9/10-1

General

Well 9/10-1 is located in the Åsta Graben of the Danish Norwegian Basin in the North Sea. The location was selected to explore the northeast regional limit of Oligocene sands at a non-structural site and to reach the Danian very low on the South flank of the seismic "L" structure. The main objectives were the first and second Oligocene sands, which were gas bearing in the 2/3-1 well. The location, in addition, tested for presence of the Danian section, which had proved to be oil bearing in the Phillips Ekofisk area approximately 40 miles to the Southwest. There was also a possibility of the development of gas bearing zones within the Miocene section.

Operations and results

Wildcat well 9/10-1 was spudded with the jack-up installation Gulftide on 30 August 1970 and drilled to TD at 2205 m in the Late Cretaceous Tor Formation. A 38" hole was drilled to 143 m with seawater. After spotting a gel slurry, 36" drive pipe was set at 123 m. Drilling was continued with a 26" bit to 221 m using seawater where lost circulation became excessive. Attempts with a 50-barrel LCM slurry and a 300-sack cement plug were unsuccessful in sealing off the thief zone. The drilling was continued "blind" to 251 m where a 450-sack gel slurry was spotted and 20" casing run to 248 m and cemented. After installing 20" BOP, 17 1/2" hole was drilled to 953 m using a 10.7 lb gel mud. Three attempts were made to log this surface section but hole bridging conditions occurring at 279 m and 457 m would not permit deeper penetration. Went into the hole with the bit, tagged bottom, and then drilled 5 m with no obstruction. The hole was conditioned and logged from 457 m to 88 m. Rigged up BHA and went to bottom with the bit, cleaned out to 957 m, and drilled an additional 6 m. The 13 3/8'' casing was then run and set with no problems to a depth of 960 m. Drilling continued with a 12 1/4" bit from under the 13 3/8'' ca