They were only able to do it because Saudi Arriba was willing to take almost all of the cuts required. In the 1970s opec vot better compliance, but cartels tend to fail because it is the benifit of the individual to defect while everyone else makes cuts. Saudi Arriba is not able to make deep enough cuts alone though, and it is hard to see anyone else making them.

I've always wondered how much black market petroleum is state sanctioned. Unofficially, of course.