34/8-7

General

Well 34/8-7 is located on the western flank of the Tampen Spur and is situated approximately 7.4 kilometres due east of well 34/8-4S, in the Visund prospect. This was the third exploration well to be drilled in the licence area. The primary objective of well 34/8-7 was to test the Jurassic Brent Group and Statfjord Formation in the hanging wall of the Visund Fault. The secondary objectives were to establish a good seismic to well correlation and to fulfil licence obligations.

Operations and results

Exploration well 34/8-7 was spudded with the semi-submersible rig "Polar Pioneer" on 21 March 1992 and drilled to TD at 5460 m in the Triassic Hegre Group. The well was drilled with spud mud down to 1444 m and with KCl/PHPA/Polymer mud from 1444 m to 3288 m. From 3288 m the mud system was gradually changed to a HTHP (high temperature stable polymers) mud. Still, towards TD of the well it was evident that some of the chemical/polymers was decomposing and forming carbonates.

Conglomeratic density flow deposits (Intra Draupne Formation sandstone) were found in the upper part of the Draupne Formation. From a gross thickness of 134.5m, 5.75m of net sand were identified of which 5.25m were regarded as net pay. An average porosity value 9.4% and average Sw of 50.1% were computed for the pay section. A core cut in the Intra Draupne sandstone gave 5.2 % core porosity on average.

The primary objective Brent Group was encountered at 4632.5 m. The entire Brent Group was interpreted as being gas bearing. From a gross thickness of 134.5m, 36.5m of net sand were recognised with 36.5m of net pay. An average porosity of 9.8% and average Sw of 30.4% were determined. A core cut in the Brent Group, gave an average porosity of 9.9 %. The sandy member of Cook Formation was found to be gas bearing, but poor reservoir properties reduced the net pay to only 2.0 m with an average porosity of 8.3 % and average Sw of 36.1 %.

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