Eni’s August 2015 Zohr discovery offshore Egypt could hold the key to unlocking further regional gas riches. ExxonMobil is the latest major to join the search.

Italian firm Eni’s August 2015 Zohr discovery in the Egyptian deepwater, with its 30tcf of gas in place, vies with Israel’s Leviathan, discovered December 2010 by US firm Noble Energy, for the title of the East Mediterranean’s largest gas discovery.

Leviathan and Noble’s other key East Med deepwater...