Private equity firms are betting big on the energy sector, seizing upon opportunities following the plunge in oil prices.

Carlyle Group has raised $2.5 billion for its first international energy fund, the largest first-time strategy fund in the firm's history. Carlyle International Energy Partners began raising capital in mid-2013 and has attracted 160 investors. The firm now has over $10 billion of capital ready to deploy globally in the energy sector.