BEIJING - PetroChina Co, the country's biggest energy producer, said it has agreed to buy a 20-percent stake in Royal Dutch Shell PLC's Groundbirch shale-gas project in Canada to obtain drilling technology and expertise.

Shell will remain the operator of the project, Mao Zefeng, the Beijing-based spokesman of PetroChina, said by telephone on Thursday. He declined to give the value of the transaction.

PetroChina plans to pay more than $1 billion for a stake in the Groundbirch property, Hong Kong-based FinanceAsia reported on its website, without saying where it got the information. Shell and PetroChina's parent agreed in June to increase cooperation in energy exploration in China, estimated to hold the world's largest reserves of shale gas.

"It's a continuation of our cooperation in China, and we can learn about shale-gas exploration and production by being a partner in the Canadian shale-gas project," Mao said. "The project will also bring us good investment returns."

PetroChina and domestic rivals Cnooc Ltd and China Petrochemical Corp, known as Sinopec Group, are seeking shale technology through overseas acquisitions. The government held its first auction of shale-gas exploration rights last year.

Bloomberg News