THE jobs of more than 2000 workers have been secured after the owners of the Grangemouth oil refinery, Ineos, signed a partnership deal with PetroChina   the biggest company in the world by stock market value.  The Chinese giant yesterday confirmed details of a joint venture with Ineos which will help protect the long-term profitability of the refinery and petro-chemical plant on the Forth.  around 1400 workers are employed at the site and Ineos chairman Jim Ratcliffe said another 7000 jobs at other firms, particularly in central Scotland, were dependent on the plant.  He claimed the deal would be  hugely beneficial , adding there would be further mutual benefits through an agreement on sharing technology.  Finance Secretary John Swinney said the joint venture enhanced security of supply for customers as well as retaining the jobs and skills that had been built up over many years at Grangemouth.  The refinery has direct access to crude oil and gas from the North Sea and processes 210,000 barrels of crude oil a day   the equivalent of nine million litres of clean fuel. It supplies petrol and diesel to Scotland, northern England and Northern Ireland.  The signing of the agreement yesterday was witnessed by Deputy Prime Minister Nick Clegg and the Chinese Vice-Premier, Li Ke Qiang. Both men said it represented a strengthening of links between the UK and China.  Following just 24 hours after the conclusion of a ?6.4 million green energy deal between Scottish and Sino-Scottish firms, concluded when Mr Li visited Edinburgh on Sunday, Mr Swinney said it was further evidence of the strengthening ties between Scotland and China.  He said:  Scotland has unrivalled energy resources and expertise and the Scottish Government is committed to working with China across this sector.  The Grangemouth refinery is a strategic asset for Scotland and this announcement represents good news for Scotland and Scottish jobs.  It further embeds the successful relation