The incident occurred when a blow-out preventer (BOP), which is installed on wells to prevent a fire, was being repaired at a well in OLPAD-31 in Ankleshwar basin.
"8-9 persons were injured in the accident," ONGC's Ankleshwar Asset Manager Har Govind told PTI.
The injured, he said, have been rushed to Surat hospital.
"They are conscious and talking. Best of medical treatment is being made available to them."
A blowout occurred as the well got activated during repair of the BOP, he said. "The fire has been contained and kept to cool, that is to say it is being allowed to burnout."