The stake sales will allow Aberdeen-based Ithaca to cut the costs of its exploration activity while maintaining an interest in the prospects concerned.
Aim-listed Ithaca has agreed to farm out a 9% working interest in the UK licences containing the Handcross prospect west of Shetland to Oyster Petroleum in exchange for the Norwegian company paying an undisclosed share of past and future licence costs. Oyster will also make an unspecified cash payment to Ithaca.
Bermuda-based Azimuth has acquired an additional 5% interest on similar terms.
Ithaca said when combined with earlier farm-outs involving European energy firms, the company will have its forecast share of the Handcross exploration well planned for the fourth quarter covered and will receive some cash.
Ithaca has agreed to farm-out a 10% interest in the licence that contains the Isabella gas condensate prospect off eastern Scotland to a subsidiary of EDF.
The French energy firm will cover a 10% working interest share of future licence costs and pay an unspecified amount to Ithaca.
Combined with an earlier farm-out with a Danish firm, Ithaca is carried for its forecast share of the Isabella exploration commitment well cost and will receive additional cash beyond the carry.
The deals continue the process of rationalising the portfolio of North Sea interests Ithaca acquired through the £203m takeover of Valiant Petroleum in March.
Ithaca's chief executive, Iain McKendrick, said: "The Company has successfully executed upon its key post-acquisition objective of removing its UK exploration cost exposure whilst still retaining potential upside."
Ithaca will retain a 31% interest in Handcross and a 10% stake in Isabella.
Azmiuth will increase its holding in Isabella to 15%.