16/1-25 S

General

Well 16/1-25 S was drilled on the Utsira High in the North Sea, 2.7 km south of well 16/1-12 (Rolvsnes discovery well). The primary objective was to prove the presence of transgressive Cretaceous and/or Jurassic sandstones overlying the basement and to test the extension of the 16/1-12 discovery in porous basement towards south.

Operations and results

Wildcat well 16/1-25 S was spudded with the semi-submersible installation Bredford Dolphin on 15 October 2015 and drilled to TD at 2210 m (2121 m TVD) m in the basement rock. The section from 2010 to 602 m was drilled first as a 97/8” pilot hole to check for shallow gas and then opened up with a 26” bit. No shallow gas was observed. The well was drilled as a deviated well (15° through basement) in order to cross more faults and test a wider area and in that way to get better control on variability, quality and thickness of the weathered zones. Operations proceeded without significant problems. The well was drilled with seawater and hi-vis sweeps down to 602 m and with Aquadril mud from 602 m to TD.

A 10 m transgressive sandstone was prognosed at the base of the Early Cretaceous Åsgard Formation but only 10 cm was observed directly above basement. The top basement was found at 2004.25 m (1922.7 m TVD). The well encountered an oil column of about 30 m in porous and fractured basement rock. The OWC is set 2034.5 m MD RKB (1952 m TVD). The pressure data shows communication with the 16/1-12 oil discovery, with approximately the same oil/water contact. The fluid type is oil with similar properties to the Edvard Grieg oil. Below OVC there was oil shows (direct, cut and residual fluorescence) down to 2067 m, and weaker shows down to 2124 m. There were no shows below this depth or above to