Po prostu zawiń go w środek BEGIN i END, a będzie działał płynnie
var content =string.Format("BEGIN {0} END;", File.ReadAllText("script.sql"));
using (var oracleConnection = new OracleConnection(_connectionString))
{
oracleConnection.Open();
using (var command = new OracleCommand(content) { Connection = oracleConnection })
{
command.CommandType = CommandType.Text;
command.ExecuteNonQuery();
}
}