BP could be forced to drill extra wells at its $4.5 billion Clair Ridge development in the UK West of Shetland area following poorer than expected performance from the nine wells drilled so far, according to a field partner.

Chrysaor said in an update on its operations that delayed drilling and poorer performance at the wells nine wells drilled so far at Clair Ridge — the second phase of development at the field — has offset good performance at the Clair Phase 1 development so far this year.