2/7-20
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General information
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Wellbore history
GeneralWell 2/7-20 was drilled on the "South Eldfisk structure", later called Embla. The 2/7-9 well, drilled in 1973, tested oil at uneconomic rates from a thick pre-Late ?Jurassic sand sequence on this structure. Well 2/7-9 established a 111 m pay section with average porosity of 13% and 55% oil saturation. A clear OWC was found at 4387 m MSL. Following a 1986 re-evaluation of the test it was concluded that the poor test results might have been due to mechanical problems. Subsequently the 2/7-20 well was spudded to test the previously encountered sandstones. The objectives of the well were to test "economic" flow rates from sands on the South Eldfisk structure below the Late Jurassic shales of the Mandal Formation. At the time of drilling the cost of a subsea completion had been estimated to be US$ 12 million which meant that flow rates in excess of 286 m3 oil/day were considered economic. Well 2/7-20 was placed on a separate and higher fault block in the structure than the one drilled by 2/7-9.Operations and resultsWildcat well 2/7-20 was spudded with the semi-submersible installation Dyvi Stena on 15 October 1987. The well was re-spudded three times because of collapsed hole problems. After drilling riserless to 608 m the lower part of the hole collapsed after encountering a gas sand that resulted in the loss of drill pipe. The well was sidetracked at 234 m, and 13 3/8" casing was set above the Eocene at 2439 m. A drilling break was encountered at 4084 m. After drilling a further 2 m, 100% sands with good shows were circulated up. High pressures together with the long section of open hole necessitated plugging back and sidetracking immediately below the 13 3/8" casing shoe. No logs were run at TD in this hole before plugging back. Drilling the sidetrack was difficult due to high pressures and gas and the coring programme above 7" casing at 4278.8 m was abandoned due to problems with balancing the well. The sidetrack was drilled to TD at 4510 m in pre-Late Jurassic sandstones that were later dated to a Devonian age.The reservoir section in the 2/7-20, the Devonian sands, was encountered at 4061 m; 217 m higher than in 2/7-9 due to faulting. This resulted in a higher average oil saturation of 81% and might have contributed to a somewhat higher average porosity of 15%.Detailed organic geochemical analyses found migrated live oil in the Ekofisk Formation, the Hod Formation, the Nordland/Hordaland Group formations and in the Devonian sands below 4097 m. This oil is similar in composition to oil from the surrounding Chalk fields. A biodegraded oil component was found in the Early Cretaceous and the sands from 4095 m to 4269 m. A highly mature bitumen was also found in the Lower Sands from 4397 m to 4508.6 in addition to the above mentioned live oil and biodegraded phases. This bitumen appears to reflect an early phase of migration from a different source.One core was cut from 3070.9 m to 3080 m in the Ekofisk Formation with 100% recovery. Three further cores were cut in the Devonian sands with 100% recovery: Core 2 from 4395.5 to 4400.4 m; Core 3 from 4400.4 to 4409.5 m; and Core 4 from 4491.2 to 4509.5 m. RFT measurements showed good permeability. No wire line fluid samples were taken.The well was suspended on 25 June 1988 as an oil discovery.TestingOne DST test was performed in the interval 4099.6 to 4258.1 m. Seven zones were perforated and tested at the same time.The test produced 599 Sm3 oil and 225000 Sm3 gas /day through a 24/64" with a drawdown of over 13 MPa. The GOR in this flow was 375 Sm3/Sm3, the oil density was 0.813 g/cm3, and the gas gravity was 0.81 (air = 1). A CO2 content of 3.5% was reported. The maximum temperature measured at 4178.8 m was 160.6 deg C.l> -
