Defying its sluggish opening, the ONGC stock gained 2.91 per cent to Rs 167.80 on the BSE.
On the NSE, the scrip went up by 2.97 per cent to Rs 167.85.
The stock was the biggest gainer on the benchmark Sensex and the Nifty.
Shares of HPCL, however, fell by 5 per cent to Rs 364.75.
The Cabinet yesterday approved sale of the government's 51.11 per cent stake in oil refiner HPCL to India's largest oil producer ONGC for a potential Rs 26,000-30,000 crore, a top source said.
ONGC, the source added, will not have to make an open offer to minority shareholders of HPCL as the government's holding is being transferred to another state-run firm and the ownership is not changing.
The deal will be completed within a year, he said.