What organization exists to protect the interests of nations for which petroleum is an important export?

"
In the early 1950s, international oil companies (IOCs) developed the posted price system to help host governments estimate oil revenues in advance. Posted prices were accounting devices that host governments used to calculate the amount of taxes the companies would pay under industry wide fifty-fifty profit-sharing agreements. Despite normal fluctuations in the real prices at which crude oil was traded, posted prices were not adjusted, and fixed posted prices became an industry norm. When competitive pressures forced the IOCs to reduce posted prices unilaterally in February 1959, an immediate outcry arose from the affected host governments."

The answer would be hard press.

Yes it was hope that works