The stock closed the day up nearly 9 percent. Cenovus share price dropped more than 13 percent Thursday.
ConocoPhillips will sell its position in the Foster Creek Christina Lake oil sands partnership and most of its western Canada Deep Basin gas assets, for $10.6 billion in cash. ConocoPhillips will also receive $2.7 billion in shares of Canada-based Cenovus.
"This is a significant, win-win opportunity for ConocoPhillips and Cenovus," ConocoPhillips CEO and chairman Ryan Lance said in a statement Wednesday.
"This transaction will make an immediate and significant impact on the company's value proposition by allowing us to rapidly reduce debt to $20 billion and double our share repurchase authorization to $6 billion. This means we will not only accelerate, but exceed, the three-year plan we laid out in November 2016," he said.
The two companies had already partnered on the Surmont oil sands.
ConocoPhillips shares 5-day performance
Cenovus shares 5-day performance —CNBC's Peter Schacknow contributed to this report
Cenovus shares 5-day performance
—CNBC's Peter Schacknow contributed to this report