Oil and gas company Shell has agreed to buy British rival BG Group for $69.7 billion in a deal that may signal a new wave of mega-mergers as the energy industry tries to adapt to lower prices.

Royal Dutch Shell said Wednesday it will pay the equivalent of 13.67 pounds in cash and stock for each share of BG Group, 50 percent more than Tuesday’s closing price. The deal will boost Shell’s oil and gas reserves by 25 percent, including offshore projects in Australia and Brazil, and give it a bigger presence in the fast-growing liquefied natural gas market, Shell said.