees but again increased to a maximum of 21 degrees by 4457 m, and then decreased to 20.25 degrees by 4570 m. Below this depth, surveys were not possible due to the hole conditions with overpull and stuck pipe on the connections and tight hole on trips. Keyseating, washout in the sandstones and the swelling nature of the clays in the Dunlin formation added to the problem caused by hole angle. At TD Schlumberger HDT log was run and the hole angle had built up to 25.25 degrees, and it was estimated that TVD was 47 m less than MD. The well was drilled with gel/seawater/Drispac down to 294 m, with gel/seawater/Lost circulation material from 294 m to 1205 m, with gypsum/Lignosulphonate/CMC from 1205 m to 2552 m, with Lignosulphonate/CMC from 2552 m to 3783 m, and with Lignosulphonate from 3783 m to TD.The Base Cretaceous Unconformity was penetrated at 3807 m where a thick section of Late Jurassic mudstones including 110 m Draupne Formation was encountered. The Brent Group clastic sediments were reached at 4204.5 m and found to be gas/condensate bearing. The sandstones were highly overpressured and 15 m of net pay was proved. The GWC was estimated at 4230 m (4195.1 m TVD MSL) using RFT data. The Statfjord Formation was water bearing.Methane gas with a weak oil show was observed on sandstone at 1830 m in Paleocene. There were further weak shows (yellow natural fluorescence with colourless cut) in the Shetland Group from 3610 to 3805 m, and there were similar weak shows throughout the Brent Group ("Dull yellow fluorescence becoming very dull orange yellow downhole, fast yellow to milky white cut fluorescence becoming very slow downhole, no natural cut colour"). Similar weak shows were seen also in the Amundsen Formation sands at 4664 to 4729 m and a further 10 m into the underlying Statfjord Formation.Seven cores were taken in the interval 4219 to 4340 m in the 8 3/8" section in the Tarbert and Ness Formations. RFT water samples were taken at 4235.5 m and at 4289.7 m (mud filtrate only).The well was permanently abandoned on 9 May 1982 as a gas/condensate discovery.TestingThree drill stem tests were performed in the Tarbert Formation of the Bren Group. The upper DST produced gas and condensate; the two deeper produced only water.DST 1 perforated the interval 4287 to 4301 m. It consisted of a 5 minutes initial flow period and a 34 minutes initial shut in. The well then flowed formation water with small quantities of gas containing 11% CO2 for 642 minutes before being shut in for 796 minutes. The final flow rate was 192 m3 water/day through a 4/64" choke. Samples were taken both at the wellhead and at the separator throughout the test. Water salinity was 71000 ppm NaCl. The maximum temperature recording taken at gauge depth 4285.66 m was 151.2 deg C.DST 2 perforated the interval 4256 to 4260 m. It consisted of a flow period of 1065 minutes (no hydrocarbons observed) and a build up period of 973 minutes. The final flow rate was 44 m3 water/day through a 4/64" choke. The maximum temperature recording taken at gauge depth 4254,98 m was 150.9 deg C.DST 3 perforated the interval 4208.5 to 4218.3 m in the uppermost Tarbert Formation. It consisted of 5 minutes initial flow followed by a 63 minutes build up and a main flow of gas and condensate (439 minutes). The final flow rate was 305822 Sm3 gas (10.8 MMft3) with 2% CO2. H2S was not detected during the test. The condensate gas ratio was 138 STB/MM ft3 (GOR = 1291 Sm3/Sm3), condensate gravity was 44 deg API, and the separator gas gravity was 0.71 (air = 1). The maximum temperature recording taken at gauge depth 4203.14 m was 152.2 deg C. -
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]290.004818.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom14219.54238.0[m ]24238.04256.0[m ]34256.04274.0[m ]44274.04292.0[m ]54292.04310.0[m ]64310.04328.2[m ]74328.24339.7[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]120.1Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
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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 typeCONDUCTOR30287.036294.00.00LOTSURF.COND.18 5/81183.0241205.01.76LOTINTERM.13 3/82541.017 1/22557.01.85LOTINTERM.9 5/83772.012 1/43783.02.15LOTLINER74375.08 3/84832.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.0428743010.02.0425642600.03.0420842183.2Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.02.03.0Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.02.03.02203000000.8080.7051363 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CALI37754832CBL VDL GR35004338CBL VDL GR35703228CBL VDL GR35704338CBL VDL GR41504280CYBERDIP37754832CYBERLOOK41504457DLL MSFL GR SP CAL41004433FDC CNL GR CAL43004831HDT37754832HRT CCL10981HRT CCL102385ISF BHC GR CAL41004413ISF BHC GR SP1491190ISF BHC GR SP23363778ISF BHC GR SP37754232ISF MSFL BHC GR SP11822550ISF MSFL BHC GR SP CAL43504832LDL CNL GR CAL41404416LDL CNL GR CAL43004830NGT37754830RFT GR37724457RFT GR37724236RFT GR37724832RFT GR37724832V55304832 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit14944786589089096912241249132015201827188118811900192220832320234823482373267836323743377738073807391542054205422144584474448945004500454646074645472947864786 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.76 -
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]pdf12.90PDF4.05PDF3.01PDF3.45PDF7.85PDF6.88PDF19.48PDF2.13PDF1.07pdf6.96PDF1.04PDF2.15PDF0.80PDF6.20 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured4001.0985.0waterbased12001.1040.0waterbased15701.2643.0waterbased21001.3360.0waterbased30001.3846.0waterbased39502.0056.0waterbased44601.9755.0waterbased47501.9460.0waterbased -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory4512.0[m]DCFUGRO4542.0[m]DCFUGRO4572.0[m]DCFUGRO4602.0[m]DCFUGRO4629.0[m]DCFUGRO4659.0[m]DCFUGRO4692.0[m]DCFUGRO4719.0[m]DCFUGRO4728.0[m]DCFUGRO4797.0[m]DCFUGRO -
Thin sections at the Norwegian Offshore Directorate
Thin sections at the Norwegian Offshore Directorate DepthUnit4328.50[m ]4323.10[m ]4317.80[m ]4312.70[m ]4303.20[m ]4299.00[m ]4294.00[m ]4289.20[m ]4281.30[m ]4275.00[m ]4271.00[m ]4259.20[m ]4237.00[m ]4231.90[m ]4228.50[m ]4225.00[m ]4222.08[m ]4219.90[m ]4249.50[m ]4230.00[m ]4257.40[m ]4220.20[m ]42661.90[m ]4261.90[m ]