ONGC says at least three wells drilled by RIL on the boundary of KG-D6 block in Bay of Bengal are within "few hundred meters" of its gas fields. It fears the fields are connected and RIL may be drawing out its gas.
RIL disputes the ONGC theory and the two firms have shared data to collaborate on their claims.
Sources said the two firms have now decided to appoint a reputed global consultant to study data on both sides.
ONGC and RIL will in next few days share names of their preferred consultants and arrive at a common name thereafter.
Also, the scope of work for the third party opinion would be finalised jointly by the two sparring companies, they said.
Previously, the Directorate General of Hydrocarbon (DGH) had asked RIL to share data on the gas reservoir on its side of the block as well as production flows with ONGC.
It also asked ONGC to share data based on which it had felt that RIL's wells -— D6-A5, D6-A9 and D6-B8 in KG-D6 block -- may be drawing gas from its gas pools called G4-2, G4-3 and D-1.
ONGC fears that gas discoveries in its nomination block G4 (Godavari PML) and Block KG-DWN-98/2 (KG-D5) extends into RIL's KG-DWN-98/3 or KG-D6 block.
Incidentally, wells D6-A5, D6-A9 and D6-B8 are among the handful of wells that have remained in production since the KG-D6 block was put on production in April 2009.
Half of the wells on Dhirubhai-1 and 3 gas field and MA oil and gas field in the KG-D6 block have shutdown due to water and sand ingress, resulting in output plummeting to about 13 million standard cubic meters per day.
Sources said DGH will take a call on the issue of reservoir connectivity onces the joint study is completed.
"Our study suggests that RIL's well D6-A5, D6-A9 and D6-B8 are drilled on the extension of G4-2, G4-3 and D-l pools of ONGC respectively. As these pools are extending across both the blocks, there is possibility that pools of KG-DWN-98/2 and G4 are being drained through wells drilled in D-6 block, as these wells are drilled close to/on block boundary," ONGC had written to DGH.
It wanted appointment of a third party independent expert to resolve the issue, sources said, adding that DGH also felt the issue can only be resolved through the appointment of an independent expert.