30/9-12 A
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General information
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Wellbore history
GeneralWell 30/9-12 A was designed as a sidetrack from well 30/9-12 on the Alpha South structure on the southern extension of the Oseberg Field. Well 30/9-12 proved a 10 m column of oil in the Tarbert Formation, but as no oil/water contact was established there remained uncertainty as to the amount of hydrocarbon resources within the southern part of the Alpha South structure. The objectives of well 30/9-12A were to sidetrack approximately 700 m down dip south-eastwards in order to establish the water pressure and oil/water contact in the Tarbert Formation in the area as well as to verify the structural mapping and geological model of the area. No drilling hazards were anticipated.Operations and resultsAppraisal well 30/9-12 A was with kicked off with the semi-submersible rig Vildkat Explorer on 9 May 1991. Kick-off point was at 1033 m, below the 13 3/8" casing shoe in well 30/9-12. The well bore was drilled to a total depth of 3061 m (2927 m TVD RKB) in the Drake Formation of the Dunlin Group. It was drilled with KCl polymer mud from kick-off to TD.The well encountered an unexpected Heather Formation sandstone development that proved to be hydrocarbon bearing. A total of 2.63 m net pay sand was calculated, with an average porosity of 23.3% and average water saturation of31.4%. Sandstones of the Brent Group were penetrated below the regional oil/water contact and were found to be totally water bearing. A total of six conventional cores were cut in this well in the interval 2874 m to 2919 m in the Tarbert and Ness Formations. A total of 30 sidewall cores were attempted and 28 were recovered. Drilling went on without any significant problems to TD. Oil was recovered from RFT samples taken at 2776.3 m and 2776.6 m. Geochemical analyses showed the Heather oil in 30/9-12 A correlate very well with Tarbert oils from 30/9-12 and 30/9-10, indicating a common source and identical maturity.The well was suspended on 4 June 1991 as a minor oil 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]1040.003060.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12874.02876.0[m ]22877.02887.0[m ]32888.02899.0[m ]42901.02904.0[m ]52906.02912.0[m ]62914.02920.0[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]38.0Cores 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 typeLaboratory1070.0[m]DCSTRAT1100.0[m]DCSTRAT1130.0[m]DCSTRAT1150.0[m]DCSTRAT1170.0[m]DCSTRAT1200.0[m]DCSTRAT1230.0[m]DCSTRAT1250.0[m]DCSTRAT1290.0[m]DCSTRAT1310.0[m]DCSTRAT1340.0[m]DCSTRAT1360.0[m]DCSTRAT1390.0[m]DCSTRAT1420.0[m]DCSTRAT1450.0[m]DCSTRAT1480.0[m]DCSTRAT1500.0[m]DCSTRAT1530.0[m]DCSTRAT1560.0[m]DCSTRAT1590.0[m]DCSTRAT1620.0[m]DCSTRAT1650.0[m]DCSTRAT1710.0[m]DCSTRAT1810.0[m]DCSTRAT1900.0[m]DCSTRAT1920.0[m]DCSTRAT1950.0[m]DCSTRAT1980.0[m]DCSTRAT2000.0[m]DCSTRAT2030.0[m]DCSTRAT2060.0[m]DCSTRAT2090.0[m]DCSTRAT2120.0[m]DCSTRAT2150.0[m]DCSTRAT2180.0[m]DCSTRAT2210.0[m]DCSTRAT2240.0[m]DCSTRAT2270.0[m]DCSTRAT2300.0[m]DCSTRAT2330.0[m]DCSTRAT2360.0[m]DCSTRAT2390.0[m]DCSTRAT2565.0[m]DCHYDRO2620.0[m]DCSTRAT2650.0[m]DCSTRAT2675.0[m]DCHYDRO2680.0[m]DCSTRAT2690.0[m]DCSTRAT2695.0[m]DCSTRAT2700.0[m]DCSTRAT2715.0[m]DCSTRAT2721.0[m]SWCHYDRO2724.0[m]SWCHYDRO2728.5[m]SWCHYDRO2735.8[m]SWCHYDRO2738.5[m]SWCHYDRO2745.0[m]SWCHYDRO2760.0[m]DCSTRAT2763.2[m]SWCHYDRO2772.0[m]SWCHYDRO2777.8[m]SWCHYDRO2780.9[m]SWCHYDRO2784.0[m]SWCHYDRO2795.0[m]SWCHYDRO2805.2[m]SWCHYDRO2812.0[m]DCSTRAT2822.5[m]SWCHYDRO2827.8[m]SWCHYDRO2835.3[m]SWCHYDRO2848.0[m]SWCHYDRO2857.0[m]SWCHYDRO2865.0[m]DCSTRAT2865.5[m]SWCHYDRO2868.2[m]SWCHYDRO2871.0[m]SWCHYDRO2877.8[m]CHYDRO2879.5[m]CHYDRO2882.0[m]CHYDRO2882.4[m]CHYDRO2883.2[m]CHYDRO2883.9[m]CHYDRO2885.2[m]CHYDRO2888.5[m]CHYDRO2897.0[m]CHYDRO2901.4[m]CHYDRO2901.6[m]CHYDRO2907.7[m]CHYDRO2915.4[m]CHYDRO2917.1[m]CHYDRO2917.8[m]CHYDRO2927.0[m]DCSTRAT2937.0[m]DCSTRAT2947.4[m]SWCHYDRO2955.0[m]DCSTRAT2975.0[m]DCSTRAT2985.0[m]DCSTRAT2995.0[m]DCSTRAT3005.5[m]SWCHYDRO3007.5[m]SWCHYDRO3020.0[m]SWCHYDRO3030.0[m]DCSTRAT3040.0[m]DCSTRAT3050.0[m]SWCHYDRO3060.0[m]DCSTRAT -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit12964684298010121353138520882088217723392417242224222638263826752676269126922692273427652781286928692887296330073007 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.41 -
Geochemical information
Geochemical information Document nameDocument formatDocument size [MB]pdf0.53 -
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]pdf8.61 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CST GR27213050DIL LSS LDL CNL NGL SP CAL27183062DIL LSS LDL GR SP AMS10402800DLL MSFL LDL CNL GR CAL27182918FMS4 GR27183060MWD GR RES DIR10333058RFT HP GR27762903RFT HP GR27762776RFT HP GR28742979VSP9303050 -
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 typeCONDUCTOR30214.036216.00.00LOTCONDUCTOR13 3/81002.017 1/21019.00.00LOTINTERM.9 5/82717.012 1/42824.01.61LOTOPEN HOLE3061.08 1/23061.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured3001.2013.07.0WATER BASED04.06.199110171.2620.012.0WATER BASED10.05.199114741.3919.012.0WATER BASED14.05.199121001.4020.011.0WATER BASED14.05.199123721.4022.010.0WATER BASED14.05.199124191.4221.010.0WATER BASED14.05.199124821.4020.014.0WATER BASED15.05.199125491.4020.013.0WATER BASED16.05.199126001.2013.07.0WATER BASED04.06.199126171.4020.08.0WATER BASED21.05.199126581.4019.011.0WATER BASED21.05.199126581.4022.010.0WATER BASED21.05.199126811.4112.013.0WATER BASED21.05.199127091.4019.07.0WATER BASED21.05.199127501.3918.09.0WATER BASED22.05.199127501.4018.06.0WATER BASED23.05.199127501.4021.08.0WATER BASED24.05.199128241.2012.06.0WATER BASED28.05.199128771.2012.07.0WATER BASED28.05.199128941.2012.06.0WATER BASED28.05.199129071.2012.06.0WATER BASED28.05.199129191.2013.06.0WATER BASED29.05.199129191.2013.06.0WATER BASED30.05.199130011.2013.06.0WATER BASED31.05.199130611.2013.07.0WATER BASED04.06.199130611.2013.07.0WATER BASED04.06.1991 -
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