By Christopher Bjork 

MADRID--Spanish oil company Repsol SA said its chairman and top executive for more than a decade, Antonio Brufau, plans to hand over his remaining executive powers to the company's chief executive later this year.

CEO Josu Jon Imaz has run day-to-day business at Repsol since he was promoted to the job in April last year. But Mr. Brufau had kept oversight of the finance and communication divisions and is still officially the firm's top executive.

Under the plans, outlined in a regulatory filing Thursday, Mr. Brufau will continue to chair Repsol's board of directors in a nonexecutive capacity for the next four years. The handover of powers will be voted on during an April 30 board meeting, Repsol said.

The carefully planned transition comes after Repsol late last year agreed to pay $8.3 billion to take over Canadian oil firm Talisman Energy Inc., in what remains the largest takeover by any integrated oil firm since crude prices started plunging last summer.

The purchase will double Repsol's daily oil production and establish it among the top 15 producers in the world.

Mr. Imaz, a chemical engineer and former politician, ran Repsol's refining operations before he was promoted to CEO.

Mr. Brufau is taking a step back after closing a particularly thorny chapter in Repsol's history. In 2012, the government of Argentina moved to nationalize its unit YPF SA, leaving Repsol without significant oil reserves and in a difficult financial situation. After first going after Argentina in international courts and through diplomatic channels, the parties reached a settlement by which Repsol received $5 billion in compensation for the expropriation. That money is now being plowed into Talisman.

Write to Christopher Bjork at christopher.bjork@wsj.com

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