31/4-9
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General information
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Wellbore history
GeneralWell 31/4-9 was drilled as an appraisal well on the Brage Field on the Bjørgvin Arch in the North Sea. The main objective was to establish the OWC and confirm reservoir trends, hydrocarbon column and reserve potential in the east flank of the structure. TD was prognosed at 2500 m, 70 m into the Dunlin Group.Operations and resultsAppraisal well 31/4-9 was spudded with the semi-submersible installation Polar Pioneer on 23 January 1987 and drilled to TD at 2480 m in the Early Jurassic Drake Formation. No significant problem was encountered in the operations. The well was drilled with spud mud down to 974 m, with KCl/polymer mud from 974 m to 2027 m, and with NaCl/CaCO3/polymer mud from 2027 m to TD.The Fensfjord reservoir came in at 2168.5 m and consisted mainly of fine to medium grained sandstones grading into and interbedded with siltstones. The Fensfjord Formation was oil bearing down to the oil-water contact at 2172 m. The Brent sandstone was found to be water bearing. Oil shows were described in the cored sections from 2103.5 m in the Draupne Formation down to 2222 m in the Fensfjord Formation.An attempt to take two cores in the Tertiary claystones failed. Eight cores were cut with good recovery in the interval 2103 to 2222 m in the Heather and Fensfjord formations. RFT oil samples were taken at 2171.5 m topmost in the Fensfjord FormationThe well was permanently abandoned on 7 March 1987 as an oil appraisal well.TestingTwo drill stem tests were performed in the Fensfjord Formation.DST 1 tested water from the interval 2193.1-2208.1 m through a 50.8 mm choke. The maximum production rate was 577.5 Sm3/day. An injection test was also performed with a maximum injection rate of 576 Sm3/day. Flowing bottom hole temperature was 90.8 deg C.DST 2 tested oil from the interval 2169.6-2171.6 m through a 12.7 mm choke. The maximum flow rate for the oil was 311.1 Sm3/day and for the gas 23253 Sm3/day. DST 2 also produced 7-8% water and emulsion on average. The GOR was 75 Sm3/Sm3, the oil gravity was 0.875 g/cm3, and the gas gravity was 0.769 (air=l) with 0.5 - 1.0 % CO2. Flowing bottom hole temperature was 88.1 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]980.002480.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom32105.02106.8[m ]42107.02114.9[m ]52116.52131.5[m ]62132.52151.1[m ]72149.52164.5[m ]82164.52176.5[m ]92176.52194.4[m ]102194.02222.0[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]116.2Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
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 availableDSTDST22169.602171.60OIL01.03.1987 - 00:00YES -
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 typeCONDUCTOR30254.036254.00.00LOTSURF.COND.13 3/8974.017 1/2974.00.00LOTINTERM.9 5/81998.012 1/42077.00.00LOTLINER72479.08 3/82480.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.02193220850.82.02170217212.7Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.0902.088Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.02.0311232530.8750.76975 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL CST VDL GR15002389CST20082471DIL LSS GR SP9451855DITE LDL CNL NGT19982471DLL MSFL SDT GR19982471GR170945MWD - GR RES1812480RFT21202409RFT21710SHDT19982474VSP3602466 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit1706858461793179318521892204320432093210221022118216923682368239824112411 -
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]pdf3.54.pdf14.45 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1691.2029.010.0WATERBASED09.03.19872531.03WATERBASED26.01.19874661.0399.099.0WATERBASED26.01.19878491.2029.010.0WATERBASED06.03.19879201.0399.099.0WATERBASED26.01.19879701.03WATERBASED27.01.19879740.0025.015.0WATERBASED29.01.19879741.0399.099.0WATERBASED28.01.198710871.2527.018.0WATERBASED30.01.198713631.2525.017.0WATERBASED02.02.198714581.4027.015.0WATERBASED02.02.198718001.2029.010.0WATERBASED05.03.198719621.4030.017.0WATERBASED04.02.198720271.4034.020.0WATERBASED02.02.198720270.0031.018.0WATERBASED03.02.198720331.2028.09.0WATERBASED05.02.198721051.2030.011.0WATERBASED09.02.198721151.2027.08.0WATERBASED09.02.198721411.2028.09.0WATERBASED09.02.198721591.2029.010.0WATERBASED04.03.198721770.0036.012.0WATERBASED27.02.198721770.0035.011.0WATERBASED02.03.198721770.0035.012.0WATERBASED02.03.198721770.0029.010.0WATERBASED03.03.198721771.2125.07.0WATERBASED09.02.198722221.2127.010.0WATERBASED10.02.198722421.2033.010.0WATERBASED20.02.198722420.0033.010.0WATERBASED23.02.198722420.0033.010.0WATERBASED24.02.198722420.0030.010.0WATERBASED25.02.198722420.0036.012.0WATERBASED26.02.198723771.2129.010.0WATERBASED11.02.198723941.2031.010.0WATERBASED19.02.198724791.2026.08.0WATERBASED18.02.198724790.0025.08.0WATERBASED18.02.198724790.0025.07.0WATERBASED18.02.198724790.0031.010.0WATERBASED18.02.198724801.2026.010.0WATERBASED12.02.198724800.0026.010.0WATERBASED13.02.198724800.0026.010.0WATERBASED18.02.1987