2/11-1
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General information
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Wellbore history
GeneralExploration well 2/11-1 is located on the southern periphery of the Valhall Field in the North Sea. The objective of this early wildcat was to test all horizons down to the Rotliegendes, estimated at 14100 ft (4298 m). Top Permian was expected at 10300 ft (3139 m). Planned TD was at 15000 ft (4572 m).The well is Reference Well for the Åsgard, Sola, and Rødby Formations.Operations and resultsWell was spudded with the semi-submersible installation on and drilled to TD at 4691 m in the Late Jurassic Tyne Group. The well started to build angle from below ca 3500 m with maximum 11 deg deviation at 4444 m. Otherwise no significant drilling problems were reported from this deep well. The well was drilled water based down to 3432 m and with an invert oil mud (Vertoil) from 3432 m to TD.Top Paleocene, Balder Formation, was encountered at 2590 m. Top chalks of the Shetland Group (Tor Formation) was encountered at 2635 m. In addition to shows from the gas detector, free oil was seen floating on the mud pits and samples showed good fluorescence and cut through the interval 2585 m to 2633 m (Balder, Sele, and Lista Formations). Post-well geochemical analyses reported significant oil staining down to 2776 m. By testing live oil was confirmed in the uppermost Tor Formation. The tests were inconclusive with regard to an OWC, but the logs indicated that the contact was at 2655 m. Base Cretaceous was at 3555 m. The well did not reach Permian sediments; in stead the well drilled 1136 m in Late Jurassic shale (Mandal, Farsund and Haugesund Formations) before final TD was set. One conventional core was cut from 3864 to 3878 m in the Farsund formation.No wire line fluid samples were taken.The well was permanently abandoned on 3 October 1969 as a minor discovery. After the 2/8-6 Valhall Discovery well was drilled 6 years later well 2/11-1 was re-classified to oil appraisal well for the Valhall Field.TestingFive drill-stem tests were conducted. DST 1 from 2632 m to 2638.3 m (Lista and topmost Tor Formations) gave some oil to the surface, but rates declined rapidly to no flow, so no viable measurements were obtained. DST 2 and 3 from 2593.8 m to 2604.5 m (Balder - Sele Formations) gave no flow to surface. DST 4 from 2628.6 - 2640.8 m plus 2645.7 - 2650.5 m (Tor Formation) gave gas and oil to the surface at rates of 12686 Sm3 gas and 146 Sm3 oil/day in the final, 4 hours and 42 min flow. The GOR was 87 Sm3/Sm3. Flow rates decreased during the test and the figures were derived from the last readings. DST 5 from 2645.7 - 2650.5 m (Tor Formation) gave no flow to the surface, but 274 m fluid was reversed out after the test and the fluid contained ca 20% oil. -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom13863.63878.3[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]14.6Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit951136259025902600261026352635266228602863288728872910298830633555355537284075 -
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]pdf19.28pdf3.15pdf5.52pdf20.45pdf1.85pdf0.79pdf3.38pdf1.88pdf1.47pdf115.37pdf0.56pdf0.37 -
Documents – Norwegian Offshore Directorate papers
Documents – Norwegian Offshore Directorate papers Document nameDocument formatDocument size [MB]pdf12.73pdf74.28pdf0.54pdf0.74pdf0.69 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.0263326390.02.0259526050.03.0262926510.04.02646265112.5Drill 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]1.02.03.04.072 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL25612683CDM24394692DIL17204692EPIN25302835FDC3653451GR91365GR CCL25612683IES3651721LL-725302835MLL-C25302835SGR-C3654692SNP25302835SNP25302835VSLOCITY3654692 -
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 typeCONDUCTOR30131.036139.00.00LOTSURF.COND.20365.026383.00.00LOTINTERM.13 3/81720.017 1/21736.00.00LOTINTERM.9 5/83443.012 1/43450.00.00LOTOPEN HOLE4693.08 1/24693.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured3821.1148.0water-based12801.3144.0water-based17351.6051.0water-based20041.6555.0water-based29141.6750.0water-based33741.6256.0water-based37001.7958.0water-based38761.5567.0water-based -
Thin sections at the Norwegian Offshore Directorate
Thin sections at the Norwegian Offshore Directorate DepthUnit12695.00[ft ]