25/5-5
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General information
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Wellbore history
GeneralExploration well 25/5-5 is located a few km east-southeast of the Heimdal field. The objective was the turbiditic sands of the Heimdal Formation, which is the reservoir for the Heimdal gas field. The Jotun oil discovery (8 km south) and a minor oil discovery on 25/4-2 (5 km north-northwest) are also in Heimdal turbiditic sands. The prognosed TD of the well was 2600 m in the Ty / Våle Formations in case of a discovery, or 2250 m in the Heimdal Formation, in case of a dry well. The chosen location was on the highest structural point of the 25/5-5 closure. Oil with a possible gas cap was the anticipated reservoir fluidOperations and resultsWildcat well 25/5-5 was spudded with the semi-submersible installation Vildkat Explorer on 27 October 1995 and drilled to TD at 2600 m in the Paleocene Våle Formation. No significant operational problems were encountered in this well and TD was reached in less than 9 days after spud. The well was drilled with seawater and hi-vis pills down to 1206 m and with Safemul oil based mud from 1206 m to TD. Due to the choice of OBM system, the 8 1/2" diameter was drilled in preference to 12 1/4" to minimize mud and cuttings volumes.Top Heimdal Formation was found at 2158.5 m, 13 m above prognosis. The formation was 334 m thick. The reservoir was oil-bearing, with an OWC at 2176.3 m. There was no recognised gas cap. As prognosed, the reservoir properties were very good. Two cores were cut from 2162.5 m to 2199.75 m in sandstone of the Heimdal Formation. The cored interval was hydrocarbon bearing, with the OWC clearly defined on the lower core. The MDT tool was run to obtain pressure and fluid samples from the reservoir. Pressure depletion from production of the Heimdal Field was confirmed. From the pressure plot some vertical barrier effects were evident in the deeper part of the aquifer zone, below 2206 m. In the upper part of the Heimdal Sand, however, no pressure barriers could be seen. Four sample bottles from 2172.1 m were transported onshore for transfer to PVT bottles. It was confirmed that the sample quality was satisfactory. Two samples from 2160.5 and 2161.6 m plugged during filling, probably due to sand production. To check for hydrocarbon fluid the samples were drained on the rig.The well was permanently abandoned on 23 November 1995 as an oil discovery.TestingOne test was performed in the interval 2158.50 - 2169.50 m in the reservoir. The test produced 428 m3 / day of oil and 15578 m3 /day of gas on 96/64" choke. The GOR was 36.4 m3/m3 with a wellhead pressure of 8.9 bars. The API gravity was near 35 deg. -
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]1220.002600.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12162.52172.3[m ]22172.32199.8[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]37.3Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
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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 availableDST2169.502158.8015.11.1995 - 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 typeCONDUCTOR30208.036210.00.00LOTSURF.COND.13 3/81198.017 1/21200.00.00LOTOPEN HOLE2600.08 1/22600.01.81LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.02170215938.1Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.02.0001.00020.000Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.0428155780.8800.70036 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]AIT DSI GR11982596CBL VDL CCL GR15862206CCL GR20452145CCL GR20452145IPL CNL EPT11982599MDT GR21582275MWD LWD - DGR EWR2131206MWD LWD - DGR EWR 412092600SWC GR20402555UIB GR11982580VSP4902580 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit14743094710321044142014332023202320752123215924932531 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.34 -
Geochemical information
Geochemical information Document nameDocument formatDocument size [MB]pdf1.57 -
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]pdf45.37 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1451.02WATER BASED2121.02WATER BASED6931.02WATER BASED9201.03WATER BASED21601.2635.0OIL BASED22171.03WATER BASED26001.2639.0OIL BASED