35/11-2
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General information
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Wellbore history
GeneralBlock 35/11 is situated at the boundary between the Horda Platform and the Viking Graben just north of the Troll Field and south of block 35/8 where two gas/condensate discoveries had been made. The work obligation for Block 35/11 included three exploration wells to be drilled to 4000 metres or to Triassic sediments, one of which must test an Early Cretaceous stratigraphic play. The first of these wells, 35/11-1, was drilled in 1984 to a depth of 3361 m in rocks of Triassic age. The primary objective of that well was to assess the hydrocarbon potential of the Middle to Upper Jurassic sands in the "A" structure. No hydrocarbons were present in any of the objectives although good quality Brent sands were encountered. The second well to be drilled on the block was 35/11-2. It was designed primarily to test an Early Cretaceous stratigraphic play, interpreted seismically as a fan development with a 130 km3 closure, and reservoir thickness of 270 m. A secondary objective was the "B" structure at Brent level.Operations and resultsWildcat well 35/11-2 was spudded with the semi-submersible rig Treasure Scout on 20 July 1987 and drilled to TD at 4025 m in Early Jurassic rocks. The hole was drilled to setting depth for 20" casing without a riser. MWD was used, but the resistivity unit was destroyed after few meters. Conventional logs did not get past 760 m, and while attempting this; there was an intrusion of formation fluid into the hole. There was no sign of shallow gas, and heavier mud was used. The hole was opened to 26" without logging below 760 m. The reason for the problems around 760 m was probably washed-out zones. When preparing the setting of 20"casing, fluid was again flowing into the hole, and the mud weight was increased. Further drilling went without significant problems. The well was drilled with spud mud down to 1026 m, with seawater and lignosulphonate from 1026 m to 2195 m, and with a seawater/low solids polymer from 2195 m to TD.The well penetrated the Early Cretaceous at 2682 m (prognosed at 2713 m) and intersected a 225 m thick, predominantly argillaceous/marly sequence. No reservoir rocks were penetrated. At 3011 m Intra Heather Formation sandstone was encountered, and at 3370 m the Brent Group was penetrated (prognosed at 3298 m). The Brent section was 231 m thick with reservoir quality sandstones in the Tarbert, Ness, Etive, and Oseberg Formations. It contained a 175 m gross hydrocarbon column, but the net/gross ratio is low. The logs and RFT pressure data showed a gas/water contact around 3545 m (3522 m SS) in the Oseberg Formation. Oil shows were observed in the Late Jurassic Intra Heather sandstone and throughout the Middle Jurassic Brent Group sandstones. Patchy shows persisted through the Dunlin Group and the Statfjord Formation to total depth. Organic geochemical analyses showed good source rock potential in the Draupne and the Heather Formations, the first of these being the best and more oil prone. The penetrated source intervals were immature to marginally mature, and certainly less mature than the sampled petroleum. Analysis of the DST oils indicated a common source, and the oils increased in maturity with depth.Eight cores were cut in the Late and Middle Jurassic reservoirs (total 129 m). Core recovery was 124.9 m (97%). Four RFT fluid samples were taken. Sample RFT 1 taken at 3040.99 m in the Intra Heather Formation sandstone filled very slowly and recovered gas and mud filtrate with a light oil film. Sample RFT 2 at 3077 m in the Tarbert Formation recovered gas and mud filtrate. Sample RFT 3 at 3481.05 m in the Etive Formation recovered gas and condensate. Sample RFT 4 at3524.98 m in