25/4-8
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General information
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Wellbore history
GeneralWell 25/4-8 was the second exploratory test of a large, irregular 4-way closure known as the Gekko structure, discovered by well 25/4-3 in 1974. The reservoir target was the Paleocene Heimdal formation, in a mapped culmination 1.7 km to the WNW of the discovery well. While well 25/4-3 found 8 m of hydrocarbons in a structurally low position, well 25/4-8 was expected to encounter a hydrocarbon column of 45m with an anticipated oil/water contact at 2107 m TVD SS.Operations and resultsWildcat well 25/8-4 was spudded with the semi-submersible installation Deepsea Bergen on 3 June 2003 and drilled to TD at 2286 m in the Paleocene Heimdal Formation. Some problems with hole fill were experienced in the top 36" hole and repeated drill string stalling and stucking in the 17 1/2" section. After setting the 13 3/8" casing at 796 m these problems ceased and the well was drilled on to TD with no significant problems. The well was drilled with seawater down to 803 m and with Carbosea oil based mud from 803 m to TD.Significant gas peaks were recorded in the interval 2096 m to 2129 m. Drilled cuttings were adversely affected by the use of PDC bits, especially in the sandstone intervals, and hydrocarbon shows were affected by the use of oil-based mud in the 8 1/2" hole section. Oil shows were however recorded on cores from 2082 m to 2134 m. Petrophysical evaluation of wire line logs acquired demonstrated that sands within the Lista Formation were gas bearing and that the Heimdal Formation is gas and oil bearing at the location with a gas-oil contact (GOC) at 2121.8 m (2098.8 m TVD SS) and an oil-water contact (OWC) at 2128.5 m (2105.5 m TVD SS). The OWC was 1.5 m shallow compared to that described for the exploration well 25/4-3 and is consistent with shows described from core and cuttings within the Heimdal. Two conventional cores were cut in the interval 2082 m to 2136 m in the Lista and Heimdal Formations. Fluid samples were taken with the MDT tool at 2097 m (gas), 2120 m (gas), and 2127.2 m (oil).The well was permanently abandoned on 22 June as a gas and oil appraisal well.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]1500.002286.20 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12082.02107.1[m ]22109.02135.6[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]51.7Cores 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 availableDST2120.000.00OILYES -
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 typeCONDUCTOR30206.036208.00.00LOTSURF.COND.13 3/8796.017 1/2803.00.00LOTOPEN HOLE2082.012 1/42082.01.45LOTOPEN HOLE2286.08 1/22286.00.00LOT -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]M LWD - GR205803MDT GR20922182PEX AIT DSI HNGS1452284VSI GR6312280 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit1453855097771219130519221922201120602113 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.28 -
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].PDF27.17.PDF0.61 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured01.03SEAWATER5601.08SPUD MUD8031.1445.0KCL13091.2823.0OIL (ENVIRON)22861.2821.0OIL (ENVIRON)