31/4-6
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General information
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Wellbore history
GeneralWell 31/4-6 was drilled on the Bjørgvin Arch in the Northern North Sea. The main objective was to appraise the 31/4-3 Discovery in the "Intra-Heather sand II" (Fensfjord Formation) and to define the oil/water contact.Operations and resultsAppraisal well 31/4-6 was spudded with the semi-submersible installation Nortrym on 28 February 1982 and drilled to TD at 2447 m in the Early Jurassic Drake Formation. No significant problem was encountered in the operations. The well was drilled with seawater and hi-vis sweeps down to 927 m, with non-dispersed Shale Trol mud from 927 m to 1865 m, and with a fully dispersed Lignosulphonate/Unical/Ligcon mud from 1865 m to TD.The Fensfjord Formation was encountered at 2150 m. It is a predominantly fine grained to silty, micaceous to very micaceous, subarcosic carbonaceous and occasionally glauconitic sandstone with a clay matrix and some heavily calcite cemented stringers. It is 89 m thick and oil bearing from 2156 m down to the OWC at 2172 m. Net pay in the oil bearing interval was 12.5 m with an average porosity of 26.4% and an average water saturation of 43.8%. As expected the overlying Sognefjord Formation seen in the 31/4-3 and 5 wells was not present at this location. Below the Heather Formation, the well penetrated 62.5 m of the Brent Group, which contained 31 m of net sand with an average porosity of 23.4% and was water saturated. No other reservoir intervals were encountered. Occasional poor oil shows were recorded in the Ness Formation and the Drake Formation.Five cores were cut through the Fensfjord Formation from 2132 m to 2214.5 m. Correlation between the cores and the logs indicates that core depths are two to three meters shallower than logger's depth. RFT fluid samples were taken in the Fensfjord Formation at 2160.5 m (oil and gas) and at 2166.5 m (oil and gas).The well was permanently abandoned on 20 April 1982as an oil appraisal.TestingOne production test was performed in the Fensfjord Formation over the combined intervals 2159.5 - 2163.5 m and 2165-2168 m. The well flowed 452 Sm3 oil and 38300 Sm3 gas through a 36/24" choke. The GOR was 85 Sm3/Sm3, the oil gravity was 34.4 deg API and the gas gravity was 0.727 (air = 1). Maximum flow temperature measured at sensor depth 2153.5 m was 90.6 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]270.002447.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12132.02148.3[m ]22149.02159.5[m ]32159.52178.0[m ]42178.12195.0[m ]52195.52214.0[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]80.7Cores 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 typeLaboratory2035.0[m]SWCIKU2037.0[m]SWCIKU2043.0[m]SWCIKU2057.0[m]SWCIKU2060.0[m]SWCIKU2084.0[m]SWCIKU2090.0[m]SWCIKU2095.0[m]SWCIKU2100.0[m]SWCIKU2106.0[m]SWCIKU2109.0[m]SWCIKU2123.5[m]SWCIKU2128.0[m]SWCIKU2130.0[m]SWCIKU2132.0[m]CIKU2138.0[m]CIKU2144.4[m]CIKU2147.5[m]CIKU2149.5[m]CIKU2154.6[m]CIKU2156.5[m]CIKU2160.1[m]CIKU2170.5[m]CIKU2177.6[m]CIKU2183.1[m]CIKU2201.6[m]CIKU2208.8[m]CIKU2213.9[m]CIKU2215.0[m]SWCIKU2220.0[m]SWCIKU2225.0[m]SWCIKU2231.0[m]SWCIKU2237.0[m]SWCIKU2242.0[m]SWCIKU2247.0[m]SWCIKU2255.0[m]SWCIKU2262.0[m]SWCIKU2268.0[m]SWCIKU2274.0[m]SWCIKU2280.0[m]SWCIKU2287.0[m]SWCIKU2295.0[m]SWCIKU2303.0[m]SWCIKU2310.0[m]SWCIKU2321.0[m]SWCIKU2337.0[m]SWCIKU2345.0[m]SWCIKU2383.0[m]SWCIKU2387.0[m]SWCIKU2395.0[m]SWCIKU2405.0[m]SWCIKU2414.0[m]SWCIKU2416.0[m]SWCIKU2420.0[m]SWCIKU2425.0[m]SWCIKU2435.0[m]SWCIKU2448.0[m]SWCIKU -
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 availableDSTDST12159.002163.0014.04.1982 - 00:00YESDST0.000.00YES -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit155676854181018101876191120612109212321232136215023182318235623802380 -
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]pdf2.15PDF13.12 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.02159216314.3Drill 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]1.0452390000.8530.72785 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL7001840CST10201850CST20352310CST20652448DLL MSFL20352212FDC CNL18452215FDC GR9131862HDT18452446ISF SON1552214ISF SON NGT21152448LDT CNL EPT22152450RFT21382377RFT21602160RFT21662166VELOCITY3602444 -
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 typeCONDUCTOR30243.036243.50.00LOTSURF.COND.20913.026927.01.68LOTINTERM.13 3/81844.017 1/21865.01.72LOTINTERM.9 5/82406.012 1/42447.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured2501.1132.0waterbased7601.1132.0waterbased9201.0341.0waterbased12401.1042.0waterbased17701.3463.0waterbased19401.2764.0waterbased21801.2854.0waterbased23101.3055.0waterbased24001.3154.0waterbased -
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]pdf0.18