15/12-8
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General information
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Wellbore history
GeneralWildcat well 15/12-8 was drilled ca 3.5 km east of the 15/12-4 well, which made the Varg oil discovery in Jurassic and Triassic sandstones. The main objective of the well was to test the potential for hydrocarbons in sandstones of Oxfordian and Triassic age. Seismic anomalies at 437, 467, 479 and 803 m indicated possibility for shallow gas. Planned TD for the well was 3260 m.Operations and resultsWell 15/12-8 was spudded with the semi-submersible installation Deepsea Bergen on 5 June 1991 and drilled to TD at 3054 m in the Triassic Skagerrak Formation. No significant problems occurred during operations. The well was drilled with seawater / hi-vis pills / CMC down to 615 m, with KCl/polymer mud from 615 m to 2855 m, and with Ancotemp/bentonite mud from 2855 m to TD. No shallow gas was encountered.Jurassic Vestland Group sandstone was encountered hydrocarbon-bearing at 2838 m. The hydrocarbon column extended 23 m into Triassic sandstone of the Skagerrak Formation. The gas/water contact was estimated to 2877 m, confirmed by FMT pressure gradients and wire line logs. The well was tested, and since no core was cut through the reservoir, the well was sidetracked at 2623 m with TD at 2940 m. The sidetrack was drilled with Ancotemp/bentonite mud. Three conventional cores were cut in the interval 2841 - 2902 m. The sidetrack was formally named 15/12-8 A.The FMT tool was run in well 15/12-8 and 15/12-8A. One segregated sample was taken at 2863 m in 15/12-8 (gas, condensate and mud filtrate) and another in the water zone at 2888 m in well 15/12-8 A (recovered mud only due to seal failure).Well 15/12-8 was permanently abandoned on 14 July 1991 as a gas/condensate discovery. The 15/12-8 A sidetrack was permanently abandoned on 29 July as a gas/condensate appraisal well.TestingOne DST test was performed in 15/12-8 in the interval 2838 - 2869 m. The well produced gas-condensate with a dew point of 230 bar at the measured reservoir temperature, which was 123 deg C. The rates were 550 000 Sm3 gas and 420 Sm3 condensate /day through a 15.9 mm choke. The condensate/gas ratio was 1308 Sm3/Sm3, the condensate gravity was 61 deg API, and the gas gravity was 0.817 (air = 1). -
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]620.003054.00 -
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 availableDSTTEST12838.002869.0009.07.1991 - 04:35YES -
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 typeCONDUCTOR30170.536172.00.00LOTINTERM.20601.026603.01.74LOTINTERM.13 3/81798.017 1/21800.01.84LOTINTERM.9 5/82837.012 1/42840.02.01LOTLINER73051.08 1/23051.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.02838286915.9Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.0123Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.04205500000.8171308 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]ACBL VDL GR1152828ACL GR ZDL17932839CDL CN GR26212933CDL GR170484DIFL AC MLL GR26212933DIFL ACL GR1703048DIPLOG GR28283046FMT GR28383009MLL ZDL CN GR28283048MWD - GR RES DIR1703054VELOCITY4853045ZDL GR6011815 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit11010821207225122512268233324412464246424962626273827702770279728292829283828542854 -
