30/6-7
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General information
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Wellbore history
GeneralWell 30/6-7 is an appraisal well on the Oseberg Field, discovered by well 30/6-1 in 1979.The primary objective was to test for hydrocarbon accumulations in the Late Jurassic sandstones of the Brent formation and the Late and Early Jurassic sandstones of the Dunlin and Statfjord formations in the Alpha north structure. Secondary objectives were to establish the type of communication between the Alpha and Alpha North structures and to define the oil/water contact on Alpha North. The well was planned to reach total depth at 3225 +- 50 m, 75 m into the Statfjord Formation.The well is Type well for the Oseberg Formation and Reference well for the Amundsen, Cook, Drake, Etive, Ness, and Tarbert Formations.Operations and resultsWell 30/6-7 was spudded with the semi-submersible installation Nortrym on 20 May 1982 and drilled to TD at 3236 m in Early Jurassic rocks of the Statfjord Formation. The 26" section was initiated by a 17 1/2" pilot hole. One small pocket of shallow gas was detected at 358 m (5.6% C1). The well was drilled with seawater and hi-vis pills down to 952 m and with KCl/polymer mud from 952 m to 2285 m. At 2285 m the 13 3/8" casing got stuck and a pill of EZY spot and diesel was pumped in the hole, without effect. The drilling fluid used in the 12 1/4" section from 2285 m to 2915 m the well was drilled with a Dextrid/KCl mud. From 2915 m to TD the mud was converted to a dispersed system by adding lignosulfonate.The Brent Group was encountered at 2631.5 m. The Brent Group was hydrocarbon bearing with a total gross thickness of 154.5 m and a net sand interval of 106.9 m. The net pay was 50.7 m. Sandstone intervals were also encountered in the Early Jurassic Cook and Statfjord formations but these were both 100% water saturated.The Tarbert Formation (2631.5 - 2646.5 m) formed the uppermost interval in the Brent Group. It consisted of very fine to fine grained sandstone which was occasionally medium to coarse grained. Wire line log evaluation gave a net pay of 14.7 m, with an average porosity of 20.7% and an average water saturation of 18.1%. Average permeability (KH, log) was 520 mD.The Ness Formation (2646.5 - 2727.5 m) consisted of interbedded sandstones, shales, siltstones and stringers of coal. The sandstones were very fine to medium, occasionally coarse grained and locally very micaceous and carbonaceous. The interval contained 38.7 m of net sand and 36 m of net pay which had an average porosity of 20.5%, average water saturation of 27.7% and an average permeability of 577 mD (KH, log). Measured average permeability (KH, core) was 1163 mD.FMT pressure measurements were taken throughout the Brent interval showing that the different sandstone intervals in the Tarbert and Ness Formations have different oil gradients. From log analysis an oil/water contact has been estimated to be at 2723.5 m in the Ness Formation. On the Alpha structure an oil/water contact has been defined at 2731 m from earlier wells and it appears therefore that the southwest - northeast fault separating the Alpha from the Alpha North structure does have some sealing properties.The Etive Formation (2727.5 - 2786 m) consists predominantly of a very fine grained to pebbly sandstone with occasional stringers of shale and siltstone. The interval contained 53.5 m of net sand with average porosity of 19.5%. A transition zone of residual hydrocarbons (2727.5 - 2747 m) had an average water saturation of 72%. This agrees with patchy oil shows seen in the cores down to 2755 m (2747 m when depth correction between logger's and driller's depths is applied). The remaining interval of the Etive Formation (2747 - 2786 m) had an average water saturation of 94%. Average permeability of the Etive Formation was 799 mD (KH, log) Measured average permeability from cores was 1670 mD (KH, core).Apart from in the hydrocarbon bearing reservoirs as described above, weak shows were described in thin limestone stringers in the Sele Formation and in limestones of the Shetland Group.A total of twelve conventional cores were cut from 2648 to 2812.4 m in the 12 1/4" section in the well. A total of 155.1 m (94.3%) was recovered. Cores were cut consecutively from the top of the Ness Formation and down into the Dunlin Group