Cnooc Ltd. and China Petrochemical Corp. may make an offer worth at least $7 billion for a minority stake in OGX Petroleo & Gas Participacoes SA as well as assets owned by the Brazilian explorer, according to two people with knowledge of the matter.

OGX, based in Rio De Janeiro, may be looking to sell an equity stake of less than 30 percent plus oil-block assets, one of the people said. Binding offers would be due around the middle to end of next month, the person said. No offer has been presented and Cnooc hasn’t decided whether to make a joint bid, the person said.

China’s oil companies are seeking assets overseas to secure supplies for the world’s fastest-growing major economy. Sinopec Group, as China Petrochemical is known, bought Addax Petroleum Corp. for C$8.3 billion ($8 billion) last year to add oil reserves, part of the record $32 billion of acquisitions by Chinese companies in natural resources.

Huang Wensheng, spokesman for Sinopec Group, and Jiang Yongzhi, spokesman for Cnooc, couldn’t be reached at their Beijing offices and mobile phones.

Reuters earlier today reported that CNOOC and Sinopec are bidding for stakes in assets owned by OGX.