25/7-2
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General information
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Wellbore history
GeneralNorwegian Continental Shelf Block 25/7 is located west of the Utsira basement High on the eastern flank of the Southern Viking Graben. The location is 5.3 km southwest of 25/7-1 which drilled into basement after the Cretaceous section without penetrating any Jurassic sediments and thus failed to test its target, Late Jurassic sandstones. With the 25/7-2 location further to the west one expected to penetrate a complete Brae analogue sequence. The main objectives of the well were to test the hydrocarbon potential of the Late Jurassic sands, the hydrocarbon potential of a structural closure at the Middle Jurassic sand level, and the hydrocarbon bearing potential of the Paleocene Heimdal sands. Trapping at Late and Middle Jurassic was assumed by sealing basement rocks to the east, and by dip closure elsewhere. Events interpreted as possible gas bearing sands occur between 200 and 300 m below sea level.Operations and resultsWildcat well 25/7-2 was spudded 8 February 1990by the semi-submersible rig Dyvi Stena, and completed 18 July 1990 at a depth of 4850 m in the Middle Jurassic Sleipner Formation. The well was drilled with Seawater and hi-vis pills down to 1220 m and with KCl Polymer WBS/200 mud from 1220 m to TD. Drilling took 131 days from spud and 142 days from taking over the rig. A further 29 days were used to log, test, and plug and abandon the well. The rig was on contract for a total of 171 days. One hundred and thirty days were used for planned operations while wait-on-weather, fishing operations, and equipment trouble accounted for the NPT. No indications of shallow gas were observed.Forty-seven metres of Cenomanian sand was encountered in the well. A gross thickness of 174 meters of hydrocarbon bearing Late Jurassic conglomerates and sandstones were encountered in the well. The Late Jurassic conglomerates and sandstones represent deposition by debris-flows, slumps and slides and minor turbidites on a fault-scarp submarine slope apron. The sequence had poor reservoir properties in the 25/7-2 location. Sedimentological interpretation and modelling as well as the DST analysis have shown the reservoir to be of limited size. It was therefore concluded that the 25/7-2 well encountered the Upper Jurassic conglomerate/sandstone sequence in a non-producible reservoir facies. The Middle Jurassic Hugin formation was 206 meters thick and was composed of sands deposited in an overall transgressive coastal barrier system. Hydrocarbons were present down to the base of the sands; however, the reservoir quality was extremely poor. The sandstones were intensely cemented and contained large amounts of fibrous illite. The Middle Jurassic Sleipner Formation had a very low sand/shale ratio. The FMS evaluation showed the sandstones to be intensely cemented. No net sand was interpreted from the log analysis.A total of 210 sidewall cores were attempted and 91 were recovered. Four conventional cores were cut in the interval from 4125 to 4169.2 m, and two in the interval from 4345 to 4488 m. No fluid samples were taken on wire line. The well was permanently plugged and abandoned on 18 July 1990 as gas and condensate discovery.TestingA single drill stem test was conducted over the hydrocarbon-bearing interval of the Late Jurassic Intra Draupne and Intra Heather -Formation Sandstone. The perforated intervals were 4148 m to 4173 m, 4194 m to 4219 m, and 4248 m to 4273 m. Contribution to flow was from the Intra Draupne Formation Sandstone in the upper set of perforations (4148 ? 4173 m). Initial flow rates through a 40/64" choke were 255700 Sm3 gas, 228 Sm3 condensate, and 2.7 Sm3 water pr day through a 15.9 mm choke. Initial GOR was 1121 Sm3/ Sm3. Pressure and flow rates declined while GOR increased during the test. Separator condensate density was 0.784 g/cm3 (at 15°C) while separator gas gravity was 0.710 (air = 1). From PVT analyses the stock tank oil density was found to be 0.775 g/cm3 and the stock tank gas gravity 0.756 (air = 1). -
