What is the fine-grained topic of the following text: The Indonesian Government has welcomed cooperation between Oman's Overseas Oil and Gas (OOG) and Indonesian state oil and gas company PT Pertamina to build a new oil refinery in Bontang, East Kalimantan, with an investment worth US$10 billion. Only return the topic.
Cooperation between Oman's OOG and Indonesia's PT Pertamina to build a new oil refinery in Bontang, East Kalimantan.