China Petroleum & Chemical Corp., or Sinopec as China’s largest refiner is known, is forming a joint venture with its parent to buy crude oil and natural gas assets in Kazakhstan, Colombia and Russia valued at about $3 billion.

Sinopec, which is owned by China Petrochemical Corp., will make the acquisitions to build up Sinopec’s petroleum reserves and cut down on the amount of crude oil it has to import to feed its network of refineries, the Wall Street Journal reported Monday.

Sinopec is 78 percent owned by China Petrochemical Corp.