The NPD's Fact-pages
	Generated 31.07.2010

Exploration wellbore: 34/7-17

General information

Wellbore history

General

Well 34/7-17 A is a sidetrack to well 34/7-17 on the Vigdis Field on Tampen Spur in the Northern North Sea. In well 34/7-17 the primary target Brent reservoir was encountered 38 m deeper than prognosed and dry with only scattered oil shows. The 34/7-17 A sidetracked well thus aimed primarily at the Brent reservoir in an up-dip position above a possible OWC. According to prognosis Brent should be truncated in this direction. A secondary objective was to test the pressure regimes in the Jurassic sequence, including possible depletion associated with pressure communication, previously identified in the nearby Tordis Field.

Operations and results

Well 34/7-17 A was spudded with the semi-submersible installation Treasure Saga on 7 April 1991. Kick off point was at 1994 m below the 13 3/8" casing shoe in well 34/7-17, in the top of the Shetland Group. The target was located up-dip in a south-easterly direction and the sidetrack was drilled deviated from its beginning. The well was drilled without significant technical problems to TD at 2650 m (2557 m TVD) in the Middle Jurassic Etive Formation of the Brent Group. It was drilled with KCl mud from kick off to TD.

Top Brent Group, Tarbert Formation, was penetrated at 2494.5 m (2439.5 m TVD). Truncation was confirmed by the absence of the Viking Group and erosion into the top of the Brent Group. The Brent Group proved to be oil bearing only in the uppermost 6.5 m TVD with a possible OWC at 2502.5 m (2446 m TVD / 2420 m MSL TVD). Above the reservoir ditch cuttings recorded a continuous sequence with good traces of oil shows between 2235 and Top Brent Group. The interval 2310 to 2370 m also had oil staining and a strong odour of hydrocarbons. No shows were reported below 2506 m.

One core was cut in the top of the reservoir between 2597 and 2617. Totally 21 m was cut, of which 20 m was recovered. Two RFT runs were conducted over the Brent Group. The resulting pressure gradients showed the Tarbert Formation to be under-pressured by 5.1 bar compared to the underlying Formations of the Brent Group with transitional pressures in the Ness Formation. Two RFT segregated samples were recovered from 2495.5 and 2495.7 m in the top of the Tarbert Formation. Both contained mud and water with a film of oil.

The well was permanently abandoned on 4 May 1991 as an oil appraisal.

Testing

One well test was carried out in the top of the Brent Group over the interval 2495 to 2499 m. The test was performed with variable, increasing choke sizes and it produced fluids with increasing water cut. At the end of the test a total liquid flow rate of 700 Sm3/day through a 15.9 mm choke was recorded at a well head pressure of 49 bar. The water cut at this end was 70%, the separator GOR was 115 Sm3/Sm3, the dead oil density was 0.850 g/cm3, and the gas gravity was 0.8 (air = 1). The maximum bottom hole temperature measured in the test was 91 deg C.

Cuttings available at the NPD

Interval [m]: 900.00 - 3114.00

Cores available at the NPD

Core length [m]: 117.70

Scanned core photos

2460-2465m	2465-2470m	2470-2475m	2475-2478m	2478-2483m
2483-2488m	2488-2493m	2493-2496m	2498-2503m	2503-2507m
2508-2513m	2513-2518m	2518-2523m	2523-2528m	2528-2531m
2534-2539m	2539-2542m	2545-2550m	2550-2552m	2554-2559m
2559-2564m	2564-2569m	2569-2570m	2571-2576m	2576-2581m
2581-2586m	2497-2502m	2502-2507m	2507-2512m	2512-2517m

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

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)

No documents presently available.

Old NPD WDSS reports, NPD papers and other related documents

You need an ACROBAT reader from ADOBE  to display the reports in pdf format.