6507/7-6

Well 6507/7 6 is an appraisal well on the crest of the Heidrun field structure on Haltenbanken off shore Mid Norway. The structure is a fault wedge. The main objectives of the well were to establish the Ti1je gas/oil contact, to define Tilje and Åre oil properties, and to investigate the Åre oil/water contact. In addition, the well was expected to prove Fangst erosion and established lateral continuity of Tilje reservoir properties.

Operations and results

Appraisal well 6507/7 6 was spudded with the semi-submersible installation Nortrym on 23 July 1986 and drilled to TD at 2525 m in Early Jurassic sediments of the Åre Formation. At 419 m the drill string torqued up and spun out five joints below the kelly, dropping the string to the seabed. The well was re-spudded after being moved approximately 8 m, and this time drilling proceeded without significant problems. The well was drilled with seawater and pre-hydrated gel sweeps down to 1030 m and with KCl/polymer mud from 1030 m to TD.

Oil shows were recorded in 3 m thick sandstone at 2096 m in the Cretaceous. A marked unconformity separates the Middle Jurassic from the overlying Late Cretaceous sequence. The total hiatus was from Aalenian-Bajocian to Campanian-Santonian. Top Middle Jurassic Fangst Group, Ile Formation was encountered at 2144.5 m and was gas bearing. From good quality RFT pressure data, cores, and electric logs a gas/oil contact was established at 2339 m in the Tilje Formation and the oil/water contact at 2440 m in the Åre Formation. Shows continued down to 2445. Below this depth no shows were reported.

A total of 191 m core was recovered from the well. Two cores were cut from the Early Cretaceous through the Fangst Group and into the top Båt Group (2129 - 2185 m), and eight cores were cut from the gas zone in the lower part of the Tilje Formation, through the OWC and into the Åre Formation (2305 - 2462 m). One RFT run was made in the 12 1/4" hole. A water sample was at