34/7-12
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General information
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Wellbore history
>Well 34/7-12 is a replacement well for well 34/7-11, which was junked for technical reasons. It is located in the Tampen Spur area in the Northern North Sea. Its overall purpose was to assess the hydrocarbon potential in the "B"-structure in the southern part of the block. The primary objectives were to establish the thickness and reservoir quality of the prospective Brent the Brent Group in Group, and to determine the OWC. The secondary objectives were to assess the potential of the Dunlin Cook Formation reservoir, the Statfjord Formation and the upper part of the Triassic Lunde unit B/C reservoir section. TD was prognosed to 2900 m.Operations and resultsWildcat well 34/7-12 was spudded 20 m north of the 34/7-11 location. It was drilled with the semi-submersible installation Treasure Saga on 11 October 1987 and drilled to TD at 2784 m in the Late Triassic Lunde Formation. The well was drilled without significant technical problems. The well was drilled with spud mud down to 852 m and with KCl mud from 852 m to TD.The Brent Group came in at 2169 m, and Statfjord Formation at 2606 m. Lunde Formation was encountered at 2763 m. Oil/water contact was defined in the Ness Formation at 2250 m.The Brent Group, from 2169 to 2340.5 m (171.5 m thick) comprised the sandy Tarbert Formation,the interbedded shaly and sandy Ness Formation, the sandy Etive and Rannoch Formations and at the base the conglomeratic Broom Formation. The Dunlin Group was penetrated from 2340.5 to 2606 m (265.5 m thick), comprising the shaly Drake Formation at the top, the Cook Formation with interbedded sandstone and claystone, the Burton Formation with claystone and minor sandstone and the Amundsen and Calcareous Amundsen Formations having clay stones with minor limestone. The Statfjord Formation, 157 m thick from 2606 to 2763 m, was dominated by sandstones with minor to interbedded claystone. The Late Triassic upper Lunde Formation was encountered at 2763 m, and comprised clay stone interbedded with siltstone.The Brent Group was hydrocarbon-bearing through the Tarbert Formation and into the Ness Formation with an OWC at 2250 m, confirmed by logs and FMT pressure gradients. Shows were seen down to 2268 m. In addition, shows were reported from a sidewall core cut at 1803 m in a Paleocene sand. Logs also indicated the presence of a two metre thick residual or hydrocarbon bearing zone from 1801 m to 1803 m. Shows were also reported in siltstones in the interval 2060 to 2142 m in the Late Cretaceous Kyrre Formation. No indications of hydrocarbons were reported below 2268 m.A total of 10 cores were cut from 2169 to 2360.5 m in the Brent Group and 20 m into the Dunlin Group. A total of 180.8 m core was recovered (94.4 % of cored section). FMT segregated fluid samples were taken at 2171 m (oil and gas), 2171.5 m (oil and gas), 2189.5 m (two samples in different runs, both with oil and gas), 2249.5 m (gas and oil-cut mud), and at 2252.5 m (water). The samples from 2171 and 2189.5 m were analysed and found to be very similar with oil densities close to 0.845 g/cm3, gas gravities in the range 0.863 to 0.879, and CO2 contents in the range 0.22 to 0.29 %.The