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Exploration wellbore: 1/3-7

General information

Wellbore history

General

Well 1/3-7 is located on the Hidra High in the North Sea. It was drilled to appraise the 1/3-6 Oselvar condensate discovery made in Paleocene Forties Formation sandstones. The well was placed down-flanks on the structure relative to the discovery well in order to penetrate the hydrocarbon-water contact and further appraise reservoir properties and production rates.

Operations and results

Appraisal well 1/3-7 was spudded with the 3 leg jack-up installation West Epsilon on 13 February 1995 and drilled to TD at 3345 m in the Paleocene Våle Formation. A gas kick was taken at 1740 m in the top of the Hordaland Group, later it was found that the gas probably originated from a limestone less than one meter thick. The hole packed off, the string had to be cut off at 1564 m, and the hole was plugged back. A technical sidetrack (1/3-7 T2) was made from 1204 m. This sidetrack failed as the bit fell back into the original hole during a wiper trip. A new and successful technical sidetrack (1/3-7 T3) was made from 1202 m. A second gas kick occurred in the T3 sidetrack when reaching 1741 m. This kick was controlled by the driller's method without significant problems or extra rig time. The extra activity caused by the first kick prolonged the rig time with 23 days. Due to poor hole conditions no open hole logging was performed in the 12 1/4" section. As the West Epsilon was available only up to 28 May open hole logging at final TD was also abandoned in order to secure time for the well test. The reservoir was logged through casing. The well was drilled with sea water down to 207 m and with gelled mud from 207 m to 1204 m. From 3103 m to TD it was drilled with a salt polymer.

Top Forties Formation was encountered at 3175 m. The Forties reservoir sandstones was encountered at 3183.5 m and proved to be oil bearing down to an oil-water contact at 3225 m. The logs indicated hydrocarbons down to 3229.4 m (3182.3 m MSL) and oil shows (direct and cut fluorescence) were reported down to 3232 m. This lower zone was considered to be only a residual oil zone, which was indicated also by the change in geochemical composition. No oil shows were reported above the Forties reservoir or below 3232 m, only background gas. The up-flanks 1/3-6 reservoir contains condensate. Hence, the 1/3-7 well suggests a ca 490 m hydrocarbon column with a gas/oil contact somewhere between the two wells. However, the depth of a GOC could not be determined, nor could it be deduced with any certainty that there is pressure communication between the reservoir sections penetrated in the two wells.

A total of 74.5 m core was cut and retrieved in 4 cores in the interval from 3164 to 3251 m. No wire line fluid samples were taken.

The well was permanently abandoned on 25 May 1995 as an oil appraisal well.

Testing

Two tests were performed on the reservoir.

DST 1A tested the interval 3183.5 to 3215.5 m. It produced 49 Sm3 oil and 16783 Sm3 gas /day through a 1/2" choke. The GOR was 333 with a well head flowing pressure (WHFP) of 15.4 bara. The density of the oil was 0.797 g/cm3.

DST 1B tested the intervals 3183.5 to 3215.5 m and 3220 to 3224.5 m. It produced 136.8 Sm3 oil and 37762 Sm3 gas /day through a 1/2" choke. The GOR was 280.9 Sm3/Sm3, with a well head flowing pressure of 35 bara. The formation temperature was measured in the tests to be 131.6 deg C. The formation temperature was taken as the highest flowing temperature just after opening the well for DST 1A. This is due to the temperature reducing with time because of the thermal expansion effect of gas (BHFP << Bubble point pressure).

Cuttings available at the NPD

No cuttings in this wellbore.

Cores available at the NPD

Core length [m]: 74.50

Scanned core photos

3164-3169m	3169-3174m	3174-3179m	3179-3181m	3188-3189m
3189-3190m	3190-3191m	3191-3192m	3192-3193m	3193-3194m
3194-3195m	3195-3196m	3196-3197m	3197-3198m	3198-3199m
3199-3200m	3200-3201m	3201-3202m	3202-3203m	3203-3204m
3204-3205m	3205-3206m	3206-3207m	3207-3208m	3208-3209m
3209-3210m	3210-3211m	3211-3212m	3212-3213m	3213-3214m
3214-3215m	3215-3216m	3216-3217m	3217-3218m	3218-3219m
3219-3220m	3220-3221m	3221-3222m	3222-3223m	3223-3224m
3224-3225m	3225-3226m	3226-3227m	3227-3228m	3228-3229m
3229-3230m	3230-3231m	3231-3232m	3232-3233m	3233-3234m
3234-3235m	3235-3236m	3236-3237m	3237-3238m	3238-3239m
3239-3240m	3240-3241m	3241-3242m	3242-3243m	3243-3244m
3244-3245m	3164-3169m	3169-3174m	3174-3179m	3179-3181m
3188-3193m	3193-3198m	3198-3203m	3203-3204m	3205-3210m
3210-3215m	3215-3220m	3220-3223m	3224-3229m	3229-3234m
3234-3239m	3239-3244m	3244-3245m

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 (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.