2/11-12 A

General

Well 2/11-12 A “West Hod Exploration” is a geological side-track to 2/11-12 S. It was drilled on the Skrubbe Fault between the Lindesnes Ridge and the Ål Basin in the North Sea. The purpose of 2/11-12 A was to assess the hydrocarbon potential below the Shetland Group. The primary reservoir target was Late Jurassic sandstones. The Early Cretaceous Tuxen Formation and Paleozoic rocks were secondary targets. The stratigraphy below BCU was highly uncertain. Base case for TD was around 300 m into the Paleozoic, at 3500 m TVDSS.

Operations and results

Wildcat well 2/11-12 A was kicked off at 1440 m in 2/11-12 S on 19 January 2019. It was drilled with the jack-up installation Mærsk Interceptor to TD at 3427 m (3244.5 m TVD) in the Permian Zechstein Group halite. Wellbore breathing/ballooning in the Mandal Formation caused several gas peaks and a sudden mud loss at 3245 m. The mud weight was adjusted, and drilling commenced. The losses were gradually reduced and stopped at 3253 m. The well was drilled with oil-based mud from kick-off to TD.

The well did not encounter reservoir in the primary Late Jurassic exploration target. Due to lack of Jurassic reservoir and the unexpected occurrence of Zechstein salt TD was set early. No Paleozoic reservoir was penetrated. In the Lower Cretaceous, the well encountered a carbonate-rich rock of about 45 metres in the Tuxen and Åsgard formations with poor reservoir properties. Petrophysical analyses indicated traces of oil, and oil shows in the form of direct and cut fluorescence was recorded in the interval 3094 to 3118 m in the Tuxen Formation limestone. The shows were confirmed by organic geochemical analysis of sidewall cores. Cut fluorescence and residual ring was observed also in Zechstein lime