The newest discovery was in the Rachel licence, and results from the well confirm earlier reports that the supergiant gas field holds an estimated 450 billion cubic metres (16 trillion cubic feet) of natural gas.
The Leviathan field is located about 80 miles offshore of Haifa, and 29 miles southwest of the Tamar discovery, which Nobel also holds the licence for. The new estimates announced by the US firm means that Leviathan dwarfs Tamar, which was previously Israel's biggest offshore field. The Tamar field has an estimated capacity of 178.4 billion cubic metres (6.3 trillion cubic feet), but it is not yet operational.
"Leviathan is the latest major discovery for Noble Energy and is easily the largest exploration discovery in our history," the firm's chairman Charles Davidson said in a statement.
"This discovery has the potential to position Israel as a natural gas exporting nation," added company president David Stover.
Even before Leviathan, a series of finds had put the so-called Levant Basin on the international energy map. In March 2010, the US Geological Survey released its first assessment of the area, estimating that it contained 1.7 billion barrels of oil and 122 trillion cubic feet of gas. That is equivalent to half of the proven gas reserves of the US.
The finds in Israel have prompted its neighbours to start their own exploration programmes. In August, lawmakers in Beirut rushed through the country's first oil-exploration law and in October, Lebanon's oil minister Gebran Bassil, an ally of Shi'a militant group Hezbollah, said the country hoped to start auctioning exploration rights by 2012.
The finds have also prompted countries in the region to get their maritime boundaries in order. Cyprus, for example, has in recent years made agreements with Lebanon, Egypt, and in December 2010, Israel.
Remaining border issues are, however, stalling development for Israel. Lebanon claims that the Tamar field is partially within Lebanese territory, and in November 2010, Iran's ambassador to Lebanon, Qazanfar Roknabada, claimed that three-quarters of the Leviathan field actually belonged to Lebanon.
Disputes over Noble's licenses in the eastern Mediterranean are nothing new. Their Mari-B field, production from which began in 2004, is on the border of the Gaza marine area, and the field may stagger the border. If this is the case, Israel is required under international law to share the proceeds from the field, and while critics of Israel have pointed this out repeatedly, Gaza's lack of legal infrastructure and weak government has meant that its potential claim has been largely overlooked.
It seems, however, that affairs in the north of Israel's waters will not be so easy to control.
Lebanon and Israel are still officially in a state of war, and both sides have threatened each other over offshore resources. Clearly, until peace is found and borders established, disputes over offshore resources will remain ever present.