A joint venture of Adani Group and Welspun Enterprises Ltd has discovered natural gas reserves in an area off the Mumbai coast, the two firms said in a statement Monday. The first-ever gas discovery was made in the NELP-VII block MB-OSN-2005/2, Adani Welspun Exploration Ltd (AWEL) said. Spread across 714.6 square kilometers, the block is located in the prolific gas-prone Tapti-Daman sector of the Mumbai Offshore basin where production is already underway by other operators.