7/11-9

General

Well 7/11-9 is located ca 5.5 km from the UK border, North of the Cod and Mime Fields on the Cod Terrace. It was designed to test the sedimentary sequences that were seismically correlateable with Ula sands in the 7/11-5 Mime Discovery. The closure of prospect was dependent on pinch-out of the Ula sands and sealing Triassic rocks over the faults to the east and west. Prognosed top of the Ula sands was at 4119 m, and the thickness 90 m. Prognosed TD was at 4260 m in Triassic rocks.

Operations and results

Well 7/11-9 was spudded with the semi-submersible installation Byford Dolphin on 26 November 1985 and drilled to TD at 4271 m in the Triassic Smith Bank Formation. The well was drilled with seawater and hi-vis pills down to 723 m and with KCl polymer mud from 723 m to 3947 m. Due to stuck drill pipe at 3706 m pills with diesel/Imco Spot/Pipelax was spotted. A total of six days were spent freeing the pipe and pulling out of hole before drilling could commence. The 8 3/8" section from 3947 m to TD was drilled with KCl polymer with additions of Chrome lignite starting at 4084 m.

Top limestone came in at 3162 m, and the limestone continued down to top Rødby Formation at 3899 m. Top Jurassic was encountered at 4027 m. Grey/brownish siltstone of the Farsund Formation was encountered at 4093 m. The Ula Formation sand came in at 4168.5 m, and three cores were cut in the interval 4165- 4209.7 m. The cores indicated a 14 m column of shows all through the Ula sands down to top Triassic rocks at 4182.5 m. RFT-tests were run and showed very low permeability, which was confirmed by a DST-test. No shows were reported from above or below the Ula Formation. One RFT sample was recovered from 4181 m. The Horner corrected temperature from 5 highly consistent wire line BHT's at TD gave a temperature of 170 deg C.

The well was permanently abandoned on 9 March 1986 as a dry well.

Testing

One DST-test