2/5-7
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General information
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Wellbore history
GeneralWildcat well 2/5-7 is located ca 9 km North of the Tor Field in the southern Norwegian North Sea. The primary objective was to test Late Jurassic and Middle Jurassic/Triassic sandstones on top of a gentle salt-induced dome structure. Secondary objectives were Late Cretaceous chalk and Paleocene sandstones.Operations and resultsWell was spudded with the jack-up installation Neddrill Trigon on 11 August 1983 and drilled to TD at 4531 m in the Triassic Skagerrak Formation. During drilling of the 17 1/2" hole several tight spots and problems with cavings were experienced. While tripping out of the hole at 3956 m, the drill string parted and 193 m of the bottom hole assembly was left in the hole. The fish was recovered after some problems due to tight hole conditions. When pressure testing the 9 5/8" casing the float collar sheared out causing the casing to jump. After re-landing, the casing was found to have dropped a couple of inches. Repair of the casing took 35 days extra rig time. A drilling break occurred at 4161 m where a 1.5 m thick marl was encountered. Maximum gas reading at bottoms-up was 30 %, and slight oil shows were observed in the mud. A kick was taken at 4519 m with an influx of 2.5 m3 water. The well was drilled with seawater and gel down to 862 m, with KCl/polymer mud from 862 m to 2254 m, with lignosulphonate mud from 2254 m to 3529 m, and with gel/lignosulphonate mud from 3529 m to TD.Only traces of sandstone were encountered in the Late Paleocene, and there were no indications of hydrocarbons. Porous chalk was encountered in the Ekofisk Formation at 3204 m and in the Tor Formation at 3289 m. Both formations tested oil, but the oil flow in the Ekofisk test was interpreted to originate from the Tor Formation (see below). The matrix permeability in these zones is low, but the results from the production tests indicated that fracture permeability is significant. No hydrocarbons were found in the Late Jurassic Ula Formation. The silty/sandy interval in the Ula Formation is thin and of poor reservoir quality. A total of 144 m of Triassic sediments with two sandy intervals of reasonable porosity was penetrated. However, the sands were water bearing. Five cores were cut in the Late Cretaceous sequence. Core no 4 recovered only 7 cm due to junk in the 12 1/4" hole. A segregated RFT sample was taken at 3321 m. It recovered only mud and mud filtrate.The well was permanently abandoned on 24 February 1984 as an oil discovery.TestingAfter the well was plugged back to 3501 m three production tests were carried out: PT-1 at 3300 - 3335 m in the Tor Formation, PT-2 at 3263 - 3287 m in the Ekofisk Formation, and PT-3 at 3210 - 3225 m in the Ekofisk Formation.The Maastrichtian interval had extremely low oil saturation as evidenced by petrophysical data. Oil shows had been detected while drilling this section and the core samples showed oil in the fracture/fissure system. RFT pressure data indicated an oil gradient over the producing zone. The PT-1 produced after acidization 120 Sm3 oil and 189 m3 water /day (water cut = 61%) on a 20/64" bean at a FTHP = 780 psig. The GOR was 27 Sm3/Sm3, the oil gravity was 42 deg API, and the separator gas gravity was 0.83 (air = 1). The gas contained no H2S and 3.5% CO2. The test results suggested an average permeability of some 3 mD, which was an order of magnitude higher than the core measured values and thus indicated a significant