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Exploration wellbore: 34/8-4 A

General information

Wellbore history

General

Well 34/8-4 A on the Visund Field was initiated as a sidetrack to well 34/8-4 S, which had been temporarily plugged and abandoned. The original well had missed the planned Statfjord Formation target due to structural complexities of the area. The sidetrack should reach the target location, Statfjord Formation, approximately 420 m north-northwest of the surface location in an area of good seismic control. The main objective was to test Statfjord Formation hydrocarbon potential, fluid composition and aquifer characteristics. Secondary objectives were to evaluate the Lunde Formation B/C aquifer characteristics, to establish stratigraphic control of the Base Cretaceous - top Statfjord interval, and to determine the mechanism for hydraulic communication with the Brent reservoir in well 34/8-4S through gravity slide Brent segment and/or through Dunlin Group reservoir.

Operations and results

Well 34/8-4 S was re-entered with the semi submersible installation Transocean 8 on 18 February 1992. The sidetrack 34/8-4 A was kicked off from below the 13 3/8" shoe at 2187 m in the primary well bore and drilled to TD at 3567 m in the late Triassic Lunde Formation. No significant problems were encountered during drilling. The well was drilled with a KCl / polymer mud from kick-off to TD.

A major unconformity was found between the top of the Early Jurassic (Pliensbachian) at 2902.5 m and the overlying Early Cretaceous (Hauterivian). A sandstone member of the Amundsen Formation was encountered from 2942 m to 2989.5 m. One core was taken in this unit and recorded good hydrocarbon shows. Subsequent wire line logs and DST results confirmed that the interval is oil bearing. A gross reservoir thickness of 31.0 m was defined, giving a net pay thickness of 22.38 m. The Statfjord Formation occurred between 3057 m and 3143 m. A total of 7 cores were cut through this interval. Good oil shows were observed throughout.The Lunde Formation was present from 3143 m to TD, at 3567 m and consisted of claystone and distinct interbedded sandstone units. Good shows were recorded in cores in individual sandstone bodies in the upper part of the formation.A total gross reservoir of 205.5 m and a net pay of 115.5 m were defined. An OWC was identified at 3340.5 m.

Altogether sixteen cores were cut from the Dunlin Group and Statfjord and Lunde Formations with a total of 174 m recovered. RFT samples were taken at 3294.5 m (46 &API oil, gas and water/filtrate) and at 3326.5 m (42 &API oil, gas and water/filtrate). The first oil show was recorded at 2909 m at the top of the Jurassic section and the last at 3342 m in the Lunde Formation.

The well was suspended on 27 May 1992 as an oil appraisal.

Testing

Five DST tests were performed in this well, one in the Lunde Formation, three in the Statfjord Formation, and one in the Dunlin Group. The following flow data are from end of main flow.

DST 1 in the Lunde Formation perforated the interval 3322.9 m to 3340.9 m and flowed 936 Sm3 oil and 212000 Sm3 gas / day. The GOR was 226 Sm3/Sm3, oil density (@15 &C) was 0.815 g/cm3, and the gas gravity (air = 1) was 0.77 with 1.4 % CO2 and <0.1 ppm H2S.

&DST 2 in the Statfjord Formation perforated the interval 3214.0 m to 3228.0 m and flowed 35 Sm3 oil and 15700 Sm3 gas / day. The GOR was 448 Sm3/Sm3, oil density (@15 &C) was 0.802 g/cm3, and the gas gravity (air = 1) was 0.81 with 1.2 % CO2 and <0.1 ppm H2S.

DST 3 in the Statfjord Formation perforated the interval 3160.6 m to 3184.6 m and flowed 821 Sm3 oil and 171000 Sm3 gas / day. The GOR was 208 Sm3/Sm3, oil density (@15 &C) was 0.820 g/cm3, and the gas gravity (air = 1) was 0.74 with 1.2 % CO2 and no H2S.

DST 4 in the Statfjord Formation perforated the interval 3056.0 m to 3108.0 m and flowed 831 Sm3 oil and 181000 Sm3 gas / day. The GOR was 218 Sm3/Sm3, oil density (@15 &C) was 0.821 g/cm3, and the gas gravity (air = 1) was 0.74 with 1.2 % CO2 and 0.5 ppm H2S.

DST 5 in the Dunlin Group perforated the interval 2988.5 m to 3019.5 m and flowed 992 Sm3 oil and 225000 Sm3 gas / day. The GOR was 227 Sm3/Sm3, oil density (@15 &C) was 0.820 g/cm3, and the gas gravity (air = 1) was 0.74 with 1.2 % CO2 and 0.5 ppm H2S.

Cuttings available at the NPD

Interval [m]: 2190.00 - 3567.00

Cores available at the NPD

Core length [m]: 174.00

Scanned core photos

2909-2913m	2913-2914m	2994-2998m	2998-3002m	3002-3006m
3006-3006m	3063-3067m	3067-3071m	3071-3072m	3072-3076m
3076-3080m	3080-3084m	3084-3087m	3088-3092m	3092-3096m
3096-3100m	3100-3102m	3103-3107m	3107-3111m	3111-3112m
3113-3117m	3118-3123m	3123-3128m	3128-3133m	3133-3134m
3135-3140m	3140-3145m	3145-3146m	3146-3151m	3151-3154m
3156-3161m	3161-3166m	3166-3171m	3171-3176m	3176-3181m
3181-3182m	3183-3188m	3188-3193m	3193-3196m	3197-3198m
3198-3201m	3247-3252m	3252-3257m	3257-3258m	3329-3334m
3334-3339m	3339-3342m

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: 0.546 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.

Old NPD WDSS reports, NPD papers and other related documents

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