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Exploration wellbore: 35/9-2

General information

Wellbore history

General

Well 35/9-2 was designed to drill on the A-Structure in block 35/9 which is located in the northern part of the Horda Platform, in the footwall of the Sogn Graben boundary fault system. The well was drilled as a combined appraisal/wildcat well. The primary objective of the well was to appraise the hydrocarbon potential in the Late Jurassic Sognefjord and Fensfjord Formations, found oil and gas bearing in the 35/9-1 well. Secondary objective was to test the Middle -Early Jurassic sequence.

The total depth of the well was prognosed to 2830 m RKB, approximately 30 m into the Caledonian basement.

Operations and results

Wildcat/Appraisal well 35/9-2 was spudded with the semi-submersible installation Vildkat Explorer on 1 January 1991 and drilled to TD at 2885 m in Caledonian basement. Due to hole angle problems, the well had to be re-spudded twice before drilling proceeded. No shallow gas or boulders were observed while drilling. In order to penetrate the target within the given tolerances, a kick-off was made at 1039 m. This resulted in a deviation of up to 14 deg. at 1287 m and TVD 8 m less than measured depth at final TD. The well was drilled with seawater and hi-vis pills down to 1018 m and with KCl/polymer from 1018 m to TD.

The well encountered oil and gas bearing sandstones from 2095 m in the Late Jurassic reservoirs. The gas/oil contact was found at 2324 m and oil was found down to 2341 m in the Fensfjord "C" Formation. Net pay gas zone was calculated to 171.26 m and net oil pay zone calculated to 13.13 m. The oil/water contact was not seen, but from extrapolation of RFT pressure gradients the OWC was estimated at 2367 m in the Fensfjord Formation. The best reservoir sand was found in the Sognefjord Formation. The Middle and Early Jurassic formations were penetrated and found water bearing. Above the Late Jurassic reservoirs only two weak shows were recorded in cuttings from thin sandstone stringers in the Tryggvason Formation. Weak patchy shows were recorded in the Fensford Formation at 2366 m to 2379 m, otherwise no shows were seen below OWC of the Late Jurassic reservoirs.

Nine cores were cut in the Viking Group, 3 in the Brent Group and 5 in the Dunlin Group. RFT fluid samples were taken at 2368.6 m (water and filtrate with small volume of gas), and at 2331.5 m (6.5 l oil and 0.81 Sm3 gas).

The well was permanently abandoned on 3 April 1991 as a gas/oil discovery.

Testing

Four production tests were performed in the Late Jurassic Formations, one oil test and three gas tests. Production test data quoted below refer to maximum rates at the specified choke sizes.

Production test No. 1 was performed in the interval 2329.9 - 2342.4 m in the Fensfjord "C" Formation. It flowed oil at 289 Sm3/d and gas at 206300 Sm3/d on a 12.7 mm choke. The GOR was 714 Sm3/Sm3. The oil gravity was 0.826 g/cc and the gas gravity was 0.608 (air=l). The wellhead pressure was 144.4 bars with a wellhead temperature of 44.6 deg C. The well produced 0.6% CO2 and no H2S. Bottom hole temperature was 83.8 deg C.

Production test No. 2 was performed in the interval 2295.5 - 2310.5 in the Fensfjord "C" Formation. It flowed condensate at 206. Sm3/d and gas at 881000 Sm3/d on a 25.4 mm choke. The GOR was 4276 Sm3/Sm3. The condensate density was 0.720 g/cc and the gas gravity was 0.668 (air=l). The wellhead pressure was 112.7 bars and the temperature was 47.3 deg C. The well produced 0.5% CO2 and no H2S. Bottom hole temperature was 83.2 deg C.

Production test No. 3 was performed in the interval 2187.2 - 2211.2 Fensfjord "D" Formation. It flowed condensate at 206 Sm3/d and gas at 803000 Sm3/d on a 25.4 mm choke. The GOR was 3897 Sm3/Sm3. The condensate density was 0.732 g/cc and the gas gravity was 0.664 (air=l). The wellhead pressure was 106.6 bars and the temperature was 43.3 deg C. The well produced 0.5% CO2 and no H2S. Bottom hole temperature was 79.3 deg C.

Production test No. 4 was performed in the interval 2100.6 - 2130.6 m in the Sognefjord Formation. It flowed condensate at 202 Sm3/d and gas at 954000 Sm3/d on a 25.4 mm choke. The GOR was 4717 Sm3/Sm3. The condensate density was 0.726 g/cc and the gas gravity was 0.664 (air=l). The wellhead pressure was 118.8 bars and the temperature was 43.8 deg C. The well produced 0.5% CO2 and no H2S. Bottom hole temperature was 76.7 deg C.

Cuttings available at the NPD

Interval [m]: 1020.00 - 2885.00

Cores available at the NPD

Core length [m]: 386.00

Scanned core photos

2110-2111m	2114-2119m	2119-2124m	2124-2129m	2129-2134m
2134-2139m	2139-2141m	2271-2276m	2276-2281m	2281-2286m
2286-2291m	2291-2296m	2296-2299m	2299-2304m	2304-2309m
2309-2314m	2314-2319m	2319-2324m	2324-2327m	2327-2332m
2332-2337m	2337-2342m	2342-2347m	2347-2350m	2365-2370m
2370-2375m	2375-2380m	2380-2385m	2385-2390m	2390-2391m
2393-2398m	2398-2403m	2403-2408m	2408-2413m	2413-2418m
2418-2421m	2483-2488m	2488-2493m	2493-2498m	2498-2503m
2503-2508m	2508-2513m	2513-2518m	2518-2510m	2520-2525m
2525-2530m	2530-2535m	2535-2540m	2540-2545m	2545-2550m
2550-2554m	2621-2626m	2626-2631m	2631-2636m	2636-2638m
2638-2643m	2643-2648m	2648-2653m	2653-2658m	2658-2663m
2663-2665m	2666-2671m	2671-2676m	2676-2681m	2681-2686m
2686-2691m	2691-2694m	2694-2699m	2704-2709m	2709-2714m
2714-2719m	2719-2722m	2722-2727m	2727-2732m	2732-2737m
2737-2742m	2742-2747m	2747-2752m	2752-2757m	2757-2759m
2759-2763m	2764-2769m	2769-2774m	2774-2778m	2778-2783m

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

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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