flow contribution from a fracture/fissure system.PT-2 produced after acidization 121 Sm3 oil and 146 m3 water (water cut = 56%) on a 36/64" choke at FTHP = 295 psig. The GOR was 48 Sm3/Sm3, the oil gravity was 41 deg API, and the gas gravity varied between 0.96 and 1.02 (air =1). The gas contained no H2S and 5% CO2. PT-2 was interpreted to have flown from the underlying Maastrichtian after acid fracturing had established communication.PT-3 showed an essentially tight and only water-bearing formation. Accurate temperature measurements in this test gave a mid-perforation temperature of 124.5 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]150.004531.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom13303.03308.4[m ]23312.03321.1[m ]33326.53335.6[m ]53339.03348.3[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]32.8Cores 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 typeLaboratory4093.0[m]DCHRS4099.0[m]DCSAGA4105.0[m]DCHRS4111.0[m]DCHRS4132.0[m]DCOD4141.0[m]DCHRS4156.0[m]DCOD4159.0[m]DCSAGA4174.0[m]DCHRS4177.0[m]DCOD4183.0[m]DCSAGA4195.0[m]DCSAGA4195.0[m]DCOD4219.0[m]DCOD4222.0[m]DCHRS4231.0[m]DCSAGA4237.0[m]DCSAGA4243.0[m]DCOD4261.0[m]DCHRS4261.0[m]DCOD4285.0[m]DCSAGA4285.0[m]DCOD4300.0[m]DCHRS4309.0[m]DCSAGA4309.0[m]DCOD4330.0[m]DCOD4345.0[m]DCHRS4357.0[m]DCOD4357.0[m]DCHYDRO4363.0[m]DCHYDRO4366.0[m]DCHYDRO4372.0[m]DCHYDRO4378.0[m]DCHYDRO4381.0[m]DCHYDRO4381.0[m]DCSAGA4384.0[m]DCSAGA4390.0[m]DCTNO4399.0[m]DCSAGA4408.0[m]DCSAGA4408.0[m]DCHYDRO4414.0[m]DCHYDRO4417.0[m]DCSAGA4435.0[m]DCSAGA4441.0[m]DCHYDRO4450.0[m]DCHYDRO4456.0[m]DCHYDRO4459.0[m]DCHYDRO4462.0[m]DCSAGA4468.0[m]DCTNO4472.0[m]DCTNO4474.0[m]DCHYDRO4477.0[m]DCHYDRO4477.0[m]DCTNO4480.0[m]DCSAGA4480.0[m]DCHYDRO4483.0[m]DCHYDRO4486.0[m]DCHYDRO4486.0[m]DCSAGA4486.0[m]DCTNO4492.0[m]DCHYDRO4507.0[m]DCSAGA4528.0[m]DCSAGA -
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 availableDSTPT-23263.003287.00YES -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit10015483028302830383047314332043204328937264087410841084120434743874387 -
Geochemical information
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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]pdf13.56pdf6.47pdf0.38pdf1.12pdf3.30pdf0.35pdf0.43pdf4.15pdf10.41pdf10.75pdf4.88 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.0330033357.92.03263328714.33.0321032250.0Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.05.00035.0002.014.00029.0003.032.000Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.0120463500.8200.830272.0121326700.8200.960483.08 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]4ARM CAL953978CBL VDL CCL1012243CBL VDL CCL8503984CDM22433994CDM39954532CDM AP22313990CDM AP39964533DLL MSFL31503675DWLD8994000ISF SLS GR1564531LDL CNL1564531RFT32163512RFT32363765RFT HP32363765TEMP1012700VELOCITY1564531 -
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 typeCONDUCTOR30156.036156.30.00LOTSURF.COND.20851.526864.01.90LOTINTERM.13 3/82244.017 1/22272.01.89LOTINTERM.9 5/83988.012 1/44007.00.00LOTLINER73993.08 1/24007.02.15LOTOPEN HOLE4531.05 3/44531.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1501.038.012.0WATER BASED4001.088.012.0WATER BASED11751.1020.022.0WATER BASED14001.1818.018.0WATER BASED15101.2027.019.0WATER BASED16301.2218.020.0WATER BASED17801.2424.014.0WATER BASED19901.4027.015.0WATER BASED22701.6528.018.0WATER BASED24751.6641.015.0WATER BASED36301.6730.014.0WATER BASED41401.9031.08.0WATER BASED42351.9337.010.0WATER BASED43301.9526.0WATER BASED45202.0830.012.0WATER BASED -
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