33/12-8 A
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General information
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Wellbore history
GeneralWell 33/12-8 A is a sidetrack from well 33/12-8 S in the Tampen Spur area. It is situated on a westerly rotated fault block on the southern part of the Beta Ridge. The main objective of well 33/12-8 A was to investigate the hydrocarbon potential in the Middle Jurassic Brent Group in the "Ole" prospect (Skinfaks segment N2), as a result of the positive hydrocarbon discovery in the Skinfaks N3 segment. The secondary objective was to identify the hydrocarbon contact in the Tarbert Formation.OperationsThe wildcat well 33/12-8 A was side-tracked from the 13 3/8" casing at 2066 m in well 33/12-8 S on 26 April 2002 with the semi-submersible installation Borgland Dolphin and drilled to TD at 5098 m /3399.5 m TVD RKB in the Rannoch Formation. The well was drilled with Versavert OBM from kick-off to TD. For well history above sidetrack, see well 33/12-8 S. Technical difficulties were experienced during the sidetrack of 33/12-8 A. Because of problems with attaining the necessary azimuth turn to reach target T1, it was necessary to pull out twice in the beginning of the well to get the desired well path.Both geology and oil-water contact came approximately as prognosed in segment N2. Gas was proven in the uppermost part of the reservoir, while the lower part is oil filled. The sediment layers in segment N2 came in 30 meters deeper than prognosed.No cores were cut. Twelve fluid samples were collected in well 33/12-8 A, in two reservoirs of the Tarbert Formation. Six of the samples were collected in the N3 reservoir. Oil was found in the samples collected from the depths 2954 and 2922 m. Gas/condensate was found at depths 2906 and 2868 m. The oil samples collected from depths 2922 and 2954 suffered different technical problems and one sample from 2922 contained 12 percent contamination. The gas/condensate samples contained 28 to 40 percent contamination. The last six samples were collected in the N2 reservoir. Water was found in the sample from depth 4606 m, oil was found in the samples collected from depth 4565 m, and gas/condensate was found in the samples from depths 4136.4 and 4033 m. The oil samples collected from depths 4565 m contained 15 percent contamination. The gas/condensate samples contained 3 to 19 percent contamination. The water sample was not registered with any contamination.The pore pressure at the top of the Brent prospect in segment N2 is calculated to be 411 Bars (2825 m TVD MSL), corresponding to 1,48 g/cm3 EMW. Well 33/12-8 A was suspended on 16 May 2002 as an oil and gas discovery and a possible future producer.TestingNo drill stem test was performed -
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]2090.005095.00 -
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 availableDST0.000.00CONDENSATEYES -
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 typeINTERM.9 5/85098.012 1/45098.00.00LOT -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]MDT TLC28504606MDT TLC31255078MWD - LWD CDR21002283MWD - LWD CDR22832411MWD - LWD CDR28145098MWD - LWD CDR BHI24112814PEX AITH GR27783801PEX AITH GR37005078PEX AITH GR MDT20663170 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit168840931180718071885203026492649286628663127318236303630390239024167416745544554477050415075 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.57 -
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].pdf2.27.pdf0.60 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured24491.6442.0VERSAVERT27751.6440.0VERSAVERT28321.6444.0VERSAVERT39621.6456.0VERSAVERT42971.6449.0VERSAVERT42971.6449.0VERSAVERT