well was permanently abandoned on 17 December 1987 as an oil discovery.TestingThree drill stem tests were performed in well 34/7-12.DST 1 tested the interval 2276.2 - 2282.2 m in the Rannoch Formation and produced up to1297 Sm3 water/day through a 12.7 mm choke. Up to 10% sand production was reported in the beginning of the main flow period. Maximum down-hole temperature recorded (at 2230.7 m) was 84.2 deg C.DST 2 tested the interval 2229 - 2235 m in the Ness Formation. On a 12.7 mm choke this test produced 881 Sm3 oil and 59383 Sm3 gas /day. The corresponding GOR was 68 Sm3/Sm3, the oil density was 0.841 g/cm3, and the gas gravity was 0.722 (air = 1). Maximum down-hole temperature recorded (at 2202.6 m) was 83.4 deg C.DST 3 tested the interval 2205.5 - 2209.5 m in the lower Tarbert Formation. On a 14.3 mm choke this test produced 1460 Sm3 oil and 96450 Sm3 gas /day. The corresponding GOR was 68 Sm3/Sm3, the oil density was 0.840 g/cm3, and the gas gravity was 0.695 (air = 1). Maximum down-hole temperature recorded (at 2161.3 m) was 82.1 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]860.002784.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom12169.02196.3[m ]22196.52212.9[m ]32214.02215.5[m ]42216.02224.9[m ]52228.02242.4[m ]62242.02261.5[m ]72262.02289.9[m ]82290.02305.0[m ]92305.52332.5[m ]102333.02356.6[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]181.5Cores 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 availableDSTDST22229.002235.0003.12.1987 - 11:30YESDSTDST32205.502209.5010.12.1987 - 23:00YES -
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 typeCONDUCTOR30327.036379.00.00LOTSURF.COND.20838.026852.01.66LOTINTERM.13 3/81851.017 1/21870.02.23LOTINTERM.9 5/82366.012 1/42784.00.00LOT -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.02276228212.72.02229223512.73.02206221014.3Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.015.00049.000842.019.00043.000833.023.00048.00082Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.016852.0881590000.8410.722683.01460960000.8400.69566 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]ACBL6001852CDL CNL GR21002479CDL GR8371836CNL CDL GR18522784CNL CDL GR21402784COREGUN8581848COREGUN18752775DIFL LS BHC GR8371852DIFL LS BHC GR18522784DIPMETER18502784DLL MLL GR21002476DLL MLL GR21252784FMT21712312FMT22102474FMT22102692MWD - GR RES DIR3272781VELOCITY15252784 -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit216989102111511308136514281644164416921834183419972154215421602161216121692169221322522269233423412341246225182547260627632763 -
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]pdf8.97pdf1.67 -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured3321.05WATER BASED14.10.19873781.135.012.0WATER BASED28.10.19878521.0520.010.1WATER BASED28.10.19878521.0522.08.7WATER BASED28.10.19878521.175.013.5WATER BASED21.10.19878521.206.012.5WATER BASED21.10.19878521.156.013.5WATER BASED28.10.19878701.0918.08.7WATER BASED28.10.198713351.1722.010.6WATER BASED28.10.198715441.2525.012.0WATER BASED26.10.198718651.5834.012.0WATER BASED26.10.198718651.5835.011.5WATER BASED28.10.198718651.5835.012.5WATER BASED28.10.198718701.5832.010.6WATER BASED28.10.198721061.7232.08.7WATER BASED29.10.198721201.7224.06.8WATER BASED14.12.198721551.7224.06.8WATER BASED16.12.198721801.7227.06.3WATER