* Well confirms Leviathan has 16 trillion cubic feet of gas
* Delek: Leviathan biggest deepwater gas find in past decade
* Israel could become exporter of natural gas
* Noble shares up 3.4 percent, Israeli firms' shares surge
* Natural gas valued at $95 billion -analyst
(Adds analysts' comments)
By Tova Cohen
TEL AVIV, Dec 29 (Reuters) - Noble Energy and its Israeli exploration partners confirmed earlier estimates that the offshore Leviathan prospect was Israel's largest natural gas find and could transform the country into an exporter of gas.
Delek Energy, one of the Israeli partners, said on Wednesday that Leviathan, 80 miles (130 km) off the Mediterranean port of Haifa, was the largest deepwater natural gas find in the world in the past decade.
Noble shares jumped 3.4 percent to $87.88. Shares in Delek Energy closed up 3.7 percent, while its subsidiaries Delek Drilling and Avner Oil rose 5.1 percent and 4.4 percent respectively. Another Israeli partner, Ratio Oil, surged 10.3 percent.
"Today we received the most important energy news since the country was founded, which will certainly bring us success and significantly impact many fields in Israel," Infrastructure Minister Uzi Landau said. "This is an important day for the Israeli market and economy."
A nearby prospect called Tamar being drilled by Noble and Delek was the largest gas find in the world in 2009, at 8.4 trillion cubic feet. Leviathan is nearly twice the size.
"Leviathan is the latest major discovery for Noble Energy and is easily the largest exploration discovery in our history," Charles Davidson, chairman and CEO of the Houston-based company, said in a statement.
Amir Kahanovich, macroeconomist at brokerage Clal Finance, estimated the gas reserves at Leviathan were worth $95 billion.
Noble said results from a well confirmed the pre-drill estimated resource range, with a gross mean for Leviathan of 16 trillion cubic feet (450 billion cubic metres) of gas.
"This discovery has the potential to position Israel as a natural gas exporting nation," Noble President and Chief Operating Officer David Stover said.
Delek Energy and its Israeli partner Ratio said they would continue to explore different options for exporting gas through a pipeline and/or as liquefied natural gas (LNG).
They said the early results from the drill may support carrying out a project for at least one of the alternatives.
TAX PROPOSAL
Delek Energy CEO Gideon Tadmor said both Leviathan and Tamar should be excluded from any proposed tax changes to be levied on oil and gas exploration companies in order to allow their immediate development.
"Realising the potential of Leviathan requires from the developers enormous investments in infrastructure to export gas, in an unprecedented amount of tens of billions of shekels," Tadmor said.
The so-called Sheshinski committee has recommended sharply raising the government's take on oil and gas revenue, which is relatively low on a global standard, through a progressive tax on companies that ranges from 20 to 60 percent.
Noble and Delek have said the tax proposal creates uncertainty around the scheduling and financing of Tamar, which was due to start production by 2013.
Guil Bashan, an analyst at IBI Investment House, said the fact there is also natural gas in Leviathan raises the chances that the committee's proposals will be adopted.
"The chances that gas will be produced from Leviathan before 2017 are slim, in our opinion," he said. "The publishing of the committee's final conclusions are far more significant to the value of the (companies') shares than this report."
Noble owns 39.66 percent of Leviathan, while Delek Energy's subsidiaries Avner and Delek Drilling each own 22.67 percent. Ratio owns the remaining 15 percent.
Migdal Capital Markets analyst Eran Yunger said the latest statement hints at a reasonable chance of further gas finds.
He said the announcement strengthens the reliability of seismic data that showed a possibility of discovering oil at Leviathan, which he estimated could be worth $500-$700 million.
The Leviathan field is estimated to cover 125 square miles (325 square km) and will require two or more appraisal wells to further define total gas resources, Noble said.
(Additional reporting by Ari Rabinovitch; Editing by Steven Scheer, Will Waterman and David Hulmes)