25/7-8 S

General

Well 25/7-8 S was drilled to test the Enniberg prospect on the Heimdal Terrace in the North Sea. The primary objective was to prove petroleum in Early Jurassic and Late Triassic reservoir rocks (Nansen, Eiriksson and Skagerrak formations). A secondary objective was to prove petroleum in a potential Middle Jurassic sequence.

Operations and results

Wildcat well 25/7-8 S was spudded with the semi-submersible installation Leiv Eiriksson on 13 November 2019 and drilled to TD at 3250 m (3213.2 m TVD) m in the Late Triassic Skagerrak Formation. A 9 7/8" shallow gas pilot hole was drilled from the 36x30" conductor shoe at 217 m to 1075 m. No shallow gas or water was observed. Following wireline data acquisition at TD, the 25/7-8 S wellbore was plugged-back to 2750 m and bypass side-track 25/7-8 ST2 drilled to acquire cores. The side-track was kicked off at 2831 m. Operations proceeded without significant problems. The well was drilled with seawater and hi-vis pills down to 217 m, with KCl/Polymer/GEM mud from 217 m to 1129 m, and with Innovert oil-based mud from 1129 m to TD.

In the primary exploration target, several oil and gas-bearing intervals with independent isolated columns were penetrated. In the Nansen Formation a total of 19 metres of sandstone with good reservoir properties was encountered. The sands were water bearing. The Eiriksson Formation contained a total of 20 metres of sandstone with moderate reservoir properties, of which 10 m are oil and gas-bearing. The Raude Formation had 11 m of gas bearing sandstone. In the Skagerrak Formation a total of 33 m of sandstone with moderate reservoir properties was encountered, of which 3 metres are gas-bearing.

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