Sterling to deepen Cladhan oil search

Offshore staff

CALGARY, Canada – Sterling Resources plans to side track its current appraisal well on the Cladhan oil discovery in the UK northern North Sea.

The semisubmersible Transocean Prospect has been drilling well 210/30a-4 in block 210/30a. It was drilled to a total MD of 12,252 ft (3,734 m), encountering oil-bearing upper Jurassic sandstones in two separate reservoir intervals, with no oil/water contact observed.

The upper reservoir sequence had a gross True Vertical Thickness (TVT) of 18 ft (5.5 m) and a net sand of 13 ft (3.9 m) TVT. This sand has an average porosity of 16% and hydrocarbon saturation of 82%.

Pressures indicate that this reservoir is in a separate pressure regime from the lower reservoir sequence, where the well encountered a gross TVT of 256 ft (78 m) and a net sand of 21 ft (6.4 m) TVT. Here the sand has average porosity of 16% and hydrocarbon saturation of 75%.

Initial pressure data suggest that the lower sand is in pressure communication with, and is part of, the original Cladhan discovery. The well proved ‘oil down to’ 10,447 ft (3,184 m) TVD subsea, implying a minimum hydrocarbon column of over 1,200 ft (366 m).

Once operations on the well are completed, the rig will start work on a first planned side track, 210/30a-4z, to evaluate the upper Jurassic sandstones down dip from the 210/30a-4 well. The aims are to define oil/water contacts for both the upper and lower reservoir units, and to investigate the potential for thickening of the upper unit.

Graham Doré, Exploration director of Sterling’s partner EnCore Oil, said: “The next side track to the east will evaluate the fan structure some 1,000 ft deeper, and has the potential to encounter improved net to gross as well as establishing oil/water contacts for both reservoir sequences. This will be followed by a side-track to the south which is designed to confirm the presence of oil in the central channel."

04/12/2011