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]1164.004852.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom110075.010105.0[ft ]214421.014437.7[ft ]314437.714469.4[ft ]414735.014792.0[ft ]Cores at the Norwegian Offshore Directorate Total core sample length [m]41.3Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
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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 availableDSTDST 14099.504258.0007.06.1988 - 00:00YES -
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 typeCONDUCTOR30172.036174.00.00LOTSURF.COND.201069.0261074.02.03LOTINTERM.13 3/82439.017 1/22448.02.01LOTINTERM.9 5/83800.012 1/43819.02.16LOTLINER74278.08 1/24284.02.22LOTOPEN HOLE4512.05 7/84512.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.0409942589.5Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.0Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.0566223000365 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CNL SLS GR24393817CST GR38104284CST GR42804510DIL MSFL SLS GR10670DIL SLS GR38104510DLL MAFL GR24393810FMS GR24393810LDL CNL GR42804513LDL CNL NGL14933817LDL CNL NGL38104285OBDT GR38104285OBDT GR42804511RFT GR38104285RFT GR42804511WSC10674510 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit9616022936293629513001305430663066314634393899390639653965406040604061 -
Geochemical information
Geochemical information Document nameDocument formatDocument size [MB]pdf0.66pdf2.58pdf12.15pdf3.29pdf1.19 -
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]pdf3.80pdf29.59 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured41.8015.09.6WATER BASED16.02.1988262.0423.010.1OIL BASED16.03.19881321.03WATER BASED22.10.19871471.04WATER BASED22.10.19871661.02WATER BASED20.10.19871731.03WATER BASED22.10.19871841.02WATER BASED20.10.19872531.0410.025.9WATER BASED27.10.19872921.0410.026.8WATER BASED27.10.19873510.00WATER BASED27.06.19883540.00WATER BASED27.06.19883921.0412.030.2WATER BASED23.10.19875931.0412.032.6WATER BASED27.10.19876081.0417.035.4WATER BASED26.10.19878341.0417.036.4WATER BASED27.10.198710741.04WATER BASED28.10.198710741.04WATER BASED29.10.198710741.04WATER BASED30.10.198710741.10WATER BASED03.11.198710741.2319.05.7WATER BASED03.11.198710741.3213.06.2WATER BASED03.11.198711571.3214.07.2WATER BASED03.11.198713731.3318.09.1WATER BASED04.11.198714981.4315.08.6WATER BASED05.11.198716141.5114.07.2WATER BASED06.11.198717991.5817.07.7WATER BASED10.11.198718412.1145.016.8OIL BASED27.06.198819372.1266.014.4WATER BASED18.10.199119831.6516.09.6WATER BASED10.11.198721161.6518.07.7WATER BASED10.11.198721491.8518.05.3WATER BASED19.01.198822701.6519.010.5WATER BASED11.11.198723881.67WATER BASED18.11.198723881.6715.05.7WATER BASED19.11.198723881.6715.04.8WATER BASED20.11.198723881.6515.04.8WATER BASED24.11.198723881.6515.05.3WATER BASED24.11.198723881.6514.05.3WATER BASED24.11.198723931.8315.05.7WATER BASED19.01.198824230.001.06.7WATER BASED21.01.198824381.8316.06.2WATER BASED22.01.198824431.8316.05.7WATER BASED26.01.198824481.6517.011.0WATER BASED11.11.198724481.6718.06.2WATER BASED16.11.198724480.4714.011.5WATER BASED16.11.198724480.4714.07.7WATER BASED16.11.198724481.656.06.2WATER BASED17.11.198724481.6514.05.3WATER BASED25.11.198724481.6518.010.1WATER BASED12.11.198724481.6520.07.2WATER BASED16.11.198724511.6513.05.7WATER BASED25.11.198724841.8017.06.7WATER BASED26.01.198826101.6714.05.3WATER BASED26.11.198726761.8017.07.7WATER BASED26.01.198827691.8018.08.6WATER BASED26.01.198828351.6818.08.6WATER BASED27.11.198729031.8018.09.6WATER BASED27.01.198829151.8016.06.7WATER