7/12-10
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General information
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Wellbore history
GeneralWell 7/12-10 was drilled a few km north of the Ula Field, on the north-eastern side of the Cod Terrace in the North Sea. The primary objective was to prove a commercial volume of oil in the Late Jurassic Ula formation for tie back to the Ula platform. Secondary reservoir potential existed in both the middle Jurassic and the uppermost part of the Triassic.Operations and resultsWildcat well 7/12-10 was spudded with the semi-submersible installation Ross Isle on 8 July 1991 and drilled to TD at 3667 m in the Triassic Skagerrak Formation. After the 30" conductor was set at 167 m, a 17 1/2" pilot hole was drilled without riser to 950 m. No indications of shallow gas were observed. The well was drilled with seawater and hi-vis slugs down to 948 m, with Ancoquat water based mud from 948 m to 2730 m, and with KCl/polymer mud from 2730 m to TD. The inhibitive Ancoquat mud system was tested for the first time on the Norwegian Continental Shelf in this well.Shows of oil were observed from 3010 m to 3100 m in the Tor limestone. Subsequent intermediate logs however indicated that there was not sufficient quantity of oil to warrant testing the limestone. Top Mandal formation was encountered at 3531 m drilled depth/3538 m logged depth. Top Ula formation was seen at 3620m drilled depth/3627 m logged depth. This was 56 m deeper than prognosed, and the formation was also ca 30 m thinner than expected. The Ula sandstone was found water bearing with no shows and it was not in pressure communication with the main Ula field. Top Triassic was identified at 3641.5 m logged depth. It was water bearing with no shows.Two conventional cores were cut from 3616 m to 3628 m and 3628 m to 3655 m with 100% recovery. Core # 1 covered the lower part of the Lower Carbonaceous member of the Farsund Formation and 7.5 m of the Ula Formation. Core # 2 covered the lowermost 7 m of the Ula formation and 20 m of micaceous sandstone of Triassic age. The core depths were ca 7 m shallower than logged depths. No wire line fluid samples were taken.The well was permanently abandoned on 29 August 1993 as a dry well with shows.TestingNo drill stem test was performed. -
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]960.003667.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom13616.03627.8[m ]23628.03655.0[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]38.8Cores 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 typeCONDUCTOR30167.036168.00.00LOTINTERM.20939.026948.01.75LOTINTERM.13 3/82724.017 1/22730.01.75LOTOPEN HOLE3667.012 1/43667.00.00LOT -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CHECKSHOT19003665CST GR29183673DLL MSFL ASL GR30963669DLL MSFL ASL GR SP27263153DLL MSFL LSS GR SP702730LDL CNL GR28293156LDL CNL NGS36003672RFT GR30133065 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit951930265826582700276328612917293529353000318032823283328432863286333233623385353835383564362736273642 -
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]pdf1.26pdf18.79 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured5501.03water based9501.03water based10641.7534.0water based13661.5537.0water based15011.5542.0water based23001.6011.0water based27241.5743.0water based31511.5529.0water based36671.5727.0water based36671.5537.0water based -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory3532.0[m]DCPETROSTR3535.0[m]DCPETROS3538.0[m]DCPETROS3541.0[m]DCPETROS3544.0[m]DCPETROS3547.0[m]DCPETROS3550.0[m]DCPETROS3556.0[m]DCPETROS3562.0[m]DCPETROS3568.0[m]DCPETROS3574.0[m]DCPETROS3580.0[m]DCPETROS3586.0[m]DCPETROS3592.0[m]DCPETROS3598.0[m]DCPETROS3604.0[m]DCPETROS3610.0[m]DCPETROS3616.0[m]DCPETROS3620.0[m]CPETROS3624.2[m]CPETROS3628.3[m]CPETROS3632.2[m]CPETROS3638.5[m]CPETROS3641.6[m]CPETROS