China Petrochemical Corp., the nation's second-largest oil and natural-gas producer, will eventually transfer its overseas assets to China Petroleum & Chemical Corp. (600028) to avoid competing with the subsidiary.

China Petrochemical, known as Sinopec Group, will also sell all remaining chemical businesses within the next five years, according to a filing by the Beijing-based unit to the Hong Kong stock exchange today.

The parent company has spent at least $18.1 billion on six Canadian purchases, including the $8.83 billion acquisition of Addax Petroleum in 2009, according to data compiled by Bloomberg. The statement gave no time frame for when the foreign assets would be transferred.

The companies signed an agreement not to compete before the unit began public trading in Hong Kong in 2000.

China National Petroleum Corp. is the nation's largest oil and gas producer.