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Exploration wellbore: 2/7-8

General information

Wellbore history

General

Well 2/7-8 is located In the Feda Graben of the southern North Sea, some 3 km west of the Eldfisk Field. It was drilled on the East Eldfisk Structure, and the main objective was to test the Danian Limestone. Secondary objective was to test the Late Cretaceous Chalk, which could by hydrocarbon bearing if porosity is present.

Operations and results

Wildcat well 2/7-8 was spudded with the jack-up installation Zapata Explorer on 8 June 1973 and drilled to TD at 3318 m in the Late Cretaceous Hod Formation. The well was drilled with seawater and hi-vis slugs down to 1220 m, and with a lignosulphonate mud (UNI-CAL / Caustic) from 1220 m to TD. According to the mud program the section below 1220 m was drilled with 4% diesel in the mud.

The Danian Limestone, which was expected to be 100 m thick with 38 m of net pay, was found to be much thinner than the other wells on Eldfisk, and was only 9 m thick. It was also less fractured than other wells on Eldfisk, but still yielded commercial quantities of oil and gas, after acidization, over the total interval on the third of three drill stem tests. This test included the top 23 m of the Late Cretaceous (Maastrichtian). The remaining tests below this interval, also in the Maastrichtian, did not produce oil or gas in commercial amounts. The truncated Danian, the lack of fracturing and secondarily porosity, and the fact that the produced oil was heavier than the oils on the main Eldfisk structure to the west, suggested that East Eldfisk structure is not in communication with the main Eldfisk structure.

No cores were cut and no wire line fluid samples were taken.

The well was permanently abandoned on 12 August 1973 as an oil discovery.

Testing

Four drill stem tests were performed.

DST 1 and 2 tested the interval 3039 - 3051 m in the Maastrichtian Tor Formation. DST 1 gave no production. DST 2, after acidization, produced 1 litre fluid (95% water and 5% oil) pr hour.

DST 3 tested the interval 3014 - 3033 m in the Tor Formation. It produced 13.5 Sm3 oil and 2407 Sm3 gas/day. The corresponding GOR is 178 Sm3/Sm3, and the measured oil gravity was 14 deg API.

DST 4 tested the interval 2969 - 3001 m in the Danian Ekofisk Formation and the upper Tor Formation. It produced 539 Sm3 oil and 53802 SM3 gas/day. The corresponding GOR is 100 Sm3/Sm3, and the measured oil gravity was 33 deg API.

Cuttings available at the NPD

Interval [m]: 1237.49 - 3318.36

Cores available at the NPD

No cores in this wellbore.

Scanned core photos

No scanned core photos available

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 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)

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Old NPD WDSS reports, NPD papers and other related documents

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NPD papers

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