7121/1-1 R
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General information
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Wellbore history
GeneralWell 7121/1-1 was drilled on the Loppa High in the northern part of the Tromsøflaket area, offshore Northern Norway.The primary objective of the 7121/1-1 exploration well was to test the reservoir and hydrocarbon potential of a possible Early Permian (Artinskian) mounded carbonate facies (biohermal build-ups) identified by seismic. Secondary objectives were Late Permian carbonates and Early Carboniferous to Devonian sandstones, Late Carboniferous - Early Permian carbonates, and Triassic sandstones. Finally, the exploration well was designed to fulfill the license's obligatory work program which committed the licensees to drill one wildcat well to test prospects down to rocks of Devonian age or 5000 m, whichever came first.Operations and resultsExploration well 7121/1-1 was spudded on 10 October 1985 in 369 m water depth with the semi-submersible installation "Zapata Ugland". Due to NPD winter season regulations drilling was stopped at 916 m. Drilling of well 7121/1-1R commenced on 19 March 1986 and reached total depth of 5000 m in Late Carboniferous sediments of the Ørn Formation. The well was drilled with sea water and gel down to 1978 m, and with Sea water / gel / polymer from 1978 m to TD. Lost Circulation Material was used below 3370 m. Triassic rocks were encountered at 698 m, unconformably underlying 178 meters of Tertiary claystone and siltstone. The Triassic sediments (2295 m thick) consisted predominantly of very fine clastics with minor interbeds of sandstone, stringers of dolomite and limestone and traces of coal.Fair to poor hydrocarbon shows were encountered in some thin and tight sandstones of Late and Middle Triassic age. The only significant hydrocarbon show was encountered in a 11.5 m thick sandstone bed, between 1932.0 and 1943.5 m, where 18.7 % gas (C1 & C4) was measured by the gas detectors. The Paleozoic section (Permian - Late Carboniferous Ørn Formation) was encountered at 2993 m. The section, +2007 m thick, consists predominantly of carbonates (silicified limestones, limestones, dolomitic limestones, dolomitized limestones and dolomites) with minor interbeds of chert, siltstones and anhydrites.& Silicification, re-crystallization and dolomitization are common and only a few intervals show reasonably fair preservation of original depositional textures.The prognosed primary objective, Early Permian (Artinskian) mounded carbonate facies (biohermal build-ups), was encountered at 3765-3994 m (thickness 229 m). However, biostratigraphic analysis dates the interval as Late Gzhelian - Early Asselian. Only 12% of the carbonate rocks have porosities above 6.0 % (6.0 - 10.0 %). The porosity types recognized in these thin, widely spaced intervals are intercrystalline - interparticle, moldic and fracture porosities.No hydrocarbon shows were encountered while drilling the Paleozoic section and the interpretation of the wireline logs confirmed that the section is 100% water bearing.Wellsite and laboratory geochemical analyses of the sediments drilled indicated that the most significant source rock sequences were Early - Middle Triassic shales between 2200 and 2800 m. Source rocks of Permian age were not found. The well was permanently abandoned as a dry hole 23 August 1986.TestingNo drill stem test was performed. -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom13137.53138.5[m ]23385.03386.0[m ]33511.03513.7[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]4.7Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
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Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory2797.0[m]DCFUGRO -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit3965195196986987922210221026052786299329933502350235863625370039903990 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.74 -
Geochemical information
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Logs
Logs Log typeLog top depth [m]Log bottom depth [m]4ARM-CAL GR90020304ARM-CAL GR19792800CBL VDL3951979DIFL ACL CBL CNL CDL SP CAL GR27815002DIFL ACL CNL CDL SP CAL GR19792805DIFL ACLCNL CDL SP CAL GR9002152DIFL LSACL CDL SP CAL GR27813368MWD DLWD9003368SWC9382123SWC21652794SWC27954995TEMP18002750VSP8005000 -
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 typeCONDUCTOR30518.036526.50.00LOTSURF.COND.20901.022916.01.51LOTINTERM.161979.517 1/22154.01.55LOTINTERM.11 3/42784.014 3/42804.01.46LOTOPEN HOLE5000.010 5/85000.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured5911.089.0WATER BASED8981.089.0WATER BASED9221.088.0WATER BASED9361.089.0WATER BASED9651.108.0WATER BASED11211.1310.0WATER BASED11311.1313.0WATER BASED12071.138.0WATER BASED12441.1410.0WATER BASED12601.1310.0WATER BASED12801.1310.0WATER BASED12921.1413.0WATER BASED13371.139.0WATER BASED14231.1413.0WATER BASED14871.1514.0WATER BASED15151.139.0WATER BASED15271.139.0WATER BASED15761.139.0WATER BASED16181.1310.0WATER BASED16501.1310.0WATER BASED16721.1310.0WATER BASED17001.1314.0WATER BASED17111.1311.0WATER BASED17391.1310.0WATER BASED17601.1312.0WATER BASED18151.1310.0WATER BASED18351.1312.0WATER BASED18841.138.0WATER BASED19071.1312.0WATER BASED19251.138.0WATER BASED19331.1310.0WATER BASED19421.1311.0WATER BASED19601.1310.0WATER BASED19931.1310.0WATER BASED19941.1311.0WATER BASED20391.1311.0WATER BASED20561.1311.0WATER BASED20641.138.0WATER BASED21071.149.0WATER BASED21131.1313.0WATER BASED21151.139.0WATER BASED21201.1310.0WATER BASED21521.138.0WATER BASED21531.158.0WATER BASED21541.1313.0WATER BASED21751.138.0WATER BASED22311.1310.0WATER BASED22361.1310.0WATER BASED23501.1315.0WATER BASED24071.1314.0WATER BASED25181.1314.0WATER BASED25551.1512.0WATER BASED26201.2115.0WATER BASED26631.2617.0WATER BASED27021.3219.0WATER BASED27211.3220.0WATER BASED28041.3220.0WATER BASED28171.2014.0WATER BASED28451.2014.0WATER BASED29001.2014.0WATER BASED29671.2010.0WATER BASED29871.1711.0WATER BASED29981.2014.0WATER BASED30561.2013.0WATER BASED31171.2015.0WATER BASED31381.1710.0WATER BASED31381.1711.0WATER BASED31401.1711.0WATER BASED31811.1711.0WATER BASED32051.1711.0WATER BASED33101.1713.0WATER BASED33701.064.0WATER BASED33861.0811.0WATER BASED34601.0812.0WATER BASED34791.0810.0WATER BASED35131.0812.0WATER BASED36841.078.0WATER BASED39241.0710.0WATER BASED41161.0811.0WATER BASED42991.0912.0WATER BASED44061.0912.0WATER BASED44691.0911.0WATER BASED46951.0911.0WATER BASED48871.0912.0WATER BASED49881.0912.0WATER BASED50001.0910.0WATER BASED