7/12-5
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General information
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Wellbore history
GeneralWell 7/12-5 was drilled ca 4 km northwest of the Ula Field in the North Sea. The objective was to test the hydrocarbon potential in Late Jurassic Sandstones. Secondary objectives were Early Jurassic and Triassic sandstones.Operations and resultsWildcat well 7/12-5 was spudded with the semi-submersible installation Borgsten Dolphin 6 February 1981 and drilled to TD at 4440 m in the Late Permian Zechstein Group. There were some problems with drilling the section from 2851 to 3741 m due to junk in hole, otherwise operations proceeded without significant problems. The well was drilled with sea water and hi-vis pills and gel down to 467 m and with gypsum/lignosulphonate/CMC mud from 467 m to TD.The Mandal Formation was penetrated at 3731 m, while the Farsund Formation was penetrated at 3763 m. The Ula Formation was penetrated at 3831 m and consisted of a 69.5 m thick homogenous sandstone, very fine to fine grained with poor reservoir characteristics (porosities from 7 to 14 % and permeabilities from 0.3 to 3 mD). All attempts to obtain reservoir pressures and fluid samples failed due to tight formation. Oil shows were recorded in the upper half of the reservoir and an oil water contact was established at 3872. Log analysis indicated that no significant hydrocarbons were present below the Ula formation where all porous zones calculated high water saturations. Weak shows were recorded in sandstone in the interval 3940 to 3960 m in the Skagerrak Formation. Weak shows were recorded also in siltstone in an isolated sample from 2235 m in the Hordaland Group.Four cores were cut from 3844.5 to 3912.15 m in the Ula, Fjerritslev, and Skagerrak formations. Core depths are 4.8 m deeper than logger's depth. No wire line fluid samples were taken.The well was permanently abandoned on 7 June 1981 as an oil discovery.TestingNo drill stem test was performed. -
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]180.004436.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom13844.53862.7[m ]23862.73876.4[m ]33876.33894.3[m ]43894.33912.2[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]67.8Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
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Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit99165026452645268627342866291229123058328933223323333233323528373137313763383138313901391741454393 -
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]pdf14.39 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.04185419714.3Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.0Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.04701180000.8280.876251 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL CCL981818CST37324113DLL MSFL GR SP CAL37334043FDC CNL GR SP CAL36954432HDT37184116HRT981804ISF BHC GR SP98463ISF BHC GR SP37374430ISF BHC GR SP MSFL4543738ISF BHC GR SP MSFL40564113 -
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 typeCONDUCTOR30182.036188.00.00LOTSURF.COND.20456.026467.01.99LOTINTERM.13 3/81658.017 1/21670.51.83LOTINTERM.9 5/83732.012 1/43740.02.06LOTOPEN HOLE4440.08 1/24440.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1881.05WATER BASED03.06.19813251.08WATER BASED03.06.19814671.29WATER BASED03.06.19815091.15WATER BASED03.06.19818491.16WATER BASED03.06.198110291.17WATER BASED03.06.198112461.22WATER BASED03.06.198116701.40WATER BASED03.06.198119241.42WATER BASED03.06.198120851.42WATER BASED03.06.198121661.42WATER BASED03.06.198122241.42WATER BASED03.06.198124141.43WATER BASED03.06.198128351.48WATER BASED03.06.198130061.48WATER BASED03.06.198131131.48WATER BASED03.06.198134171.48WATER BASED03.06.198137411.50WATER BASED03.06.198141931.50WATER BASED03.06.198142491.50WATER BASED03.06.198143321.49WATER BASED03.06.198144401.50WATER BASED03.06.1981