2/7-24

General

Well 2/7-24 was drilled on the west Valhall Prospect, a Late Jurassic structure located in the Feda Graben on the west side of the Central Trough near the Skrubbe Fault. The main objective was the Eldfisk Formation sandstones, a mass flow deposit located on the east side of the fault. A secondary objective was sandstones associated with a seismic horizon called the Intra Volgian Marker.

Operations and results

Wildcat well 2/7-24 was spudded by the semi submersible rig Ross Isle 7 November 1990 and drilled to TD at 5023 in the Late Jurassic Farsund Formation. No shallow gas was encountered in this well. At ca 3050 m, in the 5 7/8" hole section, the inclination started to increase to a maximum of 20 deg where after the inclination decreased to 12,5 deg at TD. The well was hampered by bad weather, malfunction of BOP, hole problems with loss of mud, and problems with running logging equipment properly. The well was drilled with sea water and hi-vis pills down to 465 m, with ester-based Petrofree mud from 465 m to 3042 m, and with oil based mud from 3042 m to 3388 m. Below 3388 m the mud was switched from oil based to water based in an effort to reduce the mud losses. Water based mud was used down to TD.

The base Cretaceous unconformity was encountered at 3195 m. The well penetrated 122 m of Mandal Formation and continued through 1706 m of Farsund Formation without reaching its base. Hence an 1828 m thick Late Jurassic section was penetrated, a record at the time of drilling. The Late Jurassic lithology was primarily mudstone with subordinate amounts of thinly bedded sandstone and limestone. The primary objective was encountered approximately at 4069 m, 174 m higher than prognosed. No reservoir quality clastic mass flow dep