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]1230.004850.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom14125.04136.3[m ]24136.24145.7[m ]34145.74154.6[m ]44154.74169.2[m ]54345.04347.4[m ]64461.54488.6[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]73.7Cores 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 typeLaboratory4109.0[m]DCRRI4115.0[m]DCRRI4125.1[m]CRRI4127.4[m]CRRI4162.6[m]CRRI4163.3[m]CRRI4164.4[m]CRRI4226.0[m]CRRI4245.0[m]CRRI4265.0[m]CRRI -
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 availableDST4148.004273.0011.07.1990 - 00:00YES -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit14944665168768710032098209821852216222222582318247025292698269827492925306032603295339934473714371438753948405640564119421242474293440744074613 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.71 -
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]pdf34.48 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.04148427315.9Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.09.000129Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.02282557000.7810.7321121 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CST12252691CST39524121CST41764310CST43004340CST43654839DIL GR SLS SP AMS39114851DIL LSS MSFL GR SP AMS12102963DIL SLS GR SP AMS39114344DLL MSFL GR SP40504849DLL MSFL NGS CAL SP39114012DLL MSFL NGS CAL SP39114340FMS GR40104852LDL CNL GR CAL39114345LDL CNL NGL CAL40504852LDL DIL LSS GR CAL SP AMS2591925LDL DIL SLS MSFL GR CAL AMS29693918LDL GR CAL12102964MWD DPR39144345MWD RGD2651030MWD RGD35893914MWD RGD43494850MWD RGD-M10303440RFT41384292RFT42554567 -
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 typeCONDUCTOR30259.036265.00.00LOTINTERM.201210.5261220.01.57LOTINTERM.13 3/82965.017 1/22974.01.94LOTINTERM.9 5/83906.012 1/43914.01.96LOTLINER74850.08 1/24850.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1951.9226.012.0WATER BASED17.07.19901951.9222.011.0WATER BASED17.07.19902651.07WATER BASED12.02.19902651.06WATER BASED09.02.19903421.07WATER BASED12.02.199010301.07WATER BASED12.02.199010301.08WATER BASED13.02.199010501.08WATER BASED14.02.199010501.08WATER BASED15.02.199012181.08WATER BASED16.02.199012201.08WATER BASED19.02.199012201.2017.020.0WATER BASED20.02.199012201.2017.011.5WATER BASED21.02.199012201.0219.011.5WATER BASED23.02.199012201.2018.010.5WATER BASED26.02.199012201.2019.011.5WATER BASED26.02.199012201.2019.011.0WATER BASED27.02.199012201.2019.010.5WATER BASED28.02.199012201.2018.012.0WATER BASED22.02.199012201.2018.011.5WATER BASED26.02.199012501.2016.010.0WATER BASED01.03.199014761.2515.09.5WATER BASED02.03.199016841.2919.09.0WATER BASED06.03.199019381.3521.09.5WATER BASED06.03.199019381.3921.09.5WATER BASED06.03.199019381.3921.09.5WATER BASED06.03.199019401.4122.09.5WATER BASED07.03.199019401.4121.08.5WATER BASED08.03.199019581.4124.08.0WATER BASED09.03.199020051.4127.09.0WATER BASED12.03.199021131.2529.013.5WATER BASED12.03.199021301.4129.011.0WATER BASED12.03.199021781.4127.09.5WATER BASED13.03.199023151.2532.011.0WATER BASED14.03.199024371.4030.011.5WATER BASED16.03.199024401.4031.011.0WATER BASED16.03.199025041.4039.012.0WATER BASED20.03.199025451.4029.012.5WATER BASED20.03.199025451.4029.011.0WATER BASED20.03.199025661.4027.013.0WATER BASED20.03.199026301.4027.013.0WATER BASED21.03.199026951.4033.011.0WATER BASED22.03.199027071.4026.09.0WATER BASED23.03.199027071.4027.09.0WATER BASED26.03.199027071.4026.09.0WATER BASED26.03.199027071.4022.010.0WATER BASED26.03.199027371.4030.011.5WATER BASED27.03.199027471.4035.012.5WATER BASED28.03.199027471.4030.011.0WATER BASED29.03.199027471.4029.011.0WATER BASED30.03.199027471.4028.011.0WATER