25/2-12 A
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General information
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Wellbore history
GeneralWell 25/2-12 was designed to drill the crest of a NNE-SSW trending westward tilting Jurassic fault block. The northern extension of this structure was drilled in 1975 by well 25/2-4 in a down dip position to well 25/2-12. A 70 m hydrocarbon bearing column was encountered in the Vestland Group. The Statfjord Formation was found water bearing. The main objectives of well 25/2-12 were to appraise and test the hydrocarbon discovery of the Middle Jurassic Vestland Group and to explore the Statfjord Formation up dip from well 25/2-4. Due to an unprognosed fault top Vestland came in 112 m deeper than prognosed in 25/2-12. Hence, side track 25/2-12 A was decided. The main purpose of the sidetrack was to explore the still untested Vestland up dip to the West.OperationsAppraisal well 25/2-12 A was sidetracked from 3099 m in well 25/12-2 on 17 November 1988 by the semi-submersible rig West Vanguard and drilled to TD at 3865 m in the Middle Jurassic Vestland Group. During drilling the string got stuck at 3692 m. Drilling was stopped at 3714 m, one metre above the Vestland reservoir. Fishing was unsuccessful, and the string was cut at 3485 m. When tripping out the well started to flow. Several days were needed to control the well and finally a cement plug was set from bottom to 3528 m. The cement was dressed to 3612 m and a 7" liner was set from 3600 m to 2927.5 m. After that the cement was drilled out to 3612 m before commencing to drill the 5 7/8" section. During drilling the 5 7/8" phase the string got stuck several times, and finally stuck at 3865 m. While jarring the well started flowing again. After controlling the well a 4 1/2" liner was set from 3863 m to 3562 m. Cement was drilled out to 3830 m before logging. Due to the problems no open hole logs were run in well 25/2-12 A; all logs were run behind casing and no fluid samples were taken. No cores were cut. The sidetracked well 25/2-12 A was completed 6 April 1989 as a gas and condensate appraisal.TestingTwo DSTs was planned for the sidetrack. The first was performed in the interval 3795 m to 3805 m (3653 m to 3660.6 m TVD MSL). It produced gas/condensate at a maximum rate of 198000 Sm3/day and a GOR of 1780 Sm3/Sm3. The condensate density at stock tank condition was 0.8157 g/cm3, while the gas gravity was 0.713 (air = 1). The DST1 string got stuck. Due to an unsuccessful fishing operation of the DST1 string the second DST had to be abandoned. -
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]3105.003864.00 -
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 typeCONDUCTOR30197.036199.00.00LOTSURF.COND.20890.026907.01.32LOTINTERM.13 3/82848.017 1/22867.01.88LOTINTERM.9 5/83099.012 1/43099.01.98LOTLINER73603.08 1/23714.02.10LOTLINER4 1/23865.05 3/83865.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.0380537955.6Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.037.000120Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.01022000000.8100.7001960 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL GR CCL34993812CBL VDL GR CCL DIG.SONIC28853602CNL GR CCL36853800FGL-DEN GR35903829MWD31003400TDT-P GR CCL34883819 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit137416102010731110121012551427204221692169218222862300235024192492258026222622285033423610363037083708371037153715 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.49 -
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]pdf32.58 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured31741.8148.014.2WATER BASED22.11.198831751.8148.014.2WATER BASED24.11.198831771.8148.014.2WATER BASED25.11.198832071.81464.015.6WATER BASED25.11.198832901.8446.013.7WATER BASED29.11.198833111.8541.011.7WATER BASED29.11.198833351.8538.011.2WATER BASED30.11.198833601.8540.011.7WATER BASED01.12.198833861.8540.012.2WATER BASED02.12.198834071.8541.012.7WATER BASED05.12.198834121.8546.013.2WATER BASED05.12.198834151.8550.011.2WATER BASED05.12.198834421.8548.012.7WATER BASED08.12.198834481.9053.014.2WATER BASED27.12.198834491.9051.013.7WATER BASED27.12.198834781.9050.012.7WATER BASED28.12.198835061.8546.011.7WATER BASED09.12.198835071.9051.012.7WATER BASED29.12.198835531.9054.014.7WATER BASED30.12.198835921.9056.013.7WATER BASED02.01.198936551.9150.014.2WATER BASED02.01.198936921.9148.012.7WATER BASED12.12.198837141.9153.014.7WATER BASED03.01.198937991.9551.015.6WATER BASED08.02.198938651.9547.014.7WATER BASED09.02.1989