An updated assessment of the Leviathan offshore gas field puts the Israeli offshore field's estimated resources at 16.6 trillion cubic feet (about 453 billion cubic meters), 24% lower than a previous assessment, according to energy industry sources.
The latest estimate, by Netherlands-based SGS, was prepared at the request of Israel's Energy and Water Resources Ministry.
The previous estimate, prepared for Noble Energy Inc and its Israeli partners Delek Group and Ratio Oil Exploration in July 2014 by Netherland, Sewell & Associates, put Leviathan's resources at 21.9 Tcf.
The ministry would only confirm that it had received an estimate and that it was conducting another assessment by a second international consulting company.
The ministry said in a statement that once all of the tests are concluded it would publish the figures and determine its policy regarding development of the offshore field.
The energy industry sources said that the lower estimate, if correct, could reduce the volume of gas that could be exported from Leviathan, the largest discovery offshore Israel.
"Exports would still be feasible to Egypt, Turkey and even Europe though at reduced volumes and a delayed timetable," said one source.
However, the Leviathan partners said in a statement that there has been no change in their estimate of gas resources in the field.
The partners have said they hope to begin commercial production at the end of 2019, though independent experts have said production is not likely before 2020 at the very earliest.
This is expected to depend on a final resolution of the legal issues connected to the government's gas framework.
In 2012 the Israeli government decided that it would retain 450 billion cubic meters of gas for domestic use through 2040 and 500 Bcm for exports.
