31/2-9
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General information
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Wellbore history
GeneralWell 31/2-9 was drilled northeast of the well 31/2-7 in the Troll West oil province in the Northern North Sea. The main objectives were to establish the extent of a previously proven thick oil column province in the Troll Field and to complete the well near the OWC in order to follow the development of water coning.Operations and resultsWell 31/2-9 was spudded with the semi-submersible installation Borgny Dolphin on 29 August 1982 and drilled to TD at 1770 m in the Late Jurassic Fensfjord Formation. Some problems were encountered with the well head after running the 20" casing (2.5 days lost), and with the BOP after running the 13 3/8" casing (3.5 days lost). The well was drilled with spud mud down to 460 m, with seawater and gel from 460 m to 816 m, with KCl/polymer mud from 816 m to 1509 m, and with seawater/Drispac mud from 1509 m to TD.Well 31/2-9 encountered a hydrocarbon bearing column of 34.5 m in the Late Jurassic Sognefjord Formation. The reservoir was gas bearing from 1549 -1570 m (21 m gas column) and oil bearing down to 1583.5 m (13.5 m oil column). This was a thinner oil column than expected. The gas reservoir consisted of very fine to medium grained bioturbated sandstones with a high mica content. The sandstones were very silty and well sorted. Around 1570 m a change in lithology to medium/ coarse grained sandstones with low mica content and less bioturbation was seen. In the lower part of the oil reservoir the mica content was slightly more than in the upper part and the sandstones were siltier. Below the OWC shows (moderate to very weak direct fluorescence) were observed on cores throughout the cored section down to 1628 m.Five fiberglass sleeved cores were taken in the 12 1/4" section from 1554 to 1628 m. Four RFT runs were made and 5 samples were obtained: at 1573 m (29 deg API oil), 1571 m (oil), 1565 m (gas), and two samples at 1575 m (oil)The well was permanently abandoned on 1 October 1982 as a gas and oil 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]470.001768.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom11554.01563.0[m ]21563.01571.3[m ]31573.01591.6[m ]41591.61607.8[m ]51610.01627.7[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]69.8Cores 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 typeLaboratory1279.0[m]DCRRI1288.0[m]DCRRI1297.0[m]DCRRI1306.0[m]DCRRI1315.0[m]DCRRI1324.0[m]DCRRI1333.0[m]DCRRI1342.0[m]DCRRI1351.0[m]DCRRI1357.0[m]DCRRI1369.0[m]DCRRI1378.0[m]DCRRI1387.0[m]DCRRI1396.0[m]DCRRI1405.0[m]DCRRI1414.0[m]DCRRI1423.0[m]DCRRI1432.0[m]DCRRI1441.0[m]DCRRI1450.0[m]DCRRI1459.0[m]DCRRI1468.0[m]DCRRI1477.0[m]DCRRI1486.0[m]DCRRI1538.0[m]SWCGEOCH1539.0[m]SWCGEOCH1540.0[m]CGEOCH1540.0[m]SWCGEOCH1541.0[m]SWCGEOCH1542.0[m]CGEOCH1543.0[m]CGEOCH1544.0[m]CGEOCH1545.0[m]CGEOCH1546.0[m]CGEOCH1547.0[m]CGEOCH1548.0[m]SWCGEOCH1549.0[m]SWCGEOCH1552.0[m]SWCGEOCH1554.0[m]SWCGEOCH1555.0[m]CGEOCH1559.0[m]CGEOCH1560.0[m]CGEOCH1564.0[m]CGEOCH1570.0[m]CGEOCH1574.0[m]CGEOCH1578.0[m]CGEOCH1583.0[m]CGEOCH1592.0[m]CGEOCH1602.0[m]CGEOCH1614.0[m]CGEOCH1622.0[m]CGEOCH1624.0[m]CGEOCH1625.0[m]CGEOCH1628.0[m]CGEOCH1633.0[m]CGEOCH1643.0[m]SWCGEOCH1656.0[m]CGEOCH1667.0[m]SWCGEOCH1678.0[m]CGEOCH1688.0[m]SWCGEOCH1698.0[m]CGEOCH1707.0[m]SWCGEOCH1713.0[m]CGEOCH1725.0[m]CGEOCH1730.0[m]SWCGEOCH1735.0[m]SWCGEOCH1747.0[m]SWCGEOCH1756.0[m]SWCGEOCH -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit36476712921292135614021526154015441544154916001708 -
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]pdf8.07pdf2.03pdf0.71pdf1.31pdf0.38pdf0.10pdf0.02pdf2.62pdf3.40pdf0.24pdf0.37pdf1.68pdf0.77pdf10.09pdf3.31pdf3.03pdf1.37pdf1.40pdf0.82 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL5201500CST8161496CST14981770DLL MSFL14981767FDC CNL GR CAL450814HDT14981770ISF BHC GR350812ISF BHC GR8081406ISF BHC GR14061501ISF BHC GR14981769LDT CNL GR CAL8031502LDT CNL GR CAL14981770RFT15501752WST7761769 -
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 typeCONDUCTOR30450.036460.00.00LOTSURF.COND.20808.026816.01.47LOTINTERM.13 3/81498.017 1/21509.01.54LOTOPEN HOLE1770.012 1/41770.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured4801.05waterbased7801.12waterbased9901.28waterbased12901.31waterbased17501.18waterbased -
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]pdf0.15