BASED30.10.198722141.7231.07.2WATER BASED02.11.198722241.7224.06.8WATER BASED08.12.198722341.7229.05.3WATER BASED02.11.198722671.7225.06.8WATER BASED08.12.198722671.7228.06.3WATER BASED08.12.198722761.7230.04.8WATER BASED03.11.198723131.7230.06.3WATER BASED10.11.198723301.7230.07.2WATER BASED25.11.198723301.7230.07.2WATER BASED23.11.198723301.7230.07.2WATER BASED23.11.198723571.7230.05.3WATER BASED10.11.198723661.7228.05.3WATER BASED10.11.198723811.7231.010.6WATER BASED20.11.198724801.7028.05.3WATER BASED10.11.198724801.7228.04.8WATER BASED10.11.198724801.7227.06.3WATER BASED10.11.198725101.7225.05.8WATER BASED10.11.198725951.7226.06.3WATER BASED10.11.198726091.7222.05.3WATER BASED11.11.198726221.7223.05.3WATER BASED12.11.198726551.7225.05.3WATER BASED13.11.198727051.7225.06.3WATER BASED16.11.198727781.7228.06.3WATER BASED16.11.198727841.7228.06.8WATER BASED16.11.198727841.7228.06.8WATER BASED17.11.198727841.7226.06.3WATER BASED18.11.198727841.7226.06.3WATER BASED19.11.1987 -
Palynological slides at the Norwegian Offshore Directorate
Palynological slides at the Norwegian Offshore Directorate Sample depthDepth unitSample typeLaboratory1010.0[m]DCPALEO1021.0[m]DCPALEO1025.0[m]DCPALEO1040.0[m]DCPALEO1050.0[m]DCPALEO1070.0[m]DCPALEO1080.0[m]DCPALEO1099.5[m]DCPALEO1100.0[m]DCPALEO1110.0[m]DCPALEO1130.0[m]DCPALEO1140.0[m]DCPALEO1150.0[m]DCPALEO1160.0[m]DCPALEO1170.0[m]DCPALEO1190.0[m]DCPALEO1200.0[m]DCPALEO1220.0[m]DCPALEO1228.0[m]DCPALEO1230.0[m]DCPALEO1250.0[m]DCPALEO1270.0[m]DCPALEO1280.0[m]DCPALEO1300.0[m]DCPALEO1310.0[m]DCPALEO1330.0[m]DCPALEO1340.0[m]DCPALEO1360.0[m]DCPALEO1370.0[m]DCPALEO1390.0[m]DCPALEO1400.0[m]DCPALEO1420.0[m]DCPALEO1430.0[m]DCPALEO1450.0[m]DCPALEO1460.0[m]DCPALEO1480.0[m]DCPALEO1490.0[m]DCPALEO1510.0[m]DCPALEO1520.0[m]DCPALEO1540.0[m]DCPALEO1550.0[m]DCPALEO1570.0[m]DCPALEO1580.0[m]DCPALEO1600.0[m]DCPALEO1610.0[m]DCPALEO1630.0[m]DCPALEO1640.0[m]DCPALEO1660.0[m]DCPALEO1670.0[m]DCPALEO1690.0[m]DCPALEO1696.0[m]SWCPALEO1700.0[m]DCPALEO1710.0[m]DCPALEO1730.0[m]DCPALEO1740.0[m]DCPALEO1760.0[m]DCPALEO1770.0[m]DCPALEO1790.0[m]DCPALEO1800.0[m]DCPALEO1815.0[m]DCPALEO1830.0[m]DCPALEO1845.0[m]DCPALEO1860.0[m]DCPALEO1875.0[m]DCPALEO1890.0[m]DCPALEO1900.0[m]SWCPALEO1905.0[m]DCPALEO1920.0[m]DCPALEO1935.0[m]DCPALEO1950.0[m]DCPALEO1965.0[m]DCPALEO1980.0[m]DCPALEO1995.0[m]DCPALEO2010.0[m]DCPALEO2025.0[m]DCPALEO2040.0[m]DCPALEO2055.0[m]DCPALEO2070.0[m]DCPALEO2085.0[m]DCPALEO2100.0[m]DCPALEO2115.0[m]DCPALEO2130.0[m]DCPALEO2145.0[m]DCPALEO2160.0[m]DCPALEO2162.0[m]DCPALEO2171.5[m]DCPALEO2175.0[m]DCPALEO2178.8[m]DCPALEO2198.8[m]DCPALEO2209.5[m]DCPALEO2214.5[m]DCPALEO2218.8[m]DCPALEO2220.8[m]DCPALEO2223.8[m]DCPALEO2229.5[m]DCPALEO2237.8[m]DCPALEO2243.0[m]DCPALEO2258.7[m]DCPALEO2279.5[m]DCPALEO2299.0[m]DCPALEO2305.8[m]DCPALEO2313.0[m]DCPALEO2319.5[m]DCPALEO2326.4[m]DCPALEO2341.0[m]DCPALEO2348.0[m]DCPALEO2350.9[m]DCPALEO2353.1[m]DCPALEO2355.8[m]DCPALEO2358.0[m]DCPALEO2364.0[m]DCPALEO2373.0[m]DCPALEO2391.0[m]DCPALEO2433.0[m]DCPALEO2451.0[m]DCPALEO2460.0[m]DCPALEO2490.0[m]DCPALEO2505.0[m]DCPALEO2520.0[m]DCPALEO2534.0[m]DCPALEO2553.0[m]DCPALEO2555.0[m]DCPALEO2563.0[m]DCPALEO2580.0[m]DCPALEO2622.0[m]DCPALEO2634.0[m]DCPALEO2640.0[m]DCPALEO2670.0[m]DCPALEO2682.0[m]DCPALEO2727.0[m]DCPALEO2742.0[m]DCPALEO2754.0[m]DCPALEO2768.0[m]DCPALEO2772.0[m]DCPALEO2784.0[m]DCPALEO