The Doha agreement has raised hopes for a cut in world crude supply, but such an outcome remains elusive. Participation by Iran, has not been secured. Iran has vowed to restore its market share to pre-2012 levels now that sanctions are being lifted and is unlikely to deviate significantly from that plan.

Iraq also has plans to expand crude output in coming years. Also, a broadly accepted oil agreement will require OPEC's return to an individual quota system. Arriving at an agreement will take time and oil price volatility will be exacerbated by headline news.

This week's negotiations may mark an important step in that direction. All four producers are near maximum output so their production would remain at historically high levels, ensuring that markets remain over-supplied.