He said China will continue to help Brunei in this respect, ensure the success of key joint projects and explore possible cooperation in areas such as energy and infrastructure.

Brunei's oil and gas reserves are expected to run out within two decades. The country's economy posted negative growth of 2.8 percent year-on-year in the second quarter, dragged down by slowing oil and gas production, according to Xinhua News Agency.

Hengyi Group said that when it is completed, the first phase of the refinery and petrochemical complex alone is expected to contribute as much as 40 percent to Brunei's GDP.

The second phase of the project will expand the refinery capacity to 281,150 barrels per day, and includes building units to produce 1.5 million metric tons of ethylene per year and 2 million tons annually of paraxylene, the company said on its website.

Zuo Xueqiang, an executive with the company, which is headquartered in Hangzhou, capital of Zhejiang province, said, "It (the project) is a win-win in many respects."

He said the complex on Pulau Muara Besar has provided a platform for Chinese companies to expand their operations in Brunei, as the project also requires the development of support facilities. These include plants for power generation, water supply and waste water treatment, and a port, which have been contracted to a number of Chinese companies.

"It (the island) was an absolute wilderness two years ago. Even the sand we are now standing on was shipped in from Hainan province (in South China)," Zuo said.

He added that construction of the project is only a first step, and more challenges lie in the operations, as petrochemical projects involve high risks.

The project has prioritized participation from locals, and will be jointly managed by the company and counterparts in Brunei, he said.

More than 60 percent of the project's workers will be locals, starting from the eighth year of operation, according to agreements signed between the company and the Brunei government.

As part of efforts to help with training local talent, the company has launched programs with Zhejiang University, which has catered to 68 undergraduates from Brunei working in the petrochemicals sector.

Wang Wenke, manager of the power plant project for the complex, said nearly half of the 300 workers employed on this are from Southeast Asia, and the others are from China. "For Chinese businesses, it is important to employ overseas workers in projects abroad to control costs," he said.