25/4-1
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General information
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Wellbore history
GeneralWell 25/4-1 is the discovery well on the Heimdal Field. The primary objective was Paleocene sand development (which was confirmed by the well), while Jurassic sands were regarded as a secondary objective. Planned depth was 3500 m.The well is Type Well for the Heimdal Formation.Operations and resultsWildcat well 25/4-1 was spudded with the semi-submersible installation Neptune 7 on 1 July 1972 and drilled to TD at 4060 m in the Triassic Smith Bank Formation. From 2600 m to 3580 m the well built some angle (maximum 5 deg), resulting in a 3 m deviation between measured and true vertical depth at 3580 m. In addition, logger's depth is 6 m deeper than driller's depth from seabed to 3525 m. Below 3525 m driller's depth is equal to logger's depth. This history quotes logger’s depth if not otherwise stated. While drilling at 3178 m the well started to flow and a lost circulation situation followed. The situation was adequately dealt with. The well was drilled water based all through.The well penetrated a 356 m thick Heimdal Formation from 2067 m to 2423 m. The reservoir was composed of more or less unconsolidated sands with interbedded shales and carbonates. The formation was gas filled down to a gas/oil contact at 2173 and contained oil in a thin zone down to a shale at 2177 m. The OWC could not be seen in the well. The upper Cenomanian rested unconformably on a 14 m thick Oxfordian/Callovian Draupne Formation sequence, which in turn rested unconformably on the Middle Jurassic Vestland Group at 3185 m. Several permeable reservoirs were penetrated from 3185 m to 3512.5 m (3179 m to 3506.5 m drillers depth) in the Middle Jurassic to Late Triassic. Four of these were hydrocarbon bearing, with separate fluid contacts. Oil was found from 3185 m to an OWC at 3195 m in the Hugin and Sleipner formations. The Statfjord Formation held gas from 3292.5 m to a GOC at 3297 m with oil from 3297 m to an OWC at 3303.5 m. In addition, a thin gas zone was found further down in the Statfjord Formation, from 3508 m to 3512.5 m. No contact was seen here. Finally the Late Triassic Smith Bank Formation had gas in a thin zone from 3532 m down to a GWC at 3533.5 m.An extensive coring programme was carried out with 18 cores and a total of 254 m core recovered. Cores were cut in the Balder Formation (core 1), Heimdal Formation (cores 2, 3, and 4), Tryggvason Formation (core 5), and the Sleipner and Statfjord formations (cores 6 to 18).Four drill stem tests were conducted. DST 1/Statfjord flowed from the interval 3307 m to 3321 m (3301 m to 3315 m drillers depth) in the Statfjord Formation and produced only 50 Sm3 water. The DST temperature was 112 °C. DST 2 in Sleipner produced only water and filtrate without any hydrocarbons. DST 3 flowed from the interval 3185 m to 3190 m (3179 m to 3184 m drillers depth) near top Sleipner Formation and produced 190000 Sm3 gas, 74 Sm3 oil and 384 Sm3 water pr day through a 1" choke. The DST temperature was 104 °C. DST 4 (called DST 1/Heimdal in well reports) flowed from the interval 2115 m to 2128 m in the Heimdal Formation and produced 952000 Sm3 gas and 85 Sm3 condensate pr day through a 1" choke. The temperature in this test, measured at 2099 m, was 71 °C.choke. DST 1/Statfjord flowed from the interval 3307 m to 3321 m (3301 m to 3315 m drillers depth) in the Statfjord Formation and produced only 50 Sm3 water. -
Cuttings at the Norwegian Offshore Directorate
Cuttings at the Norwegian Offshore Directorate Cuttings available for sampling?NOCuttings at the Norwegian Offshore Directorate Cutting sample, top depth [m]Cutting samples, bottom depth [m]450.004060.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom11936.01944.0[m ]22078.02095.3[m ]32096.02114.0[m ]42409.42413.5[m ]53088.03092.5[m ]63188.03195.0[m ]73195.03204.0[m ]83204.03222.4[m ]93222.43234.8[m ]103288.03306.0[m ]113306.03316.0[m ]123316.03333.9[m ]133334.03352.0[m ]143370.03388.0[m ]153388.03406.0[m ]163407.33418.0[m ]173418.03436.0[m ]183436.03454.2[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]245.5Cores 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 availableDST0.000.00WATERYES -
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 typeCONDUCTOR30181.036182.00.00LOTSURF.COND.20442.026450.00.00LOTINTERM.13 3/81917.017 1/21920.00.00LOTINTERM.9 5/82942.012 1/42950.00.00LOTLINER73524.08 1/23524.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.0330033140.02.0320832130.03.03179318425.4Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.02.03.029.000Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.02.03.0741800000.7972432 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL18502946CNT FDC29463527FDC CNT GR19222626GR1201915GR CBL CCL28773523GR SL19222626GR SL29463173GR SL31503423GR SL31503525GR SL35254055HDT19222626HDT29463485IES4411915IES19222626IES25902950IES29463173IES29463528IES31503423IES35254061LL919222626LL929463520ML MLL19222626ML MLL29463530ML MLL35264060SL4411915SL GR25902950 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit145381423826100010801317133019261926197220272067242325702620262027213062315431713171318531853190329235133513 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.51 -
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]pdf20.98pdf1.89 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1701.05seawater4501.15seawater18001.2550.0seawater28001.2550.0seawater35002.10seawater -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory1610.0[m]DCOD1620.0[m]DCOD1640.0[m]DCOD1660.0[m]DCOD1680.0[m]DCOD1690.0[m]DCOD1720.0[m]DCOD1740.0[m]DCOD1760.0[m]DCOD1780.0[m]DCOD1800.0[m]DCOD1820.0[m]DCOD1840.0[m]DCOD1860.0[m]DCOD1880.0[m]DCOD1900.0[m]DCOD1920.0[m]DCOD1945.0[m]DCOD1960.0[m]DCOD1980.0[m]DCOD2000.0[m]DCOD2020.0[m]DCOD2040.0[m]DCOD2060.0[m]DCOD2075.0[m]DCOD2088.0[m]DCOD2115.0[m]DCOD2120.0[m]DCOD2140.0[m]DCOD2160.0[m]DCOD2180.0[m]DCOD2200.0[m]DCOD2220.0[m]DCOD2245.0[m]DCOD2260.0[m]DCOD2280.0[m]DCOD2300.0[m]DCOD2320.0[m]DCOD2340.0[m]DCOD2360.0[m]DCOD2380.0[m]DCOD2400.0[m]DCOD2420.0[m]DCOD2440.0[m]DCOD2460.0[m]DCOD2480.0[m]DCOD2500.0[m]DCOD2515.0[m]DCOD2540.0[m]DCOD2560.0[m]DCOD2570.0[m]DCOD2600.0[m]DCOD3705.0[m]DC3725.0[m]DC3745.0[m]DC3765.0[m]DC3785.0[m]DC3805.0[m]DC3825.0[m]DC3845.0[m]DC3865.0[m]DC3885.0[m]DC3905.0[m]DC3925.0[m]DC3945.0[m]DC3965.0[m]DC3985.0[m]DC4005.0[m]DC4025.0[m]DC4035.0[m]DC4055.0[m]DC -
Thin sections at the Norwegian Offshore Directorate
Thin sections at the Norwegian Offshore Directorate DepthUnit2104.00[m ]2412.00[m ]3222.00[m ]3229.00[m ]3229.00[m ]3230.00[m ]3295.00[m ]3224.00[m ]3296.00[m ]3380.00[m ]3298.00[m ]3298.00[m ]3324.00[m ]