30/6-23

General

Well 30/6-23 was drilled on the Beta South structure on the Brage Horst and south of the Veslefrikk Field in the North Sea. The Beta structure is surrounded by producing oil fields or commercial discoveries. On Beta, oil has been discovered in the Middle Jurassic Brent Group reservoirs in fault-block traps. The oil is contained in two main sub-structures, i.e. the Beta Saddle and Beta South, comprising several smaller sub-compartments. The discovery well on Beta was the 30/6-5 well, but this well was not tested due to the detection of H2S in the RFT samples. Later wells proved oil in the Beta Saddle without encountering H2S. The Beta Saddle is characterized by a multicontact reservoir having prominent shale barriers. There are also slight differences in fluid composition between the two compartments, which suggests that the saddle through is acting as a structural spill point at the top Etive level. Primary target for the well was Base Brent Group prognosed to come in at 2891 m. Secondary objective was top Statfjord prognosed at 3141 m. OWC was expected at 2880 m.

Operations and results

Appraisal well 30/6-23 was spudded 29 April 1990 by the semi-submersible rig Transocean 8 and drilled to TD at 3209.5 m in the Early Jurassic Eirikson Formation. Shallow gas was indicated from mud gas and MWD at several levels between 440 m and 603 m. Gas influx occurred during a wiper trip back from 601 m to the 30" casing shoe at 261 m. Otherwise drilling proceeded without any significant issues. The well was drilled with spud mud down to 378 m and with KCl/polymer mud from 378 m to TD.

Formation tops came in approximately as prognosed. Top Viking Group was encountered 2534 m and consisted of 82 m Draupne Formation and 177 m Heather Fo