Shares in Melrose Resources fell back after the oil and gas group said had plugged and abandoned its Kaliakra East-1 exploration well in the Bulgarian Black Sea after the reservoir interval was found to be eroded.Nevertheless Melrose is pressing on with exploration of the Galata Block, where the well is located."Notwithstanding the Kaliakra East-1 well results, the Galata Block remains relatively under-explored and we are looking forward to receiving the results of the 3D seismic survey over the central area of the concession," said chief executive David Thomas. "The combination of low development costs, strong regional gas prices and competitive terms make this one of the very attractive exploration environments for the company."At 09.50am, shares in Melrose were down by 2.1% at 188p.---RG