6407/7-3

General

Well 6407/7-3 was drilled on the northern part of the A structure of the Njord Field. The main objectives of the well were to test the hydrocarbon potential of the Ile Formation, to test the hydrocarbon potential of the Tilje Formation above the oil down to level in the Tilje Formation in well 6407/7-1, and to obtain formation pressure data to indicate the relationship between the A-north and the A-east/A-central compartments.

Operations and results

Well 6407/7-3 was spudded with the semi-submersible installation Polar Pioneer on 3 March 1988 and drilled to TD at 3222 m in the Triassic Grey Beds. At 891 m, after setting of 30" casing, gas started to stream out of the casing. It was assumed that the gas came from the bottom of the hole, since there were no previous peaks on the MWD log. Three cement plugs were set in the interval 780 - 891 m, but the gas continued to stream. A plug was then set in the interval 510 - 570 m, and the gas stream decreased. The hole was drilled up again to 525 m, where 20" casing was set, originally not a part of the program. Two zones had shallow gas, 553 - 570 m and 652 - 685 m, which was in agreement with what was assumed in the site survey. Further drilling proceeded without any significant problems. The well was drilled with spud mud down to 536 m, with gel and seawater from 536 m to 1098 m, with Newdrill/KCl/PAC from 1098 m to 3048 m, and with Newdrill/PAC.

Top Jurassic was encountered at 2795 with a 12 m thick Spekk Formation overlying the Middle Jurassic Not Formation. Top of the reservoir sections was encountered at 2851 m. Light oil was encountered in two differently pressured reservoir zones. The upper reservoir was the Ile Formation from 2851 to 2867 m with a net pay of 10.8 m. The lower reservoir was the Tilje Formation and into the Åre Formation. The oil bearing interval was from 2936.5 m and down to siltstones at 3068 m with a total net pay of 50.4 m. The Åre Format