Replace your code with below snippet and it should work.
public static System.Data.DataTable GetOracleDataTable(string Query, string tblName)
{
System.Data.DataSet dSet = new System.Data.DataSet();
OracleConnection con = new OracleConnection(Globals.OracleConnectionString) ;
con.Open();
OracleCommand cmd = new OracleCommand(Query);
cmd.Connection = con;
cmd.CommandText = CommandType.Text;
OracleDataAdapter adapter = new OracleDataAdapter(cmd);
adapter.Fill(dSet, tblName);
return dSet.Tables[tblName];
}