6406/8-1

General

Block 6406/8 is located on the Haltenbanken offshore Mid-Norway, in the southwestern corner of the Halten Terrace, approximately 215 km west north west of Trondheim. The primary objective of exploration well 6406/8-1 was to test the hydrocarbon potential in the Middle Jurassic Fangst group and the Lower Jurassic Båt group (Ror and Tilje formations). Possible intra-Cretaceous sands related to a seismic marker were considered as second target. Well 6406/8-1 was the first well drilled on the licence. It is located on a domal structure at the Base Cretaceous Unconformity. The prognosed TD for the well was 5027 m.

Operations and results

Well 6406/8-1 was spudded with the semi-submersible installation SSDV Vinni on 15 September 1987 and drilled to final TD at 4914 m in the Early Jurassic Åre Formation. The well was drilled water based.

It was drilled initially to a total depth of 4942 m where it had penetrated the Fangst Group. The well kicked and the drill string was lost in the hole. Due to incomplete fishing operation a sidetracked well was drilled. The sidetrack was spudded on 22 January 1988 at 4262 m. The Fangst Group was once again penetrated and an intermediate logging was performed. Drilling commenced to 4914 m. Due to hazardous drilling with gains and stuck pipe it was agreed that 4914 m was to become the TD of this well. A final logging operation was made comprising FMT and RFT. The Fangst Group down to top Ile Formation was interpreted from data available from the first hole. Due to failed MWD and no wire line logs below 4500 m in the first hole the Båt Group is interpreted from the sidetrack. Horner corrected wire line log BHTs at TD gave a formation temperature of 172 deg C.

Some gas dissolved in water was tested in the Ile Formation; otherwise no moveable hydrocarbons were seen in the well. Dull yellow spots and weak pale green cut fluorescence was described on sandstone from 3145 to 3190 m. Dull orange