April 17 (Reuters) - Kazakhstan has raised its

arbitration claims against the international oil majors that

developed the Kashagan oilfield to more than $150 billion,

Bloomberg News reported on Wednesday, citing people familiar

with the matter.

Kazakhstan's energy minister said last year it was pressing

ahead with $16.5 billion in claims against the consortium over

disputed project costs and had no plans for a possible

out-of-court settlement.

The report on Wednesday said the figure had jumped after the

Kazakhstan government added a claim for as much as $138 billion,

"reflecting the calculation of the value of oil production that

was promised to the government but not delivered by the field

developers."

The legal wrangling underscores the risks for foreign

companies operating in the former Soviet Union state and is one

of many court battles between the international majors and the

government.

The offshore Kashagan field, one of the biggest discoveries

in recent decades, is being developed by Eni, Shell

, TotalEnergies, ExxonMobil ( XOM ),

KazMunayGas, Inpex ( IPXHF ) and CNPC.

Their consortium, called the North Caspian Operating Company

(NCOC), has invested some $50 billion in the project.

Bloomberg cited NCOC as saying it has as number of disputes

concerning the application of certain provisions of the Kashagan

production sharing agreement that are subject to arbitration.

"The contracting companies consider that they have acted in

accordance with" that contract, according to NCOC's statement.

NCOC did not immediately respond to a Reuters request for

comment. A Shell spokesperson declined to comment.

A spokesperson for Eni confirmed that Kazakh authorities had

commenced an arbitration procedure against the consortium

partners and terms of the arbitration were confidential.

"Whilst we are reviewing the complex allegations, we do not

believe (as a general comment) the basis for the claims or the

specific amounts of compensation requested to be reasonably

substantiated or credible," Eni said.