Eni SpA, Italy's largest energy company, is selling a stake in a shale natural gas prospect in Mozambique to a unit of China National Petroleum Corporation (CNPC) for $4.2 billion, Eni said Thursday.

CNPC's Petrochina Company Limited will acquire a 20 percent stake in Mozambique's Area 4, which holds one of the world's largest shale natural gas reserves. Eni will retain a 50 percent stake in the property and continue to manage the project.

Other stakeholders are Empresa Nacional de Hidrocarbonetos de Mocambique with 10 percent, Kogas with 10 percent and Galp Energia with 10 percent.

Area 4 holds an estimated 75 trillion cubic feet of gas, Bloomberg News reported, an amount that exceeds all of Norway's natural gas reserves.