the Oseberg Formation recovered gas and condensate.The well was plugged and abandoned on 4 December 1987 as a gas and condensate discovery.TestingFive drill stem tests, including one in the water leg, were undertaken. The Intra Heather sandstone was tight, with a low net/gross, and was not tested.DST 1, the water test in the lower Oseberg Formation, produced 315 m3 water/day through a 28/64? choke in the main flow. The reservoir temperature was 136 °C.DST 2B in the upper Oseberg Formation produced at maximum 280 Sm3 condensate and 369000 gas /day through a 48/64? choke. The GOR was 1319 Sm3/Sm3. The reservoir temperature was 133.3 °C.DST 3 in the Etive Formation produced at maximum 510 Sm3 condensate and 531000 gas /day through a 40/64? choke. The GOR was 1041Sm3/Sm3. The reservoir temperature was 133.3 °C.DST 4 in the Ness Formation produced at maximum 425 Sm3 condensate and 402400 Sm3 gas /day through a 44/64? choke. The GOR was 946 Sm3/Sm3. The reservoir temperature was 135 °C.DST 5 in the Tarbert Formation produced 415 Sm3 condensate and 177400 Sm3 gas /day through a 32/64? choke in the main flow. The GOR was 427 Sm3/Sm3. The reservoir temperature was 130 °C. This test indicated that there is a thin Tarbert Formation on the top without connection to the rest of the reservoir because the GOR is less than half of the GOR in the other tests. -
Cuttings at the Norwegian Offshore Directorate
Cuttings at the Norwegian Offshore Directorate Cuttings available for sampling?NOCuttings at the Norwegian Offshore Directorate Cutting sample, top depth [m]Cutting samples, bottom depth [m]1030.004025.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom23042.03045.2[m ]33369.03391.6[m ]43392.93413.7[m ]53414.03428.9[m ]63452.03462.5[m ]73463.03489.3[m ]83490.03516.3[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]124.4Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory1040.0[m]DCRRI1240.0[m]DCRRI1440.0[m]DCRRI1490.0[m]DCRRI1640.0[m]DCRRI1840.0[m]DCRRI2015.0[m]DCRRI2175.0[m]DCRRI2332.0[m]DCRRI2335.0[m]DCRRI2495.0[m]DCRRI2605.0[m]DCRRI2694.0[m]DCRRI2720.5[m]SWCRRI2745.0[m]DCRRI2760.0[m]DCRRI2772.0[m]DCRRI2808.0[m]DCRRI2835.0[m]DCRRI2841.0[m]DCRRI2865.0[m]DCRRI2940.0[m]DCRRI2950.0[m]DCRRI2970.0[m]DCRRI2991.0[m]DCRRI3012.0[m]DCRRI3033.0[m]DCRRI3042.3[m]CRRI3042.9[m]CRRI3044.2[m]CRRI3044.8[m]CRRI3045.0[m]DCRRI3045.2[m]CRRI3135.0[m]DCRRI3174.0[m]DCRRI3246.0[m]DCRRI3300.0[m]DCRRI3354.0[m]DCRRI3371.4[m]CGEOSTRAT3375.0[m]CRRI3376.6[m]CGEOSTRAT3382.3[m]CGEOSTR3383.0[m]CRRI3393.5[m]CGEOSTRAT3397.0[m]CRRI3400.2[m]CGEOSTRAT3411.0[m]CRRI3411.6[m]CGEOSTR3412.0[m]CRRI3421.7[m]CRRI3422.0[m]CRRI3456.8[m]CGEOSTRAT3462.1[m]CGEOSTR3462.3[m]CRRI3468.7[m]CGEOSTRAT3474.0[m]CRRI3478.9[m]CGEOSTR3480.2[m]CRRI3492.9[m]CGEOSTRAT3505.3[m]CGEOSTR3511.0[m]CRRI3515.8[m]CGEOSTRAT3525.0[m]CRRI3612.0[m]DCRRI3630.0[m]DCRRI3648.0[m]DCRRI3672.0[m]DCRRI3690.0[m]DCRRI3762.0[m]DCRRI3777.0[m]CRRI3822.0[m]DCRRI3846.0[m]DCRRI3870.0[m]DCRRI3900.0[m]DCRRI3942.0[m]DCRRI3960.0[m]DCRRI3978.0[m]DCRRI -
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 availableDSTDST23524.003542.0003.11.1987 - 00:00YESDST3524.003542.0009.11.1987 - 00:00YESDSTDST2B0.000.0009.11.1987 - 00:00YESDSTDST33477.003486.5012.11.1987 - 00:00YESDSTDST43370.003378.0014.11.1987 - 00:00YESDSTDST40.000.0014.11.1987 - 02:00YESDSTDST43427.003432.0014.11.1987 - 00:00YESDST3374.003378.0019.11.1987 - 00:00YESDSTDST 53378.003374.0019.11.1987 - 00:00YESDSTDST5A3374.003378.00YES -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit3957418241081166316631721175319261950195020872675268226822710272129272927301130423370337033803475348735243601360136153712373037753798 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.73 -
Geochemical information
