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Exploration wellbore: 33/9-11

General information

Wellbore history

General

Wildcat well 33/9-11 was drilled to test the 33/9-Epsilon prospect 6 kilometres north of the 33/9-Beta oil discovery and 10 kilometres northeast of the Murchison Field (UK). The Epsilon structure is a northwest tilted fault block and is expressed as a topographic high at the Kimmerian Unconformity surface. Primary target was the Middle Jurassic Brent Sand with the Early Jurassic Statfjord Sand as secondary objective.

Operations and results

Exploration well 33/9-11 was spudded with the semi-submersible installation Fernstar on 17 June 1978. The spud location turned out to be in a 25 m diameter crater in the sea floor. Due to problems with tilting of the temporary guide base two unsuccessful spuds were made before the third and successful spud was made with a modified guide base on 24 June 1978. Final position refers to this hole. The well was drilled with seawater and gel down to 820 m, with KCl polymer mud from 820 m to 1870 m, and with a fresh water/lignosulfonate mud from 1870 m to TD. The lignosulfonate mud was treated with a "Protectomacig" additive dissolved in diesel so that the total diesel content in the mud was about 4 % & 6 %. The well was drilled to TD at 3528 m, 91 m into the Early Jurassic Statfjord Formation.

Grey clays and claystones dominated the Tertiary. Sands, silts and carbonates were only minor occurrences except for the sands in the intervals, 989 to 1034m and 1205 to 1225m. In the Paleocene Balder Formation typical tuffaceous grey and red claystone were present and were also observed above and below the Balder. The Late Cretaceous Shetland Group was comprised of grey and brown claystones and siltstones with only minor sands and carbonates. The electric log pick of the top of the Early Cretaceous Cromer Knoll Group was taken at 3037.8 m. The Early Cretaceous was 58 m thick and consisted of 8.6 m of Barremian limestone at the base with red marl interbedded with the overlying claystone section.

The Late Jurassic Viking Group was encountered at 3096.2 m, 28.8 m high to prognosis. Of the 29.8 m thick shale section the upper 2.8 m was the Draupne Formation and the lower 27 m was the Heather Formation.

The primary objective Brent Formation came in at 3126 m. It was 149.6 m thick and had 102 m net sand. The sandstone was argillaceous; medium grained and had fair porosity. The Brent porosity and permeability was better in 33/9-11 than in the 33/9-10 well. Brent was water bearing. No shows were seen in the ditch samples. One core was cut from 3134 m to 3152 m. Weak shows were observed in the core in the top of the reservoir from 3136 m to 3134 m, but electric logs indicated the Brent Formation to be water-wet. The shows were explained by flushing of the core with diesel and Protectomagic mud. No residual oil was measured in the core plugs. Core porosity averaged 22.2 percent and horizontal liquid permeability averaged 370 mD, ranging up to 1874 mD.

The Dunlin Formation at 3275.6 m was 161 m thick with a silty, micaceous claystone lithology.

While the Statfjord Formation came in at 3436.6 m. No shows were seen in the samples and electric log analysis confirmed the Statfjord Formation to be water-wet. The Statfjord sand waskaolinitic, coarse and had fair to good porosity but with several tight calcareous-cemented sand streaks.

A mini submarine inspection of the well site was conducted after abandonment. It showed that two small intermittent streams of gas bubbles (bubble size less than 1 cm) were observed coming from the crater. The well was permanently abandoned as dry on 28 August 1978.

Testing

No drill stem test was performed

Cuttings available at the NPD

Interval [m]: 590.00 - 3527.00

Cores available at the NPD

Core length [m]: 18.00

Scanned core photos

3134-3136m	3136-3139m	3139-3142m	3142-3144m	3144-3147m
3147-3150m	3150-3152m

Palynological slides available at the NPD

No palynological slides in this wellbore.

Oil samples available at the NPD

No oil samples available.

Casing and leak-off tests

Mud

Drill stem test

No drill stem test in this wellbore.

Available logs

Lithostratigraphy

Composite log

Composite log (Format:PDF. Size: 0.472 Mb)
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Geochemical information available at the NPD

No geochemical data presently available. Regional geochemical studies which include data from this well may however be filed on a different well.

Documents reported by the licencees (period for duty of secrecy expired)

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Old NPD WDSS reports, NPD papers and other related documents

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