Photo taken on June 16, 2015 shows the Xingwang deep-sea semi-submersible drilling platform at Liwan3-2 gasfield in the South China Sea, south China. China's largest offshore oil and gas producer CNOOC Ltd. announced on July 3, 2015 that its Xingwang deep-sea semi-submersible drilling platform has started drilling at 1,300 meters underwater level in Liwan 3-2 gas field in the South China Sea. Photo: Xinhua

Photo taken on June 13, 2015 shows the Xingwang deep-sea semi-submersible drilling platform at Liwan3-2 gasfield in the South China Sea, south China. China's largest offshore oil and gas producer CNOOC Ltd. announced on July 3, 2015 that its Xingwang deep-sea semi-submersible drilling platform has started drilling at 1,300 meters underwater level in Liwan 3-2 gas field in the South China Sea. Photo: Xinhua

Photo taken on June 14, 2015 shows the Xingwang deep-sea semi-submersible drilling platform at Liwan3-2 gasfield in south China Sea. China's largest offshore oil and gas producer CNOOC Ltd. announced Friday that its Xingwang deep-sea semi-submersible drilling platform has started drilling at 1,300 meters underwater level in Liwan 3-2 gas field in the South China Sea. Photo: Xinhua

Photo taken on June 12, 2015 shows the Xingwang deep-sea semi-submersible drilling platform at Liwan3-2 gasfield in the South China Sea, south China. China's largest offshore oil and gas producer CNOOC Ltd. announced on July 3, 2015 that its Xingwang deep-sea semi-submersible drilling platform has started drilling at 1,300 meters underwater level in Liwan 3-2 gas field in the South China Sea. Photo: Xinhua

Photo taken on June 13, 2015 shows the Xingwang deep-sea semi-submersible drilling platform at Liwan3-2 gasfield in the South China Sea, south China. China's largest offshore oil and gas producer CNOOC Ltd. announced on July 3, 2015 that its Xingwang deep-sea semi-submersible drilling platform has started drilling at 1,300 meters underwater level in Liwan 3-2 gas field in the South China Sea. Photo: Xinhua