Sinopec Oilfield Service, whose biggest customer is China's second largest oil and gas producer Sinopec - has turned its focus to the overseas market and domestic natural gas projects for growth, as low oil prices cut domestic oil drilling work volumes and saw it post a loss last year. The drilling and construction services arm of state-owned China Petrochemical - parent of listed Sinopec - is aiming for overseas business to contribute up to 35 per cent of its revenues by 2020, up from 23 per cent last year.