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Exploration wellbore: 2/5-11

General information

Wellbore history

Well 2/5-11 was drilled primarily to explore the S&rimne prospect located in the southwestern part of PL 067, which is north of the existing Tor field. The prospect was a stratigraphic chalk play thought to be separate from the hydrocarbon-bearing formation in the nearby well 2/5-7. The main purpose for drilling the well 2/5-11 was to test the hydrocarbon potential within the Maastrichtian Tor formation. A secondary target was to test the hydrocarbon potential in the Ekofisk Formation Tjatse prospect.

The 2/5-11 well was spudded on 6 September 1997. "Transocean Nordic", a Jack-Up Rig, was used to drill and abandon the well. Operations took 20 days longer than planned. Main reasons for the extended time were 2 days of unplanned coring and 9 days waiting on weather. The well was drilled to a total depth of 3550 m in the Tor formation in the chalk. High viscosity bentonite mud was used to 780 m. From 780 m to TD the well was drilled water based with various combinations of KCl, polymer, PAC, and glycol.
The expected reservoir was encountered at 3362 m, 2 m deeper than prognosed. A FMT fluid sample containing mainly mud filtrate, some gas and small amounts of floating scummy oil was taken at 3444.3 m. An extensive logging program was employed to evaluate the Chalk sequence. After logging was completed, the logging information indicated that hydrocarbons were present and down hole testing was performed. Testing the well in two zones showed that, although hydrocarbons were present, there was a high content of water. Four cores were cut, one in the Ekofisk Formation (3312 m - 3330 m), one across the Ekofisk - Tor boundary (3330 m - 3366 m), and two in the Tor Formation (3393 m - 3419 m and 3418 m - 3465 m). The well was permanently plugged and abandoned as an oil discovery.

Two tests were performed in the well. Test 1 in interval 3363 - 3381 m in the Tor Formation produced a total of 3.8 Sm3 of 38.7 API gravity oil with a Bottom Sediments and Water percentage (BSW) close to 94%. Test 2 in interval 3289 - 3329 m in the Ekofisk Formation involved an acid job to improve recovery. Before the acid job the test produced a total of 12.8 Sm3 of 38.7& API gravity oil with a BSW of 45%. After the acid job the test produced a total of 92 Sm3 oil of 37.1 API gravity with a BSW close to 90%.

Cuttings available at the NPD

Interval [m]: 290.00 - 3550.00

Cores available at the NPD

Core length [m]: 125.00

Scanned core photos

3312-3317m	3317-3322m	3322-3327m	3327-3330m	3330-3335m
3335-3340m	3340-3345m	3345-3350m	3350-3355m	3355-3360m
3360-3365m	3365-3366m	3393-3398m	3398-3403m	3403-3408m
3408-3413m	3413-3418m	3419-3424m	3424-3429m	3429-3434m
3434-3439m	3439-3444m	3444-3449m	3449-3454m	3454-3459m
3459-3464m	3464-3465m

Palynological slides available at the NPD

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

Composite log (Format:PDF. Size: 0.267 Mb)
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Geochemical information

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

No documents presently available.