7/8-3
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General information
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Wellbore history
GeneralWell 7/8-3 is located in the North Sea, north of the Mime field on the margin of the Cod Terrace. The primary objective of 7/8-3 was to explore the hydrocarbon potential of the Late Jurassic sandstones. Secondary objectives were to explore the Cretaceous Chalk and the Triassic sandstones. Planned TD was at 4275 m in Permian salt.Operations and resultsWildcat well 7/8-3 was spudded with the semi-submersible installation Borgny Dolphin on 12 September 1983 and drilled to TD at 4320 m in the Late Permian Zechstein Group. While running 13 3/8" casing this got stuck and had to be pulled out of the hole. The hole was cleaned and new casing was set without further complications. Otherwise no significant problems were encountered during drilling. The well was drilled with spud mud down to 199 m and with KCl polymer mud from 199 m to TD.The Cretaceous Chalk was encountered at a depth of 3024 m, the Late Jurassic Ula Formation at 3724 m, and the Triassic at 3767 m. The Ula Formation sandstones were hydrocarbon bearing within a 43.5 m gross sand interval. No oil/water contact was encountered. Oil shows were recorded in shales and porous sections from 3699 m to 3751 m.Four cores were cut in the interval 3731 m to 3773 m, three in the Upper Jurassic Ula Formation and one into Upper Triassic sandstones. A RFT fluid sample from the Triassic section at 4049.5 m recovered only mud filtrate.The well was permanently abandoned on 12 December 1983 as an oil discovery.TestingTwo DST's were performed in the Ula Formation sandstones: DST 1 from interval 3762 m to 3767 m, and DST 2 from interval 3734.5 m to 3740.5 m. The first produced oil at a slightly declining rate during the final 5-hours flow period, the average rate being 207 Sm3/day through a 2" choke. The GOR was 32 Sm3/Sm3, API oil gravity was 29 deg, and gas gravity was 0.88 (air = 1). The second DST produced 70 Sm3 oil/day through a 2" choke. API oil gravity was 29 deg . Gas was also produced, but the rate was not obtainable. Reservoir temperatures based on the DST measurements were 156 deg C in DST 1 and 154 deg C in DST 2. -
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]210.004321.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom13731.03739.5[m ]23739.83741.5[m ]33741.73760.1[m ]43760.13768.2[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]36.7Cores 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 availableDSTDST13762.003767.0002.12.1983 - 00:00YESDSTDST23734.503740.5005.12.1983 - 00:00YES -
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 typeCONDUCTOR30199.036199.00.00LOTSURF.COND.20610.026622.01.88LOTINTERM.13 3/81981.017 1/21995.01.65LOTINTERM.9 5/83554.012 1/43561.02.03LOTLINER73827.08 1/24320.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.03762376750.02.03734374150.0Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.02.0Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.02070.8820.880322.0700.882 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL GR33503801CST25173550CST36394236CYBERLOOK37004240DLL GR35584257DLWD6453719DUALDIP20004262ILD LSS GR19844261ISF LSS MSFL GR1994261LDL CNL GR6103566LDL CNL NGL GR35584262RFT37244170SHDT ARROW19754250SHDT CYBERDIP35584262SHDT GEO19844262SHDT GR19844262TEMPERATURE109980WST2054250 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit1061334271727172753277828312858285830243275336133673393339336393639367537243724376737674237 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.91 -
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]pdf9.77pdf7.95pdf1.97pdf1.42pdf0.45pdf0.42pdf3.64pdf0.25pdf2.47pdf0.68pdf0.55pdf0.72pdf2.66 -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory3586.0[m]DC3592.0[m]DC3601.0[m]DC3610.0[m]DC3619.0[m]DC3628.0[m]DC3637.0[m]DC3640.0[m]DC3649.0[m]DC3658.0[m]DC3667.0[m]DC3676.0[m]DC3685.0[m]DC3691.0[m]DCHALIB3694.0[m]DC3703.0[m]DC3706.0[m]DCHALIB3721.0[m]DCHALIB3730.0[m]DCPETROSTR3731.0[m]DCHALIB3735.1[m]CPETROSTR3736.2[m]CHALIB3738.4[m]CPETROSTR3742.2[m]CPETROS3745.3[m]CHALIB3746.9[m]CPETROSTR3748.0[m]CHALIB3750.9[m]CPETROSTR3753.6[m]CHALIB3754.8[m]CPETROSTR3758.3[m]CHALIB3758.9[m]CPETROSTR3760.0[m]DCPETROS3767.0[m]DCPETROS3775.0[m]DCPETROS3817.0[m]DCSAGA3829.0[m]DCSAGA3841.0[m]DCSAGA3856.0[m]DCSAGA3868.0[m]DCSAGA3880.0[m]DCSAGA3892.0[m]DCSAGA3904.0[m]DCSAGA3916.0[m]DCSAGA3931.0[m]DCSAGA3943.0[m]DCSAGA3955.0[m]DCSAGA3967.0[m]DCSAGA3979.0[m]DCSAGA3991.0[m]DCSAGA4003.0[m]DCSAGA4024.0[m]DCSAGA4042.0[m]DCSAGA4069.0[m]DCSAGA4099.0[m]DCSAGA4126.0[m]DCSAGA4153.0[m]DCSAGA4180.0[m]DCSAGA4210.0[m]DCSAGA4237.0[m]DCSAGA4243.0[m]DCSAGA4255.0[m]DCSAGA4267.0[m]DCSAGA4276.0[m]DCSAGA4291.0[m]DCSAGA4306.0[m]DCSAGA4315.0[m]DCSAGA4321.0[m]DCSAGA