It turned into a glut because OPEC is pretty much an international cartel on oil. What happened was that prices went up, along with incentives for country to break the pact, which lead towards the Oil glut in the 1980's.
It also led the way for the US to find different partners such as Mexico and Canada for oil as well as drilling in their own country such as Alaska.
Now the position that OPEC had has weakened.