BASED28.01.198829651.7122.012.4WATER BASED30.11.198729991.7121.012.9OIL BASED30.11.198730191.8017.07.7WATER BASED29.01.198830242.1046.016.8OIL BASED23.06.198830481.8517.04.3WATER BASED12.01.198830481.8520.06.2WATER BASED13.01.198830711.7122.013.4WATER BASED30.11.198730711.7121.09.6WATER BASED01.12.198730981.7123.08.6WATER BASED02.12.198731011.8017.011.0WATER BASED02.02.198831011.8017.012.0WATER BASED02.02.198831951.7522.010.5WATER BASED03.12.198732521.8017.09.6WATER BASED02.02.198832991.7522.010.5WATER BASED04.12.198733211.7520.09.6WATER BASED09.12.198733301.8017.09.6WATER BASED02.02.198833821.7520.011.5WATER BASED09.12.198734031.9812.02.9WATER BASED12.01.198834030.00WATER BASED12.01.198834051.8019.010.1WATER BASED03.02.198834551.7519.010.1WATER BASED09.12.198734681.8017.010.5WATER BASED04.02.198834811.6821.011.0WATER BASED09.12.198734861.7522.011.5WATER BASED10.12.198734931.8016.010.1WATER BASED09.02.198835841.8017.09.6WATER BASED09.02.198836101.7421.011.5WATER BASED14.12.198736311.8015.010.1WATER BASED09.02.198836551.8016.010.1WATER BASED09.02.198836771.8015.012.9WATER BASED09.02.198836961.7520.012.4WATER BASED14.12.198737121.8014.07.7WATER BASED10.02.198837121.8014.06.7WATER BASED11.02.198837241.7519.012.4WATER BASED15.12.198737301.7518.09.6WATER BASED15.12.198737411.8016.07.7WATER BASED12.02.198837611.7518.010.5WATER BASED15.12.198737862.1147.016.8OIL BASED20.06.198837862.1142.016.3OIL BASED22.06.198837862.1143.012.0WATER BASED22.06.198837862.1140.013.9OIL BASED22.06.198837862.1151.013.9OIL BASED22.06.198837862.1145.016.3OIL BASED22.06.198837901.8015.010.1WATER BASED16.02.198838151.7517.08.6OIL BASED16.12.198738151.7520.010.1WATER BASED16.12.198738161.8016.010.1WATER BASED16.02.198838191.8617.010.1WATER BASED16.02.198838191.9220.09.6WATER BASED17.02.198838191.9219.08.1WATER BASED23.02.198838191.9219.09.6WATER BASED23.02.198838191.9221.05.7WATER BASED23.02.198838191.9221.05.7WATER BASED24.02.198838191.9421.05.7WATER BASED25.02.198838191.9423.06.2WATER BASED26.02.198838191.9424.06.2WATER BASED01.03.198838191.9421.03.8WATER BASED01.03.198838191.9318.04.8WATER BASED01.03.198838191.9318.04.3WATER BASED02.03.198838191.9317.04.3WATER BASED02.03.198838191.9319.04.8WATER BASED03.03.198838191.9418.06.7WATER BASED04.03.198838191.9219.010.1WATER BASED18.02.198838191.9219.09.1WATER BASED19.02.198838191.9219.08.6WATER BASED23.02.198838261.9432.09.6OIL BASED08.03.198838261.9431.09.1OIL BASED08.03.198838681.9429.012.9OIL BASED08.03.198838811.9431.013.4OIL BASED08.03.198838811.9430.012.9OIL BASED10.03.198838981.7517.09.1WATER BASED17.12.198739041.7520.09.6WATER BASED18.12.198739251.7521.01.0WATER BASED22.12.198739461.9460.012.9OIL BASED10.03.198839561.7520.08.1WATER BASED22.12.198739931.9426.012.9OIL BASED14.03.198840181.7520.011.0WATER BASED22.12.198740631.9426.011.5OIL BASED14.03.198840841.9926.012.4OIL BASED14.03.198840842.0427.013.9OIL BASED14.03.198840842.0323.014.4OIL BASED15.03.198840861.8520.06.2WATER BASED14.01.198840861.8519.07.2WATER BASED15.01.198840861.8523.04.8WATER BASED19.01.198840861.8523.05.3WATER BASED19.01.198840861.7719.010.1WATER BASED22.12.198740861.8730.017.7OIL BASED23.12.198740861.8721.012.0WATER BASED29.12.198740861.8724.014.8WATER BASED29.12.198740861.8728.07.7WATER BASED29.12.198740861.8519.05.3WATER BASED29.12.198740861.8525.04.8WATER BASED29.12.198740861.8715.04.3WATER BASED30.12.198740861.9812.08.6WATER BASED07.01.198840861.9812.05.7WATER BASED07.01.198840861.9813.05.3WATER BASED07.01.198840867.7914.06.7WATER BASED07.01.198840860.0012.012.0WATER BASED07.01.198840861.9813.05.7WATER BASED07.01.198840861.9813.05.3WATER BASED08.01.198840861.9812.02.9WATER BASED11.01.198840862.1619.06.2WATER BASED12.01.198840861.8720.07.2WATER BASED29.12.198740861.9810.07.2WATER