25/4-5

General

Well 25/4-5 was drilled ca 1 km SW of the 25/4-1 Heimdal Discovery well. The primary objective was to test the Vestland Group and the Statfjord Formation on a down-thrown panel west of the high drilled by the 25/4-1 well, which found several hydrocarbon bearing Jurassic levels in addition to the main Heimdal Discovery. The secondary objective was to appraise the gas-bearing section in the Paleocene Heimdal Formation.

Operations and results

Wildcat well 25/4-5 was spudded with the semi-submersible installation Dyvi Alpha on 26 June 1980 and drilled to TD at 4355 m in the Triassic Smith Bank Formation. Operations were interrupted by a strike that led to 4.5 days down time.

The Heimdal reservoir was found at 2150 m with gas down to a GOC at 2172 m and a 7 m oil column down to the oil-water contact at 2179 m. Drill with 8 1/2" bit from 3600 m to 4198.5 m When running in hole in the 8 1/2" section the bit stuck at 4174. The hole was then backed off to 3891 m and a technical sidetrack was made from 3769 m.

A 128 m thick Vestland Group was penetrated from 3692 m to 3820 m. The Hugin and Sleipner formations were found water bearing with residual hydrocarbons with the exception of a thin oil bearing interval from 3777.5 m to 3781.5 m. RFT sampling over this zone indicated a water gradient, but an RFT fluid sample recovered both oil (0.25 l) and gas (139 l).

The Statfjord was encountered at 3949 m and was 178 m thick. It contained sandstones in the upper 50 m and in the interval from 4064 to 4098 m. The upper interval could be interpreted as hydrocarbon bearing. Direct fluorescence (yellow) and cuts (yellow -pale blue) were observed on the cores from this formation, and migrated hydrocarbons were also found by post-well organic geochemical analyses. Tests (DST and RFT) recovered only water.

The triassic Group contained a 50 meters sandstone reservoir, which was drilled with good shows. The tests