ExxonMobil and Shell have decided not to proceed with a planned sale of their joint assets in the southern UK North Sea to Viaro Energy. Despite months of work to complete the transaction, completion conditions have not been met and the deal has been subject of a lengthy review by the UK’s regulator, the North Sea Transition Authority (NSTA). Last year, Viaro Energy signed an agreement to take over Shell and Exxon’s UK Southern North Sea assets, which are one of the largest and longest producing gas asset portfolios in the…