New Delhi: State-owned Oil and Natural Gas Corporation (ONGC) has made two significant back-to-back natural gas discoveries in a Mahanadi basin deepwater block in the Bay of Bengal as its calculated game plan of venturing into high-risk deep water exploration starts yielding results. The firm made the discoveries in the block MN-DWHP-2018/1, which it had won in the third round of auction under the open acreage licensing policy in 2019, two sources with direct knowledge of the development said.