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Exploration wellbore: 2/5-2

General information

Wellbore history

General

Well 2/5-2 was drilled as an appraisal well on the 2/5-1 Tor Discovery in the southern Norwegian North Sea. The objective was to evaluate the eastern part of the structure.

Operations and results

Appraisal well 2/5-2 was spudded with the jack-up installation M ærsk Explorer on 15 January 1971 and drilled to TD at 3597 m in the Late Cretaceous Tor Formation. The well was drilled water based, but with diesel addition below 1830 m.

The well encountered top Paleocene (Balder Formation at 2978 m, top Danian chalk (Ekofisk Formation) at 3118 m, and top Late Cretaceous chalk (Tor Formation) at 3360 m. Commercial quantities of hydrocarbons were encountered in the Ekofisk Formation where a total of approximately 57 m net pay out of a gross section of 244 m was found. This was a significant reduction from the 89 m net pay in the 2/5-1 discovery well. Furthermore, the water saturation in Ekofisk was higher in 2/5-2 compared to 2/5-1 (41% and 22%, respectively).

Five conventional cores were cut in the intervals 3120 - 3188 m and 3235 - 3311 m in the Ekofisk Formation. No wire line fluid samples were taken.

The well was permanently abandoned on 20 April 1971 as a an oil appraisal.

Testing

Six drill stem tests were carried out: DST 1 in Late Cretaceous chalk (Tor Formation), DST 2 in the Late Cretaceous/ Danian boundary, and DST 3 - 6 in Danian chalk (Ekofisk Formation). The following results are after acidization:

DST 1 in the interval 3511 to 3513 m flowed minor quantities of slightly oil-cut mud.

DST 2 at 3350 - 3361 m flowed 165 Sm3, 34 m3 water, and 39077 Sm3 gas /day on 64/64" + 32/64" choke. The oil gravity was 39 deg API and the GOR was 237 Sm3/Sm3.

DST 3 at 3299 - 3314 m flowed 629 Sm3 oil and 159900 Sm3 gas /day on a 23/64" choke. The oil gravity was 40.5 deg API and the GOR was 254 Sm3/Sm3. Maximum bottom hole temperature recorded in the test was 134 deg C.

DST 4 at 3165 - 3183 m flowed initially 362 Sm3 and 6400 Sm3 gas /day, declining to 4.6 Sm3 oil and 1010 Sm3 gas /day.

DST 5 at 3162 - 3179 m produced a total accumulated of 15 Sm3 oil and 36 Sm3 water in a 7.5 hours test.

DST 6 at 3150 - 3188 m produced sluggishly a total accumulated of 2.4 Sm3 oil and 3.5 Sm3 water in 8 hours test.

Cuttings available at the NPD

Interval [m]: 137.16 - 3596.64

Cores available at the NPD

Core length [m]: 53.64

Scanned core photos

10235-10253ft	10253-10271ft	10271-10289ft	10289-10307ft	10307-10321ft
10321-10415ft	10415-10423ft	10415-10432ft	10249-10458ft	10432-10449ft
10614-10630ft	10630-10647ft	10647-10664ft	10664-10850ft	10850-10865ft

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 (intervals and pressures)

Drill Stem Test (recovery)

Available logs

Lithostratigraphy

Composite log

No composite log presently available.

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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