31/4-5
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General information
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Wellbore history
GeneralAppraisal well 31/4-5 was drilled on the 31/4-3 Discovery on the Bjørgvin Arch in the northern North Sea. The primary objective was to test "Intra Heather Formation" sands on the "B structure" in a crestal position, up dip from the discovery well 31/4-3. The well was planned to delineate known hydrocarbons in the "Intra Heather Sand I" (Sognefjord Formation) and to test the prospect for additional up dip oil and gas reserves in the "Intra Heather Sand II" (Fensfjord Formation). The well was planned to enter the "Intra Heather Sand I" reservoir approximately 20 m below the OWC in order to provide evidence of the extent of the reservoir. The lower oil bearing zone ("Intra Heather Sand II") was prognosed approximately 20 m higher than in well 31/4-3 and significant amounts of up dip oil were thought to exist. The Brent, Dunlin and Statfjord Groups were secondary objectives, possibly prospective in an up dip position.Operations and resultsWildcat well 31/4-5 was spudded with the semi-submersible installation Nortrym on 27 May 1981 and drilled to TD at 2930 m in the Triassic Hegre Group. The well was drilled without significant problems. It was drilled with seawater and hi-vis pills down to 926 m, with KCl mud from 926 m to 1966 m, and with a lignosulphonate/XC polymer/Drispac mud from 1966 m to TD.The well penetrated the Sognefjord Formation at 2070 m and the Fensfjord Formation at 2104 m. The Sognefjord Formation was 8.5 m thick and water bearing, but with good oil shows. The Fensfjord Formation was hydrocarbon bearing with a net sand of 60 m and a net pay of 37 m. The oil/water contact was not possible to define exactly, but RFT pressure gradients and shows on cores placed it at ca 2150 m. Shows on sandstones on cores continued down to 2192 The Brent Group was encountered at 2278 m. Sandstones were penetrated in the Brent, Dunlin and Statfjord Groups, but all were water bearing. Weak oil shows were recorded the Dunlin Group and also above the Jurassic, in the Paleocene Maureen Formation at 1992 - 2002 m.Nine cores were cut. Cores 1 to 8 were cut in succession from 2063 m to 2191 m in the Draupne, Sognefjord, Heather, and Fensfjord formations. Core 9 was cut in the Brent Group from 2292.4 m to 2309.8 m. RFT samples were taken in the Sognefjord Formation at 2072.5 m (formation water, filtrate and trace hydrocarbons) and in the Fensfjord Formation at 2131.5 m (one litre 34.9 deg API oil and 0.4 Sm3 gas).The well was permanently abandoned on 29 July 1981 as an oil appraisalTestingThree DST's were performed in the Fensfjord Formation.DST 1 tested the interval 2152 - 2158 m. After 10 min initial flow and 80 min shut in the well was opened for the main flow. The well ceased flowing after a few minutes.DST 2 tested the intervals 2130 - 2133 m and 2134.5-2140 m. It flowed 397 Sm3 oil and 33400 Sm3 gas /day through a 32/64" choke. The GOR was 84 Sm3/Sm3 the oil gravity was 36.2 deg API and the gas gravity was 0.73 (air = 1).DST 3 (also called DST 3A in well reports) was a combination test over the interval of DST 2 plus the interval 2107-2113 m. It flowed 334 Sm3 oil and 27500 Sm3 gas /day through a 32/64" choke. The GOR was 82 Sm3/Sm3, the oil gravity was 36.2 deg API, and the gas gravity was 0.724 (air = 1). -
