MORE than four million barrels of oil could leak into the North Sea in a worst-case scenario spill at a new well proposed for Scottish waters.  US energy firm Hess admitted that anything up to 683 million litres could be spilled in a disaster echoing the Deepwater Horizon accident in the Gulf of Mexico.  a catastrophe on that scale could engulf the Shetland coast and penetrate as far south as Norfolk, the company told the UK Government.  However, such a large spill