34/10-4

General

Well 34/10-4 was drilled in the Delta closure in the north-eastern part of block 34/10 in the northern North Sea. The Delta structure consists of several separate fault blocks and 34/10-4 targeted one of these. It was the third well drilled in the Delta closure. Two other separate fault blocks had previously proved oil bearing by well 34/10-1 located to the south, and well 34/10-3 located about 2 km north-west. The primary objective of well 34/10-4 was to test sandstones of Middle Jurassic age. Secondary objectives were sandstones of Early Jurassic age.

Operations and results

Well 34/10-4 was spudded with the semi-submersible installation Ross Rig on 12 August 1979 and drilled to TD at 2600 m in the Late Triassic Lunde Formation. No specific problems were encountered in the operations. The well was drilled with sea water and gel slugs down to 641 m and with sea water, gel, lignite and lignosulphonate in various proportions from 641 m to TD.

A minor hydrocarbon-bearing interval was encountered in the Eocene from 1290 to 1307 m but the type of hydrocarbons could not be determined. The net Eocene "pay" was 8.25 m with average porosity of 34.4% and average water saturation of 38.5%. The main target Brent Group sandstones were encountered at 1816 m and were found oil bearing down to claystone at 1912 m. It contained 81 m of net pay with an average porosity of 33.7% and an average water saturation of 12.5%. The Statfjord Formation (2350 - 2481 m) was water bearing with 61 m of net sand with an average porosity of 23.3%.

The first show was recorded on a well site sample from 1280 m, just above the Eocene pay. It was described with "dead oil, dull fluorescence"