White & Case and Shearman & Sterling are assuming the lead roles on a $7 billion investment by state-owned Saudi Arabian Oil Co., known as Saudi Aramco, into its Malaysian counterpart Petroliam Nasional Bhd., or Petronas.

In a deal signed in February during Saudi Arabian King Salman Bin Abdulaziz Al Saud’s state visit to Malaysia, Saudi Aramco agreed to buy a 50 percent stake in a joint venture with Petronas to build a refinery and petrochemical project in southern Malaysia’s Johor state.