The shutdown of a major Russian pipeline that sends crude to European refineries has fueled concerns of tightness in the global oil market, driving futures prices higher. Problems with the Druzhba pipeline began in late April, when crude in the line was discovered to be heavily contaminated with organic chlorides. The issues have had an immediate impact on prices for Brent, the global benchmark for crude. In recent days, traders have been tacking on a premium of about $1 a barrel for immediate deliveries of oil compared with…