The sale will result in Santos exiting the offshore Victoria area, with the company selling its interest in the Kipper gasfield in March for A$520m ($395.8m).
As part of the deal, Cooper Energy will acquire a 50% interest and operatorship of the Casino-Henry gas project in the offshore Otway Basin and a 100% interest in the non-operating Patricia Baleen gasfield and associated infrastructure in the offshore Gippsland Basin.
Onshore assets being acquired include a 10% interest in the Minerva gas field and Minerva Gas Plant in the Otway Basin, 50% interests in the Sole gasfield and Orbost gas plant in the Gippsland Basin.
Cooper Energy said it will approach the Casino-Henry joint venture partners AWE and Mitsui for their approval to serve as the operator of the project.
The company also plans to approach relevant regulators for approval to become the operator of the Casino-Henry, Sole and Patricia Baleen projects, which are currently operated by Santos.
Cooper Energy managing director David Maxwell said: “The transaction will transform Cooper Energy by substantially increasing our production, further enhancing our gas reserves and resources for supply to south-east Australia and adding proven technical and project expertise.
“In the near-term, Cooper Energy will be repositioned within the oil and gas sector with a fourfold lift in its Australian production and nine-fold increase in Australian 2P reserves.”
Upon completion of the acquisition, Cooper will be able to boost its production, reserves, technical, engineering and project management capabilities.
Cooper Energy will acquire an equity share of 45 PJ of uncontracted gas 2P reserves in the Casino Henry gas project.
Acquisition of the remaining 50% of Sole will add a further 121 PJ of gas 2C contingent resources.
Subject to customary consents and regulatory approvals, the transaction is expected to complete in early next year.