Sterling Reaches TD at Cladhan Appraisal Well

Transocean Prospect
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Sterling Resources has completed drilling a fourth well on the Cladhan discovery in the UK sector of the North Sea.

Well 210/30a-4X, drilled by the Transocean Prospect semisub, was designed to further appraise the extent of the Cladhan reservoir. It was drilled in the most southern limit of the northern core area in a potentially separate channel.

The objectives of the 210/30a-4X sidetrack well were to core the full reservoir section about .6 mile (1 kilometer) south and approximately 60 feet (18 meters) up-dip of the oil bearing 210/30a-4 well, and evaluate the southern fringe of the northern core area.

The well was drilled to a total measured depth of 10,614 feet (3,235 meters) encountering 171 feet (52 meters) gross, 105 feet (32 meters) net of high-quality Upper Jurassic sands. Sterling said almost 180 feet (55 meters) of core was recovered across the full reservoir section.

Petrophysical analysis of the interval showed 5 feet (2 meters) of oil-bearing sand at the top of the interval with an oil-down-to at 10,177 feet (3,102 meters) true vertical depth susbsea. A further 100 feet (30 meters) of water-bearing sand was encountered below thin shale which separates the top and bottom sands.

No clear contact was observed, although the top and bottom sands appear to be in pressure communication. Sterling stated that generally, the reservoir quality is very good with porosities of up to 25%, substantiated by measurements obtained while taking fluid samples.

These pressure measurements also confirm that the interval is over-pressured on trend with the 210/30a-4Y well, but some 900 psi lower than the discovery area. The implication of this information is that the southern fringe of the northern channel area is in communication with the central channel, being distinct from the main reservoir in the northern channel area. The operator will suspend the well for use as a potential future development well at this location or elsewhere after a sidetrack.

Development options include either a subsea tie-back or FPSO development of the main northern core area with further definition of reserves and resources during the company’s next drilling campaign.  

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