25/2-7
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General information
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Wellbore history
General Block 25/2 is located on the eastern margin of the Viking Graben towards the Bjørgvin Arch. The main targets for well 25/2-7 were the Middle Jurassic Vestland Group and the Early Jurassic Statfjord Formation, which were hydrocarbon bearing in the surrounding wells 25/2-4, 25/2-5 and 25/2-6. In addition possible Late Callovian sands, as in the 25/2 -4 well, constituted a second target.Operations and resultWildcat well 25/2-7 was spudded with the semi-submersible installation Borgsten Dolphin on 1 April 1982 and drilled to TD at 4110 m in the Early Jurassic Dunlin Group. Operations took 103 days including 13 days of down time. Four and a half days were lost due to WOW, 5.5 days due to rig compensator damage, and 3 days were lost due to a leaking pack off assembly in the 9 5/8" casing. No Callovian sands (Intra Heather Formation) were encountered. Of the two main objectives the Vestland Group was confirmed and tested as a reservoir. The Vestland Group sandstones were encountered at 3406 m, 174 m higher than prognosed. It was 389 m thick, which was thicker than expected, and it consisted of an upper and a lower interval. Massive beds of sandstone, locally slightly shaly or well cemented with some layers of black shales and coal were encountered in the upper interval from 3406 m to 3628 m. The gross thickness of this interval was 222 m and net thickness approximately 179 m. Porosity as estimated from cores 1 and 2 and logs ranged from 2.5 % to 21 % with an average of 12 %. Permeability in this zone was rather low (0.01 to 15.55 mD). The second zone was penetrated from 3628 m to 3795 m. This interval was composed of shales and sandstones alternating in a regular sequences of 15 to 20 m. Net thickness was approximately 77 m with a porosity ranging from 16 % to 21% based on logs. Some oil shows were recorded on cores 1 and 2 in the upper Vestland sand interval. They must be considered as residual shows as the reservoir is water bearing according to the logs. The RFT results confirmed this, showing a hydrostatic pressure gradient. Sandstones of the Statfjord Formation was not found. A silty/shaley interval at 3870 m, 198 m thick, was thought to be an equivalent of them, according to log correlation with the 25/2-5 well, but this was not supported by biostratigraphic data. Due to lack of seismic information at this level there was no incitement to drill deeper. A yellow direct florescence cut was observed on cuttings from this interval from 3917 m to 3920 m. Four conventional cores were cut in the well. Two were cut in the interval 3409 m to 3444 m in the Vestland Group (Sandstone with coals), two were cut in the Dunlin Group. Of the latter one was cut in shale from 3791 m to 3799 m and the other was cut at TD in red brown shale. One RFT fluid sample was taken at 3436.7 m (filtrate, formation water, and traces of oil), another at 3410 m (filtrate and formation water). The well was permanently abandoned on 12 July 1982 as a well with shows.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]220.004102.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom13409.03414.0[m ]23424.53443.5[m ]33791.03798.0[m ]44101.04110.0[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]40.0Cores 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 typeCONDUCTOR30201.036203.00.00LOTSURF.COND.20727.026739.01.06LOTINTERM.13 3/82194.517 1/22210.01.17LOTINTERM.9 5/83275.012 1/43290.01.27LOTOPEN HOLE4110.08 1/24110.00.00LOT -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]BGT7272182BHC GR21983180CBL VDL3002198CBL VDL18003279CIS21983285CIS32794084CST21622183CST23453280CST33804080DLL MSFL33503630HDT21983285HDT32794084ISF GR BHC SL1384097LDT CNL GR CAL2014088NGST32794077RFT34083591VELOCITY1384097 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit14110492023214921492189219423182475258932053263326332753406340634183628 -
Geochemical information
Geochemical information Document nameDocument formatDocument size [MB]pdf1.75 -
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]pdf9.97 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured2101.09spud mud5401.11water based7901.06water based16401.22water based22101.17water based29901.23water based32401.27water based36351.21water based -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory2450.0[m]SWCSNEA2550.0[m]SWCSNEA2789.0[m]SWCSNEA2850.0[m]SWCSNEA3050.0[m]SWCSNEA3135.0[m]SWCSNEA3150.0[m]SWCSNEA3220.0[m]SWCSNEA3265.0[m]SWCSNEA3270.0[m]SWCSNEA3275.0[m]SWCSNEA3380.0[m]SWCSNEA3398.0[m]SWCSNEA3409.0[m]CSPT3410.0[m]CSPT3412.0[m]CSNEA3413.5[m]CSPT3426.2[m]CSPT3427.3[m]CSNEA3428.6[m]CSPT3430.6[m]CSPT3431.5[m]CSNEA3434.3[m]CSPT3435.0[m]CSNEA3439.3[m]CSPT3630.0[m]SWCSNEA3701.0[m]SWCSNEA3791.1[m]CSPT3795.5[m]CSPT3797.6[m]CSPT3798.5[m]CSNEA4101.4[m]COD4103.3[m]COD4106.2[m]COD4109.0[m]COD