FTSE 250 oil exploration and production company Premier Oil is to offload its stake in two blocks in the Norwegian North Sea to sector peer Cairn Energy.Chief Executive Simon Lockett said that this was part of Premier's ongoing programme of non-core asset disposals.Premier Oil has sold its 20% interest in PL378 and PL378B to Cairn's subsidiary, Capricorn Norge, for a cash consideration of $16m. These blocks - jointly owned by Wintershall Norge (the operator with a 45% stake) and Talisman Energy Norge (35%) - contain the Grosbeak discovery and potentially an extension to the Skarfjell discovery located nearby."We continue to concentrate our efforts on projects where Premier is best positioned to add value," Lockett said.Premier Oil is to report its first-half results on Thursday, August 22nd.BC