BASED02.04.199027471.4027.010.5WATER BASED02.04.199028111.4023.011.5WATER BASED02.04.199028431.4027.011.5WATER BASED05.04.199028431.4022.010.0WATER BASED04.04.199028641.4129.010.0WATER BASED06.04.199028951.4028.010.5WATER BASED09.04.199029241.4032.012.0WATER BASED10.04.199029581.4027.012.0WATER BASED10.04.199029741.4027.010.5WATER BASED11.04.199029741.4028.011.0WATER BASED18.04.199029741.4026.010.0WATER BASED18.04.199029741.4022.09.0WATER BASED18.04.199029741.3416.02.5WATER BASED18.04.199029741.4021.08.5WATER BASED18.04.199029741.4028.011.0WATER BASED10.04.199029741.4026.010.0WATER BASED18.04.199030341.3422.07.5WATER BASED18.04.199031351.3421.08.5WATER BASED19.04.199032501.3423.012.0WATER BASED23.04.199033491.3425.012.5WATER BASED23.04.199034221.4426.013.0WATER BASED23.04.199034401.4426.012.0WATER BASED24.04.199034451.4426.012.0WATER BASED25.04.199035061.4419.09.0WATER BASED26.04.199035611.4721.010.0WATER BASED27.04.199035891.4722.010.0WATER BASED30.04.199036421.5124.011.5WATER BASED30.04.199037131.9220.05.0WATER BASED16.07.199039121.6521.06.5WATER BASED03.05.199039141.6516.06.0WATER BASED08.05.199039141.6516.05.5WATER BASED08.05.199039141.6520.05.5WATER BASED04.05.199039201.6817.04.5WATER BASED08.05.199039691.7618.05.5WATER BASED08.05.199040311.8721.06.0WATER BASED09.05.199040791.9221.07.0WATER BASED10.05.199041201.9218.07.5WATER BASED11.05.199041251.9219.09.5WATER BASED15.05.199041311.9217.08.0WATER BASED15.05.199041361.9218.05.5WATER BASED15.05.199041461.9217.05.0WATER BASED15.05.199041551.9216.04.5WATER BASED16.05.199041691.9218.05.5WATER BASED18.05.199041951.9217.06.0WATER BASED21.05.199042401.9215.07.0WATER BASED21.05.199043021.9416.08.0WATER BASED21.05.199043421.9814.07.5WATER BASED22.05.199043451.9515.07.0WATER BASED23.05.199043451.9214.07.0WATER BASED25.05.199043451.9214.07.5WATER BASED29.05.199043451.9214.07.0WATER BASED29.05.199043451.9214.07.5WATER BASED29.05.199043451.9213.06.0WATER BASED30.05.199043451.9213.011.0WATER BASED01.06.199043451.9215.09.0WATER BASED06.06.199043451.9214.09.0WATER BASED06.06.199043451.9814.08.0WATER BASED22.05.199043451.9214.07.5WATER BASED25.05.199043451.9214.04.5WATER BASED31.05.199043451.9214.09.0WATER BASED05.06.199043491.9215.010.0WATER BASED06.06.199043491.9215.010.0WATER BASED07.06.199043491.9214.010.0WATER BASED08.06.199043981.9218.014.0WATER BASED08.06.199044621.9217.012.0WATER BASED08.06.199044891.9216.013.0WATER BASED12.06.199044951.9216.011.0WATER BASED12.06.199045201.9216.010.0WATER BASED12.06.199046241.9217.012.0WATER BASED12.06.199046431.9217.015.0WATER BASED13.06.199047271.9217.07.5WATER BASED14.06.199047391.9210.011.0WATER BASED15.06.199047691.9215.05.0WATER BASED19.06.199048021.9214.06.0WATER BASED19.06.199048091.9216.08.5WATER BASED19.06.199048121.9212.05.0WATER BASED05.07.199048121.9312.05.0WATER BASED09.07.199048121.9213.05.0WATER BASED10.07.199048121.9210.05.0WATER BASED10.07.199048121.9211.06.0WATER BASED02.07.199048121.9211.05.5WATER BASED02.07.199048121.9212.05.5WATER BASED03.07.199048121.9212.05.0WATER BASED10.07.199048121.9212.07.0WATER BASED16.07.199048301.9214.07.5WATER BASED19.06.199048501.9214.07.0WATER BASED20.06.199048501.9214.07.5WATER BASED21.06.199048501.9213.07.5WATER BASED25.06.199048501.9212.07.5WATER BASED25.06.199048501.9213.06.5WATER BASED27.06.199048501.9214.05.5WATER BASED28.06.199048501.9212.05.5WATER BASED04.07.199048501.9210.05.0WATER BASED10.07.199048501.928.014.0WATER BASED11.07.199048501.9212.07.5WATER BASED12.07.199048501.9220.07.0WATER BASED02.07.199048501.9213.06.5WATER BASED02.07.199048501.9212.07.5WATER BASED13.07.199048501.9215.06.5WATER BASED22.06.199048501.9212.08.0WATER BASED25.06.199048501.9212.05.5WATER BASED26.06.1990 -
Thin sections at the Norwegian Offshore Directorate
Thin sections at the Norwegian Offshore Directorate DepthUnit4131.00[m ]4146.25[m ]4148.25[m ]4152.75[m ]4160.25[m ]4166.00[m ]4168.00[m ] -
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