34/7-31
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General information
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Wellbore history
GeneralWell 34/7-31 was drilled in the Borg structure, which is situated on the western side of the Vigdis and Tordis Fields. The primary objective was to appraise the 34/7-23 Discovery in Intra-Draupne Formation Sandstone in this structure. Proven reserves, if sufficient, would most probably be produced through the Vigdis Field installations. Secondary objectives were Paleocene sand (Sele/Lista Formations) in a down-flank position from well 34/7-18 were these sands were oil-filled, and Early Cretaceous sands, found oil filled in well 34/7-21. The well was to be drilled 50 m into the Brent Group, which was expected to be water bearing at well location. In case of encountering an oil-filled Intra-Draupne sand thicker than 10 m TVD in the well, a sidetrack should be drilled, kicked off below the 13 3/8" casing to further appraise the Borg structure.Operations and resultsWell 34/7-31 was spudded with the semi-submersible installation Scarabeo 6 on 10 March 2001 and drilled to TD at 2650 m in the Middle Jurassic Tarbert Formation. A 9 7/8" pilot hole was drilled from seabed 233 m to 1150 m. Logs (MWD) presented from seabed 233 m to 1150 m were recorded in the 9-7/8" pilot hole. The 9 7/8" pilot hole was then opened to 36" and 30" casing run to 306 m. The 26" hole (using 26" hole opener) deviated from the original 9 7/8" pilot hole below 306 m and the two holes were ca 27 m apart at 1150 m. Well 34/7-31 was drilled with returns to Seabed down to 1150 m. Sampling started at 1170 m. The well was drilled with seawater and hi-vis pills down to1150 m, and with Glydril KCl/polymer mud from 1150 m to TD. No gas related problems were experienced in the well. However, the MWD logs show possible gas levels at 280 m - 282 m, 372 m - 374,5 m and 558 m - 561 m.The Intra-Draupne Formation Sandstone was encountered at 2470 with ca 35 meters net oil-bearing reservoir. Then, fourteen m of Draupne Formation shale was penetrated before entering the Heather formation. For the secondary objectives, both were water-filled and only Brent had significant sand (Tarbert Formation). Pressure points were taken with the MDT-tool in order to obtain formation pressures and fluid gradients from all reservoirs encountered in well 34/7-31. Especially the degree of depletion in the Intra-Draupne Sandstone was regarded as crucial information. The measured Intra-Draupne reservoir pressure was the same as the shut-in pressure in the Main Borg field. The gradient and reservoir fluid density was well defined, 0.69 g/cc or 0.067 bars/meter, and the reservoir pressure was measured to 307.04 bar at 2494.7 m. There was an ODT situation; hence the OWC is still not defined. Six high quality MDT oil samples were recovered from the Draupne Formation at 2496 m. Four of these were 250 cc single-phase samples. Two conventional cores were cut from 2472 m to 2506m in the Intra-Draupne Formation Sandstone.The well bore was plugged back to the 13 3/8" casing and permanently abandoned on 13 April 2001 as an 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]1170.002650.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12472.02499.3[m ]22499.32505.7[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]33.7Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit233105710621268130114701482170017001738189118912160245824582460247024702506252026022602 -
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].PDF7.64.PDF24.56 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]MDT18422618MSCT18402641MWD - GR RES DIR2332650PEX DSI VSP17002627VSP16902620 -
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 typeCONDUCTOR30306.036306.00.00LOTSURF.COND.201144.0261144.01.83LOTINTERM.13 3/81779.017 1/21785.01.82LOTOPEN HOLE2650.08 1/22650.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured2331.05WATER BASED3061.05WATER BASED6881.05WATER BASED9051.05WATER BASED11500.00WATER BASED17851.4818.0WATER BASED20921.6026.0WATER BASED25051.6227.0WATER BASED26501.6226.0WATER BASED -
Pressure plots
Pressure plots The pore pressure data is sourced from well logs if no other source is specified. In some wells where pore pressure logs do not exist, information from Drill stem tests and kicks have been used. The data has been reported to the NPD, and further processed and quality controlled by IHS Markit.Pressure plots Document nameDocument formatDocument size [MB]pdf0.22