15/12-5
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General information
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Wellbore history
GeneralWell 15/12-5 was drilled on the Beta Central structure ca 3.3 km north-east of the 15/12-4 Varg discovery well in the North Sea. Primary objective was the Jurassic sandstones. Secondary objective was the Frigg Formation sand and fractured limestone of Cretaceous age. Seismic anomalies indicated shallow gas. Prognosed TD was 3100 m RKB in sandstone of Triassic age.Operations and resultsWell 15/12-5 was spudded with the semi-submersible installation Ross Isle on 12 March 1986 and drilled to TD at 3150 m in the Late Triassic Skagerrak Formation. No shallow gas was encountered. Drilling proceeded without significant problems. The well was drilled with Spud mud down to 217 m, with gel/seawater/XC-polymer from 217 m to 619 m, with gypsum/polymer mud from 619 m to 2889 m, and with gel/lignosulphonate/lignite from 2889 m to TD.Top Cretaceous came in at 2457 m, and top Jurassic at 2841 m. Top of the reservoir, an Oxfordian sandstone, was encountered at 2918 m with good shows. The OWC was found at 2942 m, 28 m below that of well 15/12-4. This is probably due to a flow barrier caused by the fault system with a maximum throw of ca 100 m that separates the Beta West and Beta Central structures. Due to FMT pressure measurements and fluid samples, Statoil decided to go for "sole risk" testing, since Esso denied participating in the testing program.Three cores were cut in the interval 2892 m to 2967 m with 100% recovery. The core-log depth shifts were small, in the range 0.0 to -0.5 m for all three cores. FMT fluid samples were taken at 2919.3 m (oil), 2923.5 m, 2937.0 m (oil), and at 2941.5 m (water mud filtrate and a little oil).The well was permanently abandoned on 4 May 1986 as an oil appraisal of the Varg Field.TestingOne DST test was performed in the interval 2926 m to 2936 m. The test produced 520 Sm3 oil and 42000 Sm3 gas /day through a 40/64” choke. The GOR was 81 Sm3/Sm3, oil gravity was 0,909 g/cm3, and the gas gravity was 0.795 (air = 1). The test temperature was 127 °C. -
Cuttings at the Norwegian Offshore Directorate
Cuttings at the Norwegian Offshore Directorate Cuttings available for sampling?NOCuttings at the Norwegian Offshore Directorate Cutting sample, top depth [m]Cutting samples, bottom depth [m]240.003150.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12892.02904.0[m ]22910.52938.5[m ]32939.02967.0[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]68.0Cores 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 availableDSTFMT22937.002937.0020.04.1986 - 00:00YES -
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 typeCONDUCTOR30217.036217.00.00LOTSURF.COND.20597.026618.01.37LOTINTERM.13 3/81608.017 1/21625.01.72LOTINTERM.9 5/82875.012 1/42892.02.18LOTLINER73149.08 1/23150.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.02926293615.9Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.033.00024.00034.000Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.0560460000.90081 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]ACBL VDL GR1003100CDL CNL GR CAL2173150COREGUN22802885COREGUN28793138DIFL ACL GR SP CAL2173150DIP28763150FMT29193009FMT29332950FMT29370MLL GR28753134MWD1062883VSP2853150 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit1061024124722762276229123252418243924392457261527402792279228272841284128882918291830773077 -
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]pdf1.67pdf18.98 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured2171.1010.0WATER BASED17.03.19862171.106.013.4WATER BASED17.03.19866181.167.017.0WATER BASED20.03.19866981.1052.08.0WATER BASED24.03.198610681.1054.08.5WATER BASED02.04.198613371.1152.08.1WATER BASED02.04.198616001.5720.04.3WATER BASED02.05.198616221.1852.09.0WATER BASED02.04.198616221.2255.88.5WATER BASED02.04.198617681.2260.08.6WATER BASED02.04.198620841.2763.08.6WATER BASED02.04.198622231.2765.09.1WATER BASED02.04.198623411.5760.011.0WATER BASED03.04.198624451.5732.010.0WATER BASED04.04.198624451.5732.010.0WATER BASED07.04.198625701.5731.08.6WATER BASED07.04.198625901.5730.08.6WATER BASED07.04.198626871.5730.08.6WATER BASED09.04.198627351.5733.09.1WATER BASED09.04.198627981.5730.08.6WATER BASED10.04.198628401.5731.08.6WATER BASED11.04.198628761.5730.09.1WATER BASED14.04.198628851.3519.06.2WATER BASED30.04.198628891.5730.09.1WATER BASED14.04.198628891.5728.08.6WATER BASED14.04.198628921.3526.07.2WATER BASED16.04.198629181.3518.06.2WATER BASED17.04.198629651.3517.05.3WATER BASED18.04.198629661.3520.06.2WATER BASED23.04.198631501.3519.05.3WATER BASED23.04.198631501.3519.06.2WATER BASED25.04.1986 -
Thin sections at the Norwegian Offshore Directorate
Thin sections at the Norwegian Offshore Directorate DepthUnit2944.30[m ]