6507/8-5

General

Well 6507/8-5 was designed to drill the Omega prospect, a horst, located east of the Heidrun Field. Structurally the area is situated on the Sør High with the Halten Terrace to the southwest and the Trøndelag Platform to the East. The Omega horst had only a minor structural closure of 10-20 m, but assuming scaling capacity of a fault, a stratigraphic closure would exist both up-dip and further down-dip of the structural closure. The fault was prognosed with a maximum throw of 140 m on top Ror Formation level. The main objective of the well was to test the hydrocarbon and reservoir -potential of sandstones of the Middle/Early Jurassic Fangst Group supposed to be present on the downthrown eastern side of the fault. None of the nearby correlation wells penetrated highly over pressured formations. Shallow gas warnings were given for three levels in the interval 518 to 960 m.

Operations and results

Wildcat well 6507/8-5 was spudded with the semi-submersible installation Ross Rig on 3 March 1991 and drilled to TD at 2000 m MD in the Early Jurassic Tilje Formation. The well was drilled in 13 days without major problems. However, while drilling 9 7/8" pilot hole at 854 m shallow gas was encountered. The well was plugged back and a 13 3/8" casing was set above the gas. The well was drilled with seawater and hi-vis pills down to 818 m and with Gyp/PAC mud from 818 m to TD.

Six meter of the Late Cretaceous Shetland Group was encountered at 1781 m; otherwise the Cretaceous section was absent in the well. Three meter of Spekk was penetrated at 1787 m. It was described as silty carbonaceous claystone with traces of coal fragments. The potential reservoir sands of the Fangst and Båt Groups were penetrated but proved not to be hydrocarbon bearing. No shows were recorded in any section of the well, not even in the claystone of the Spekk Formation. One conventional core was cut in the interval 1856.7 m to 1884.5 m in the Not/Ile