China has approved plans by China Petroleum & Chemical Corp (Sinopec) and Kuwait Petroleum Corp for a 5 billionl US dollars joint venture refinery project in Guangdong Province, the Shanghai Daily reported.   The venture will become the largest Sino-foreign joint venture in terms of investment scale, overtaking a US$4.3 billion project - also in Guangdong - by China National Offshore Oil Corp and Royal Dutch Shell. The Nansha project is designed with an annual oil refining capacity of up to 15 million tons and a further 1 million ton production capacity of ethylene, a key petrochemical building block, said the paper. "For such big scale projects, China still needs to partner with foreign firms for help in both capital and technical support," said Yin Xiaodong, a CITIC Securities Co analyst to the paper. "And the 1 million ton ethylene plant will become the largest of its kind in China."