A consortium of investment groups is planning to acquire Origin Energy Ltd., Australia’s largest integrated utility, in a deal that could make ConocoPhillips upstream operator of the natural gas fields that feed the Australia Pacific LNG (APLNG) facility.

Brookfield Renewable Partners LP and U.S.-based institutional energy investor EIG reached an agreement with Origin’s board to pursue an acquisition for about $12.4 billion, the firms disclosed Monday. The deal is expected to be finalized sometime in early 2024, subject to regulatory and shareholder approval.

As a part of the deal, ConocoPhillips could acquire up to 2.5% of Origin’s stake in the APLNG joint venture and take over as operator of the assets in Queensland’s Bowen and Surat Basins, which supply coal seam gas...