7/8-4
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General information
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Wellbore history
GeneralWildcat well 7/8-4 was drilled on the northern flank of the Central Graben. The prospect was a structural/stratigraphic trap situated on the north flank of a high standing Triassic fault block. The objective was to test the hydrocarbon potential of a prognosed Late Jurassic sand body at 3840 m. Isolated sands within the Triassic were also postulated as hydrocarbon traps and potential secondary targets.Operations and resultsWell 7/8-4 was spudded with the semi-submersible installation Nortrym on 11 December 1984 and drilled to TD at 4400 m in Early Triassic sandstones and shales of the Smith Bank Formation. The overall operation took 72 days from spud. Problems with gumbo and keeping the hole clean were experienced. A weighted KCl polymer mud was used to keep the hole open and prevent shale spalling. From 4192 m onwards, problems of tight hole was experienced with the drill string becoming permanently stuck at 4400 m. Differential sticking was thought to be the problems, so the mud weight was reduced to compensate for this. While attempting to free the pipe the well started to flow but this was quickly stopped by raising the mud weight. While pulling out of the hole the drill pipe got stuck with the bit at 4382 m. The pipe was unscrewed at 4250 m and during fishing operations two more sections of pipe were lost in the hole, one with the top at 4192 m, the other at 4183 m. The operator then decided on a sidetrack, and the hole was cemented back to 4130 m and a sidetrack was kicked off from 4140 m. Eleven days were lost due to the plug back and sidetrack operation. The well was drilled with seawater down to 619 m and with KCl polymer mud from 619 m to TD.Two cores were cut from 3825.5 m to 3859 m in what was believed to be the Ula sandstone of the Late Jurassic, the primary objective. Subsequent analysis revealed the Lower Cretaceous to unconformably overlie Middle Triassic formations with no Jurassic rocks present at this location. Hence, the cored section was in the upper Smith Bank Formation. No hydrocarbon indications were registered in the well. No pressure or fluid samples were taken on wire line.The well was permanently abandoned on 20 February 1985 as a dry 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]200.004397.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom13825.03831.3[m ]23831.53859.0[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]33.8Cores 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 typeCONDUCTOR30204.036205.00.00LOTSURF.COND.20607.026619.01.67LOTINTERM.13 3/81946.017 1/21970.01.93LOTINTERM.9 5/83796.012 1/43808.02.23LOTOPEN HOLE4400.08 1/24400.00.00LOT -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CST37994014ISF LSS GR MSFL SP203613ISF LSS GR MSFL SP LDT CNL GR6061957ISF LSS MSFL GR CAL LDT CNL GR C19463813ISF LSS MSFL LDT CNL SHDT GR37954405MWD GR RES DIR6494397TEMPERATURE1073694TEMPERATURE1071917VSP2504400 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit107145029552955298930403099312531253187352936293705372837283817381738263826 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.98 -
Geochemical information
Geochemical information Document nameDocument formatDocument size [MB]pdf1.88 -
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]pdf7.74 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1751.07WATER BASED11.12.19842051.07WATER BASED12.12.19846191.13WATER BASED17.12.19846190.0017.0105.3WATER BASED15.12.19846191.0917.0105.3WATER BASED16.12.19848301.1920.0114.7WATER BASED19.12.19848301.1920.0114.7WATER BASED18.12.198412411.3925.0114.7WATER BASED20.12.198415341.5027.0100.5WATER BASED20.12.198416941.5030.095.8WATER BASED26.12.198419151.5032.0301.6WATER BASED26.12.198419631.5723.0110.1WATER BASED27.12.198419631.6127.095.8WATER BASED27.12.198419631.6127.095.8WATER BASED27.12.198419701.6023.095.8WATER BASED14.12.198421191.5428.081.4WATER BASED14.12.198421941.4830.086.2WATER BASED14.12.198422931.4830.095.8WATER BASED14.12.198423541.4834.0105.3WATER BASED14.12.198425921.4829.091.0WATER BASED15.12.198426421.4833.0105.3WATER BASED30.12.198429191.4824.095.8WATER BASED25.12.198429941.4822.0110.1WATER BASED25.12.198431051.4821.0100.5WATER BASED25.12.198431281.4726.0134.1WATER BASED02.01.198531961.4826.0110.1WATER BASED04.01.198532541.4824.0129.2WATER BASED07.01.198533421.4825.0110.1WATER BASED14.01.198534241.4822.0119.7WATER BASED14.01.198534381.4823.0100.0WATER BASED14.01.198534531.4822.0129.3WATER BASED14.01.198535591.4825.0119.7WATER BASED15.01.198535711.4427.0110.1WATER BASED16.01.198536171.5427.0119.7WATER BASED17.01.198536601.5427.0119.7WATER BASED17.01.198536841.5425.0124.5WATER BASED21.01.198537831.7153.081.0WATER BASED16.02.198538081.5436.0134.0WATER BASED24.01.198538261.7438.0143.6WATER BASED28.01.198538571.7433.0114.9WATER BASED28.01.198538591.7434.0124.5WATER BASED27.01.198539111.7426.0148.4WATER BASED29.01.198539431.7438.0114.9WATER BASED30.01.198540921.74360.0110.1WATER BASED31.01.198540921.7436.0110.1WATER BASED31.01.198540921.74360.0110.1WATER BASED31.01.198541301.7233.072.0WATER BASED10.02.198541401.7132.071.8WATER BASED11.02.198541921.7431.0100.5WATER BASED31.01.198541921.6930.0110.1WATER BASED31.01.198541921.7431.0100.5WATER BASED31.01.198541921.6930.0110.1WATER BASED31.01.198543471.6831.081.4WATER BASED31.01.198544001.6728.067.0WATER BASED02.02.198544001.6928.057.4WATER BASED06.02.198544001.7131.062.0WATER BASED07.02.198544001.6928.057.4WATER BASED06.02.198544001.6628.048.0WATER BASED05.02.198544001.7131.062.0WATER BASED07.02.198544001.7138.086.2WATER BASED16.02.198544001.6628.048.0WATER BASED05.02.1985 -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory3701.0[m]DCOD3710.0[m]DCOD3719.0[m]DCOD3728.0[m]DCOD3740.0[m]DCOD3749.0[m]DCOD3758.0[m]DCOD3770.0[m]DCOD3806.0[m]DCOD3809.0[m]DCOD3812.0[m]DCOD3815.0[m]DCOD3818.0[m]DCOD3821.0[m]DCOD3827.0[m]COD3828.1[m]COD3829.5[m]COD3830.1[m]COD3832.4[m]COD3854.9[m]COD