31/7-1 A
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General information
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Wellbore history
Wellbore historyGeneralWell 31/7-1 A is a geological sidetrack to 31/7-1 on the northern part of the Bjørgvin Arch between the Brage and Oseberg Sør fields in the North Sea. The 31/7-1 Brasse mainbore found oil and gas in the Late Jurassic Sognefjord Formation. The Brasse sidetrack was drilled in the southeast direction from 31/7-1, across a minor fault. The purpose was to reduce the uncertainty for the hydrocarbon contacts as well as to investigate the continuity and facies development of the reservoir.Operations and resultsAppraisal well 31/7-1 A was kicked off at 913 m in the main bore on 22 June 2016. It was drilled with the semi-submersible installation Transocean Arctic to TD at 2530 m in the Middle Jurassic Fensfjord Formation. No significant problem was encountered in the operations. The well was drilled with KCl/polymer/GEM mud from kick-off to TDThe well encountered the Sognefjord Formation at 2370.5 m (2166.5 m TVD) at the prognosed depth, just below the Draupne shales. The Fensfjord Formation was encountered at the prognosed depth of 2477 m (2254.5 m TVD).The Sognefjord Formation sandstones / siltstones were gas and oil bearing with a gross vertical hydrocarbon column of 5.5 m gas and 24.4 m oil. The Sognefjord Formation had 88 m gross vertical reservoir, with 41.2 m net reservoir and 12.3 m net vertical pay zone. The Fensfjord Formation was water bearing. The GOC was interpreted at 2380 (2172 m TVD) and the OWC at 2409.7 m (2196.4 m TVD), confirming the contacts from the mainbore. The only oil shows reported from the well were on the cores from the hydrocarbon-bearing part of the Sognefjord Formation.Two cores were cut from 2362 to 2425 m with 100% recovery. MDT fluid samples were taken at 2399.5 m (oil) and 2409.8 m (water).The well was permanently abandoned on 14 July 2016 as an oil and gas 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]940.002530.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12362.02398.0[m ]22398.02425.6[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]63.6Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit14367983783719641964205221082268227522752355235523712478 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]LWD - ECD GR RES DIR DEN CAL NEU23252530LWD - NBI RES ECD GR DIR9132317 -
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 typeCONDUCTOR30209.036209.00.00SURF.COND.13 3/8902.017 1/2908.01.70LOTPILOT HOLE908.09 7/8908.00.00INTERM.9 5/82309.012 1/42317.01.59LOTOPEN HOLE2530.08 1/22530.00.00 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured2501.02Sea water3721.039.0Sweeps4391.1540.0KCL/Polymer/Glycol4421.4936.0Kill/DIsplacment Mud5041.0313.0Sweeps5041.4934.0Kill/DIsplacment Mud5871.1540.0KCL/Polymer/Glycol5871.4934.0Kill/DIsplacment Mud8501.4113.0KCL / Polymer / GEM10251.4927.0KCL / Polymer / GEM20911.4428.0KCL / Polymer / GEM21541.5132.0KCL / Polymer / GEM22081.4128.0KCL /Polymer / GEM22411.4422.0KCL / Polymer / GEM23171.2615.0KCL / Polymer / GEM23171.4426.0KCL / Polymer / GEM23271.2415.0KCL / Polymer / GEM25301.2421.0KCL / Polymer / GEM