30/6-17 R
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General information
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Wellbore history
GeneralWell 30/6-17 was drilled on the Alpha structure on the western side of the Oseberg Field in the northern North Sea. The structure is a tilted and rotated fault block with a Jurassic sequence dipping towards the east. The main objective was to prove hydrocarbons in the Statfjord Formation. Prognosed depth was 200 m into the Statfjord Formation with TD at ca 2682 m. Well 30/6-17 was drilled by Vildkat Explorer to a depth of 615 m where it was temporary abandoned due to technical problems. The re-entry 30/6-17 R was made to fulfil the original objectives.Operations and resultsWildcat well 30/6-17 was re-entered with the semi-submersible installation Treasure Hunter on 14 August 1985 and drilled to TD at 2650 m in the Early Jurassic Statfjord Formation. The well was drilled without significant technical problems, but about one third of the time was counted as downtime. The main contribution to the excessive downtime was waiting on weather. The well was drilled with KCl/polymer mud from 615 m to 2409 m and with NaCl/polymer mud from 2409 m to TD.Oil shows were recorded on limestone and dolomite stringers in the Tertiary and Late Cretaceous, beginning at 1650 m and all the way down to near BCU at 2290 m. These oil shows were most frequent, and strongest, in the interval 1750 to 1810 m in the lower part of the Tertiary Hordaland Group. Two gas bearing sandstones units, possibly reworked Brent Group, were found at the BCU (2296 - 2300 m and 2303 - 2308 m).The prognosed target for the 30/6-17 well was the Statfjord Formation. The well was, however, drilled ca 600 m east of the proposed location at a structurally down flank position. At this position also the Cook Formation was penetrated.The Cook Formation (2401.5 - 2441 m) consists of medium to fine grained sand sandstones in the upper part, becoming fine to very fine with depth. The sandstones were found oil bearing down to 2419.5 m (free water level from RFT). No gas/oil contact was seen in the well, but the presence of a gas cap was indicated in the DST. The net pay is calculated from logs to 15.9 m, with an average porosity of 26.4% and average water saturation of 40.1%. Cut off criteria were: PHI < 12%, Vsh > 40%, Sw > 60%. The Statfjord Formation (2563 m - TD) was encountered water bearing. Of a gross thickness of 73 m (log) penetrated by the well, 57.6 m was net sand with an average porosity of 24.3%. The RFT results indicate no pressure communication between the Statfjord and the Cook Formations.A total of six cores were cut. Core 1 at 2324 - 2342.15 m was an attempt to cut a core from the gas bearing sands at BCU, but did not really capture the sands. Cores 2 - 4 were cut in the Cook Formation, while cores 5 and 6 were cut in the Statfjord Formation. There is a discrepancy between loggers and drillers depth of 2 m for cores no 1 - 4, and 4 m for cores no 5 and 6, the logger's depth being the shallower. SFT/RFT pressure tests and sampling were performed in the Cretaceous and Jurassic. In the Cretaceous interval sixteen SFT good pressure tests were taken. A segregated SFT fluid sample was unsuccessfully attempted taken at 2297.9 m in one of the gas sands. RFT was used for pressure recordings and sampling in the Cook and Statfjord Formations. Twenty one pressure measurements were recorded, and one segregated sample was taken in the Cook Formation at 2408.5 m (5.82 litre oil with some gas and water/filtrate in 1st. chamber).4 February the well bore was plugged back to the 13 3/8" casing shoe for an up-dip sidetrack to the original target Statfjord Formation. The well is classified as an oil and gas discovery.TestingOne DST was performed in the Cook Formation at 2401.7 - 2414.7 m. Seven flow periods with different chokes and rates were tested. In the second flow period the well produced oil at a rate of 701.1 Sm3/d and gas at a rate of 110 000 Sm3/d Through a 14.29 mm choke. The gas/oil ratio was 156.9 Sm3/Sm3. The oil gravity was measured to 0.824 g/cc (40.1 API) and gas gravity was 0.662 (air = 1). The GOR varied from 130 to 274 Sm3/Sm3. When the well was produced at higher rates the GOR increased substantially. This indicated the presence of a gas cap, and that the well penetrated the reservoir just below the gas/oil contact. In the three final flows the measured bottom hole temperature stabilised at 97.8 deg C, independent of very variable flow rate and GOR. -
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]240.002650.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12324.02342.2[m ]22411.02417.0[m ]32423.02443.9[m ]42444.02445.4[m ]52570.02588.3[m ]62588.32612.6[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]88.9Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
Core photos 
2324-2329m2329-2334m2334-2339m2339-2342m2411-2417m
2417-2423m2423-2429m2429-2435m2435-2441m2441-2443m
2444-2445m2570-2576m2576-2582m2582-2588m2588-2588m
2488-2594m2594-2600m2600-2606m2606-2612m2612-2613m -
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 availableDSTDST12401.002414.0028.10.1986 - 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 typeSURF.COND.20601.026615.00.00LOTINTERM.13 3/81593.017 1/21621.01.74LOTINTERM.9 5/82386.012 1/42406.00.00LOTLINER72638.08 1/22650.01.70LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.02401241514.3Drill 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]1.07011100000.8200.660157 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL4922544CDL CNL CAL GR6012643DIL LSS GR SP5602643DLL MSFL21472642FED18992638GR20842405ISF LSS GR221609RFT24052628SFT21722307SGR23782644X-Y CAL6012638 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit13565287689094296012801301140514631915191519932057216821812181229623092309240224412563 -
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]pdf3.65pdf18.67 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured23971.5033.0water based23991.5030.0water based24211.3218.0water based25541.32water based25541.3215.0water based26131.3217.0water based26501.3217.0water based
