A consortium comprising Chevron and a group led by an investment bank continues negotiations with Lukoil and U.S. officials to buy the Russian firm’s international assets, even as Lukoil has signed a preliminary non-exclusive deal with Carlyle, multiple sources with knowledge of the ongoing talks tell Reuters. Last week, Lukoil announced it had agreed to sell most of its international assets to private equity giant Carlyle. The agreement is not exclusive and is subject to conditions such as the procurement of necessary…