34/7-21
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General information
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Wellbore history
GeneralExploration well 34/7-21 was drilled the south-western part of block 34/7 on Tampen Spur, on the H-prospect northwest of the Tordis Field. The main objective was to test the hydrocarbon prospectivity within the Late Jurassic (Viking Group) interval. The target was a Late Jurassic sand wedge, truncated in the up-dip direction towards the east by the Base Cretaceous Unconformity. Sufficient amounts of reservoir sand were conditioned by erosion and re-sedimentation from the underlying Middle Jurassic Brent Group, which is progressively truncated up-dip in the same direction. The secondary objective was to test the Paleocene in which an oil discovery had been made in well 34/7-18.Operations and resultsWell 34/7-21 was spudded with the semi-submersible installation Treasure Saga on 19 October 1992 and drilled to TD at 3015 m in the Early Jurassic Drake Formation. Tight and sticky formation was reported in the 12 1/4" section, but no significant technical problems occurred in the operations. Based on the site survey, possible shallow gas was predicted at 298, 548 and 612 m. The MWD confirmed a gas bearing sand at 541 m - 548 m. A flow check proved negative. The well was drilled with spud mud down to 1113 m and with KCl polymer mud from 1113 m to TD.In the Nordland, Hordaland, and Upper Rogaland Groups, the well penetrated mainly clay/claystone with minor sand, except for the sandy Utsira Formation between 929-1040 m. At the base of the Rogaland Group, the Lista Formation sandstone was encountered and proven dry, but with shows. In the Shetland and the condensed Cromer Knoll Group, claystone with limestone beds and massive marls/limestones were penetrated, respectively. A hydrocarbon-bearing interval was proven in a sand in the Cromer Knoll at 2498-2501 m. The top of the Late Jurassic reservoir was reached at 2508 m, which was 29 m shallower than prognosed. Within the Draupne Formation, two separate oil bearing sandstone intervals were proven between 2508-2545 m and between 2565.5-2569 m. The latter contained high concentrations of H2S. All three hydrocarbon bearing intervals had separate formation pressure regimes, and did not communicate. No OWC was identified at any level. The overall ODT was 2569 m (2543 m MSL).Apart from the three hydrocarbon bearing reservoirs shows were reported in several intervals. In the base of the Rogaland Group, traces of good oil shows were detected in argillaceous sandstones (intra Lista Formation) at 1850-1858 m. In the Shetland Group, good oil shows occurred in thin sandstone horizons from about 2270 m. The shows in this interval decreased progressively from below 2425 m. In the top of the Heather Formation, traces of weak oil shows was identified in a siltstone bed at 2587.5-2588.5 m. No shows were reported below this depth.A total of 5 cores were cut in well 34/7-21. Core 1 was cut in the interval 1858 to 1885.7 m in the Sele/Lista Formations. Cores 2-5 were cut in the Draupne Formation and down into the top of the Heather Formation, at 2515 to 2594 m.FMT fluid samples were taken at 2498.5 m (oil), 2529.7 m (oil), and at 2567.5 m (two samples in different runs, both with oil).After testing the well was plugged back and prepared for sidetracking to explore the extension of the Late Jurassic reservoirs. The plugged back hole was permanently abandoned on 11 December 1992 and the well was classified as an oil discovery.TestingThe interval 2510.5-2537.5 m, covering the main part of the upper Intra-Draupne Sand, was perforated and tested. The oil rate at the end of the second main flow was measured to 884 Sm3/day through a 12.7 mm choke. The corresponding wellhead pressure was 146 bar and the GOR was 95 Sm/Sm3, while the dead oil density was 0.85 g cm3 and the gas gravity was 0.89 (air = 1). The reported bottom hole temperature/reservoir temperature from the test was 91 deg C. -
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]340.003014.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom11858.01880.7[m ]22515.02522.2[m ]32530.02547.0[m ]42547.02565.8[m ]52566.02592.2[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]91.9Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
