2/4-21
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General information
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Wellbore history
GeneralWell 2/4-21 was drilled on the King Lear prospect in the Central Graben of the Norwegian North Sea, approximately 20 km north of the Ekofisk Field. The prospect was considered a part of the same reservoir as in the 2/4-14 well that ultimately ended up in a major underground blowout in 1989. The main objective of the well was to prove commercial hydrocarbons in intra-Farsund Formation sandstone units.Operations and resultsWell 2/4-21 was spudded with the jack-up installation Mærsk Gallant on 19 Jan.2012 and drilled to TD at 5395 m in the Late Jurassic Farsund Formation. No over-pressured shallow gas was seen, but a 2-3 m thick sand at 627 m contained normal-pressured gas with a composition consistent with a biogenic origin. The well was planned as an HPHT well with pressure prognosis based on results from the 2/4-18 well. Pressures proved to be even higher than prognosed and at 5029 m influx of gas occurred. The well was shut in and after several days control operations the mud was weighted up to 2.1 g/cm3 and drilling continued to TD. Well 2/4-21 was plugged back after having reached TD. All data acquisition was carried out in the main track, but it was decided to drill a parallel vertical sidetrack (2/4-21 T2) for the purpose of achieving good cores from the main reservoir level (the Farsund II sandstone). The sidetrack was kicked off successfully at 4933m and the operations were carried out according to plan. The well was drilled with sea water/spud mud down to 248 m, with spud mud/KCl/Polymer mud from 248 to 453 m, with KCl/polymer/GEM mud from 453 to 1019 m, with oil based XP07-low ECD mud from 1019 m to 3022 m, and with oil based XP07-HPHT mud from 3022 m to TD. Oil based XP07-HPHT mud was used also in the coring side track.Top Mandal Formation was encountered at 4767 m and top Farsund Formation at 4795 m. A main Intra Farsund Formation sandstone was penetrated as prognosed from 5122 to 5173 m. This interval had 23 m good quality reservoir sand with 21% porosity and 13 mD permeability. It contained rich gas-condensate in a gas-down-to situation. The pressure survey indicated pressure depletion compared to thin sandstones above and below the main reservoir due to the underground blow-out in well 2/4-14. Prognosed sandstone units below this level proved to be thin cemented sandstone and limestone stringers. No fluorescent shows are described from the cuttings in the Farsund II unit / main reservoir. Descriptions from the sidewall cores indicate oil stain and hydrocarbon odour on samples as shallow as 4996 m and tar filled voids down to 5182 m.One core was cut in the Farsund Formation in the primary well bore from 5069 m to 5083. 5 m. Two further cores were cut in the Farsund Formation in the 2/4-21 T2 sidetrack from 5116 m to 5166 m. Wire line fluid samples were taken at 5053.5 m (oil and gas; considered as the best sample with only 2.3% mud contamination), 5122.5 m (oil and gas; medium quality sample), and 5167.5 m (oil and gas). PVT analyses of the samples showed a GOR in the range 1200 - 1400 Sm3/Sm3.The well was permanently abandoned on 24 May 2012 as a gas-condensate discovery.TestingNo drill stem test was performed.l> -
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]260.005394.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom15069.05083.4[m ]25116.05136.9[m ]35139.05166.2[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]62.5Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Oil samples at the Norwegian Offshore Directorate
Oil samples at the Norwegian Offshore Directorate Test typeBottle numberTop depth
MD [m]Bottom depth
MD [m]Fluid typeTest timeSamples availableMDT0.005167.50CONDENSATEYESMDT0.005121.50CONDENSATEYESMDT0.005053.50CONDENSATEYES -
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 typeCONDUCTOR30240.036248.01.20FITSURF.COND.20434.026453.01.40FITPILOT HOLE447.09 7/8447.00.00INTERM.161005.0201019.01.68FITINTERM.143003.017 1/23022.01.90FITINTERM.9 7/84638.012 1/44649.02.16FITOPEN HOLE5395.08 1/25573.00.00 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL GR31004625CORGUN50685083CTN ALD EWR P4 DGR PWD DIR FTWD50305250DIR PWD253447EWR - P4 DGR DIR PWD2535030EWR P4 DEG GEOPILOT PWD10153019GEOTAP GM EWR P4 PWD ALD CTN DIR52505395HNGS AIT PEX46005256MDT49945243MDT50535122MDT51675167MSCT49955245MWD115253OBMI IS MSIP GR36005257VSI ZO25695256XPT00 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit1151823316831683192326233543382338235053977451945204540454045604605476847684795 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured2481.1033.0KCl/Polymer4471.2015.0KCl/Polymer/GEM4471.1316.0KCl/Polymer6521.1615.0KCl/Polymer/GEM10151.2216.0KCl/Polymer/GEM12441.4519.0OBM-Low ECD23201.6021.0OBM-Low ECD30191.6023.0OBM-Low ECD34141.6128.0OBM-Low ECD41401.6128.0OBM-Low ECD45131.7432.0OBM-Low ECD-HTHP46462.0443.0OBM-Low ECD-HTHP46461.7836.0OBM-Low ECD-HTHP46461.7634.0OBM-Low ECD46492.0877.0OBM-Low ECD-HTHP48402.0441.0OBM-Low ECD-HTHP49322.0864.0OBM-Low ECD-HTHP50132.0445.0OBM-Low ECD-HTHP50292.0854.0OBM-Low ECD-HTHP50292.0951.0OBM-Low ECD-HTHP50292.0952.0OBM-Low ECD-HTHP50632.0858.0OBM-Low ECD-HTHP50832.0856.0OBM-Low ECD-HTHP51152.0867.0OBM-Low ECD-HTHP51392.0873.0OBM-Low ECD-HTHP51662.0873.0OBM-Low ECD-HTHP52502.1061.0OBM-Low ECD-HTHP52502.1061.0OBM-Low ECD-HTHP53922.0863.0OBM-Low ECD-HTHP53952.0862.0OBM-Low ECD-HTHP