Europa Oil and Gas has seen its share price plummet in morning trading following the announcement that drilling at its Horodnic-1 exploration well in northern Romania has been a failure.It says of the operation, which cost Europa £720,000, that "no potentially commercial hydrocarbon bearing interval was found."In oil exploration, failures are simply part of the game, although Afren has had a particularly rough time this year, falling 76% from its peak share price in February.At 1132am Europa's shares were down 27% on the open.BS