Offshore staff

CALGARY, Canada -- Sterling Resources has completed a second appraisal side track on it Cladhan discovery in the UK northern North Sea.

The 210/30a-4Z well was drilled by the semisubmersible Transocean Prospect in block 210/30a, 1.6 km (1 mi) east and a further 1,240 ft (378 m) downdip of the 210/30a-4 well.

Main objectives were to appraise the field further east of previous well control, and to prove the presence of sand and oil presence in a fan system deeper than probed by previous wells, which were drilled into channel systems on a terrace structure.

The side track was drilled to a MD of 15,900 ft (4,846 m), having encountered two separate Upper Jurassic reservoir zones of 12 ft (3.6 m) and 169 ft (51.5 m) vertical thickness, with oil shows through both intervals. No oil/water contact was encountered.

Petrophysical analysis of the open-hole logs revealed porosities up to 13.5%, but with a high degree of dolomitic cement.

"We have been able to prove-up a large depositional feature as prognosed from our seismic interpretation and with hydrocarbons quite deep in the structure," said COO John Rapach.

"Our challenge will be to understand the variation in reservoir quality in the eastern area of the field … the next well will target the central channel and the final well will be drilled to the southern portion of northern channel. These wells are planned into areas with similar seismic characteristics that have already encountered movable hydrocarbons.”

"While we would have preferred to see better quality sands in what appears to be a large package of oil-filled reservoir, this is the first well into a deeper portion of the field and we have to remember that we are still exploring in an area with little well control," said Mike Azancot, president and CEO.

The partners plan to reprocess existing seismic data and to commission possible further seismic acquisition in an attempt to improve understanding of reservoir quality variation.

“Given that the first two wells of the current campaign have still not encountered an oil/water contact, the uncertainty of the prospective oil in place at least in the terrace area has been significantly reduced and should be further refined by the next two wells," Azancot said.

05/05/2011