Competition is what OPEC was created to end. Rival cartels defeats the purpose which is to set artificially high prices.
Precisely. :^) Ages ago, or rather, even ages ago, when I was in college, one of the econ profs (he was a big deal back then, although he only worked in the Carter White House) mentioned in lecture that cartels don't normally last as long as OPEC had by then (it was formed around 1960 I think), and for their duration they tend to "leak" because members want to cheat, whether they are national entities or individual companies.