candidate: In September 2011 , shortly after China and Vietnam had signed an agreement seeking to contain a dispute over the South China Sea , India 's state - run explorer , Oil and Natural Gas Corporation ( ONGC ) said that its overseas investment arm ONGC Videsh Limited had signed a three - year deal with PetroVietnam for developing long - term cooperation in the oil sector and that it had accepted Vietnam 's offer of exploration in certain specified blocks in the South China Sea .