2/1-9 A

General

Well 2/1 ?9 A was drilled to appraise the 2/1-9 discovery in the Late Jurassic "Gyda sandstone member" (Ula Formation), by side-tracking up-dip to the crest of the Gyda South structure. If successful, the well could at a later stage be completed as a producer and tie back to Gyda platform. The structure is a fault/dip closure, which lies in the Late Jurassic fairway on the eastern flank of the Central Graben, 6 kilometres south of the Gyda field in the North Sea.

Operations and results

Well 2/1-9 was re-entered on 18 January 1992 by the semi submersible installation Ross Isle. The appraisal sidetrack well 2/1-9 A was kicked off in the 8 1/2" hole from 3270 m in the Late Cretaceous Tor Formation and drilled to TD 4379 m in the Late Jurassic Ula Formation. It took 25 1/2 days (18 1/2 days longer than planned) to drill to coring point at 4140 m. This delay was mainly due to difficulties in controlling the directional tendencies of the BHA's, which required a number of correction runs. In addition, poor bit performance and harder than expected formations exacerbated the slow progress. Hole inclination was 52.8 degrees at coring point. Problems were also experienced during TD logging with stuck logging tools and stuck pipe whilst attempting to retrieve the tool. In addition a 9 bbl influx had to be circulated out during this time. The well was drilled with Novamul ether-based mud from kick-off to TD.

The target Ula Formation sandstone was encountered at 4099 m (3966 m TVD RKB). It was 120 m thick (TVD) and oil-bearing all through. The logs observed no OWC.

Six cores (178 m) were cut in the 8 1/2" hole. All cores had 100% recovery with excellent shows being observed throughout. Core 1 to 5 covered the sandstone of the Ula Formation while core 6 entered into a mud stone member at the base. No H2S was observed whilst coring -despite having high level contingency due to H2S seen on well 2/1-9. The RFT wa