25/1-8 S
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General information
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Wellbore history
GeneralThe Frigg Field was discovered by well 25/1-1 in 1971 and set in production in May 1977. Well 25/1-8 S was drilled to monitor changes in gas/fluid contact, uncover permeability barriers and pressure gradients in the Frigg Formation, refine the geological model, and provide ties for seismic interpretations. Before production started the Frigg Field fluid contacts were: OWC = 1955.9 m TVD MSL and GOC = 1948.2 m TVD MSL. Due to the close proximity to the Odin pipeline, the well had to be drilled with a slight deviation. The well was to be entered several times to monitor further changes in the gas/water contact as a response to field production.Operations and resultsAppraisal well 25/1-8 S was spudded with the semi-submersible installation Byford Dolphin on28 May 1985 and drilled to TD at 2650 m (2572 m TVD / 2547 m TVD MSL) in the Paleocene Lista Formation.Top Frigg Formation came in at 1930.2 m (1853 m TVD MSL). The formation was gas-bearing with a water saturation of only 6.1% in the gas zone down to the gas/water contact (GWC) at 1901.5 m TVD MSL. A residual gas zone with 74.9% water saturation was found from 1901.5 m TVD MSL down to 1909.3 m TVD MSL. Within this zone, at 1903.5 m TVD MSL was a thin oil layer, which indicated a fingering effect caused by edge water drive. Otherwise the original oil-leg in Frigg had been all swept by water since production start. A three phase zone (oil+gas+water) with 51.5% water saturation was seen below the gas zone from 1909.3 m TVD MSL down to the original GOC at 1948.2 m TVD MSL, and from 1948.2 TVD MSL down to 1981.1 m TVD MSL there was a zone of residual oil and water with 88.2% water saturation. Below 1981.1 m TVD MSL there was only water in the porosity.A total of 9 cores were cut in the interval between 1939 and 2112 m, covering the whole Frigg gas sand including the fluid contacts. Fifty-six RFT pressure measurements were recorded on three different runs. They proved no pressure barriers throughout the hydrocarbon bearing sands of the Frigg Formation and 10 m into the water zone at 1990 m TVD MSL. The Frigg Formation below this level had 6 pressure barriers based on the RFT data. No wire line fluid samples were taken.The well was suspended on 25 July 1985 for later re-entry and monitoring of the reservoir parameters. It is classified as a gas appraisal wellTestingNo 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]200.002650.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom11939.01948.9[m ]21950.01953.2[m ]31953.21968.3[m ]41971.01996.5[m ]51997.81999.0[m ]62025.02055.0[m ]72055.02082.5[m ]82082.52094.4[m ]92094.42110.5[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]140.4Cores 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 typeCONDUCTOR30187.536190.00.00LOTINTERM.13 3/81015.017 1/21030.01.44LOTINTERM.9 5/81910.012 1/41921.01.69LOTLINER72201.08 1/22650.01.40LOT -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]BGT1871896CBL VDL1201015CBL VDL7481868CBL VDL17412117CET17402120CST00DISFL LSS GR18122644DLL MSFL GR19122150ISF LSS GR1872108LDT CNL19122644LDT GR1871897RFT19302103RFT19302240RFT19412508SHDT19122645TDT19102128VSP WA3002460 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit1277311930223222322237225023292532 -
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]pdf1.57pdf0.83 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1651.07120.0WATER BASED29.05.19851901.07150.0WATER BASED31.05.19852091.04WATER BASED03.06.19855271.0818.019.0WATER BASED03.06.19855941.0719.015.5WATER BASED03.06.19858971.0921.015.5WATER BASED04.06.198510301.1024.017.0WATER BASED04.06.198510301.1526.014.0WATER BASED05.06.198510301.1526.014.0WATER BASED10.06.198510301.1526.014.0WATER BASED05.06.198510301.1526.014.0WATER BASED10.06.198510721.1130.010.5WATER BASED10.06.198512791.1233.012.5WATER BASED13.06.198514511.1412.025.0WATER BASED13.06.198515871.1632.012.0WATER BASED13.06.198517391.1626.010.0WATER BASED13.06.198519081.2023.011.0WATER BASED17.06.198519211.2326.08.0WATER BASED19.06.198519211.2326.08.0WATER BASED28.06.198519211.0615.05.0WATER BASED28.06.198519211.2326.08.0WATER BASED18.06.198519211.0519.05.0WATER BASED02.07.198519211.2326.08.0WATER BASED17.06.198519211.2326.08.0WATER BASED18.06.198519211.2326.08.0WATER BASED19.06.198519211.2326.08.0WATER BASED28.06.198519211.0615.05.0WATER BASED28.06.198519211.0519.05.0WATER BASED02.07.198519251.0417.05.0WATER BASED02.07.198519271.0518.05.0WATER BASED03.07.198519291.0627.09.5WATER BASED04.07.198519501.0724.08.5WATER BASED04.07.198519701.0824.08.0WATER BASED08.07.198520531.0827.07.5WATER BASED08.07.198520991.1028.08.0WATER BASED08.07.198521121.1023.06.5WATER BASED08.07.198521921.1024.08.5WATER BASED09.07.198524191.1022.08.0WATER BASED11.07.198525911.1028.07.0WATER BASED11.07.198526501.1330.09.0WATER BASED14.07.198526501.1352.010.0WATER BASED16.07.198526501.1352.010.0WATER BASED16.07.1985 -
Thin sections at the Norwegian Offshore Directorate
Thin sections at the Norwegian Offshore Directorate DepthUnit1948.00[m ]