Dublin-based Petroceltic said the ratification of the deal, in which Sonatrach increased its interest in the Ain Tsila gas asset to 43.75 per cent from 25 per cent, was a critical step in the development of the field.
It triggers a $20m cash payment to Petroceltic by Sonatrach. The Algerian firm will pay $140m of Petroceltic's share of the project development cost and a further $20m if specified project milestones are passed.
The partners in the field expect the development to cost around $1.6bn, most of which will be incurred from 2015 through 2017.
Last month Petroceltic agreed a peace deal with a Swiss hedge fund, Worldview Capital Management, which had opposed a $100m share placing it completed.
The deal resulted in Melrose's former chief executive David Thomas losing his seat on the Petrolectic board. He remains chief operating officer.
Robert Adair, founder of Melrose, remained chairman of Petroceltic.
The company has 38.25 per cent of Ain Tsila. Italy's Enel has 18.375 per cent.