25/7-8 S
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General information
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Wellbore history
GeneralWell 25/7-8 S was drilled to test the Enniberg prospect on the Heimdal Terrace in the North Sea. The primary objective was to prove petroleum in Early Jurassic and Late Triassic reservoir rocks (Nansen, Eiriksson and Skagerrak formations). A secondary objective was to prove petroleum in a potential Middle Jurassic sequence.Operations and resultsWildcat well 25/7-8 S was spudded with the semi-submersible installation Leiv Eiriksson on 13 November 2019 and drilled to TD at 3250 m (3213.2 m TVD) m in the Late Triassic Skagerrak Formation. A 9 7/8" shallow gas pilot hole was drilled from the 36x30" conductor shoe at 217 m to 1075 m. No shallow gas or water was observed. Following wireline data acquisition at TD, the 25/7-8 S wellbore was plugged-back to 2750 m and bypass side-track 25/7-8 ST2 drilled to acquire cores. The side-track was kicked off at 2831 m. Operations proceeded without significant problems. The well was drilled with seawater and hi-vis pills down to 217 m, with KCl/Polymer/GEM mud from 217 m to 1129 m, and with Innovert oil-based mud from 1129 m to TD.In the primary exploration target, several oil and gas-bearing intervals with independent isolated columns were penetrated. In the Nansen Formation a total of 19 metres of sandstone with good reservoir properties was encountered. The sands were water bearing. The Eiriksson Formation contained a total of 20 metres of sandstone with moderate reservoir properties, of which 10 m are oil and gas-bearing. The Raude Formation had 11 m of gas bearing sandstone. In the Skagerrak Formation a total of 33 m of sandstone with moderate reservoir properties was encountered, of which 3 metres are gas-bearing.In the secondary exploration target, both the Sleipner and Hugin formations were encountered. The Sleipner Formation had three thin gas-bearing sandstone intervals totalling 3 metres with moderate reservoir properties. The Hugin Formation contained several sandstone layers with moderate reservoir properties and a total net thickness of 30 metres. The Hugin Formation was water-bearing.Intermittent oil shows, direct and cut fluorescence with occasional stain and weak odour, were observed in the intervals 2825 to 2895 m and 2978 to 3225 m.Three cores were cut in succession from 2969 to 3134.24 m in the Amundsen, Nansen, Eriksson and Raude formations in the bypass side-track 25/7-8 ST2. The recovery was 100%. The distance to the main wellbore is 5 m at top reservoir and 10 m at TD. After coring one petrophysical log was run on wireline (PEX-HNGS-GR). MDT samples were taken at 2977 m (water), 3040.9 m (wet gas), 3050 m (water), 3063 m (oil), 3079.1 m (wet gas), and 3116 m (wet gas),The well was permanently abandoned on 9 January 2020 as an oil and gas discovery.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]490.003250.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12969.03023.8[m ]23023.83079.4[m ]33079.43134.2[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]165.2Cores 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 typeCONDUCTOR36217.042217.00.00PILOT HOLE1075.09 7/81075.00.00SURF.COND.13 3/81123.017 1/21129.01.69LOTLINER9 7/82659.012 1/42660.01.92LOTOPEN HOLE3213.08 1/23213.00.00 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]HNGS PEX AIT26613165LWD - ATK ZT GCP OT TT ST10422657LWD - ATK ZT GOT27382967LWD - ATK ZT GOT LT29643163LWD - ATK ZTG OT ORD CCN TT ST25613247LWD - OT151208LWD - OT II2011123LWD - OT ST1831073MDT GR28573116MDT GR29773116NEXT PEX HNGS CMR GR26593250NGI26603249XL ROCK29733150ZAIT MSIP XPT17203216ZVSP41483182 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit151483674674699699699139618721918191820052031215322112355249424942537264726972743275527572757277028022802284728722872297629762995306731203120