25/8-20 S
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General information
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Wellbore history
GeneralWell 25/8-20 S Prince with side-track 25/8-20 B King is a dual branch exploration well that tested several independent targets. The well is situated north of the Balder Field on the Utsira High in the North Sea. The primary well 25/8-20 S Prince targeted Jurassic and Triassic sandstones as primary objectives and the Paleogene Hermod sandstone as secondary objective.Operations and resultsPrior to the main hole an 8 1/2" pilot hole 25/8-20-U-26 was spudded on 11 April 2021 to check for shallow hazards. The Pilot was drilled to 1107 m without encountering shallow gas or other hazards.Wildcat well 25/8-20 S was spudded with the semi-submersible installation Scarabeo 8 on 15 April 2021 and drilled to TD at 2733 m (2408 m TVD) m in the Late Triassic Skagerrak Formation. The well was drilled vertical down to ca 1020 m and deviated from there to TD with a deviation mostly between 25 and 45 . Operations proceeded without significant problems. The well was drilled with seawater and hi-vis pills down to 243 m, with a KCl Polymer mud from 243 m to 1103 m, and with Rheguard Prime oil-based mud from 1103 m to TD.The Early Jurassic Statfjord Group was penetrated at 2313 m (2053.5 m TVD), directly underlying the Early Cretaceous Cromer Knoll Group. The Statfjord was water wet, but with good reservoir sands in the lower part. Oil was discovered in the Skagerrak Formation. Gross thickness was 105 m with NTG of 0.34 and averaged porosity PHIT of 19%. Oil bearing sands constitute net thickness of 6.4 m. The oil-water contact was indicated by logs and pressure points to be between 2642 m and 2659 m (2325 m and 2341 m TVD). Secondary target Hermod was water bearing having gross thickness of 55.5 m, NTG of 0.96 and averaged PHIT of 34.6%.The only oil shows described in the well was a weak hydrocarbon odour from the core in the Skagerrak Formation.A 52.12 m core was cut in Skagerrak Formation from 2644 to 2698 m representing 96.5% recovery. MDT fluid samples were taken in the lower Statfjord Group at 2421.5 m (water), and in the Skagerrak Formation at 2614.48 m (filtrate and oil) and 2640.31 (oil)The well was plugged back for side-tracking and permanently abandoned on 10 May 2021 as an oil discovery.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]250.002733.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12644.02696.1[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]52.1Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit163163533737737100411971226190219021988202320962141224922592303231325042504 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]AIT PEX GPIT PPC MSIP JAR10941586LWD - ARC TELE2431860LWD - PDGR ECO TELE ST SON18602733LWD - TELE162243MDT CMR JAR20282733VSI-42812590 -
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 typeCONDUCTOR30235.036243.00.00INTERM.13 3/81094.017 1/21103.01.75FITLINER9 5/81854.012 1/41860.01.70FITOPEN HOLE2733.08 1/22733.00.00 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured2171.0528.016.6Prime2361.2014.012.1KC5281.03Prime8131.209.07.9Prime11031.3911.014.1Prime17051.4025.05.5Prime17911.4223.07.5Prime24811.3519.04.2Prime26441.3723.03.7Prime27331.4023.05.1Prime