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Exploration wellbore: 2/1-9

General information

Wellbore history

General

Well 2/1-9 was drilled on the Gyda South structure, a fault/dip closure in the Late Jurassic fairway on the eastern flank of the Central Graben, 6 km south of the Gyda Field. The main objective of the well was to test the Late Jurassic "Gyda sandstone" (Ula Formation) target and prove a volume of oil that was commercial as a tie back development to the Gyda platform. Secondary reservoir potential existed in both the Middle Jurassic and in the uppermost part of the Triassic. Estimated TD was 4275 m TVD RKB.

Operations and results

Appraisal well 2/1-9 was spudded with the semi submersible rig Ross Isle 15 March 1991 and drilled to TD at 4298 m in the late Permian Zechstein Group. No significant problems were encountered in the operations. No shallow gas was detected. The well was drilled with seawater and high viscosity slugs down to 900 m, and with Aquamul ether-based invert emulsion mud system from 900 m to TD.

A 59 m Forties Formation sandstone sequence was encountered at 2923 m in the Late Paleocene and another ca 30 m thick sandstone sequence at 3025 m within the Lista Formation. Top Mandal Formation was encountered at 4013.5 m, 10.5m deeper than predicted. Top Ula Formation was encountered hydrocarbon bearing from 4048 to 4209 m, which was 111 m thicker than expected. The OWC was interpreted from logs to be at 4137.0 m, while the cores taken had good oil shows all through the cored section, i.e. down to 4153 m. No reservoir sections were encountered in the Middle Jurassic. No Triassic sediments were penetrated by the well.

Five cores were cut continuously from 4019 m to 4153 m with 100% recovery. Core 1 covered the lower part of the Mandal, Farsund, and the upper part of the Ula Formation. Cores 2, 3, 4 and 5 were cut in the Ula Formation. Good oil shows was observed throughout the cored section of the Ula sandstone. RFT fluid samples were taken at 4088.7 m (oil), 4137.0 m (oil), 4151 (water), and 4177 m (water).

Well 2/1-9 was considered a potential water injector for the Gyda South discovery, and to be sidetracked up-dip as a producer. A full evaluation of the DST and PVT data would be performed together with a geological remapping and evaluation of the discovery. The well was thus suspended on 6 July 1991, as an oil discovery. It would be re-entered later, after the above evaluations had been completed.

Testing

One DST was run in the interval 4078 - 4108 m and resulted in an oil rate of 166 Sm3 oil/day through a 32/64" choke. The gas rate was 91180 Sm3/day and the water rate was 120 Sm3/day. The GOR was 548 Sm3/Sm3 and the oil gravity was 43 deg API. Due to the presence of H2S the lower part of the Ula Formation was not tested.

Cuttings available at the NPD

No cuttings in this wellbore.

Cores available at the NPD

Core length [m]: 133.54

Scanned core photos

4019-4024m	4024-4029m	4039-4034m	4034-4039m	4039-4044m
4044-4046m	4046-4051m	4051-4056m	4056-4061m	4061-4066m
4066-4071m	4071-4074m	4074-4079m	4079-4084m	4084-4089m
4089-4094m	4094-4099m	4099-4102m	4102-4107m	4107-4112m
4112-4117m	4117-4122m	4122-4124m	4125-4130m	4130-4135m
4135-4140m	4140-4145m	4145-4150m	4150-4152m

Palynological slides available at the NPD

No palynological slides in this wellbore.

Oil samples available at the NPD

Casing and leak-off tests

Mud

Drill stem test (intervals and pressures)

Drill Stem Test (recovery)

Available logs

Lithostratigraphy

Composite log

No composite log presently available.

Geochemical information

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

No documents presently available.

Old NPD WDSS reports, NPD papers and other related documents

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