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]pdf2.80pdf22.14 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1711.03WATER BASED06.06.19912781.03WATER BASED10.06.19916011.3520.011.0WATER BASED17.06.19916011.3525.012.5WATER BASED17.06.19916011.3519.03.0WATER BASED17.06.19916151.03WATER BASED10.06.19916150.00WATER BASED10.06.199110361.2015.04.0WATER BASED14.06.199114601.3017.04.0WATER BASED14.06.199114601.3020.06.5WATER BASED14.06.199117891.5122.03.5WATER BASED20.06.199117891.5326.03.5WATER BASED20.06.199117981.5122.03.5WATER BASED18.06.199118151.3520.011.0WATER BASED17.06.199118151.3520.06.5WATER BASED14.06.199118151.3525.012.5WATER BASED17.06.199118181.4019.03.0WATER BASED17.06.199122401.5325.04.5WATER BASED21.06.199122401.5330.05.0WATER BASED25.06.199122401.5122.03.5WATER BASED18.06.199122401.5122.03.5WATER BASED20.06.199122401.5326.03.5WATER BASED20.06.199122401.5330.04.5WATER BASED25.06.199122401.5331.04.5WATER BASED25.06.199122401.5328.05.0WATER BASED25.06.199122401.5329.04.5WATER BASED26.06.199122401.5329.06.0WATER BASED27.06.199124821.5122.03.5WATER BASED20.06.199124951.5326.03.5WATER BASED20.06.199125991.5325.04.5WATER BASED21.06.199127251.5330.05.0WATER BASED25.06.199128121.5330.04.5WATER BASED25.06.199128301.5331.04.5WATER BASED25.06.199128501.2718.03.5WATER BASED01.07.199128501.2718.03.5WATER BASED03.07.199128501.2718.04.0WATER BASED03.07.199128551.5329.06.0WATER BASED27.06.199128551.5329.04.5WATER BASED26.06.199128551.5328.05.0WATER BASED25.06.199129071.2721.07.0WATER BASED01.07.199130541.2718.03.5WATER BASED01.07.1991 -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory1210.0[m]DCGEOCH1250.0[m]DCGEOCH1270.0[m]DCGEOCH1280.0[m]DCGEOCH1300.0[m]DCGEOCH1310.0[m]DCGEOCH1330.0[m]DCGEOCH1340.0[m]DCGEOCH1360.0[m]DCGEOCH1370.0[m]DCGEOCH1390.0[m]DCGEOCH1400.0[m]DCGEOCH1420.0[m]DCGEOCH1430.0[m]DCGEOCH1450.0[m]DCGEOCH1460.0[m]DCGEOCH1480.0[m]DCGEOCH1490.0[m]DCGEOCH1510.0[m]DCGEOCH1520.0[m]DCGEOCH1540.0[m]DCGEOCH1550.0[m]DCGEOCH1570.0[m]DCGEOCH1580.0[m]DCGEOCH1600.0[m]DCGEOCH1610.0[m]DCGEOCH1630.0[m]DCGEOCH1640.0[m]DCGEOCH1660.0[m]DCGEOCH1670.0[m]DCGEOCH1690.0[m]DCGEOCH1700.0[m]DCGEOCH1720.0[m]DCGEOCH1730.0[m]DCGEOCH1750.0[m]DCGEOCH1760.0[m]DCGEOCH1780.0[m]DCGEOCH1790.0[m]DCGEOCH1810.0[m]DCGEOCH1822.8[m]SWCSTATO1840.0[m]DCGEOCH1850.0[m]DCGEOCH1868.8[m]SWCSTATO1880.0[m]DCGEOCH1900.0[m]DCGEOCH1910.0[m]DCGEOCH1930.0[m]DCGEOCH1939.8[m]SWCSTATO1960.0[m]DCGEOCH1970.0[m]DCGEOCH1986.8[m]SWCSTATO2000.0[m]DCGEOCH2020.0[m]DCGEOCH2030.0[m]DCGEOCH2050.0[m]DCGEOCH2067.3[m]SWCSTATO2080.0[m]DCGEOCH2090.0[m]DCGEOCH2109.8[m]SWCSTATO2120.0[m]DCGEOCH2130.0[m]DCGEOCH2150.0[m]DCGEOCH2160.0[m]DCGEOCH2177.3[m]SWCSTATO2190.0[m]DCGEOCH2203.0[m]DCGEOCH2215.0[m]DCGEOCH2230.0[m]DCGEOCH2246.3[m]SWCSTATO2251.0[m]DCGEOCH2258.8[m]SWCSTATO2272.8[m]SWCSTATO2286.8[m]SWCSTATO2310.8[m]SWCSTATO2318.8[m]SWCSTATO2335.0[m]DCGEOCH2350.0[m]DCGEOCH2365.0[m]DCGEOCH2380.0[m]DCGEOCH2410.0[m]DCGEOCH2419.8[m]SWCSTATO2440.0[m]DCGEOCH2831.8[m]SWCSTATO2834.8[m]SWCSTATO2836.8[m]SWCSTATO2837.0[m]DCGEOCH2841.0[m]CSTATO2843.0[m]CSTATO2844.7[m]CSTATO2846.5[m]CSTATO2847.4[m]CSTATO2848.7[m]CSTATO2850.4[m]CSTATO2852.8[m]CSTATO2885.0[m]DCGEOCH2900.0[m]DCGEOCH2912.0[m]DCGEOCH2960.0[m]DCGEOCH2990.0[m]DCGEOCH3020.0[m]DCGEOCH3054.0[m]DCGEOCH