* Global LNG fleet needs to grow by 225 vessels by end-2020 * About 125 vessels already on order, mostly to S.Korean builders * China builders to grab a fifth of LNG ship orders to 2020 -ABS SINGAPORE, Aug 5 (Reuters) - Chinese shipyards are aiming to take some $10 billion in orders for new LNG tankers over the rest of the decade, part of a plan to restructure the country’s ailing shipbuilding sector and secure China’s energy supply chain.