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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 availableDSTTEST10.000.00OIL03.12.1992 - 09:10YESDSTTEST20.000.00OIL05.12.1992 - 15:40YES -
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 typeCONDUCTOR30316.036330.00.00LOTINTERM.201094.0261113.01.67LOTINTERM.13 3/81795.017 1/21810.01.85LOTINTERM.9 5/82639.012 1/43015.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.02510253712.7Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.014.00032.00091Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.08840.8500.89095 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBIL GR17961900CBIL GR24842550CBIL GR25452999DIPL ZDL CN GR17942560DIPLOG GR17943014DLL ACL ZDL GR10891805DLL MLL GR17942562DLL MLL GR24803015DPIL DAC ZDL CN SL17953015FMT GR17943014FMT GR25102538MWD CDR - GR RES DIR2183015SWC18532978VELOCITY9902990 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit2181025104012001278132214031711171117541856186319001900216824992499250225082508254525652569258826922692276328652903296629722972 -
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]pdf21.08 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured3261.04WATER BASED3301.05WATER BASED6751.164.0WATER BASED11101.175.0WATER BASED11131.176.0WATER BASED11221.2522.0WATER BASED14041.3032.0WATER BASED17631.5041.0WATER BASED18101.5042.0WATER BASED18581.5139.0WATER BASED20811.6049.0WATER BASED21961.6460.0WATER BASED23071.6453.0WATER BASED25101.6241.0WATER BASED25301.6450.0WATER BASED25521.6443.0WATER BASED25661.6444.0WATER BASED25941.6438.0WATER BASED26011.6139.0WATER BASED26351.6442.0WATER BASED26541.6139.0WATER BASED29711.5536.0WATER BASED30151.6138.0WATER BASED -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory350.0[m]DCPALEO380.0[m]DCPALEO410.0[m]DCPALEO440.0[m]DCPALEO470.0[m]DCPALEO500.0[m]DCPALEO530.0[m]DCPALEO560.0[m]DCPALEO590.0[m]DCPALEO620.0[m]DCPALEO650.0[m]DCPALEO680.0[m]DCPALEO710.0[m]DCPALEO740.0[m]DCPALEO770.0[m]DCPALEO800.0[m]DCPALEO830.0[m]DCPALEO860.0[m]DCPALEO890.0[m]DCPALEO920.0[m]DCPALEO950.0[m]DCPALEO980.0[m]DCPALEO1010.0[m]DCPALEO1040.0[m]DCPALEO1070.0[m]DCPALEO1100.0[m]DCPALEO1130.0[m]DCPALEO1160.0[m]DCPALEO1190.0[m]DCPALEO1220.0[m]DCPALEO1250.0[m]DCPALEO1280.0[m]DCPALEO1310.0[m]DCPALEO1340.0[m]DCPALEO1370.0[m]DCPALEO1400.0[m]DCPALEO1430.0[m]DCPALEO1460.0[m]DCPALEO1490.0[m]DCPALEO1520.0[m]DCPALEO1550.0[m]DCPALEO1580.0[m]DCPALEO1610.0[m]DCPALEO1640.0[m]DCPALEO1670.0[m]DCPALEO1700.0[m]DCPALEO1710.0[m]DCPALEO1720.0[m]DCPALEO1730.0[m]DCPALEO1740.0[m]DCPALEO1750.0[m]DCPALEO1760.0[m]DCPALEO1770.0[m]DCPALEO1780.0[m]DCPALEO1790.0[m]DCPALEO1800.0[m]DCPALEO1810.0[m]DCPALEO1815.0[m]DCPALEO1825.0[m]DCPALEO1835.0[m]DCPALEO1845.0[m]DCPALEO1855.0[m]DCPALEO1880.0[m]CRRI1885.0[m]DCPALEO1895.0[m]DCPALEO1915.0[m]DCPALEO1940.0[m]DCPALEO1975.0[m]DCPALEO2005.0[m]DCPALEO2035.0[m]DCPALEO2065.0[m]DCPALEO2095.0[m]DCPALEO2125.0[m]DCPALEO2155.0[m]DCPALEO2185.0[m]DCPALEO2215.0[m]DCPALEO2245.0[m]DCPALEO2275.0[m]DCPALEO2305.0[m]DCPALEO2335.0[m]DCPALEO2365.0[m]DCPALEO2395.0[m]DCPALEO2425.0[m]DCPALEO2455.0[m]DCPALEO2485.0[m]DCPALEO2515.0[m]DCPALEO2516.0[m]CPALEO2517.0[m]CPALEO2518.0[m]CPALEO2520.0[m]CRRI2531.0[m]CRRI2532.0[m]CRRI2533.0[m]CPALEO2541.0[m]CPALEO2548.0[m]CPALEO2556.0[m]CPALEO2557.0[m]CRRI2558.0[m]CRRI2560.0[m]CRRI2561.0[m]CRRI2563.0[m]CRRI2564.0[m]CPALEO2568.0[m]CRRI2569.0[m]CRRI2571.0[m]CPALEO2579.0[m]CPALEO2582.0[m]CPALEO2590.0[m]CPALEO2633.0[m]DCPALEO2648.0[m]DCPALEO2663.0[m]DCPALEO2688.0[m]DCPALEO2693.0[m]DCPALEO2708.0[m]DCPALEO2723.0[m]DCPALEO2753.0[m]DCPALEO2768.0[m]DCPALEO2783.0[m]DCPALEO2798.0[m]DCPALEO2813.0[m]DCPALEO2828.0[m]DCPALEO2843.0[m]DCPALEO2858.0[m]DCPALEO2873.0[m]DCPALEO2888.0[m]DCPALEO2918.0[m]DCPALEO2933.0[m]DCPALEO2948.0[m]DCPALEO2963.0[m]DCPALEO2978.0[m]DCPALEO2993.0[m]DCPALEO3008.0[m]DCPALEO3014.0[m]DCPALEO -
Thin sections at the Norwegian Offshore Directorate
Thin sections at the Norwegian Offshore Directorate DepthUnit1868.70[m ]1875.65[m ]2531.60[m ]2537.35[m ]2566.20[m ]2566.80[m ]2567.70[m ]2568.50[m ]2570.45[m ]2571.40[m ]2576.45[m ]