Nexen Energy, the Calgary-based oil and gas company acquired last year by Chinese state-owned firm CNOOC Ltd., is replacing Kevin Reinhart as CEO.
CNOOC made the decision because it wanted to bring in someone with "operational and technical depth," said spokeswoman Diane Kossman.
Reinhart ushered Nexen through its contentious sale to CNOOC last year for $15.1 billion. He previously served as the company's chief financial officer.
Prior to the takeover, announced in mid-2012, investors had been losing patience with performance at Nexen's Long Lake oilsands project. Kossman said the leadership change is "not associated with any one thing."
The deal caused Ottawa to rethink its rules on ownership of Alberta's vast oilsands resources by state-owned foreign enterprises.
CNOOC executive vice-president Fang Zhi will be Nexen's new boss.
The company says Fang is well known to Nexen's leadership and that the company's strategy and priorities remain unchanged.
Kossman said the CEO switch does not conflict with any commitments CNOOC would have made to Ottawa to get the deal through.
"Nexen's senior management team does continue to lead the organization and there are no issues associated with our personnel management. It's like any other organization: we're continually reassessing business needs and need to make the necessary adjustments."