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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]pdf46.01 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.03551355910.72.03524354218.33.03477348715.94.03427343217.45.03374337812.7Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.036.00050.0001362.045.00049.0001333.042.00049.0001334.031.00048.0001355.029.00048.000130Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.052.0280369000.8110.71913193.05105310000.8200.73910414.04254024000.8220.7409465.04151774000.8280.780427 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL GR8572184CBL VDL GR21633348CBL VDL GR33563972CET GR32623596CST00DIL BHC GR547759DIL BHC GR10022188DIL LSS GR390759DIL LSS GR21853372DIL SDT GR33504028DLL MSFL GR21853372DLL MSFL GR33504026LDL CNL GR7252188LDL CNL GR21853373LDL CNL NGS33504030MWD - GR RES DIR3724025MWD - GR RLL33783517NGS33504030RFT29453042RFT29953373RFT33773963SHDT21853373SHDT33504029VELOCITY14304030 -
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 typeCONDUCTOR30546.8361026.00.00LOTSURF.COND.201004.0261026.01.39LOTINTERM.13 3/82184.617 1/22195.01.62LOTINTERM.9 3/53348.812 1/43377.01.85LOTLINER74025.08 1/24025.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured11.03WATER BASED23.07.19874611.02WATER BASED22.07.19875501.03WATER BASED23.07.19875501.06WATER BASED27.07.19875561.06WATER BASED27.07.19876491.006.003WATER BASED28.07.198710261.06OIL BASED29.07.198710261.06WATER BASED03.08.198710261.30WATER BASED03.08.198710261.32WATER BASED03.08.198711801.2610.014.4WATER BASED10.08.198713351.2616.027.8WATER BASED10.08.198713351.2616.027.8WATER BASED11.08.198713501.3011.028.3WATER BASED13.08.198713501.2616.023.0WATER BASED11.08.198713501.2614.015.4WATER BASED11.08.198713501.2612.031.1WATER BASED12.08.198713501.3013.029.7WATER BASED18.08.198713501.3013.026.8WATER BASED18.08.198713501.3018.023.5WATER BASED19.08.198713501.3012.034.5WATER BASED14.08.198713501.3013.029.2WATER BASED18.08.198721951.2026.08.6WATER BASED20.08.198723101.2018.08.6WATER BASED21.08.198723431.2023.07.7WATER BASED24.08.198724421.2025.08.1WATER BASED24.08.198725441.2026.08.6WATER BASED24.08.198725591.2232.09.1WATER BASED25.08.198726311.2425.010.5WATER BASED26.08.198726851.2027.09.6WATER BASED27.08.198727381.2027.09.6WATER BASED28.08.198727881.2031.011.0WATER BASED31.08.198728861.2028.012.5WATER BASED31.08.198729341.2024.012.5WATER BASED31.08.198729501.2225.012.0WATER BASED03.09.198729501.2225.011.0WATER BASED03.09.198729501.2233.012.5WATER BASED04.09.198729501.2225.012.0WATER BASED07.09.198729501.2223.011.0WATER BASED07.09.198729501.2223.012.0WATER BASED07.09.198733771.4328.011.0WATER BASED09.09.198733771.5125.08.6WATER BASED09.09.198733771.5430.011.0WATER BASED10.09.198733771.5729.010.0WATER BASED11.09.198733771.5729.012.0WATER BASED14.09.198733771.5728.010.5WATER BASED14.09.198733771.5729.09.1WATER BASED16.09.198733771.6243.01.1WATER BASED18.09.198733771.5733.014.4WATER BASED14.09.198733771.5823.06.7WATER BASED07.10.198733771.5815.06.2WATER BASED08.10.198733771.5816.04.8WATER BASED09.10.198733791.6233.08.6WATER BASED21.09.198733981.6227.07.2WATER BASED21.09.198734171.6228.06.7WATER BASED21.09.198734381.6222.06.7WATER BASED21.09.198734611.6231.08.1WATER BASED22.09.198734881.6230.08.1WATER BASED23.09.198735041.6230.07.7WATER BASED24.09.198735211.6225.07.7WATER BASED25.09.198735801.6225.09.1WATER BASED28.09.198736821.6225.09.6WATER BASED28.09.198737191.6222.07.7WATER BASED28.09.198737741.6224.09.6WATER BASED29.09.198737871.6218.08.1WATER BASED01.10.198738351.6222.09.6WATER BASED30.09.198739611.6220.06.2WATER BASED05.10.198739621.5825.07.7WATER BASED06.10.198740251.6215.04.8WATER BASED05.10.198740251.6215.44.8WATER BASED05.10.198740251.5820.06.7WATER BASED05.10.1987 -
Thin sections at the Norwegian Offshore Directorate
Thin sections at the Norwegian Offshore Directorate DepthUnit3043.36[m ] -
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]pdf0.23