The United States-based consultant DeGolyer & MacNaughton has assessed the in-place gas reserves at Reliance Industries Ltd's deep-water block D6 in Krishna Godavari Basin at 10 trillion cubic feet, lower than the company's claim of 14.5 tcf reserves.

"D&M, which performed an assessment of the reserves on behalf of RIL's partner Niko Resources of Canada, has assessed gross in-place gas reserves of 10 tcf in the KG-DWN-98/3 block (also called D6)," Niko sources said in New Delhi on Friday.

The study said the 10 tcf comprises 3.4 tcf of technically proven reserves, 3 tcf of probable and 3.6 tcf of possible reserves.

The 10-tcf reserves as on April 1, 2003, do not include results from the A2 well - the last of the eight wells drilled by Reliance in the first phase of exploration - which were under evaluation when the study was being undertaken.

However, RIL stands by its earlier assertion that the block's in-place resources are in excess of 14 tcf of gas and says "the numbers would near these levels over time when the ongoing analysis is completed."

"We believe the gas reserves in D6, which are equal to 2.3 billion barrels or 300 million tonnes of oil, are set to produce 2.12 billion cubic feet per day versus the combined output of 2.2 bcfd from all of India's other gas fields," senior Reliance officials said.

Production from the deep-water block will add annual incremental revenues of Rs 10,000 crore (Rs 100 billion) to the D6 operator and 90 per cent equity holder - Reliance Industries Ltd - from 2006.

Niko Resources holds the remaining 10 per cent stake in the block.

RIL's current exploration programme has evaluated less than 16 per cent of the total D6 block area. A 2,500 sq km 3D seismic survey will be shot in October 2003, which will provide the basis for a second exploration drilling campaign, they said.

Of the eight wells drilled so far in the block, four discoveries - Dhirubhai-1, Dhirubhai-2, Dhirubhai-3 and Dhirubhai-4 have been announced.