1/9-1
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General information
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Wellbore history
GeneralWell 1/9-1 was drilled on a salt diapir structure located in the Feda Graben in the southern North Sea. The primary objective was to test hydrocarbon accumulations in the Danian and Late Cretaceous chalk. A secondary objective was to test the Jurassic and Triassic sandstones.Operations and resultsWildcat well 1/9-1 was spudded with the semi-submersible installation Ross Rig on 14 October 1976 and drilled to TD at 3706 m in Cenomanian age limestone (Hidra Formation). The Jurassic was not reached. The anchor chain broke on three occasions. The third breakdown occurred during the last DST. The decision was then made to suspend the well for later re-entry. The well was drilled with seawater and gel slugs down to 433 m, and with seawater-lime-lignosulphonate from 433 m to TD.The Danian chalk (Ekofisk Formation) was reached at 3043.5 m just below a marl section. It consisted of two hydrocarbon bearing zones. Zone 1 from 3043.5 m to 3071.5 m and a tighter zone 2 from 3071.5 m to 3103.5 m. Maastrichtian (Tor Formation) starts at about 3103.5 m and is also hydrocarbon bearing with water saturations below 50% down to 3141.5 m. A transition zone with gradually increasing water content is seen from 3134.0 m down to 3182.5 m. Apart from in the oil bearing reservoirs weak oil shows on minor sandstones were recorded in the interval 2947 to 2958 m; weak to good oil shows were seen on limestone in the interval 3300 m to 3500 m; and finally weak oil shows were seen occasionally from 3645 m to 3675 m.The chalk section was cored in 11 cores from 3048 m to 3235.5 m (Ekofisk and Tor formations) and one core (core no 12) from 3327.2 m to 3336.7 m (Hod Formation). Total core recovery was nearly 100%. No wire line fluid samples were taken.The well was suspended on 17 February 1977 as a gas/condensate discovery.TestingEight drill stem tests were performed in the Late Cretaceous and Danian chalk sections. The tests indicated an oil reservoir with a retrograde gas cap. However PVT analyses indicated that the hydrocarbon system was close to its critical point and therefore difficult to interpret.DST 1B tested the intervals 3298 - 3302 and 3306 - 3312 m (Tor Formation). After acidizing the test produced water with less than 1% oil emulsion at a rate of 48 - 51 m3 /day on a 48/64" choke. Maximum recorded temperature was 120 deg C.DST 2A tested the interval 3210 - 3220 m (Tor Formation). The test produced water at a rate of 53 m3 /day on a 48/64" choke. Maximum recorded temperature was 116 deg C.DST 3 tested the interval 3174 - 3182 m (Tor Formation). The test produced water at a rate of 13 m3 /day on a 48/64" choke. Maximum recorded temperature was 117 deg C.DST 4 tested the interval 3148 - 3157 m (Tor Formation). After acidizing the test produced 253 - 420 Sm3 oil, 152910 Sm3 gas and 108 - 180 m3 water /day on a 24/64" choke. The GOR was 365 - 606 Sm3/Sm3, oil density was 0.849 g/cm3 and gas gravity was 0.699 (air = 1). Maximum recorded temperature was 120 deg C.DST 5 tested the interval 3120 - 3133 m (Tor Formation). After acidizing the test produced 405 - 461 Sm3 oil, 242000 -251000 Sm3 gas /day on a 24/64" choke. The GOR was 534 - 618 Sm3/Sm3, oil density was 0.818 g/cm3 and gas gravity was 0.680 (air = 1). Maximum recorded temperature was 120 deg C.DST 5A tested the interval 3129 - 3133 m (Tor Formation). The test produced 71 - 98 Sm3 oil with 1% water, 34000 - 45000 Sm3 gas /day on a 12/64" choke. The GOR was 409 - 640 Sm3/Sm3, oil density was 0.836 g/cm3 and gas gravity was 0.710 (air = 1). Maximum recorded temperature was 121 deg C.DST 6 tested the interval 3105 -3108.5 m (Tor