BASED12.01.198840861.8516.06.2WATER BASED20.01.198841642.0527.012.4OIL BASED17.03.198842382.1131.09.6OIL BASED10.05.198842562.0527.010.5OIL BASED18.03.198842562.0931.011.0OIL BASED22.03.198842562.0777.06.7OIL BASED22.03.198842562.1028.09.1OIL BASED22.03.198842562.1028.08.6OIL BASED22.03.198842562.0625.07.2WATER BASED23.03.198842702.1034.09.6OIL BASED13.05.198842702.0937.012.9OIL BASED13.05.198842702.1038.012.0OIL BASED13.05.198842702.1041.013.9OIL BASED08.08.198842702.1149.06.2OIL BASED08.08.198842702.1120.015.8OIL BASED10.05.198842702.1035.011.0OIL BASED10.05.198842702.1036.013.4OIL BASED18.05.198842702.1037.012.9OIL BASED18.05.198842702.0937.013.4OIL BASED19.05.198842702.1136.012.4OIL BASED19.05.198842702.0939.013.4OIL BASED25.05.198842702.1033.012.0OIL BASED25.05.198842702.0941.012.9OIL BASED25.05.198842702.1042.013.4OIL BASED25.05.198842702.1041.012.9OIL BASED26.05.198842702.1041.012.9OIL BASED27.05.198842702.0943.012.0OIL BASED30.05.198842702.0942.012.0OIL BASED30.05.198842702.1041.09.6OIL BASED30.05.198842702.1042.012.0OIL BASED31.05.198842702.0942.011.5OIL BASED01.06.198842702.0941.011.5OIL BASED02.06.198842702.1040.012.9OIL BASED03.06.198842702.1040.012.4OIL BASED07.06.198842702.1041.012.9OIL BASED07.06.198842702.1142.014.8WATER BASED15.06.198842702.1142.011.5OIL BASED15.06.198842702.1142.015.3OIL BASED15.06.198842702.1141.016.8OIL BASED15.06.198842702.1144.015.8OIL BASED15.06.198842702.1142.015.8OIL BASED17.06.198842702.0940.013.4OIL BASED25.05.198842702.1040.013.4OIL BASED08.08.198842812.0928.07.2OIL BASED24.03.198842842.1130.07.7OIL BASED25.03.198842842.1130.07.2OIL BASED30.03.198842842.1130.08.1OIL BASED05.04.198842842.1331.07.7OIL BASED05.04.198842842.1130.05.3OIL BASED05.04.198842842.1130.07.7OIL BASED05.04.198842842.0729.07.2OIL BASED06.04.198842842.1131.07.2OIL BASED29.03.198842842.1130.07.2OIL BASED29.03.198842840.00WATER BASED05.04.198842842.1130.07.2OIL BASED05.04.198842932.0727.05.7OIL BASED07.04.198842942.0730.06.2OIL BASED08.04.198843062.0731.08.1OIL BASED12.04.198843072.0730.07.7OIL BASED12.04.198843202.0731.07.2OIL BASED12.04.198843272.0730.07.7OIL BASED12.04.198843702.0730.08.1OIL BASED13.04.198843832.1132.06.2OIL BASED14.04.198843832.1130.08.6OIL BASED15.04.198843832.1131.08.6OIL BASED19.04.198843872.1130.08.6OIL BASED19.04.198843962.1131.08.6OIL BASED19.04.198844002.1131.08.6OIL BASED19.04.198844102.1132.010.1OIL BASED20.04.198844182.1130.08.1OIL BASED22.04.198844392.0728.07.7OIL BASED22.04.198844502.1030.08.6OIL BASED27.04.198844862.0929.08.1OIL BASED27.04.198844912.0930.07.2OIL BASED27.04.198845102.1031.014.4OIL BASED10.05.198845102.1135.011.0OIL BASED10.05.198845102.0931.07.2OIL BASED27.04.198845102.0930.07.2OIL BASED28.04.198845102.0931.07.7OIL BASED29.04.198845102.0931.07.7OIL BASED10.05.198845102.0930.05.7OIL BASED10.05.198845102.1032.09.1OIL BASED10.05.198845102.1132.09.6OIL BASED10.05.198845102.1131.09.6OIL BASED10.05.198845102.1132.010.1OIL BASED10.05.198845142.1264.012.9WATER BASED18.10.199145142.1266.014.4OIL BASED18.10.199145142.1266.014.4OIL BASED21.10.199145142.1266.014.4OIL BASED21.10.199145142.1266.014.4OIL BASED21.10.199145141.9547.017.2WATER BASED31.10.199145141.9544.022.0WATER BASED04.11.199145141.9544.019.2WATER BASED05.11.199145141.9544.019.2WATER BASED05.11.199145141.9544.019.2WATER BASED05.11.199145141.44WATER BASED06.11.199145141.44WATER BASED11.11.199145141.44WATER BASED11.11.199145141.44WATER BASED12.11.199145142.1259.08.6OIL BASED15.10.1991 -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory13360.0[ft]DCOD13400.0[ft]DCOD14425.8[ft]COD14426.1[ft]COD14430.1[ft]COD14442.8[ft]COD14451.6[ft]COD14463.0[ft]COD14466.4[ft]COD14745.6[ft]COD14751.1[ft]COD14758.6[ft]COD14766.6[ft]COD14782.8[ft]COD14789.4[ft]COD