SYDNEY—Santos Ltd. said it would buy Quadrant Energy, the natural-gas company whose owners include Brookfield Business Partners, the publicly traded arm of Toronto-based Brookfield Asset Management Inc., for US$2.15 billion as it seeks to build up its Australian gas business.
Santos, one of the largest independent oil-and-gas producers in the Asia-Pacific region, has been chasing growth close to home, pledging to build out its presence near existing infrastructure and diversify its mainly oil-linked revenues. The company has...