RESULTS from an exploration well drilled by BP at the controversial North Uist prospect west of Shetland has put is commercial exploitation in doubt.

Drilling found "varying reservoir quality", according to an announcement by Faroe Petroleum, the Aberdeen-based oil explorer which has a 6.25% interest in the prospect.

Faroe chief executive Graham Stewart said: "After a long period of drilling on this wildcat exploration well, we are pleased to have made a discovery in the North Uist exploration well, although we hoped for a better quality reservoir.

"The result proves another working hydrocarbon system in the frontier west of Shetlands which is good news for further prospectivity in these waters.

"The partnership will now undertake extensive analysis of the considerable volumes of data and samples collected from the well operations before deciding on the next steps."

Faroe wrote: "The well reached a total vertical depth of 4700 metres and encountered gas condensate in sandstone reservoirs in the target section. Preliminary results indicate varying reservoir quality and the commercial potential has yet to be evaluated. The shallower Cardhu prospect encountered traces of hydrocarbons."

The well will now be plugged and abandoned, as planned. Environmental groups have warned there are risks in drilling in the waters off Shetland.