The NPD's Fact-pages
	Generated 10.02.2012

After more than 10 years as a fact provider NPDs FactPages version 1 will be shut down in Dec. 2011. Start using FactPages version 2 now! See also FactPages version 2 Quick Reference' If you have any questions or comments please send an e-mail to FactWEB@npd.no.

Exploration wellbore: 30/6-7

General information

Wellbore history

General

Well 30/6-7 is an appraisal well on the Oseberg Field, discovered by well 30/6-1 in 1979.The primary objective was to test for hydrocarbon accumulations in the Late Jurassic sandstones of the Brent formation and the Late and Early Jurassic sandstones of the Dunlin and Statfjord formations in the Alpha north structure. Secondary objectives were to establish the type of communication between the Alpha and Alpha North structures and to define the oil/water contact on Alpha North. The well was planned to reach total depth at 3225 +- 50 m, 75 m into the Statfjord Formation.

The well is Type well for the Oseberg Formation and Reference well for the Amundsen, Cook, Drake, Etive, Ness, and Tarbert Formations.

Operations and results

Well 30/6-7 was spudded with the semi-submersible installation Nortrym on 20 May 1982 and drilled to TD at 3236 m in Early Jurassic rocks of the Statfjord Formation. The 26" section was initiated by a 17 1/2" pilot hole. One small pocket of shallow gas was detected at 358 m (5.6% C1). The well was drilled with seawater and hi-vis pills down to 952 m and with KCl/polymer mud from 952 m to 2285 m. At 2285 m the 13 3/8" casing got stuck and a pill of EZY spot and diesel was pumped in the hole, without effect. The drilling fluid used in the 12 1/4" section from 2285 m to 2915 m the well was drilled with a Dextrid/KCl mud. From 2915 m to TD the mud was converted to a dispersed system by adding lignosulfonate.

The Brent Group was encountered at 2631.5 m. The Brent Group was hydrocarbon bearing with a total gross thickness of 154.5 m and a net sand interval of 106.9 m. The net pay was 50.7 m. Sandstone intervals were also encountered in the Early Jurassic Cook and Statfjord Formations but these were both 100% water saturated.

The Tarbert Formation (2631.5 - 2646.5 m) formed the uppermost interval in the Brent Group. It consisted of very fine to fine grained sandstone which was occasionally medium to coarse grained. Wire line log evaluation gave a net pay of 14.7 m, with an average porosity of 20.7% and an average water saturation of 18.1%. Average permeability (KH, log) was 520 mD.

The Ness Formation (2646.5 - 2727.5 m) consisted of interbedded sandstones, shales, siltstones and stringers of coal. The sandstones were very fine to medium, occasionally coarse grained and locally very micaceous and carbonaceous. The interval contained 38.7 m of net sand and 36 m of net pay which had an average porosity of 20.5%, average water saturation of 27.7% and an average permeability of 577 mD (KH, log). Measured average permeability (KH, core) was 1163 mD.

FMT pressure measurements were taken throughout the Brent interval but it was not been to accurately define an oil/water contact from these measurements as the different sandstone intervals in the Tarbert and Ness Formations have different oil gradients. An oil/water contact has been estimated to be at 2723.5 m from log analysis. On the Alpha structure an oil/water contact has been defined at 2731 m from earlier wells and it appears therefore that the southwest - northeast fault separating the Alpha from the Alpha North structure does have some sealing properties.

The Etive Formation (2727.5 - 2786 m) consists predominantly of a very fine grained to pebbly sandstone with occasional stringers of shale and siltstone. The interval contained 53.5 m of net sand with average porosity of 19.5%. A transition zone of residual hydrocarbons (2727.5 - 2747 m) had an average water saturation of 72%. This agrees with patchy oil shows seen in the cores down to 2755 m (2747 m when depth correction between logger's and driller's depths is applied). The remaining interval of the Etive Formation (2747 - 2786 m) had an average water saturation of 94%. Average permeability of the Etive Formation was 799 mD (KH, log) Measured average permeability from cores was 1670 mD (KH, core).

Apart from in the hydrocarbon bearing reservoirs as described above, weak shows were described in thin limestone stringers in the Sele Formation and in limestones of the Shetland Group.

A total of twelve conventional cores were cut from 2648 to 2812.4 m in the 12 1/4" section in the well. A total of 155.1 m (94.3%) was recovered. Cores were cut consecutively from the top of the Ness Formation and down into the Dunlin Group shales. Core depths are approximately 5 m shallower than logger's depths at the top of Core No 1 and 8.5 m shallower at the base of Core No 12. FMT fluid samples were taken at 2633.5 m (gas, oil and water/filtrate), 2643m (gas, oil and water/filtrate), 2666 m (gas, oil and water/filtrate), 2676 m (gas, oil and water/filtrate), 2684 m (gas, oil and trace of water/filtrate), 2713 m (water/filtrate), and 2714 m (water/filtrate).

The well was permanently abandoned on 24 August 1982 as an oil and gas appraisal well.

Testing

Four DTS' were performed in the Brent formation sandstones.

DST 1 was taken over the interval 2729 -2736 m and produced 770 m3 water/day through an 80/64" choke. Reservoir pressure was 4255.5 psig and the BHT was 110 deg C.

DST 2 was taken over the interval 2711 - 2716 m and produced 1028 SM3/day of 34.9 deg API oil and 116100 Sm3 of 0.72 SG gravity gas through a 56/6 4" choke. Separator GOR was 113 Sm3/Sm3, CO2 content was 0.8%, reservoir pressure was 4250 psig and the BHT was 110 deg C.

DST 3 was taken in the interval 2681 -2684 m and produced 534 Sm3 of 33.9 deg API gravity oil and 65130 Sm3 of 0.702 SG gravity gas through a 32/64" choke. Separator GOR was 122 Sm3/Sm3, CO2 content was 0.2%, and reservoir pressure was extrapolated to be 4222 psig. This test was aborted due to bad weather conditions and no bottom hole samples were obtained.

DST 4 was taken in the interval 2633 -2636 m and produced 1339 Sm3 of 34.1 deg API oil and 146681 Sm3 of 0.700 SG gravity gas through a 72/64" choke. Separator GOR was 110 Sm3/Sm3, CO2 content was 1.0%, and reservoir pressure was extrapolate to be 4178 psig.

Cuttings available at the NPD

Interval [m]: 230.00 - 3237.00

Cores available at the NPD

Core length [m]: 154.26

Scanned core photos

2648-2652m	2652-2656m	2656-2660m	2660-2664m	2664-2666m
2666-2670m	2670-2674m	2674-2675m	2679-2683m	2683-2687m
2687-2691m	2691-2692m	2692-2693m	2694-2698m	2698-2702m
2702-2705m	2707-2711m	2711-2715m	2715-2719m	2719-2719m
2720-2724m	2724-2728m	2728-2732m	2732-2733m	2733-2737m
2737-2741m	2741-2745m	2745-2749m	2749-2750m	2751-2755m
2755-2759m	2759-2761m	2762-2766m	2766-2770m	2770-2774m
2774-2778m	2778-2779m	2780-2784m	2784-2788m	2788-2792m
2792-2793m	2793-2797m	2797-2801m	2801-2805m	2805-2808m
2809-2812m

Palynological slides available at the NPD

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

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

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

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

Old NPD WDSS reports, NPD papers and other related documents

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