25/1-7
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General information
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Wellbore history
GeneralWell 25/1-7 was drilled on the main Frigg structure close to the UK border. The Frigg Field was discovered by well 25/1-1 in 1971. Production from the field started in 1977. Well 25/1-7 was designed to monitor the remaining producible gas accumulation in the Frigg Field, and to determine the Frigg Formation heterogeneity north of the producing platforms including the integrity and nature of the barrier between the Frigg sands and the Cod aquifer (Hermod Formation). The main objectives were to observe changes in gas/oil and oil/water contacts as the Frigg Field is produced, and to core the whole Frigg and Balder Formations. The prognosed depth was 2700 m.Operations and resultsAppraisal well 25/1-7 was spudded with the semi-submersible installation Byford Dolphin on 8 March 1985 and drilled to TD at 2719 m in the Late Cretaceous Jorsalfare Formation. Drilling proceeded without significant problems. The well was drilled water based.The Frigg Formation came in at 1919 m, 34 m deeper than prognosed. The Frigg Formation in this well consist of an upper part down to 1977 m with fine grained shale interbedded with sand layers; a massive fine to very fine sand, occasionally micaceous and glauconitic, slightly shaly down to 2044 m; and a basal part consisting of sand and sandstone (calcareous), occasionally micaceous, with shale and silt layers down to 2180 m. The oil/water and gas/oil contacts were in the upper part and were difficult to define from the logs due to the shale. The following contacts were however defined for later reference: base of deepest gas at 1964.5 m (1938.7 m MSL), top of highest oil at 1965.8 m (1940 m MSL), and top of highest water at 1976.5 m (1950.7 m MSL). Residual oil was seen down to 1999.5 m.Twenty-nine cores were cut in the interval 1876 m, (43 m above top Frigg Formation) to 2271 m (lower Balder Formation). Four more cores were cut in the Hermod, Lista, and Jorsalfare formations further down in the hole. Sixty-three good RFT pressure points were acquired over the Frigg, Balder, and Hermod Formations. No wire line fluid samples were taken. From the RFT pressures it was estimated that the gas/oil contact in the well had been lifted ca 7 m above the pre-production gas/oil contact (1972 m) in the area.After setting the 9 5/8" casing at 2187 m the well was logged through casing with a Thermal Neutron Decay (TDT) log from 2127.5 m to 1900 m. This log measures primarily the content of chlorine (salt water) in the formation and the run made at this point will serve as reference for later monitoring of the fluid contacts.The well was suspended on 26 May 1985 as a gas appraisal well. It will be re-entered several times in order to check the hydrocarbon contacts.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]200.002710.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom11876.01879.0[m ]21880.01880.9[m ]31882.01890.0[m ]41891.01897.8[m ]51900.11917.4[m ]61918.01933.5[m ]91939.01947.8[m ]111959.01985.0[m ]121987.02007.0[m ]132007.02033.1[m ]142033.42045.0[m ]152046.52063.0[m ]162064.02065.8[m ]172066.52079.0[m ]182090.02101.9[m ]192103.02116.0[m ]202127.02132.5[m ]212134.02146.0[m ]222150.02165.3[m ]232168.52177.3[m ]242179.52195.0[m ]252195.52202.8[m ]262213.02220.8[m ]272222.02240.2[m ]282241.12246.6[m ]292252.02270.0[m ]302412.02419.0[m ]332710.02719.9[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]330.3Cores 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 typeCONDUCTOR30187.036188.00.00LOTSURF.COND.20846.026863.01.41LOTINTERM.13 3/81856.017 1/21876.01.56LOTINTERM.9 5/82187.012 1/42719.00.00LOTOPEN HOLE2720.08 1/22720.00.00LOT -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL4352127CET13302127CET17502127CST22712701CST22872701DLL MSFL GR18502065HDT18562720HRT13302127HRT13502115ISF LSS GR1882720LDL CNL NGT18502720LDL GR1881872RFT19192685SHDT18562720TDT19002127 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit1267461919218021802185221522902439268027102710 -
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]pdf1.60pdf2.23 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1441.04WATER BASED11.03.19851881.04WATER BASED12.03.19851881.04WATER BASED11.03.19851881.04WATER BASED12.03.19853481.0831.06.0WATER BASED14.03.19857491.0928.010.0WATER BASED17.03.19858631.0927.013.0WATER BASED17.03.19858631.1526.011.5WATER BASED18.03.19858631.1526.011.5WATER BASED18.03.19859401.1130.012.7WATER BASED24.03.198511301.1530.08.3WATER BASED24.03.198512591.1629.016.5WATER BASED25.03.198513591.2032.010.5WATER BASED27.03.198515201.2231.012.0WATER BASED27.03.198516011.2433.011.0WATER BASED29.03.198517471.2635.013.0WATER BASED02.04.198517471.2434.013.0WATER BASED02.04.198517471.2635.013.0WATER BASED02.04.198518701.2637.013.0WATER BASED02.04.198518761.0719.08.0WATER BASED10.04.198518801.0825.010.0WATER BASED10.04.198518871.0827.011.0WATER BASED10.04.198519001.0825.09.0WATER BASED11.04.198519181.0924.08.0WATER BASED11.04.198519381.1024.08.0WATER BASED15.04.198519481.1024.06.0WATER BASED15.04.198519481.1024.06.0WATER BASED15.04.198519481.1024.06.0WATER BASED15.04.198519781.1026.09.0WATER BASED15.04.198520331.1026.08.0WATER BASED19.04.198520641.1126.09.0WATER BASED19.04.198520671.1229.09.0WATER BASED23.04.198520961.1127.09.0WATER BASED23.04.198521221.1129.08.0WATER BASED25.04.198521431.1127.07.0WATER BASED25.04.198521481.1027.07.0WATER BASED29.04.198521501.1130.09.0WATER BASED02.05.198521981.1132.09.0WATER BASED02.05.198522021.1432.010.0WATER BASED21.05.198522021.1332.010.0WATER BASED20.05.198522021.1432.010.0WATER BASED21.05.198522131.1230.08.5WATER BASED03.05.198522301.1232.010.0WATER BASED03.05.198522521.1231.011.0WATER BASED04.05.198522711.1231.010.5WATER BASED04.05.198524121.1237.09.0WATER BASED07.05.198524901.1229.010.5WATER BASED08.05.198525301.1228.010.0WATER BASED09.05.198525841.1234.010.0WATER BASED09.05.198526111.1232.010.0WATER BASED10.05.198526641.1232.010.0WATER BASED13.05.198526901.1230.011.0WATER BASED13.05.198527101.1234.013.0WATER BASED13.05.198527191.1232.011.0WATER BASED15.05.198527191.1232.011.0WATER BASED15.05.198527191.1232.011.0WATER BASED20.05.198527191.1228.011.5WATER BASED14.05.198527191.1232.011.0WATER BASED20.05.1985 -
Thin sections at the Norwegian Offshore Directorate
Thin sections at the Norwegian Offshore Directorate DepthUnit1922.00[m ]1980.00[m ]2080.00[m ]2120.00[m ]2124.00[m ]2167.00[m ]2068.00[m ]2181.00[m ]2181.00[m ]2182.00[m ]2182.00[m ]2190.00[m ]2192.00[m ]2195.00[m ]2199.00[m ]2199.00[m ]2199.00[m ]2200.00[m ]2217.00[m ]2218.00[m ]2223.00[m ]2230.00[m ]2416.00[m ]