25/8-21 S
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General information
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Wellbore history
GeneralWell 25/8-21 S was drilled to appraise the Skagerrak Formation Iving oil discovery made in well 25/8-19 S and 25/8-19 A. The Iving discovery is located at the northern part of the Utsira High in the North Sea. The primary objective of the appraisal well was to establish the oil-water contact in the Triassic Skagerrak Formation in Segment 1 of the Iving structure. The well was planned to penetrate 50 m into pre-Permian basement.Operations and resultsAppraisal well 25/8-21 S was spudded with the semi-submersible installation Transocean Barents on 13 May 2021 and drilled to TD at 2703 m (2627 m TVD) m in Basement rock. The well is vertical down to 1000 m, building to a ca 19 sail angle from ca 1450 m to TD. Operations proceeded without significant problems. The well was drilled with seawater and hi-vis pills down to 1040 m and with Innovert oil-based mud from 1040 m to TD.Top Skagerrak Formation/BCU was penetrated at 2390.5 m. The middle Skagerrak Formation contained gas over oil in sandstones of poor to good reservoir quality. The gas/oil and oil/water contacts were derived from pressure gradients to be at 2511.5 m (2445.5 m TVD) and 2534.3 m (2467.4 m TVD), respectively. Pressure data indicates communication in the Skagerrak reservoir between the discovery (25/8-19 S & A) and the appraisal well.Oil was also encountered in the lower part of the Skagerrak Formation with an oil sample at 2633 m (2561 m TVD), and a separate oil column of about 50 metres was encountered in basement rock. The reservoir properties in the Lower Skagerrak and in the Basement was poor and hydrocarbon contacts were not established. Oil shows, mostly discontinuous, were recorded from 2522 m and downwards to 2641 m, the strongest were in the upper part down to 2585 m.Two cores were cut in succession from 2483 to 2593 m in the Skagerrak Formation. Core recoveries were 99.64% and 100% respectively for core 1 and 2. The core-log depth shift is -0.7 m for Core 1 and -1.2 m for core 2. RDT fluid samples were taken at 2507.32 m (gas), 2524.91 m (oil), 2543.94 m (water), 2559.75 m (water), and 2633.24 m (oil).The well was permanently abandoned on 20 June 2021 as an oil and gas appraisal well.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]1060.002703.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12483.02537.8[m ]22538.02593.0[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]109.8Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
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 typeINTERM.30233.236233.20.00INTERM.201032.8261040.01.50FITINTERM.13 5/82004.5162010.01.59LOTLINER9 5/82440.012 1/42441.02.03FITOPEN HOLE2524.08 1/22524.02.33FITOPEN HOLE2703.08 1/22703.00.00FIT -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CSNG GEM XMR22402703HRSCT20102441LWD - GR RES DIR PWD2331040LWD - GR RES DIR PWD DEN NEU CAL24412703LWD - GR RES DIR PWD DN NE SO CA20102441LWD - GR RES DIR SON PWD1671040LWD - GR RES DIR SON PWD10402010RDT DPS20102441RDT DPS EPS SPS25072674VSP17352635XSI HFB16 CAST23682703 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit1681685007087081021106518531870187019532034214421612286228623102391239123912633 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1681.0436.0Oil1681.0436.0Water2171.031.0Water2341.0473.0Water3501.3111.0Oil5681.0436.0Water10401.316.2Oil10401.3023.0Water10431.316.7Oil24101.2215.0Oil24411.1417.0Oil27031.1415.0Oil