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]270.002930.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12063.02065.0[m ]22065.02083.0[m ]32083.02100.1[m ]42100.12119.0[m ]52119.02136.6[m ]62137.52155.6[m ]72156.52173.8[m ]82173.82191.7[m ]92292.42309.9[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]144.3Cores 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 typeLaboratory1984.0[m]SWCIKU1992.0[m]SWCIKU2002.5[m]SWCIKU2006.0[m]SWCIKU2010.5[m]SWCIKU2017.0[m]SWCIKU2022.5[m]SWCIKU2030.5[m]SWCIKU2034.0[m]SWCIKU2045.0[m]SWCIKU2051.0[m]SWCIKU2061.0[m]SWCIKU2063.5[m]CIKU2064.0[m]CIKU2064.5[m]CIKU2065.1[m]CIKU2065.6[m]CIKU2066.0[m]CIKU2066.6[m]CIKU2067.0[m]CIKU2067.5[m]CIKU2070.0[m]CIKU2072.0[m]CIKU2074.0[m]CIKU2076.0[m]CIKU2078.0[m]CIKU2080.0[m]CIKU2081.9[m]CIKU2083.0[m]CIKU2084.8[m]CIKU2086.9[m]CIKU2089.2[m]CIKU2091.1[m]CIKU2093.0[m]CIKU2095.1[m]CIKU2097.0[m]CIKU2099.1[m]CIKU2102.1[m]CIKU2103.1[m]CIKU2105.0[m]CIKU2106.9[m]CIKU2108.2[m]CIKU2112.9[m]CIKU2115.0[m]CIKU2116.0[m]CIKU2119.0[m]CIKU2124.0[m]CIKU2134.0[m]CIKU2139.0[m]CIKU2144.0[m]CIKU2149.0[m]CIKU2164.7[m]CIKU2169.0[m]CIKU2170.8[m]CIKU2174.2[m]CIKU2180.8[m]CIKU2186.0[m]CIKU2191.5[m]CIKU2204.0[m]SWCIKU2215.0[m]SWCIKU2220.0[m]SWCIKU2225.0[m]SWCIKU2240.0[m]SWCIKU2241.0[m]SWCIKU2246.0[m]SWCIKU2255.0[m]SWCIKU2259.0[m]SWCIKU2262.5[m]SWCIKU2272.0[m]SWCIKU2274.0[m]SWCIKU2294.0[m]CIKU2295.0[m]CIKU2296.0[m]CIKU2297.0[m]CIKU2300.0[m]CIKU2302.0[m]CIKU2305.9[m]CIKU2309.9[m]CIKU2323.0[m]SWCIKU2339.5[m]SWCIKU2352.0[m]SWCIKU2359.0[m]SWCIKU2388.0[m]SWCIKU2390.0[m]SWCIKU2420.0[m]SWCIKU2432.0[m]SWCIKU2445.0[m]SWCIKU2451.5[m]SWCIKU2468.0[m]SWCIKU2507.0[m]SWCIKU2520.0[m]SWCIKU2536.0[m]SWCIKU2557.0[m]SWCIKU2570.0[m]SWCIKU2575.0[m]SWCIKU2577.5[m]SWCIKU2582.0[m]SWCIKU2677.0[m]SWCIKU2691.0[m]SWCIKU2714.0[m]SWCIKU2792.0[m]SWCIKU2810.0[m]SWCIKU2836.0[m]SWCIKU2858.0[m]SWCIKU2863.5[m]SWCIKU2875.0[m]SWCIKU2887.0[m]SWCIKU2905.0[m]SWCIKU2918.0[m]SWCIKU2929.0[m]SWCIKU -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit1686969111772177218241862198020112050206020602070207821042278235623562482252126452849 -
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]pdf2.43pdf29.59 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.0215221580.02.02130213314.33.02107214014.3Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.02.03.0Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.02.0398330000.8450.730843.0334280000.8440.72482 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL18272523CPI21042210CST19842274CST22842582CST26772929CYBERDIP19532580DLL MSFL19502250FDC CNL25602929FDC GR9111935HDT19522929HRT9111935ISF SON9112928LDT CNL19532580MERGE ISF BHC FDC CNL19532584MERGE ISF BHC FDC CNL25602930NGT19532581RFT20712514RFT20722072RFT21312131VELOCITY7202929 -
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 typeCONDUCTOR30257.536259.00.00LOTSURF.COND.20911.026925.01.71LOTINTERM.13 3/81953.017 1/21966.01.65LOTINTERM.9 5/82570.012 1/42585.01.65LOTOPEN HOLE2930.08 1/22930.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured6001.0634.0waterbased10001.4057.0waterbased13401.4154.0waterbased16301.4054.0waterbased19901.3547.0waterbased21801.2447.0waterbased25701.2443.0waterbased28901.2150.0waterbased -
Thin sections at the Norwegian Offshore Directorate
Thin sections at the Norwegian Offshore Directorate DepthUnit2068.00[m ]2070.00[m ]2104.00[m ]2107.00[m ]2113.00[m ]2115.00[m ]2122.00[m ]2128.00[m ]2130.00[m ]2135.00[m ]2151.00[m ]2160.00[m ]2166.00[m ]2207.00[m ]2222.00[m ] -
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