New Zealand Oil & Gas plans to take a 60% stake in what's considered a highly prospective offshore Taranaki field.
Earlier this year it made a conditional offer to buy a 15% stake in the Kaheru exploration permit off the south Taranaki coast from AGL Upstream Gas.
Australia-based ROC which owned half of the permit recently announced it was pulling out.
New Zealand Oil & Gas will still pay AGL the previously-agreed $3 million but will now also be assigned AGL's 42.86% stake in the permit, taking its stake to 60%.
Canadian company TAG will have the remaining 40%
Meanwhile, New Zealand Oil & Gas says applied to extend the commitment date for drilling to 18 September and well is to be drilled by May 2014.
It has started a global search for a partner to join the joint venture for a late 2013 early 2014 drilling programme.