shales. Core depths are approximately 5 m shallower than logger's depths at the top of Core No 1 and 8.5 m shallower at the base of Core No 12. FMT fluid samples were taken at 2633.5 m (gas, oil and water/filtrate), 2643m (gas, oil and water/filtrate), 2666 m (gas, oil and water/filtrate), 2676 m (gas, oil and water/filtrate), 2684 m (gas, oil and trace of water/filtrate), 2713 m (water/filtrate), and 2714 m (water/filtrate).The well was permanently abandoned on 24 August 1982 as an oil and gas appraisal well.TestingFour DTS' were performed in the Brent formation sandstones.DST 1 was taken over the interval 2729 -2736 m and produced 770 m3 water/day through an 80/64" choke. Reservoir pressure was 4255.5 psig and the BHT was 110 °C.DST 2 was taken over the interval 2711 - 2716 m and produced 1028 SM3/day of 34.9 deg API oil and 116100 Sm3 of 0.72 SG gravity gas through a 56/6 4" choke. Separator GOR was 113 Sm3/Sm3, CO2 content was 0.8%, reservoir pressure was 4250 psig and the BHT was 110 °C.DST 3 was taken in the interval 2681 -2684 m and produced 534 Sm3 of 33.9 deg API gravity oil and 65130 Sm3 of 0.702 SG gravity gas through a 32/64" choke. Separator GOR was 122 Sm3/Sm3, CO2 content was 0.2%, and reservoir pressure was extrapolated to be 4222 psig. This test was aborted due to bad weather conditions and no bottom hole samples were obtained.DST 4 was taken in the interval 2633 -2636 m and produced 1339 Sm3 of 34.1 deg API oil and 146681 Sm3 of 0.700 SG gravity gas through a 72/64" choke. Separator GOR was 110 Sm3/Sm3, CO2 content was 1.0%, and reservoir pressure was extrapolated to be 4178 psig. -
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]230.003237.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12648.02666.1[m ]22666.12675.0[m ]32679.52692.2[m ]42692.22693.7[m ]52694.02705.0[m ]62707.02719.4[m ]72720.02733.1[m ]82733.12750.0[m ]92751.02761.4[m ]102762.02778.8[m ]112780.02793.9[m ]122793.92812.4[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]154.1Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
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Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory2507.0[m]SWCRRI2530.0[m]SWCRRI2545.0[m]SWCRRI2602.0[m]SWCRRI2609.5[m]SWCRRI2615.0[m]SWCRRI2620.0[m]SWCRRI2625.0[m]SWCRRI2628.0[m]SWCRRI2662.0[m]CRRI2692.1[m]CRRI2693.7[m]CRRI2698.0[m]CRRI2699.0[m]CRRI2705.0[m]CRRI2712.4[m]CRRI2717.8[m]CRRI2726.9[m]CRRI2730.8[m]CRRI2734.1[m]CRRI2745.0[m]CRRI2765.1[m]CRRI2780.3[m]CRRI2795.1[m]CRRI2800.5[m]CRRI2805.0[m]CRRI2807.0[m]SWCRRI2810.0[m]CRRI2812.0[m]CRRI2817.0[m]SWCRRI2836.0[m]SWCRRI2869.0[m]SWCRRI2892.0[m]SWCRRI2908.9[m]SWCRRI -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit13970489313441376201020102083219222722290229023602560256026322632264627272737273927862786297530233152 -
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]pdf18.46 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.02729273631.72.02711271622.23.02681268412.74.02637263919.0Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.02.03.04.0Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.02.010281160000.8500.7201133.0534650000.8350.7001224.013391460000.8530.700109 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL8252285CBL VDL22502928CCL GR1302928CDL CNL CR CNL9523233CST13002433CST24442908CST291432132DIFL LS BHC GR SP1373232DLL MLL GR CAL26002908FMT26332775FMT26332633FMT26432643FMT26660FMT26662666FMT26762676FMT26842695FMT26842684FMT26942714FMT27132713FMT27432743FMT29773188HRD20003232MWD24752885VELOCITY2303232 -
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 typeCONDUCTOR30227.036227.50.00LOTSURF.COND.20952.026965.01.62LOTINTERM.13 3/82285.017 1/21787.01.78LOTINTERM.9 5/82900.012 1/42916.01.75LOTOPEN HOLE3236.08 3/83236.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured4901.0846.0waterbased9701.2038.0waterbased17951.3560.0waterbased22001.4369.0waterbased24501.3662.0waterbased27201.3545.0waterbased30451.2649.0waterbased31201.2767.0waterbased32101.2658.0waterbased -
Pressure plots
Pressure plots The pore pressure data is sourced from well logs if no other source is specified. In some wells where pore pressure logs do not exist, information from Drill stem tests and kicks have been used. The data has been reported to the NPD, and further processed and quality controlled by IHS Markit.Pressure plots Document nameDocument formatDocument size [MB]pdf0.22