30/8-3
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General information
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Wellbore history
GeneralWell 30/8-3 was drilled just west of the Oseberg Sør Field in the North Sea. The primary objective of the well was the deltaic sands of the Tarbert Formation in the Brent Group. Draupne Formation wedge sand was a secondary objective. Furthermore, the well was placed in a position that should penetrate across the "A-East 1/A-East 3 fault zone in order to get cores and pressure data to evaluate fault seal capacity.Operations and resultsWildcat well 30/8-3 was spudded with the semi-submersible installation West Vanguard on 13 November 1997 and drilled to TD at 3720 m in the Early Jurassic Drake Formation. Due to shallow gas warnings a 9 7/8" pilot hole was drilled from 214 to 440 m. No gas was observed, and the hole opened up to 17 1/2". The non-productive rig time was 35% of the total for this well. WOW caused 4 days down time. Down hole motor and bit was lost in the 121/4" section. Fishing took ca 10 hours. Unstable hole conditions with mud losses and gains were experienced in the interval 3263 to 3284 m. The hole was sealed off by squeezing cement into the formation and this cured the problem. There were also problems with the TD logging due to tight/sticky hole, lost MDT tool, and erratic signals from the tool causing ca 2.5 days fishing and repairs. The well was drilled with spud mud down to 1588 m, and with KCl/Polymer mud from 1588 m to 3720 m.There were no indications of reservoir deposits in the Viking Group section. The Tarbert 2 reservoir was penetrated at 3333.0 m, one meter deeper than prognosed. A total of 64.5 m net reservoir was calculated between 3333 m and 3419 m, giving a net to gross ratio of 0.75, somewhat higher than expected. The Tarbert 2 reservoir was dry, with very weak shows of hydrocarbons. A Petroleum Geochemistry study concluded that there were no indications of migrated hydrocarbons within the Tarbert 2 reservoir section. The reservoir properties were moderately good. The average porosity was 17.3 %, slightly higher than prognosed. The majority of the permeability measurements were between 1 mD and 100 mD. The Ness Formation channels, 18 m net, contained gas/condensates. No fluid contacts could be established.Well 30/8-3 showed about 20 bar overpressure in Tarbert 2, indicating a main pressure barrier between the A-Main and the A-East structures.Two cores were cut from 3342 to 3435 m in the Tarbert 2 reservoir section. A third core was cut from 3531 to 3559 m to cover a prognosed fault. From FMS data it was later observed that the fault cut the well in a deeper position, between 3645 m and 3659 m. Two MDT fluid samples were collected from 3601.7 m and 3635.3 m.The well was permanently abandoned on 5 January 1998 as a gas/condensate discovery.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]1600.003720.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom13342.03378.9[m ]23379.03435.0[m ]33531.03559.2[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]121.0Cores 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 typeCONDUCTOR30212.036214.00.00LOTPILOT HOLE440.09 7/8440.00.00LOTSURF.COND.13 3/81581.017 1/21588.00.00LOTINTERM.9 5/83249.012 1/43260.00.00LOTOPEN HOLE3720.08 1/23720.00.00LOT -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CST GR31343250CST GR32943712FMS NGT ACTS32493712GR DSI ACTS30073714HALS TLD HGNS ACTS37193249MDT GR AMS33353340MDT GR AMS33383635MDT GR AMS34953510MDT GR AMS35453660VELOCITY30003750 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit11560988591591597410771142153815582111211121802239238924312431245426493044314131893189319231923197325232523473365936633663 -
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]pdf6.17 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1391.05water based2141.05water based3501.05water based4401.05water based7401.05water based15881.20water based21231.4534.0water based22401.4535.0water based25001.4332.0water based30451.4537.0water based31791.4536.0water based32601.4634.0water based32841.6236.0water based33081.6239.0water based33421.6237.0water based35311.3223.0water based37201.3723.0water based