25/2-4
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General information
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Wellbore history
GeneralWell 25/2-4 was drilled in the north west corner of block 25/2. It lies on the eastern flank of the Viking basin in the Viking Graben and to the east of the Frigg Field and Frigg Kitchen. The main targets was the Jurassic with a mapped seismic structure of 30 ms vertical closure and 30 square km acreage spreading on the Shell block 30/11. Well 25/2-4 was located on the west flank near the top of the structure. Agreement with Shell management was signed for a bottom hole contribution with obligation for the operator to reach the Triassic red shales or to set TD at 3360 m.The well is Reference Well for the Drake Formation.Operations and resultsExploration well 25/2-4 was spudded with the semi-submersible installation Neptune 7 on 14 may 1975 and drilled to TD at 4384 m in the Triassic Smith Bank Formation. The well was drilled water based with salt/gel/Flosal/seawater down to 733 m and with FCL/LC mud from 733 m to TD. At 3375 m the well kicked due to an under balanced hydrostatic mud pressure.The well penetrated Danian, Paleocene and Eoceneá sandstone sequences (Frigg Formation, Intra Balder Formation Sandstones, Hermod and Ty formations). All these sands were water wet without shows. In the Late Cretaceous limestones were found fairly well developed overlying a thick shaly and marly sequence with some more limestone levels, particularly in the Campanian and Turonian. The latter limestones contained significant shows, but a production test proved tight formation. The Kimmerian unconformity was penetrated at 3632 m with 8 m Draupne shale. In the Jurassic two reservoir sandstone sequences were encountered: the Vestland Group and the Statfjord Formation. The Vestland sequence was first interpreted as oil and gas bearing from 3640 m to 3708 m (Hugin Formation) with a probable gas/oil contact 3660 m and an oil/water contact between 3704 m to 3708 m. Net pay in the 25/2-4 Hugin reservoir was estimated around 40 m with porosity from logs averaging 25% and water saturation lower than 25%. The Statfjord sandstones had similar reservoir properties, but were water wet. Due to high pressure the hydrocarbon zone in Hugin Formation was not production tested, in stead fifteen FIT samples were taken, of which five were taken in the "gas zone" and 11 in the "oil zone". Four of the tests were unsuccessful, the remaining samples recovered oil and gas but PVT analyses indicated that the fluids were not fully representative of the formation fluid. After a well test in a later well, 25/2-12 A, it became clear that the reservoir fluid was actually gas with high condensate content. Logs in 25/2-12 confirmed the hydrocarbon/water contact found in 25/2-4 (3678m MSL).Shows were recorded as follows: At 2750 m gas index and formation pressure increased significantly and remained high down to 3710 m. Peaks of gas were recorded when entering limestone stringers throughout the Late Cretaceous and at the top of the Jurassic sandstones. Direct fluorescence and cuts were observed over the interval 2900 m to 3877 m on limestones and sandstones.Three cores were cut in the Hugin Formation and three in the Sleipner Formation, 81.75 m in total. In addition to the FIT samples in the Hugin Formation one FIT was taken in the Tryggvason Formation (3374 m: mud filtrate and trace gas) and one in the Statfjord Formation (4116 m: mud filtrate only).TestingCampanian limestones were tested over the interval 2902m to 2913 m. No significant flow was recorded even after acid treatment. Only 3.2 m of mud mixed with water and gas were recovered by reverse circulation. No production test was conducted on the Jurassic oil column because rig equipment was inadequate for the reservoir pressures encountered. -
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]210.004360.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom13650.03659.0[m ]23659.03676.0[m ]33677.03695.0[m ]43817.03833.8[m ]53835.03845.0[m ]63852.03863.0[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]81.8Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
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 typeCONDUCTOR30195.036200.00.00LOTINTERM.20723.026733.00.00LOTINTERM.13 3/82860.017 1/22870.00.00LOTINTERM.9 5/83353.012 1/43374.00.00LOTOPEN HOLE4360.08 1/24360.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.0290229110.0Drill 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]1.0 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]BHC7243351BHC-C33514358CBL28004253CBL28253350CBL30203350CBL32503725CBL40504138CDM19504259CDM AP19504259CDM FP19514258CDM SP19504259DLL35503903FDC20002100FDC25502867FDC CNL33513909GR137724IES7244361ML MLL28592949MLL ML33513913TEMP127724TEMP15802004TEMP31503500 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit137427102510771111121312502012206120982098217722082223225023252400259026062617261729253370363236323640364037523876387639273965408442614261 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.39 -
Geochemical information
Geochemical information Document nameDocument formatDocument size [MB]pdf3.27 -
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]pdf7.82pdf0.17pdf15.24pdf2.45pdf2.86 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1361.06100.0water based7001.05100.0water based14371.1860.012.0water based21471.2555.011.0water based33801.9153.018.0water based36401.9260.0water based39151.9354.022.0water based42601.9456.022.0water based43601.7766.0water based -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory2580.0[m]DCOD2600.0[m]DCOD2620.0[m]DCOD2640.0[m]DCOD2660.0[m]DCOD2680.0[m]DCOD2700.0[m]DCOD2720.0[m]DCOD2740.0[m]DCOD2760.0[m]DCOD2780.0[m]DCOD2800.0[m]DCOD2820.0[m]DCOD2840.0[m]DCOD2860.0[m]DCOD2880.0[m]DCOD2900.0[m]DCOD2920.0[m]DCOD2940.0[m]DCOD2960.0[m]DCOD2980.0[m]DCOD3020.0[m]DCOD3040.0[m]DCOD3060.0[m]DCOD3080.0[m]DCOD3100.0[m]DCOD3120.0[m]DCOD3140.0[m]DCOD3160.0[m]DCOD3180.0[m]DCOD3200.0[m]DCOD3220.0[m]DCOD3235.0[m]DCOD3255.0[m]DCOD3275.0[m]DCOD3295.0[m]DCOD3315.0[m]DCOD3335.0[m]DCOD3355.0[m]DCOD3380.0[m]DCOD3400.0[m]DCOD3420.0[m]DCOD3440.0[m]DCOD3460.0[m]DCOD3485.0[m]DCOD3500.0[m]DCOD3520.0[m]DCOD3540.0[m]DCOD3560.0[m]DCOD3585.0[m]DCOD3600.0[m]DCOD3620.0[m]DCOD