(ShareCast News) - Shares in Lansdowne Oil & Gas tanked after the company said it did not encounter any significant gas at the Midleton exploration well in the Celtic Sea.The independent oil and gas company, which is focused on offshore Ireland, said the well will now be plugged and abandoned.Chief executive Stephen Boldy said: "The results from the Midleton exploration well are disappointing but we retain substantial resources in the Celtic Sea via our 20% interest in the Barryroe oil field. We will continue to work hard to move forward with this project and to unlock its value for our shareholders."At 1452 BST, Lansdowne shares were down 34% at 4.85p.