6407/8-4 A

General

Well 6407/8-4 A is a sidetrack from the Galtvort well 6407/8-4 S, located on the eastern margin of the Gimsan Basin in the Norwegian Sea, ca 7 km northwest of the Draugen Field. A main fault separates the middle and northern segments of the Galtvort structure from the southern segment. The southern segment was tested in well 6407/8-4 S and found gas in the Fangst Group. The primary objective of the sidetrack was to test the hydrocarbon potential of prospective formations in the middle and northern segments in order to test the sealing potential of the main fault crossing the structure.

Operations and results

Wildcat well 6407/8-4 A was drilled with the semi-submersible installation West Alpha as a sidetrack. It was kicked off from a milled window (1497 - 1502 m) in the 13 3/8" casing in 6407/8-4 S on 22 May 2008 and drilled to TD at 2473 m (2319 m TVD) in the Early Jurassic Åre Formation. The well was drilled with Glydril mud from kick-off to TD. No significant technical problems were encountered in the operations.

Prior to drilling it was prognosed that the sidetrack should penetrate the same formations as well 6407/8-4 S. Due to a much larger fault throw between the Middle and the South Galtvort Segments and hence more extensive uplift and erosion of the Middle and North Segments than anticipated, the entire Fangst Group was eroded. As a result the well penetrated directly from the Cretaceous Kvitnos Formation and into the Båt Group at 2117.8 m (2026.7 m TVD). The upper part of the Båt Group consisted of Ror Formation mudstones and only thin Tofte equivalent sandstones of mediocre reservoir quality. The underlying Tilje Formation came in at 2217 m (2106 m TVD) and was gas bearing down to a GWC somewhere in the inter