2/10-2
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General information
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Wellbore history
GeneralWell 2/10-2 is located in the western area of block 2/10 in PL163, in an inverted half graben structure at the Grensen Spur. The block, being the southernmost in the Norwegian North Sea sector, borders both the UK and Danish sector lines, and held only one previously drilled exploration well at the time of drillingThe main objective of the well was to test the hydrocarbon potential of Late Jurassic sandstones, prospect-A, a combined structural and stratigraphic trap located in the hanging wall of a half graben structure. The well should also test the prospectivity of the Shetland Group, which held oil in the Tor Formation in well 2/7-2; the reservoir potential of the Cromer Knoll Group in stratigraphic closures formed by pinch outs against Base Cretaceous Unconformity; and possible hydrocarbon potential of the pre-Triassic/Rotliegendes Group.Operations and resultsExploration well 2/10-2 was spudded with the semi-submersible installation "Treasure Saga" on 16 February and drilled to TD at 4164 m in rocks of undefined age. The well was drilled with spud mud down to 1169 m, with KCl mud from 1169 m to 3681 m, and with "HI TEMP" polymer mud from 3681 m to TD. The Tor and Hod limestones slowed down the penetration rate in the 12 1/4" section. Drill string vibrations and torque fluctuations were created which ruined several bits and resulted in one drill string failure.The 8 3/8" section was surprisingly easy to drill. It was easy to achieve penetration rates of 15 m/hr, but due to geological and pressure control, the penetration rate had to be controlled through most of the section. The pore pressure increased very rapidly at top of the Mandal Formation, and the mud weight had to be adjusted accordingly. The mud weight was increased from 1.70 SG to 1.95 SG over an interval of approximately 30 m. Maximum estimated bottom hole static temperature was approximately 150°C based on Horner plot.The predicted Late Jurassic sandstone section was not present in the well position, and no hydrocarbons were encountered. The possible sandy sequences within the Lower Cretaceous, Cromer Knoll Group, were also absent.In the Nordland and Hordaland Groups the well penetrated mainly claystones with sandstone beds.The Rogaland Group consisted of 4 formations, the Balder, Sele, Lista and the VåÅle Formations. The top of the Balder Formation was penetrated at 2893 m and consisted of tuffaceous claystones with minor traces of sandstones and dolomites/limestones. The Top Sele Formation was reached at 2910 m and the formation comprised claystones with minor sandstones. The Top Lista Formation was penetrated at 2952 m and the VÅle Formation at 2990 m. Both formations consisted of claystones with traces of limestone lamina.The Shetland Group consisted of the Ekofisk, Tor, Hod, Blodøks, and Hidra Formations. In the Tor Formation cores showed limestones with weak shows in the upper part, from 3085 to 3086.63 m and 70 - 80 cm zone of residual oil from 3090 to 3091 m. Also cuttings from the Tor Formation showed minor shows, otherwise there were no significant hydrocarbon indications. Average log porosity in the Tor Formation was 20%. In general the formations in the Shetland Group comprised of limestones with minor traces of cherts and marl. At 3709 m the Cromer Knoll Group was penetrated. The Cromer Knoll Group consisted of the Røby and Åsgard Formations. The formations comprised claystones with minor marl beds. No shows were seen. The top Tyne Group was reached at 3882 m and consisted of the Mandal Formation. The lithology was claystones. The Smith Bank Formation was penetrated at 3905 m and comprised claystones alternating with siltstones. There were traces of sandstones and anhydrite beds. The Zechstein Group consisted of anhydrites. An undefined formation was penetrated at 4128 m and consisted of argillaceous sandstones with an average log porosity of 10.2%.Four cores were cut during drilling of well 2/10-2. The first core was cut in the Tor Formation from 3085.0 - 3089.0 m. The core recovery was 1.63 m (41%). The second core was also cut in the Tor Formation from 3089.0 m - 3098.18 m. The core recovery was 9.18 m (100%). The third core was cut in an undefined formation from 4151.0 m - 4154.0 m. The core recovery was 2.1 m (70%). The fourth core was also cut in the undefined formation from 4154.0 m - 4164.0 m. The core recovery was 9.55 m (95%). The FMT tool was run on wire line, but due to tight formation few representative pressure points were obtained and no fluid samples taken.The stratigraphic tops prognosed for the well were well within the expected margins for all of the present horizons.The well did however build an angle from the last casing point and downwards which resulted in a total deviation of approximately 90 m eastwards and up dip of the planned well bore. This resulted both in a penetration of the deeper horizons somewhat shallower than predicted, but of more importance a deviation towards the fault separating the up thrown block of the prospect. A possible crossing of the fault plane must therefore be considered in the interpretation of the strata encountered in the well. The operator held a structural model where the well had been drilled into a pop-up block, not representative for the entire half graben, as one of the more likely cases. The well was therefore temporarily plugged. A technical sidestep of the well in westward direction, from the last casing point and down, were also considered and proposed by the operator, but it was agreed that such an operation would not generate enough deviation from existing well bore to be conclusive. The well was suspended on 25 April 1993 as a well with oil shows.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]1180.004151.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom13085.03086.6[m ]23089.03098.2[m ]34151.04153.1[m ]44154.04163.6[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]22.5Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
Core photos 
3085-3086m3089-3093m3093-3097m3097-3098m4151-4153m
4154-4158m4158-4162m4162-4163m -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit97150828932893291029522990301430143084322135613566370937093720388238823905390540624128 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.62 -
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]pdf16.92 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBIL30003150DIFL ACL CDL GR11512719DIFL ACL ZDL CN GR26993684DIFL ACL ZDL CN GR36654165DIFL ACL ZDL GR1931163DIPLOG36654165DIPLOG GR26993684DLL MLL GR29653205FMT30783128FMT GR41294162FMT GR41524153MWD - GR RES DIR974151MWD CDR - S/D RES36814164MWD CDR - SNR1971165SWC11982445SWC37014148SWC39084149VSP5004160 -
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 typeCONDUCTOR30194.036197.00.00LOTINTERM.201152.0261165.02.02LOTINTERM.13 3/82699.017 1/22722.01.97LOTINTERM.9 5/83665.012 1/43686.02.17LOTOPEN HOLE4164.08 3/84164.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1601.039.0WATER BASED1601.039.0WATER BASED1971.03WATER BASED2101.03WATER BASED6091.03WATER BASED11651.05WATER BASED11691.20WATER BASED36811.7018.0WATER BASED41641.9720.0DUMMY -
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]pdf0.22