Formation). The test produced 111 - 127 Sm3 oil with 1% water, 125000 - 130000 Sm3 gas /day on a 22/64" choke. The GOR was 989 - 1201 Sm3/Sm3, oil density was 0.796 g/cm3 and gas gravity was 0.708 (air = 1). Maximum recorded temperature was 118 deg C.DST 7 tested the interval 3082 - 3088 m (Ekofisk Formation). The test gave no flow.DST 8 tested the interval 3055 - 3068 m (Ekofisk Formation). The test produced 79 - 90 Sm3 oil with 0.5% water, 198000 - 218000 Sm3 gas /day on a 12/64" choke. The GOR was 2330 - 2740 Sm3/Sm3, oil density was 0.760 g/cm3 and gas gravity was 0.691 (air = 1). Maximum recorded temperature was 116 deg C. Attempts to test this interval with acid (DST 8A and 8B) failed as a consequence of the problems with the anchor chains. -
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]430.003706.00 -
Cores at the Norwegian Offshore Directorate
Cores at the Norwegian Offshore Directorate Core sample numberCore sample - top depthCore sample - bottom depthCore sample depth - uom13048.03057.2[m ]23057.23075.8[m ]33075.83094.0[m ]43094.03105.3[m ]53105.33123.9[m ]63123.93142.6[m ]73142.53160.0[m ]83161.03179.6[m ]93179.63197.6[m ]103198.33216.9[m ]113216.93234.1[m ]123327.23335.3[m ]Cores at the Norwegian Offshore Directorate Total core sample length [m]192.5Cores at the Norwegian Offshore Directorate Cores available for sampling?YES -
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 availableDSTDST 13298.003302.0023.12.1976 - 00:00YESDSTTEST1A0.000.0025.12.1976 - 01:00YESDSTTEST1B3312.003306.0025.12.1976 - 14:30YESDSTTEST43148.003157.0011.01.1977 - 01:55YESDSTTEST53120.003133.0017.01.1977 - 19:25YESDSTDST63105.003109.0026.01.1977 - 00:00YESDSTDST 83055.003068.0031.01.1977 - 15:15YES -
Lithostratigraphy
Lithostratigraphy Top depth [mMD RKB]Lithostrat. unit10315722872287228842944294729523013303630363104331236483662 -
Composite logs
Composite logs Document nameDocument formatDocument size [MB]pdf0.64 -
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]pdf3.17pdf2.15pdf32.92pdf38.52 -
Drill stem tests (DST)
Drill stem tests (DST) Test numberFrom depth MD
[m]To depth MD
[m]Choke size
[mm]1.03298331019.02.03210322019.03.03174318219.04.0314831579.55.0312031339.55.1312931335.06.0310531098.47.0308230880.08.0305530684.68.13055306818.3Drill stem tests (DST) Test numberFinal shut-in pressure
[MPa]Final flow pressure
[MPa]Bottom hole pressure
[MPa]Downhole temperature
[°C]1.01202.01163.01174.041.0001205.027.0001205.121.0001216.014.3001187.08.011.1001168.113.300111Drill stem tests (DST) Test numberOil
[Sm3/day]Gas
[Sm3/day]Oil density
[g/cm3]Gas grav. rel.airGOR
[m3/m3]1.02.03.04.04201540000.8490.6993805.04602510000.8180.6805505.198450000.8360.7106006.01271300000.7960.7089907.08.0902180000.7600.69123368.11007 -
Logs
Logs Log typeLog top depth [m]Log bottom depth [m]CBL VDL GR5001457CBL VDL GR20452821CBL VDL GR27153325CBL VDL GR28213693CPI28713328DST GR28213335FDC CNL GR4223705HDT28213335IES SP28213705ISF SONIC1513705VDL SONIC28213705 -
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 typeCONDUCTOR30152.036152.00.00LOTSURF.COND.20423.026433.00.00LOTINTERM.13 3/81343.017 1/21355.01.49LOTINTERM.9 5/82825.012 1/42836.00.00LOTLINER73369.08 1/23706.00.00LOT -
Drilling mud
Drilling mud Depth MD [m]Mud weight [g/cm3]Visc. [mPa.s]Yield point [Pa]Mud typeDate measured1431.04spud mud4321.3750.0spud mud13581.4646.0spud mud19601.9154.0waterbased25771.8459.0waterbased28361.6856.0waterbased33281.6653.0waterbased36831.6550.0waterbased -
Thin sections at the Norwegian Offshore Directorate
Thin sections at the Norwegian Offshore Directorate DepthUnit3048.00[m ]3061.00[m ]3070.00[m ]3105.00[m ]3116.00[m ]3134.00[m ]3144.00[m ]3149.00[m ]3154.00[m ]3160.00[m ]3217.00[m ]3226.00[m ]3233.00[m ]3328.00[m ]3336.00[m ]