OPEC often has difficulty agreeing on policy decisions because its member countries differ widely in their oil export capacities , production costs , reserves , geological features , population , economic development , budgetary situations , and political circumstances . Indeed , over the course of market cycles , oil reserves can themselves become a source of serious conflict , instability and imbalances , in what economists call the " natural resource curse " . A further complication is that religion-linked conflicts in the Middle East are recurring features of the geopolitical landscape for this oil-rich region . Internationally important conflicts in OPEC 's history have included the Six-Day War ( 1967 ) , Yom Kippur War ( 1973 ) , a hostage siege directed by Palestinian militants ( 1975 ) , the Iranian Revolution ( 1979 ) , Iran – Iraq War ( 1980 – 1988 ) , Iraqi occupation of Kuwait ( 1990 – 1991 ) , September 11 attacks by mostly Saudi hijackers ( 2001 ) , American occupation of Iraq ( 2003 – 2011 ) , Conflict in the Niger Delta ( 2004 – present ) , Arab Spring ( 2010 – 2012 ) , Libyan Crisis ( 2011 – present ) , and international Embargo against Iran ( 2012 – 2016 ) . Although events such as these can temporarily disrupt oil supplies and elevate prices , the frequent disputes and instabilities tend to limit OPEC 's long-term cohesion and effectiveness
September 11 attacks
September 11 attacks
OPEC