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, KazMunayGas, Inpex 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. (Reporting by Deep Vakil and Harshit Verma in Bengaluru, editing by David Evans)