Reliance's key Indian gas fields may run out in 5 yrs-analysts

* Reliance, BP yet to get approvals for development work

* Pick-up in volumes not seen before 2015-16

NEW DELHI Oct 8 (Reuters) - Reliance Industries' key gas producing fields off India's east coast could be exhausted in five years, Morgan Stanley analysts said in a report.

The researchers' findings are based on estimates by block D6 partner Niko Resources that total proved plus probable reserves at the block had decreased to 1.93 trillion cubic feet as of March 31.

Canadian Niko has a 10 percent stake in the D6 block in the Krishna Godavari basin, while Reliance and BP, the operators, have 60 percent and 30 percent share respectively.

The block was expected to contribute up to a quarter of the gas supply for Asia's third-largest economy, but its unforeseen decline in output has left India more dependent on expensive liquefied natural gas (LNG) imports.

The gas output from the D6 block was projected to decline to 20 million standard cubic metres a day (mscmd) in 2014/15, less than half the 60 mscmd it produced in 2010 and well below planned peak capacity of 80 mscmd.

Reliance has 10 other discoveries in the block that are yet to be developed

It has won approvals for the pre-development work and needs further regulatory approvals for development activities, the note said.

"We currently assume that D6 production will increase to 40 mscmd of gas in 2015/16 once these discoveries are developed," Morgan Stanley said.

India's federal auditor had last year criticised the government as well as Reliance over development of the KG gas field, which has been beset by arguments over spending and strategy for its complex geology.

No immediate comment was available from Reliance.