35/11-21 S
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General information
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Wellbore history
GeneralWell 35/11-21 S was drilled to appraise the 35/12-2 Grosbeak discovery on the Ryggsteinen Ridge in the North Sea. The primary objective was to explore the reservoir potential of the Ness Formation and to prove oil in the Etive Formation.Operations and resultsAppraisal well 35/11-21 S was spudded with the semi-submersible installation Transocean Arctic on 26.July 2018 and drilled to TD at 2800 m (2588 m TVD) m in the Early Jurassic Cook Formation. Operations proceeded without significant problems. The well was drilled with seawater and bentonite sweeps down to 449 m, with KCl/polymer/GEM mud from 449 to 996 m, and with Innovert NS oil-based mud from 996 m to TD.Top of Brent Group, Ness Formation was penetrated at 2595.2 m (2383 m TVD). The Ness and Etive formations were oil-bearing down to top Rannoch Formation at 2686 m (2474 m TVD). Of this ca 90 m oil column 45 m was effective reservoir sandstone with good to very good reservoir properties. In addition to shows in Ness-Etive, there were oil shows in Rannoch Formation sandstone, described as very weak patchy pale yellow direct fluorescence, very slow, very weak, blue white to pale yellow cut fluorescence, weak, pale yellow fluorescent residue. Otherwise there were no shows in the well.Three 54 m cores were cut from 2566 to 2620.9 m, from 2620.90 to 2675.4 m, and from 2675.4 to 2729.8 m. Each core was cut with 100% recovery. MDT fluid samples were taken at 2615.5 m (oil), 2634.49 m (oil), 2657.54 m (oil), 2681 m (oil), and 2698.5 m (water).The well was permanently abandoned on 5 September 2018 as an oil appraisal well.TestingA formation production test (DST) from 2625 to 2637 m in the Ness Formation was performed. The test produced 825 Sm3 oil and 92517 Sm3 gas /day through a 46/64” choke in the main flow. The GOR was 112 Sm3/Sm3. The gas contained 1.3% CO2 and 1.9% H2S. The DST temperature was 97°C. -
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]460.002800.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12566.02620.9[m ]22620.92675.4[m ]32675.42729.8[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]163.8Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
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 typeCONDUCTOR30449.536449.50.00INTERM.13 3/8990.217 1/2996.01.46FITINTERM.9 5/82445.012 1/42451.01.52FITLINER72794.08 1/22800.00.00 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]0.02625263718.3Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]0.097Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]0.082592517112 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]LWD - GR PWD RES CIB DEN NEU CAL24512800LWD - GR PWD RES VIB DIR SON9962451LWD - PWD DIR384449LWD - PWD RES GR VIB DIR SON449996MDT25952777NEXT ADT PEX CMR24452801VIVSP GR4002798ZAIT MSIP NGI24002801 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit384384579720720114213751375145016031620178419501990199020802318231823612390239825952595266526862724275827582771 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured4491.3927.0KCL- GEM- Polymer WBM4491.02Water based bentonite sweeps8781.3318.0INNOVERT OBM9961.3318.0Innovert OBM9961.3932.0KCl-Gem-Polymer10001.3419.0Innovert OBM22161.3217.0INNOVERT OBM23601.3420.0Innovert OBM24001.1913.0Innovert OBM24001.3420.0Innovert OBM24551.1912.0Innovert OBM27301.2115.0Innovert OBM27301.2015.0Innovert OBM28001.1916.0INNOVERT OBM28001.192.0Packer Fluid