31/2-13 S
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General information
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Wellbore history
GeneralWell 31/2-13 S was drilled as an appraisal in the Troll West oil province in the Northern North Sea. The main objectives of were to investigate the reservoir properties and accumulation conditions between the wells 31/2-5 and 31/2-11. Water and/or gas -coning tests were to be conducted.Operations and resultsAppraisal well 31/2-13 S was spudded with the semi-submersible installation Borgny Dolphin on 2 January 1984 and drilled to TD at 2010 m in the Middle Jurassic Fensfjord Formation. Due to bad weather the string parted and was observed lying across the temporary guide base when the well was spudded. The fish was recovered. Straight hole was drilled down to 500 m where the hole was kicked off with an angle of 1 1/2 degree. Some problems due to tight hole occurred in the 17 1/2" hole. Mud losses to the formation occurred at 1531 and 1700 m, 100 bbls at each depth. A drill break occurred at 1744 m in the 12 1/4" hole section. The well was drilled with seawater and viscous pills down to 473 m, with Gelled mud from 473 m from 473 m to 750 m, with seawater from 750 m to 825 m, and with oil based mud from 825 m to TD. The Oil based mud used was termed "Fazekleen, low toxicity invert oil emulsion mud, based on Shell Sol D70 oil"Top reservoir (top Sognefjord Formation) was penetrated at 1732 m (1526.5 m TVD), top Heather Formation at 1855 m (1613 m TVD), and top Fensford Formation sandstone at 1934 m (1671 m TVD). Oil and gas were encountered in the Sognefjord Formation. The GOC was at 1790 m (1567 m TVD) and the FWL was estimated at 1828.5 m (1594 m TVD). Strong to moderate fluorescence was observed on the cores down to 1844 m (1606 m TVD), but heavy contamination from the oil-based mud made shows detection somewhat uncertain. The upper half of the oil bearing formation consisted of generally clean sandstones. Below 1555 m TVD the sands were micaceous. Tight calcareous streaks occurred over the whole section. The core permeability in the clean sands ranged from 4 D to 15 D. In the micaceous sands the permeability were from 10 mD to 100 mD.Eight fibreglass sleeve cores were cut from 1744 to 1844 m in the Sognefjord Formation sands. Seventy metres (70%) were recovered. An RFT segregated fluid sample was taken in the oil zone at 1800 m.The well was permanently abandoned on 15 March 1984 as a gas and oil appraisal well.TestingA Production test was performed through a 5" production tubing in the Late Jurassic sequence. During clean-up producing 810 Sm3 oil/day gas cap gas broke through. The well was then produced at rates up to 604 Sm3/day. The gas-oil ratio increased from solution GOR (57 Sm3/Sm3) to 552 Sm3/Sm3. The produced oil had a gravity 0.88 - 0.89 G7cm3 (28 deg API), the gas 0.70-0.63 (air = 1). No formation water produced. The estimated critical rate (to gas coning) in 31/2-13, ca 315 Sm3/day, was significantly lower than in 31/2-5 (795 Sm3/day). Maximum down-hole temperature recorded in the production test was 65.2 deg C. -
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]480.002006.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom11744.01754.0[m ]21754.01757.0[m ]31772.01782.0[m ]41784.01795.0[m ]51795.01807.0[m ]61807.01813.0[m ]71813.01824.0[m ]81825.01840.7[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]78.7Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
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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 availableDSTDST11801.001806.00OIL03.03.1984 - 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 typeCONDUCTOR30455.536468.00.00LOTSURF.COND.20806.026813.01.81LOTINTERM.13 3/81700.017 1/21710.01.61LOTINTERM.9 5/81999.012 1/42007.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.01801180721.0Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.060Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.05401441800.8800.630267 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL GR6351697CBL VDL GR14501968CST00DIL BHC GR8051675DIL LSS GR16992006ISF BHC GR455823LDL CNL GR8041677LDL CNL GR16992007LDT CNL GR455825NGS16992007RFT18001800RFT GR HP17501992VELOCITY4552006 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit3587831460146015401577171817281732173218551934 -
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]PDF7.74pdf5.93pdf0.10pdf0.72pdf2.16pdf1.50pdf1.03pdf0.43pdf0.26pdf1.63pdf6.68pdf5.80pdf2.66pdf2.27pdf0.72pdf0.91pdf0.87pdf0.83pdf0.44pdf0.14pdf1.74pdf0.20pdf0.26pdf0.15pdf0.77pdf2.45pdf0.72pdf26.29 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured5001.05WATER BASED5501.07WATER BASED6001.10WATER BASED8001.12WATER BASED8301.30OIL BASED9001.31OIL BASED11401.40OIL BASED15501.41OIL BASED17501.25OIL BASED