31/2-5
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General information
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Wellbore history
GeneralWildcat well 31/2-5 is located in the southern part of the oil province in the Troll West area, some 6 km west of the discovery well 31/2-1, in a downthrown fault block. The objectives of the well were to test presence and nature of hydrocarbons in a structure west of the main gas reservoir; to test lateral variation in reservoir characteristics westwards; to investigate possible causes for the difference in flat spot appearance in this fault block; and to get a good geologic identification of the various seismic reflectors for lateral extrapolation of well data.Operations and resultsProblems were experienced during positioning and anchoring of semi-submersible installation West Venture for the wildcat well 31/2-5. After 6 days efforts the installation had to be repositioned 25 m from the intended location and the anchors were successfully laid out and tensioned. The well was spudded on 26 October 1980 and drilled to TD at 2532 m in the Triassic Hegre Group. The well was drilled with seawater and viscous pills down to 443 m, with gelled seawater from 443 m to 810 m, with KCl/polymer mud from 810 m to 1807 m, and with seawater/gel from 1807 m to TD.Well 31/2-5 confirmed that the Late Jurassic Sognefjord Formation sandstone reservoir was well developed also in the western part of the structure. A gas column was penetrated from 1536 m to 1579 m (43 m), followed by a 21 m thick oil column down to an OWC at 1600 m. Good oil shows continued down to 1644.5 m. The GOC was found at the same depth as seen in the other wells in the area. The most interesting observation in this well was the presence of the thick oil column below the gas, some 9 m thicker than seen in any of the other wells, and the oil was encountered in a section of the reservoir with very good clean sand. It is yet too early to explain the difference in oil thickness, and the importance of a thicker oil column in a good sand will remain unknown until a full production test of the oil has been carried out. A few carbonate cemented, apparently field-wide bands occur with very low poroperm values. A seal over the structure is provided by the Paleocene claystones.A total of 21 cores (125.8 m) were cut using five Christensen core heads with a total recovery of 98.51 m (78%) from 1511.7 - 1652 m. RFT sampling of pressure points and two successful fluid samples (gas at 1578 m and oil/gas at 1597 m) were consistent with the fluid contacts assessed from the electrical logs. The oil sampled from 1597 m had a gravity of 30.5 deg API compared to 25 deg API in other 31/2 wells.The well was plugged from 1204 m to 1465 m and suspended on 21 December 1980 as an oil and gas appraisal well.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]450.002532.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom11511.71514.3[m ]21514.81517.4[m ]41536.01538.0[m ]51539.51540.5[m ]61542.01545.6[m ]71547.01563.7[m ]81555.01555.2[m ]91555.51564.5[m ]101565.01573.4[m ]111573.41573.9[m ]121573.91577.4[m ]131589.51589.6[m ]141590.51599.5[m ]151599.51604.0[m ]161604.01611.9[m ]171613.01615.4[m ]181616.01625.0[m ]191625.01633.4[m ]201634.01642.9[m ]211643.01651.6[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]108.5Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
Core photos
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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 typeCONDUCTOR30443.036446.00.00LOTCONDUCTOR30446.036446.00.00LOTSURF.COND.20810.026820.01.55LOTINTERM.13 3/81470.017 1/21480.01.60LOTINTERM.9 5/81801.012 1/41812.01.69LOTOPEN HOLE2532.08 1/22532.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.0158215880.0Drill 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]1.0 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL GR3621465CBL VDL GR8101798DLL MSFL GR14681804FDC CNL CAL GR439821FDC CNL CAL GR8071467FDC CNL CAL GR14681805FDC CNL CAL GR18002527HDT14681805HDT18002524HDT.214681805HDT.218002522ISF BHC GR SP363820ISF BHC GR SP6301468ISF BHC GR SP14681805ISF BHC GR SP18002526LDT GR14681806LSS GR14681805RFT14681805TMP3001261TMP3301630TMP13901630VELOCITY3632526 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit36578878881513461346139614261533153615361617169317891860195720702070220122772308238724042471 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.32 -
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]pdf1.18pdf1.01pdf7.30pdf1.36pdf1.58pdf4.06pdf2.90pdf9.86pdf5.69pdf4.28pdf17.20pdf13.11pdf75.61pdf7.24pdf2.17pdf1.85pdf2.09pdf0.15pdf0.15pdf0.14pdf0.16pdf0.15pdf0.12pdf0.15pdf0.28pdf1.40pdf17.02pdf8.22pdf18.40pdf1.78pdf0.16pdf1.10pdf0.89pdf2.14pdf0.91pdf1.09pdf5.83pdf6.03pdf1.21pdf1.13pdf0.42pdf0.05pdf0.58pdf1.66pdf0.81pdf0.20pdf0.42pdf0.67pdf0.14pdf0.14pdf0.14pdf0.14pdf0.80pdf0.81pdf0.11pdf0.54pdf0.76pdf0.21pdf0.39pdf10.45pdf12.59pdf21.53pdf20.70pdf0.33 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured4141.03seawater4731.0536.0seawater7881.2075.0waterbased12701.2154.0waterbased14481.2555.0waterbased18061.1550.0waterbased -
Thin sections at the Norwegian Offshore Directorate
Thin sections at the Norwegian Offshore Directorate DepthUnit1540.00[m ]1545.00[m ]1556.00[m ]1559.00[m ]1567.00[m ]1570.00[m ]1574.00[m ]1601.00[m ]1605.00[m ]1608.00[m ]1618.00[m ]1621.00[m ]1626.00[m ]