25/10-2

General

Well 25/10-2 was drilled to test a structural closure on the down faulted west flank of the basement high on which Esso wells 25/11-1 (Balder Discovery well), 25/8-1 and 25/10-1 had been drilled. The original primary objective, as stated in the Operator's Final Well Report from 1972, was Early Paleocene to Late Eocene sands, which had a thin oil leg in the three wells drilled previously. It was anticipated that appreciably thicker Early Eocene sands would be encountered in the oil leg of 25/10-2. Additional prospects were in Middle - Late Eocene sands, Danian carbonates, and sands of Early Cretaceous, Jurassic or Triassic age.

The results of the well given below is reported with today's knowledge of the area (anno 2003) and cannot be compared directly with the original objectives.

Operations and results

Wildcat well 25/10-2 was spudded with the drilling vessel "Glomar Grand Isle" on 5 August 1970 and drilled to TD at 2191 m (7187 feet) in the Paleocene Lista Formation. Drilling operations went without mechanical problems and there was no lost time waiting on weather. Well 25/10-2 was suspended 25 August 1970 as a well with oil shows. The well was re-entered (25/10-2 R) using "Glomar Grand Isle" on 2 May 1972 and drilled to a total depth of 3180.6 m (10435 feet) in basement rock.

After drilling out the plug in the bottom of the casing in the re-entry some difficulty was experienced in staying in the old hole. The well was drilled to a depth of 2369 m where lost circulation was encountered. Later the pipe became stuck, with the bottom of the fish at 2213 m, and it became necessary to sidetrack the hole. Six cones were lost in the hole while drilling at 2497 m in the sidetrack hole; otherwise no problems were experienced. Initial drilling from the sea floor to 396 m was with seawater and gel. From 396 m to 1036 m the hole was drilled with seawater / Spersene / XP 20 / Salinex sys