26/4-1
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General information
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Wellbore history
GeneralWell 26/4-1 was the first well drilled in the Stord Basin. The well was designed to test a Paleocene mound, and sandstones of Jurassic age within a footwall closure. The Paleocene sandstone was prognosed to come in at 2268 m. Another primary objective was to gain information on reservoir quality and hydrocarbon source. A secondary target was the Sleipner Formation prognosed at 2783 m. Prognosed TD was 3500 m MSL.Operations and resultsWildcat well 26/4-1 was spudded with Wi1h. Wilhelmsen semi-submersible installation Treasure Scout on 8 may 1987 and completed 17 July 1987 at a depth of 3690 m in Triassic Hegre Group. Drilling proceeded without significant problems, except for several occurrences of lost circulation due to increasing formation pressure in Tertiary rocks. The well was drilled with seawater and bentonite down to 236 m, with seawater / bentonite /PAC from 236 m to 723 m, with KCl / Polymer mud from 723 m to 2680 m, and with seawater / polymer from 2680 to TD.The Paleocene Mound (Ty Formation sand) came in at 2246 m. Pressure measurements taken 7 m into the mounds displayed normal pressure conditions, and the sandstone proved to be water bearing. The Jurassic Draupne Formation came in at 2637 m with a total thickness of 88 m. An extremely radioactive layer was found between 2688 and 2693 m. The Sleipner Formation sandstone came in at 2820 m. Top Statfjord Formation came in at 3308 m. Sands in Jurassic (Hugin and Statfjord Formations) displayed a very slow white cut fluorescence and traces of oil on cores, but were otherwise found dry. Post well geochemical analyses revealed very good source rock intervals in the Draupne Formation (oil prone) and the Statfjord Formation (oil and gas prone). Draupne shale and Sleipner coal are immature with Vitrinite reflectance around 0.5 %Ro, while the Statfjord coals may be marginally mature with Vitrinite reflectance around 0.6 %Ro and Tmax approaching 450 °C.Four cores were cut in the intervals: 2253 m to 2265.7 m (Ty Formation), 2270 m to 2297.7 (Ty Formation), 2754 m to 2781.68 m (Hugin Formation), and 3308 m to 3316.85 m (Statfjord Formation). Wire line RFT fluid samples were taken at 2247 m, 2302 m, 2771 m, and 3314.1 m, but none were reported to contain hydrocarbons.The well was plugged and abandoned as a dry hole with weak shows.TestingNo drill stem test was performed -
Cuttings at the Norwegian Offshore Directorate
Cuttings at the Norwegian Offshore Directorate Cuttings available for sampling?NOCuttings at the Norwegian Offshore Directorate Cutting sample, top depth [m]Cutting samples, bottom depth [m]730.003589.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12253.02265.7[m ]22270.02297.7[m ]32754.02781.7[m ]43308.03316.9[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]76.9Cores 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 typeSURF.COND.20711.026873.00.00LOTINTERM.13 3/81675.017 1/21680.00.00LOTINTERM.8 3/82667.012 1/42681.00.00LOTOPEN HOLE3690.08 1/23690.00.00LOT -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]BGL GR7111680CST26723675CST GR16752653CST GR16752663DIS GR BHC16752665DIS GR BHC CBL VDL26683685DIS LSS GR SP7111680LDL CNL GR16801935LDL CNL GR19242663LDL CNL GR26683679MWD LWD2353690RFT27663571RFT GR16832249RFT GR17132406SHDT16752665SHDT26683685VSP7123683 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit1447687921094168217332050205021062142224623222350235025842584262326372637272527532753282028722872309533083665 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.48 -
