1/6-5
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General information
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Wellbore history
GeneralWell 1/6-5 is located in the Feda Graben between the Flyndre and Tommeliten Gamma discovery in the North Sea. The well was drilled on the crest of a major salt diapir. The objective of the well was to test the existence of a chalk raft and the presence of reservoired hydrocarbons.Operations and resultsWildcat well 1/6-5 was spudded with the semi-submersible installation Dyvi Stena on 20 July 1990 and drilled to TD at 1854 in Late Permian salt of the Zechstein Group. An 8 1/2" pilot hole was drilled from 156m to 600m. The hole was control drilled at 30m/hr maximum ROP as a precaution for encountering shallow gas. No shallow gas was encountered. Pore pressure prediction while drilling in the 1/6-5 well was difficult as the only pore pressure detection parameters that appeared to work were gas measurements, resistivity and sonic log measurements. Other parameters such as shale cuttings density, Electric log density, D-exponent and rate of penetration were not successful in determining high pore pressure zones. However, despite the abnormally high pressures and temperatures encountered drilling went forth without major incidents. A minor salt water flow accompanied by a 37.1 % gas peak occurred during a trip at core point at 1725 m. The mud weight was increased from 15 ppg to 15.3 ppg and finally 15.5 ppg as a result of this flow. In the following coring 119 bbls of mud was lost to the formation, but this was cured by setting an LCM pill. The well was drilled with seawater and viscous pre-hydrated bentonite sweeps down to 600 m and with fresh water polymer mud/Duponol WBS 200 wellbore stabilizer from 600 m to TD.From 864 m gas readings showed all components from C1 to C4. Gas peaks from the formation were experienced all the way down to the Ekofisk Formation, some of which originated from thin sandstone beds. Oil shows were first observed at 1434 and 1585 m, both in thin limestone beds of Oligocene age. On reaching the top Ekofisk Formation at 1721 m, limestone with oil stain and bright yellow fluorescence was observed.Two cores were cut. Core 1 was cut from 1725 to 1742.5 m in the Tor and Hod Formations. Only 22% was recovered and most of it was rubble, indicating a highly fractured limestone. Core 2 was cut from 1742.5 to 1751.5 m in the salt. Ten RFT pressure tests were taken in the Shetland Group of which 6 were classified as valid tests. They indicated a formation pressure in the range of 4520 to 4540 psi, being equivalent to 15.6 ppg equivalent mud weight. No obvious pressure gradient could be derived from these 6 points.The well was permanently abandoned on 2 September 1990 as a dry well with shows.TestingOne drill stem test was performed from perforations in the Shetland Group from 1722 to 1740.9 m. The well flowed only salt water at a rate of 231 m3/day on a 24/64" choke. There was no trace of oil and the gas content was too low to be measured. The shut-in pressure after final build-up was 4531 psia. The maximum bottom hole temperature recorded in the test was 98.3 deg C. This corresponds to a mean gradient of 56 deg C/km, assuming 6 deg C at the sea floor. This is an exceptionally high temperature gradient for the Norwegian North Sea. -
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]620.001854.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom11725.01728.9[m ]21742.51751.1[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]12.5Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
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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 typeCONDUCTOR30156.036156.00.00LOTINTERM.20588.026600.00.00LOTINTERM.161126.0221132.01.42LOTINTERM.9 5/81521.012 1/41530.01.74LOTLINER71843.08 1/21854.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.0172217419.5Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.098Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.0 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]BHC GR15211854CST15501754DIL GR SP AMS15211854DIL LSS GR SP LDL AMS11261509DIL SLS LDL GR CAL SP AMS156598DLL MSFL GR15211854FMS15211854LDL CNL NGT15211854LDL GR CAL5881055LSS GR5881055MWD - DPR GR TEMP DIR1561855RFT17221740VSP11351854 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit9511401695169517011710171517211721172517321742 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.30 -
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]pdf1.15pdf29.72pdf20.44 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1561.8826.018.5WATER BASED24.07.19902081.4425.012.5WATER BASED24.07.19906001.05WATER BASED24.07.19906001.05WATER BASED24.07.19906001.03WATER BASED25.07.19906001.1914.010.5WATER BASED26.07.19906671.1911.09.5WATER BASED27.07.199010361.2319.06.5WATER BASED31.07.199011321.3326.017.5WATER BASED31.07.199011321.4126.014.5WATER BASED31.07.199011321.4124.014.0WATER BASED31.07.199011321.4124.021.0WATER BASED01.08.199011321.4122.012.0WATER BASED02.08.199011321.2333.010.5WATER BASED03.08.199011321.4120.07.0WATER BASED06.08.199012751.4530.013.0WATER BASED06.08.199013871.5632.014.0WATER BASED06.08.199015301.6437.08.0WATER BASED09.08.199015301.6430.011.0WATER BASED10.08.199015331.6433.08.0WATER BASED13.08.199016501.7136.08.0WATER BASED13.08.199017251.8336.09.0WATER BASED13.08.199017251.8542.09.0WATER BASED14.08.199017431.8542.09.0WATER BASED15.08.199017561.8535.011.0WATER BASED16.08.199018541.8521.06.0WATER BASED27.08.199018541.8532.016.0WATER BASED20.08.199018541.8530.015.0WATER BASED20.08.199018541.8537.016.0WATER BASED20.08.199018541.8533.012.0WATER BASED21.08.199018541.8528.014.0WATER BASED22.08.199018541.8520.04.0WATER BASED23.08.199018541.8521.04.0WATER BASED27.08.199018541.8521.06.0WATER BASED27.08.199018541.8520.06.0WATER BASED27.08.199018541.8522.06.0WATER BASED28.08.1990