Canadian natural gas prices are heating up this spring and so is the pace of deal-making in the sector. Tourmaline Oil Corp., already the country’s largest gas producer, announced Friday it acquired privately held Black Swan Energy Ltd. in a deal valued at $1.1 billion. It’s another key purchase for Tourmaline as it continues to gobble up prime gas assets, and it comes while mergers and acquisitions have swept through the hard-hit sector. By the...