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]pdf2.44pdf21.70 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1901.228.1WATER BASED17.07.19871900.00WATER BASED20.07.198715321.3553.013.9WATER BASED27.05.198716021.4558.015.4WATER BASED27.05.198716401.5155.013.9WATER BASED27.05.198716801.6254.011.5WATER BASED27.05.198716801.6254.012.5WATER BASED27.05.198716801.6258.013.0WATER BASED27.05.198716831.6248.011.0WATER BASED29.05.198717221.6241.08.6WATER BASED29.05.198719511.6857.011.5WATER BASED01.06.198720481.0750.08.2WATER BASED01.06.198720581.6644.07.7WATER BASED01.06.198720671.6354.010.6WATER BASED03.06.198720771.6372.015.4WATER BASED03.06.198720770.003.013.4WATER BASED05.06.198720771.6312.5WATER BASED04.06.198720821.92WATER BASED10.06.198721081.604.013.0WATER BASED10.06.198721771.9215.4WATER BASED10.06.198722381.584.015.8WATER BASED10.06.198722521.585.017.3WATER BASED10.06.198722531.3513.4WATER BASED11.06.198722701.3011.0WATER BASED12.06.198722941.3013.9WATER BASED15.06.198722941.3013.0WATER BASED15.06.198723701.3013.9WATER BASED15.06.198724481.3047.012.0WATER BASED16.06.198725271.3012.0WATER BASED17.06.198725631.217.7WATER BASED17.07.198726031.3042.010.6WATER BASED18.06.198726801.3041.010.6WATER BASED19.06.198726801.3342.010.6WATER BASED23.06.198726801.3340.010.1WATER BASED24.06.198726801.3341.010.6WATER BASED23.06.198726811.2039.010.1WATER BASED24.06.198727381.2030.07.2WATER BASED25.06.198727811.2037.09.1WATER BASED26.06.198728981.2027.08.2WATER BASED30.06.198730031.2039.08.6WATER BASED30.06.198731061.2036.07.7WATER BASED30.06.198732271.2036.07.7WATER BASED30.06.198732701.2037.08.2WATER BASED01.07.198733081.888.2WATER BASED02.07.198733081.158.2WATER BASED03.07.198733081.1519.080.6WATER BASED06.07.198733201.158.6WATER BASED06.07.198734271.157.7WATER BASED06.07.198735421.1518.0WATER BASED07.07.198736241.178.2WATER BASED13.07.198736671.177.7WATER BASED13.07.198736901.179.1WATER BASED13.07.198736901.208.2WATER BASED13.07.198736901.179.1WATER BASED13.07.198736901.209.1WATER BASED14.07.198736901.219.1WATER BASED14.07.198736901.218.2WATER BASED15.07.1987 -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory1600.0[m]DCBP1640.0[m]DCBP1680.0[m]DCBP1710.0[m]SWCBP1736.0[m]SWCBP1780.0[m]DCBP1820.0[m]DCBP1860.0[m]DCBP1900.0[m]DCBP1940.0[m]DCBP2000.0[m]DCBP2033.0[m]DCBP2047.0[m]SWCBP2051.0[m]DCBP2069.0[m]DCBP2090.0[m]DCBP2102.0[m]SWCBP2105.0[m]DCBP2126.0[m]DCBP2141.0[m]SWCBP2150.0[m]DCBP2189.0[m]DCBP2210.0[m]DCBP2222.0[m]DCBP2243.0[m]DCBP2252.0[m]DCBP2260.8[m]CBP2262.0[m]CBP2640.0[m]DCBP2678.0[m]SWCBP2704.0[m]DCBP2707.0[m]SWCBP2725.0[m]SWCBP2733.0[m]SWCBP2750.0[m]SWCBP2764.6[m]CBP2765.0[m]CBP2785.0[m]DCBP2821.0[m]DCBP2854.0[m]DCBP2878.0[m]DCBP2900.0[m]SWCBP2941.0[m]DCBP2980.0[m]DCBP3019.0[m]DCBP3064.0[m]DCBP3100.0[m]DCBP3150.0[m]SWCBP3190.0[m]DCBP3220.0[m]DCBP3250.0[m]SWCBP3295.0[m]DCBP3311.7[m]CBP3314.6[m]CBP3340.0[m]DCBP3382.0[m]DCBP3424.0[m]DCBP3466.0[m]DCBP3508.0[m]DCBP3550.0[m]DCBP3592.0[m]DCBP3647.0[m]SWCBP3665.0[m]SWCBP3675.0[m]SWCBP3691.0[m]SWCBP