The Stella development lies in the Central North Sea, 15 km northwest of the Joanne Field and was discovered in 1979 by well 30/6-2 when gas/condensate was encountered throughout a 25 ft section of Paleocene Andrew sand. Oil was also observed in the underlying Ekofisk Chalk reservoir.  The accumulation is draped over a salt induced anticline with ~1,000 ft of closure, covering 22 km². Subsequent appraisal wells 30/6-3 and 3Z were drilled in 1996 on the crest of the structure. The 3Z well achieved flow rates of 2,900 boepd and 23 mmscf per day from the Andrew sands.  In 2005 Maersk, the operator, drilled well 30/6-5 and sidetracks 5Z and 5Y, to further appraise the Chalk and Andrew reservoirs. Gas condensate bearing Andrew and oil bearing Chalk was encountered.  The sidetrack well, 30/6-5Y, tested at a maximum rate of 3,000 barrels of condensate per day and 17 mmscfpd from the Andrew sands. 

Ithaca drilled an appraisal well and a sidetrack (30/6a-8 and 30/6a-8Z respectively) on the Stella discovery in 2010.  The appraisal well was spudded on 18^th February 2010 and sidetrack 30/6a-8Z was kicked off on the 26^th April 2010. Both wells were drilled using the Galaxy II heavy duty jack-up drilling rig.  The 30/6a-8 well was a vertical well, drilled targeting a down flank location from the previous appraisal wells and close to the structural closure of the discovery.  The 30/6a-8Z sidetrack was a deviated well, targeting a mid flank location. The well was completed on budget with all the principle objectives of the well having been achieved.

The Andrew Sand reservoir section was encountered at 9,905 ft TVDSS in the 30/6a-8 well and the whole interval was cored successfully before the well reached TD (total depth) in the underlying Ekofisk Formation on 25^th March 2010.  A comprehensive logging program was carried out which indicated that the well had penetrated 22.5 ft gross of high quality, oil bearing Andrew Sand reservoir and 60 ft gross water bearing porous chalk reservoir at the top of the Ekofisk. Average Net reservoir Porosity in the Andrew Sandstone was 22 % (max 26 %) with an average permeability of 30 mD (max 74 mD).  The presence of good quality, productive reservoir down flank on Stella confirmed the pre-drill reservoir distribution model and the reservoir parameters were within the ranges expected pre-drill.

The 30/6a-8Z sidetrack, drilled up-dip from the 30/6a-8 well to establish the nature of the fluids in the Stella structure, encountered Andrew Sandstone reservoir at 9,627 ft TVDSS before reaching TD in the Ekofisk on 30th April 2010. The same comprehensive logging program deployed in the 30/6a-8 well was also carried out in the 30/6a-8Z sidetrack. As planned, no coring or well testing was carried out in the sidetrack. The data from the sidetrack indicated that the well had penetrated Andrew Sand with an average Porosity of 22 % (max 27 %).

The oil saturations observed in the reservoir in the 30/6a-8 well predict a free water level (base of the hydrocarbon to water transition zone) at ~9,950 ft TVDSS which matches the geological spill point of the Stella structure to the East. Successful recovery of hydrocarbons from this down flank location supports the conclusion that Stella is filled to spill with hydrocarbons.  The presence of hydrocarbons at this location also significantly deepens the previous "deepest proven hydrocarbons" (used to assign reserves) and consequently increases the proven hydrocarbon column height by over 500 ft.
 

 
As is common in gas / condensate fields, the hydrocarbon composition in Stella changes with depth.  The sidetrack (30/6a-8Z) was drilled up dip to ascertain the pressure and nature of the hydrocarbons at a mid-flank location. This information is important to allow development wells to target the most valuable fluids; it is essential to clearly understand the ratio of oil to gas / condensate before finalising the development scheme.  The sidetrack also provided additional information about the reservoir presence, thickness and quality.
 

*Assumes CMI transaction completes