CALGARY, Canada – Sterling Resources has completed its latest appraisal well on the Cladhan discovery in the UK northern North Sea.
Well 210/30a-4X, drilled on block 210/30a by the Transocean Prospect, was the fourth well and the third side-track of a campaign designed to delineate the extent of the Cladhan reservoir.
It was drilled in the southernmost part of the northern core area in a potentially separate channel. The main objectives of the sidetrack were to core the full reservoir section, 1 km (0.6 mi) south and 60 ft (18 m) up dip of the oil-bearing 210/30a-4 well, and to evaluate the southern fringe of the northern core area.
The well was drilled to an MD of 10,614 ft (3,235 m), encountering 171 ft (52 m) gross and 105 ft (32 m) net (vertical thickness) of good quality Upper Jurassic sands. Almost 180 ft (55 m) of core was recovered across the full reservoir section.
Petrophysical analysis of the interval revealed 5 ft (1.5 m) of oil-bearing sand at the top of the interval with an oil-down-to at 10,177 ft (3,102 m) TVD subsea.
A further 100 ft (30.5 m) of water-bearing sand was encountered below thin shale separating the top and bottom sands. No clear contact was observed, although the top and bottom sands appear to be in pressure communication.
Analysis suggests the interval is over-pressured on trend with the 210/30a-4Y well, but around 900 psi (62 bar) lower than in the discovery area. This implies 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.
Sterling will suspend the well for use as a potential future development well either at this location or elsewhere following a sidetrack.
John Rapach, Sterling's COO, said: "We have proved that our current seismic model can adequately predict sand thickness but reservoir quality definition is now paramount for further appraisal and development drilling.
“Our next planned subsurface activity is to complete full reprocessing and interpretation of the existing seismic dataset incorporating all of the log, core, fluid and pressure results obtained during this current drilling campaign. Consequently, the next drilling campaign will probably commence in early 2012.
"Our development planning is concentrating on either a subsea tie-back or FPSO development of the main northern core area with further definition of reserves and resources during our next drilling campaign. We are commencing pipeline route and environmental survey work within the next few weeks."
Mike Azancot, Sterling's CEO, added: “Our plan towards development with options for increased resource exploitation after further drilling is now under way with a target for first oil in 2014."