China Petrochemical Group, better known as Sinopec, has agreed to buy 50 per cent of China National Chemical Import & Export Corp's share of oil and gas fields in the Arabian Gulf and offshore Tunisia.

Last week, China National Chemical Import & Export Corp, or Sinochem, bought the Isis oilfield off Tunisia and gas fields in the Arabian Gulf from Atlantis, a business unit of Petroleum Geo Services ASA for $US215 million.

Atlantis has more than 500 billion cubic feet of proven and probable gas reserves in the Arabian Gulf and at least 20 million barrels of oil offshore Tunisia and in the Arabian Gulf fields.

Earlier this month, China's third largest oil company, China National Offshore Oil Company or CNOOC, paid Repsol YPF SA $US585 million for five Indonesia oil and gas fields. Last week, China National Petrochemical Corporation announced it had acquired a stake in an oilfield in Azerbaijan.

Last month CNOOC announced it had shipped its first offshore drilling rig into south east Asia, signalling its intent to enter the drilling rig fabrication market.